TWIN SPARK - WHY, HOW and why it isn't more widespread
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- Опубликовано: 19 май 2024
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In 1986 a company called Alfa Romeo introduced the first ever twin spark engine. Instead of having one spark plug in each cylinder Alfa Romeo decided to double things up and install two spark plugs in each cylinder. This resulted in improved combustion inside the engine which lead to increased power and efficiency and to this day twin spark engines are the absolute pinnacle of internal combustion design, often imitated but never duplicated….
Did you buy all this? Well some of it is actually true...but the rest is absolute nonsense. Do you know which part is true and which is not?
1986 ..nope that's a big lie. The first functional dual ignition engine was introduced in 1914 on this car. Was it an Alfa....yes it was! This right here is the 1914 ALFA 40/60 Grand Prix. The car was a creation of Giuseppe Merosi who not only had an incredible mustache but also created an engine that was light-years ahead of it's time. It was a 4.5 liters inline with double overhead cams, four valves per cylinder, 90 degree valve angle and twin spark ignition. In 1914. Although the overall engine architecture was inspired by the Peugeot engines from 1912 and 1913 whose design is claimed by Swiss engineer Ernest Henry, the twin sparks were definitely an Alfa original creation.
Once initiated the combustion flame front travels from the spark plug outward until it covers the combustion chamber and obviously this takes time. The time required to complete a combustion depends on the flame speed of the combustion which depends on the type of fuel, octane rating, compression ratio, how well air and fuel are mixed together and what is the ratio of the air to fuel. But in general as the rpms increase the speed of the piston will outrun the speed of the combustion.
This means that we must rely on ignition advance to fire the spark plug before the piston reaches top dead center in order to give the combustion enough time to spread and build up maximum combustion pressure by the time the piston reaches just a bit past top dead center so that maximum pressure is exerted onto the piston at the correct time leading to maximum power and efficiency.
But there's a limit to ignition advance. Too much ignition advance eventually results in the spark plug being fired too early and creating combustion as the piston still moves upward which is essentially pre-ignition and can damage the engine because it forces the piston to work against the combustion exposing it to massive heat and mechanical stress.
So if we run out of ignition advance and still want to rev the engine to high rpm our only other choice is the increase the speed of the combustion and we can do this by initiating combustion at two different points. If we install two spark plugs and fire them at the same time the travel path for the flame front becomes much shorter. By installing two spark plugs we're not increasing the flame speed, we're simply reducing the travel path of the flame front which obviously decreases combustion time making it possible to fully cover the combustion chamber even at high rpm.
So if twin spark plugs offer the benefits of better combustion which leads to more power potential, improved economy and reduced emissions this must make them very desirable and one would expect to see dual ignition on all car engines on the road today. In reality the opposite is true and as many of you know twin spark plugs are a pretty rare occurrence on car engines. Dual ignition did pop on the engines of various manufacturers through the years. Nissan had it in 1978 on their NAPS-Z and NAPS-X cars. Ford also had it in the 80s and early 90s on their four cylinder Ford Rangers and Mustangs m. Honda also had intelligent and dual sequential ignition on their I-DSI engines found in their smaller cars in the early 2000s. But today there's virtually zero mass produced cars that have twin sparks per cylinder. In fact starting with around 2010 or so twin spark plugs are virtually extinct on car engines.
CHRYSLER HEMI ENGINE
So why do Hemi engines have dual sparks? Well first of all the hemi engine isn't a true hemi anymore, the combustion chambers aren't really hemispherical, instead they have a more complex oval shape. But more importantly than this the modern hemi is still a bit of a 2 valve dinosaur. Some versions do have cam phasing but that's pretty much it. There's no direct or dual injection, no variable intakes, no variable valve lift meaning that the Hemi needs all the help it can get meet recent emissions and economy standards.
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I remember during my flying lessons we would turn off one magneto (airplane ignition coil) and you'd lose about 200 rpm.
Same with the Mercedes twin spark engines. You can shut off a single circuit to use for diagnostics and see an RPM change even when switching between the two
Aircraft with piston engines have 2 spark plugs per cylinder is also for reliably not only power.
@@fchanMSI redundancy
Yep, checking for lead fouling on the plugs too.
Magneto are quite a bit different than automotive ignition coils, its a very old technology with the main advantage of being completely independent from the aircrafts electric system.
When I was learning to fly, they used twin (magneto) ignition for redundancy. You'd test each mag by shutting the other off just before takeoff. RPMs would drop by 100 or so, meaning you got more power with two vs one.
That said, cylinders were HUGE (90 cu in/1.5L each!) That, along with the antiquated ignition system, probably meant a performance bump for twin mags. Also, mag advance is fixed and optimized for twin plugs.
As I remember reading somewhere Charles Lindbergh airplane ' Spirit of St. Louis ' had dual spark plugs. According to Charles he flew all the way to Paris and it never missed even one time.
As I understand it, the magnetos are also isolated from the rest of the electrical system; their only job is to provide spark. Cars used to work this way, too (100+ years ago) but that design was phased-out as a cost-saving measure.
@@hibob841 Exactly. Airplane Engine require absolutely no external electricity to run, a bit like a Diesel. I like to fly an old Piper (Super) Cub, (a PA-19, officially a Super Cub but it has no Flaps and only the left Wing Tank) and it is still a Hand Start and has no Alternator or Generator at all. It has a Glider Battery for the Radio that gets recharged after each Day of flying and that's it.
@MyFabian94 uhh , ASE diesel technician here. Diesel engine has no ignition whatsoever wheras the airplane engine has a externally generated electrical current generating an internal spark therefore needing an externally created spark...its created by a component bolted to an engine just like an alternator or generator just a very crude and basic version of em, you can run lights and stuff off a magneto.an external electrical charge is forced to jump a gap causing spark .it comes from the engines rotation spinning a flywheel with permanent magnents attatched passing by coils of copper wires creating a magnetic field exiting electrons which are in microseconds stored in capacitors( some do ,some just yeet that shit down the wire) surge from there either through cap & wire or coil delivery contactors and dwell in the form of spark AKA a magneto spark ignition system. Diesel engines have NO spark and rely on excessive cranking to cause friction and pressures love child (heat) which detonates the fuel oil . Other forms of starting zee diesel engine are introducing a low flash point atomized detonation inducer such as ether or more commonly used today world wide a big ass resistor aka heating element known as a glow plug. Though commonintodays diesels they were notused in the early years making diesel startup a pain in the a$$ back then or for modern ford powerstrokes that hate life....thought id clarify that up for ya. The more you know.. .
@@TomAss-it5cp I am well aware of that, but in the practical Application of an Aircraft Engine, the Engine requires only 3 Connection/Control Points the Airframe:
1. Fuel
2. Throttle/Injection
3. Ground/Shut-Off
And then there are optional extras like Glow Plugs/Carb Heat, Wastegate/Mixture and so on.
And if the Ground or Shutoff Switch doesn't work, the Engine will keep running until it runs out of fuel.
So, for all intents and purposes of Operation, the Petrol Engine and the Diesel Engine are in this case equally independent and mechanical.
There is no Digital Ignition Box, no Vacuum Advance, no mechanical Advance, no Coil to burn out etc.
It's Electromechanical, but without any external source of Electricity. Same as a Diesel.
I'm pretty sure Mercedes Benz has a lot of dual spark plug engines too. Great work,keep it coming!!
Yes M112 v6 and M113 v8 comes to mind. Probably the V12s too. The only downside is maintenece, but the coils rarely fails.
My E55 M113k has dual spark plugs and being a 3 valve design its easy to locate them... Even before these modern engines Mercedes was using twin sparks in some of their engine but yes, Alfa is definitely the pioneer here.
@@Rourkeize alas, at some point one has to replace the spark plugs, and I am told they are not cheap either... By my mechanic, who had bought my brother's w211 with the 2.6 litres V6.
@@woongah . Modern Spark-Plugs have a very long Service Life . Brake Rotors need replacing from time to time too , as a Service item .
@@woongah they're not cheap if you give it to a mechanic to service them, in reality, spark plugs are probably the cheapest and easiest things you can do on an engine, and I've done spark plugs on an m112 clk, the only thing is you're now buying 12 plugs instead of 6.
The Mercedes M112 V6 and the M113 V8 both have twin spark ignition and 3 valves per cylinder. The V6 was introduced in 1997 as a 1998 MY and the V8 was introduced thereafter. Both are 90 degree blocks, the V6 employing a balancing shaft to counter the uneven mass of this engine layout in addition to a 30 degree splay angle on the adjacent crank pin journals to achieve an even firing order. These engines have a SOHC driven by a duplex timing chain with 2 (smaller) intake valves per cylinder and 1 (larger) exhaust valve per cylinder. Each cylinder has a high output, coil-near-plug ignition coil. These engines also use a variable length intake plenum to increase torque at low engine speeds (longer path), and improve flow at high engine speeds (shorter path). Both engines are great and very torquey.
Correct, I have a 2006 CLS500 with the M113 V8 & I replaced all 16 spark plugs recently.
Yup. I have a Chrysler Crossfire with the M112 and was unpleasantly surprised when I realized I only ordered half the spark plugs I needed 🙄. I never understood why the heck there were 12 plugs until I watched this video I just assumed “bigger spark make bigger boom” lmao
Great engines. I had a 99 C240 Mercedes with a manual, so I could experience the real behavior of the engine. Lots of torque down low, nice top end power (170@5600rpm) and a reliability level its successor lacks during its first production phase. Curious mix of low and high cost solutions. Magnesium manifold, but SOCH. No VVT, but twin spark. Clearly not cost-driven decisions. Anyway, I miss it.
I believe MB made a twin spark V-12 as well.
They are very torquey, but they are also very truck-like and aren't particularly smooth in operation or sound and don't particularly enjoy being revved.
They're definitely not a bad motor, they're just not very refined or sporty
My old 04 Honda jazz had a 1.4l 4 cylinder twin spark engine(DSI) . That thing ran amazingly well. At low rpms there was a slight delay between them. At high rpms they fire simultaneously.
Indeed, I remember that tiny engine had an amazing amount of torque down low for what it was. It was also decent higher up. The mileage was also great.
Porsche also used twin plugs on their later air-cooled production engines. Also on some of their earlier racing engines.
The Maserati in-line 6 cyl in the 3500 Sebring uses twin spark too.
Maserati one of the companies part of the huge list of companies like fca belongs to and dodge hellcats still uses this in their hellcats currently.
BMW 1200 boxer engines had two plugs but the secondary was there purely for emissions reasons. You “could” unplug them and feel no difference. I suspect their main benefit was to burn low octane fuel more effectively.
Mercedes also used it on the c230 kompressor w202
Well researched video! An item of note: in both flight training, and aircraft maintenance training we are taught that the primary purpose of dual ignition is to provide more complete combustion, and the redundancy is an important secondary purpose. (I personally could see it either way, and like the safety of having a dual system while flying.)
This channel got big really fast, i remember you having 150k like it was last week
And you mean 'Bigger'.
It's growing and at this rate it's not long until it has subscribers in the millions.
Sadly that pretty much depends on viewers these days and if they have the balls to actually thumbs up the content they enjoy and are given for FREE.... which is a very low chance nowadays.
One word: quality
Yea didn’t he have long hair before?
@@idus Yes, he did. 👍
My M113K uses twin-spark.
Only downside is the $90 in extra plugs every few years.
Hardly a downside. That's like saying having a car is a downside because you have to fuel it.
You see it a lot in thumper type motorcycles where you have this huge pancake of a piston, and trying to get the flame front to spread horizontally is just as much of a challenge as trying to get it to spread vertically. So using two helps to actually get it all ignited in such a large area.
It can also be useful in 2 strokes for the redundancy to stave off oil based carbon build up issues- oh and the free/rarely used head space in them means there's no real downside to doing it.
Toyota had a twin spark setup on the 1.8L 3T-GTE, their first factory turbocharged engine. It was available in the 1982-1985 Celica, Corona and Carina. Toyota also used a racing version of the engine, the 2.1L 4T-GT. It was used in IMSA GTO class, Le Mans 24 hours and WRC Group B. It had a homologated version (4T-GTE) in the 1982-1983 Toyota Celica Twincam Turbo GT-TS TA64.
As always, cracking content. Very informative.
You alluded to VW groups fuel stratification technology when discussing fuel mixture homogeneity. Any chance you could do a video. The idea of changing fuel ratio within individual cylinders is fascinating, and I'd like to see The pros and cons of doing so and the rationale behind a stratified mixture.
Once again, fantastic content, you're a knowledgeable and likeable presenter.
The Ford truck 6.2L OHC engine also uses dual spark plugs. Thanks for the video!
Was gonna say this… I’m sure it was for emissions… but it still has them…
Thank you for this content.
Relevant to me as I begin on a '69 Bultaco MK2 Campera motorcycle rebuild/refresh.
From factory, had electronic ignition (?!), single cylinder [two stroke] engine - with a head featuring "2" spark plug holes.
(one typically to park a spare plug - OR - a compression release valve)
I for one am all excited about fitting a modern, dual spark set up.
The Alfa Romeo AR67204(CF1) engine that was found in the 145/146 and 916 GTV Phase 1(among others) produced about 110kw when new. Although there are several upgrades Alfa brought to the AR32301(CF2) engine that you found in the 156 the biggest change was the cast aluminum intake manifold was dropped in favor of a modular plastic intake manifold. The AR32301(CF2) engine produced 114kw when new. The extra 4kw was however lost when the AR32310(CF3) engine came out. These engines were introduced along with the very popular 147. The AR32310(CF3) engine still had the modular manifold and featured several electronic upgrades, the biggest of which was the switch from a throttle cable to a drive by wire system. The 147 also had a different exhaust and featured two pre-cats in the down-pipes with one more cat located just behind the engine. The AR32310(CF3) also had lighter piston crowns weighing about 10 grams per piston less than the ones used in the AR67204 and AR32310 engines. I always thought that the slight power loss between the AR32301 and AR32310 was due to the change in exhaust systems but the change in the way that the ignition system works migh have also played a part it seems.
Excellent engines, sensitive to timing belt maintenance, nothing more, but compared to the design disasters and the very low reliability of today's engines, it was a great engine.
I've had many Alfa Twin Sparks over the years, the 75 being my favourite for handling. But the 147's I've owned over the years have been my overall favourite. A very underrated car. The 1.6 didn't get the variable intake manifold, nor balance shafts, and in my opinion handled better than the 2.0 (the 1.6 didn't get stability control either) but in general, either of those engines were bulletproof. As long as you checked the oil level regularly! I want another one now...
On a different note - the Honda Shadow 750 (VT750) has twin spark, both in carb and fuel injected form. Those are wonderful bikes and very popular.
I’d happily delve back into twin spark for that bike.
Had one, great bike.
I've been running STD Dual-plug heads on my 1949 Harley panhead since 1998, initially in single plug mode with a magneto. After a few years I upgraded the mag to dual-fire ignition and immediately noticed much smoother performance and improved mileage, even on this old tractor engine.
I had always understood the use of two plugs in any engine with a hemispherical combustion chamber was because of inherently poor flame propagation in hemi chambered engines. Which I imagine would give you more flexibility in timing curves.
Nitro engines are around 60° of advance
Great video! It was quite informative. In my experience, i've observed that the last twin spark heads make the engine run with less ignition advance if both spark plugs are used, i had to postpone at least 8 degrees of ignition advance when i used two spark plugs instead of one, in some areas even more. The engine was defintely making more torque ad horsepower and it felt more responsive overall. Also improved the fuel economy a little bit
I forgot to mention, i'm talking about the latest alfa romeo double spark plugs head
Man, it's taken a long time but I finally caught one! The newer 5.7/6.4 Hemi do have variable intake length runners. And, my beloved 3rd gen Hemi retains most of the advantages of a "true" hemispherical combustion chamber w/o the flame front problems associated with the domed pistons usually required to maintain a decent compression ratio.
Ford also has twin plugs on the 6.2L Modulars found in their 12th gen F150s(Quite rare), F250 and up Super Dutys and E-series Vans. Aswell as the 1st gen Raptor.
yep I have the 6.2L F250
@@stephenrich5905 They are great engines, very durable.
They did it in the 80s and 90s with the 2.3
@@MUredhawk111 Funny that he mentions "4-cylinder Mustangs...in the late 80's", which were 2.3L but put the picture of a 5.0 which have a 4.9L V8. The twin plug 2.3L was not available in the 80'. The production started in 91.
@@ZZZHarpy101 ranger was 88 or 89. I've got one that's about to be replaced with the tbird turbo 4 cyl.
Thanks for explaining this so well! I work on motorcycles in SEAsia, and came across the twin and triple spark Bajaj models here. I was curious why, and now I know!
Was pretty common on all Mercedes V engines from late 90s to mid 2000, namely M112, 113, 138 and 275. Nice vid and great explanation.
Twin spark plugs were very common in the 80’s when Nissan/Datsun equipped a lot of vehicles with NAPS-Z (Nissan Anti-Pollution System) engines in North America. It made a lot of sense in 2-valve per cylinder SOHC engines. As 4-valve per cylinder DOHC engine with centrally located spark plugs became more and more common, I had a feeling it twin spark plugs would become less and less common and that’s what happened.
My Dad had one of the Nissan trucks with twin sparkplugs. Once he took it for emissions testing and the tester said that those trucks never failed. Testing was just a formality.
As a former owner of Nissan vehicles, the Datsun/Nissan syatem did not fire at the same time, like earlier ALFA syatems.
I loved the cars but hated the ignition systems and leaky exhaust valve seals.
4:37 I don't know why, but this is, to me, one of the craziest things - cars going down a highway are moving faster than the explosions in the engine.
Excellent video as always, I always learn something. I have a Suzuki DR650 with dual spark plugs, and I'm almost positive it's that way for redundancy. It doesn't really spin that fast, and the plugs are close together, and a DR650 is exactly the kind of bike that you're going to drop in the woods, which could break a plug.
An important factor is the the area they have to cover. Combustion only has to cover 50-60mm and it's doing 16 METERS per SECOND. Whereas cars have to cover hundreds of kilometers and are doing 120 kilometers per HOUR. It's important not to imagine combustion as an explosion. Explosion is uncontrolled and a detonation. Combustion is controlled and it's deflagration. Hydrogen engines are dealing with far less controllable conditions for example and their combustion does close to 50 m/s at 1500 rpm.
The same reason a supersonic bullet can be accelerated faster than the speed of sound while black powder and even modern smokeless burn or combust at subsonic speeds. The air is heated and expanding faster than the burn rate. Plus at higher temps and higher pressures the speed of sound is increased. Physical properties and behaviours change with pressure and temp and we assume from our daily observations within a narrow window of temp and pressure that every chemical reaction or state of matter remains the same. On planets on our solar system it can be so cold that gases on earth become solids and become rain or snow . Look what water does solid liquid or gas within 180 degree F difference. We cant fathom steel evaporating or something boiling at super low temps like. oxygen. Inside an engine is a unique set of conditions that causes normal atmospheric combustion to behave differently
What I really like about your videos is the ease with which you explain complex concepts. Hats off to you. Amazing work, keep em coming.
About 15 years ago I had 2 (!) Nissan Prairie m10 4wd 1988 model year. A blue that I drove with and a white as a spare car. These were not so common, so I found by chance one more just weeks after I bought the first one. It was a 2.0 engine of 100 hp with double spark plugs and two ignition coils. I regret today that I sold them. A very practical car with sliding rear doors and no doorpost between front and rear doors. Easy to load. Perfect winter car and fun to drive.
My first car was a 1984 Nissan Stanza GXE. It had twin plugs. 2.0 litre 4 cyl was quite quick and smooth running. 5 speed transmission. Good practical car.
My dad had a 88 which had it too.
Que motor era?
@@JoseAlvarez-il3iy If I remember correctly it was a CA20E 2.0l (1974cc) 4 cyl
I have a dual plug car! My 1985 Datsun/Nissan 200SX. My S12 has a CA20E. Definitely not a powerful engine, but it scoots the lightweight car alright. One interesting point is that the plugs are on either side of the head. They use a one step colder plug on the exhaust side than the intake side. Pretty clever I thought!
Yeeees! Dual spark is a very important step for me! Thanks for explaining it further lad!
Also, its usage on the airplane engines isn't just easier by that, even if they would use 4 valves, the compressed chamber on these have such a huge fillment due to their volume (Lycoming io-360 has ca. 1495 ccm per cylinder at a compression of either 7,5:1 or 10:1) that no matter how they're planned, they always have room for spark plugs.
And really you did great on information there... Although i Don't get the VW joke. But that's just me.
Also... As you talked about leanburners....
Leanburner engines look like a thing that could easily need some explanation, especially its correlation to catalysts.... As the 3 way catalysts can't convert said properly to make them better for emissions.
But also i saw once a website, talking about an engine switching between lean and rich with an NOx storage reduction or NSR for short. I'm not too sure about the last bit as it is not necessarily my main base of knowledge.
Thank those for mentioning the Mercs C , E and S class 320 s V6, not to mention some V8s. I have a long history rebuilding Aircraft Engines. Lycoming, Continental, Pratt & Whitney Radial; all use now, and will in future use twin spark, twin magneto, not just to increase power, but improve reliability. I like watching ur vids, and reading the comments.
Excellent description of a complex subject , this channel gets better and better , keep it up and thanks , much appreciated
The HEMI material in the description would really be interesting for a Part 2 on Twin Spark Plugs! 😉
I certainly didn't know of this fact about the HEMI before watching this video and reading the description!
However the "new" Harley-davidson M8 motors use their own 'twin spark" set up
it is interesting when have to buy 16 spark plugs and to replace it
Yes, 16 spark plugs can get interesting. Expensive and time consuming as well!
@@brianmason8400 Yup.. I had an 04 Hemi Durango and now have a 2012 Ram Hemi.. I have a buddy withthe 4.7L Ram who claims ot have 16 spark plugs.. but I don't believe him. Anyhow... I just bought 8 coil packs and 16 iridium plugs... yay!... y '08 Suzuki C109RT motorcycle is also dual plug so 4 plugs for it.. 2 you can get to easy, 2 you need to take the tank and airbox off to get to.
The Hemi is a thoroughly obsolete design.
Chrysler actually knew this back in the 1950s when they designed the Wedgehead.
They could have easily pulled out all of the stops on a 440 to make a “Wedgie Cuda” that would have easily outperformed the 426.. but for product differentiation they used the Hemi and marketed something inferior as superior. And since the other Big Two were more interested in making money.. they didn’t challenge it.
And thus it entered into history and the NHRA made the elephant engine the basis for their Top Fuel engines even though other designs would have been fine. I imagine reducing runs to 1000 foot passes would have happened a lot sooner with DOHC engines.
And so Gen III… all of those nostalgic boomers who didn’t know that HP numbers were giant lies (forget underrated from the factory… no air filter, no headers, no accessories, not even a water pump) which is why HP fell so quickly after 1971 and the switch to SAE Net.
Gen III was a semi-Hemi because there was no way they’d get a true Hemi through emissions. The 2nd spark plug was to clean up the exhaust.
This explains why my 20 years old 156 never failed to start, had it for 9 years so far, had lots of problems but never an engine that refuses to start.
As with all your videos, I already knew a lot of the information, but I still learned a few new things, and I thoroughly enjoyed your presentation! Great photos and graphics! And I just love your enthusiasm, word choice, phrasing, accent, etc. All very cool!
😎👍
The 6.4 Hemi has variable intake (2 settings), variable valve timing. It does not have direct injections but has cylinder deactivation (4 cylinder mode).
Yeah, weird that he barely mentions the best modern use of dual spark plugs, then completely ignores the eagle hemi
Modern chamber design had more to do with single plugs being the most common system now, with squish areas built into the head and piston the comb. chamber is effectively much smaller when the piston is at TDC, and the mixture is also more turbulent.
Right near the end you mentioned motorcycles briefly. Up until that point I had noticed you emphasized the word "car" when explaining the history of it. This is noticable to me because I spent some time riding a dual spark version of a bmw r1150rt. For those, I believe the main reason they did it was for fuel efficiency, and it was really effective. As a touring bike I was still able to get close to 60mpg consistently. I should never have sold that bike
I enjoy all your videos. Your enthusiasm is contagious and your explanations are some of the few I know that keep is simple, but also include enough good information to get the concept across. I got hooked with your balancing videos. I've always had a love/hate relationship with balance. Obviously, the smoother an engine's balance, the better it can physically perform independently of any power modification as compared to a relatively unbalanced engine of the exact same specs otherwise. And I like symmetry and smoothness. However, I've found that over the years, I am really getting into less balanced/"not as even" firing order engines simply for the nostalgia and the sounds, since much of an engine's sound characteristics are created by how the exhaust pulses interact with each other pressure-wise and rhythm-wise within the exhaust system. And sure, older or not-as-well designed engines are less powerful, less efficient, and sometimes less dependable depending also on the materials they are comprised of. But just like the "thump" of a 45 degree single crank pin V twin, or the relatively unique gurgle of a 90 degree crank V8, the sound and feel make them desirable to many. So when I hear of a stranger engine than usual (say a 2 crank pin V4, an inline 7, or a 90 degree crank inline 4), I get really interested even if only for the sound and to find out about its balance/how the firing order and spacing effects the sound. The great thing is you actually cover topics like this pretty thoroughly. So my conceptual understanding has increased greatly. Thanks for that!
From the beginning I was thinking airplanes the whole time wondering if you’d bring them up lol
My 2013 Raptor with the 6.2L V8 had dual spark plugs per cylinder. I think it was primarily for emissions also.
In 1957, Maserati introduced its first full-production model, the 3500GT. Its engine was a detuned version of its straight 6 racing engine, as used in the 350S, which featured twin plugs.
The 3500GT used twin-plug ignition from the start, coupled to triple Weber sidedraught carburetors. From 1962 it was also fitted with Lucas fuel injection . . . . and became the first car ever to be called a 'GTi'. Later 6-cylinder models, the Sebring and Mistral, used the same set-up in larger 3.7 and 4.0 litre form, and featured the script 'Iniezione' on the back. The power was quoted as being 15 bhp more than the carb versions, which supports your video analysis. Good video, btw.
Another brilliant video.. I've been a licensed technician for almost 50 years.. i absolutely love twin plugs.. different sound, better power, fuel economy -maybe,,,, my 2015 Hemi pickup has twins,, what a pain in the ass and expensive (16 plugs at 76$ a plug)...I also work on aviation and motorcycles.. best is always twin plugs.. when I use to fly helicopters, i had a mag go,,, didn't even panic, just turned it off,,,,recalculated and returned home..
Keep up the great work..
I think that twin or even triple sparks makes sense on engines with pre-combustion, like F1 engines, where two sparks are at the side of the main chamber and a single one is in the pre-chamber, so at low RPMs the two sparks ignite the air-fuel mixture, while at high RPMs only the pre-chamber spark is used, so you get even better efficiency using three sparks and a pre-chamber.
Another reason why rotaries are weird and great!
They have had dual plugs for decades before the Alfa engine, and with nothing but real estate to put the plugs in (that long chamber is why they need more plugs) the benefits you mentioned helped rotaries to at least partially keep up with efficiency and emissions requirements of the time. With a leading plug wasted spark system adopted in 1986, they essentially had three plugs per chamber, as the rotor sweeps by the plugs rather than retreat away from them. This is a great mod to do on older rotaries that still used distributors.
Not decades before 1914 I guess?😀
@@dollbagius Yea, despite its design being from the 50's, Id say that most cars that had rotary engines would still fall into the modern automotive camp.....1914 was a LONG time ago!!
Alfa used twinspark in 1914, rotary engine exists since the 50s. How did the rotary engines have dual plugs for decades before the Alfa engine?? Dont get it
@@petardenchev75 Simply comparing the somewhat modern rotary to the somewhat modern Alfa mentioned at the beginning of the video. Yes, the 1914 Alfa was WAY before it, but it's hardly modern. Twin sparkplugs would not be common in mass produced engines until the modern era (70's-80's, about the time computers and electronics brought about the kind of cars we still produce today)
I had a 2001 Honda FIT with I-DSI and it was quite absurd having a 1.3 litre motor with 8 coils and 8 spark plugs.
Honda abandoned it in favor of I-VTEC on the smaller 1.3 engines, which is much better anyway.
I wonder if their reputation for developing ignition faults is due to unaware owners/technicians servicing only half the plugs and coils! (I have a 2006 i-DSI Fit myself.)
@@thromboid - well I thought I was having coil issues in mine, as it turns out someone had replaced only the front spark plugs - and not the rear - so I did all 8 and she was as good as gold. Quite the job for such a small engine.
@@StratfordDanBurrell Good catch! It is pretty hilarious having 8 plugs and coils for such a small engine. I was relieved that I didn't have to remove the cowl to do the back ones, though I did have to get creative with stacking up socket extensions.
Our country only got the 1.5L version of i-DSI engine in Honda Jazz (Fit) and Honda City (Fit Aria) from 2003 to 2008 . The fuel consumption is so good that can put some lower displacement 3 cylinder engines to shame. Additional 4 spark plugs costs can be offset by fuel savings.
@@fleurdewin7958 -I have the 1.5 I-VTEC Honda Fit now and I must say it’s better for the driving I do. - the 1.3 did struggle on the hill roads and commuting that I do. I assume as a town car it would be ideal and very efficient.
I mean I am still getting around 5-5.5 litres per 100kms from my 1.5 litre FIT - so it’s still very good even on the motorway here in NZ
There is a HUGE amount of Mercedes-engines from the late 90s to the early 10s - M112/M113/M137 V6/V8/V12 Engines.
These are not only dual-plug engines but also 3-valve engines (with 2 in- and a single outlet-valve). There’s also no space to Center the plug, so the sidemounted two, each fireing every second cumbustion to prevent the piston from gettin damaged by onside ignition.
Suzuki made a 1.8L V-Twin engine that used twin spark. It didn't rev particularly high but it had the largest bore on a production motorcycle. They put it in the M109R (VZR1800.)
I have a Ford 2.3L with twin spark plugs. I reordered the ignition wires on the secondary coil and it runs much better now that both plugs fire at once.
As a owner of a 2015 6.4L V8 Charger I can attest the benefits of using Dual Spark. Despite the high compression ratio and required use of premium fuel the motor hardly ever knock or misfired. Even though Chrysler uses this primarily for emissions it does help the engine on high RPM range. However I can see why this technology does not benefit or makes sense on smaller displacement engines since the spacing on the cylinder heads is quite limited. Now in bigger displacement engines this makes sense not just in sports applications but commercial fleet gas engines.
My mom used to have a Honda City (basically a Jazz/Fit sedan) with the 1.5L i-DSi engine. Only rated at 90HP, but it had peak torque around 3,000RPM, so it was a surprisingly fun little car to drive!
@8:44 The note about the (modern) Hemi reminded me that there were also racers messing around with dual plugs on the classic Chrysler Hemi (such as the 426). The production Hemi engines were al 8 plug, but some heads were modified to accept 16 plugs. These were very high performance versions, usually running a LOT of boost (which creates a dense mixture harder to ignite), and many were running fuels like alcohol and nitromethane (so different flame speeds than gasoline).
Another reason to use twin spark in an air cooled beetle motor is to allow the use of a more radical cam profile and still enjoy more torque at lower rpm's which would be much worse without it. I have also experienced other minor benefits as well as you previously mentioned. The heads used are much more efficient than stock vw heads and in a motor that sees 8000rpm when required. However I agree that with other tech used today, Twin Sparks advantages only show in particular circumstances and hence its limited use today.
there is also a trend for multispark(rapid firing of spark) at low rpms. wonder what happened to it? or is it now commonplace that people don't talk about it?
I also wonder this!
Are you talking MSD, very powerful ignition, used in pretty much all top end engines, only one to have in top fuelers
Mercedes used that on a couple of engines
@@davidwarland2680 MSD was one of the aftermarket system that offer it. but multi spark ignition seems like it was a thing a decade ago in some OEMs
@@davidwarland2680 Top Fuel engines generally use MSD Promag 44 magnetos. They produce one single relatively long duration spark.
Gotta throw in the ford 6.2 engine. Love the dual plugs when trying to light turbos
Fascinating. Thank you! I have a twin spark 2002 W220 Mercedes-Benz S320 with an M112 3.2l V6. With 12 spark plugs and 18 valves.
Early 80's Mazda B2000 pickup had twin plugs as well, may have been a B3000. I was in the service then, it was a friends truck. I run twin plugs on my old Harley Sportster, 45 Degree valve included angle means a huge dome piston, the plugs are on each side of the dome. Harley even did it on stock Sportsters in the late 90's on the "S" model 1200.
As a 147 Twin Spark driver I find this quite interesting. Now I know it's virtually useless in my CF3 engine :D
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Correct me if i'm wrong, but recent direct fuel injection have never been made to optimize homogenization. Carburetors were in fact quite good at it, even though they were mechanlical devices. Single point injection was also good at it, since the air-fuel mixture had to travel the whole intake manifold lenght before reachng the cylinder.
Direct injection were optimized to run lean mixtures, but they are particle emmiters compared to older solutions, because of unmixed gas being burned in the cylinder.
Otherwise your videos are great, and it is really amazing to find such detailed explanations on youtube, keep up the great work ! I believe your accent (and subtitles) also help non-native english speakers understand your explanations.
Direct Injectors operate at VERY high Fuel Pressure that Atomises the Fuel basically Instantly . Into a Pre-existing Fire .
@@johncunningham4820 gasoline injectors don't. "VERY high" fuel pressure is 2500Bars Diesel, and guess what ? They produce particles too. Also the goal of lean mixture engine is not to have a "pre-existing fire" but rather a pre heated air pocket, not hot enough though to get pre-ignition nor knock
@@spootneo64 . Ah ! Tech Talk , huh ?
Diesel Injection IS the Ignition Cycle for that type of Engine And Yes EXTREMELY high Injection Pressures .
Stand Alone Direct Petrol Injection is at Very High Pressure , for fast atomisation and SHORT duration , at very slightly before the Spark Event .
And Dual Injection , the Direct Injector WILL be adding to the Already burning Port Injected Fuel .
I personally LIKE Properly Set Up and adjusted Carburettor(s) . And a Digital Ignition to go with it .
More reliable and No Reason it can't be just as economical AND clean burning . Just needs Care-Taking .
Great vid&explanation job-this basically answers all my questions re this burning twin spark topic I had for long.
Also on the topic of extra spark plug the four-rotor rotary engine in the Mazda 767 and 787 cars received an extra spark plug per rotor for improved combustion, despite both the 13J and the later 26B engines having a variable-length induction system.
While it is true that introducing an extra spark plug is more hassle for maintenance purposes in production engines, I'm surprised Mazda out of all companies didn't try to squeeze more bang from the rotary engines, especially the Renesis engines in the RX-8 which was purposefully designed to milk every single performance out of a naturally-aspirated 1.3L engine AND still meeting the emissions standards at the time. Even the rotary range extender in the new MX-30 hybrid didn't have an extra spark plug.
Actually all 13b rotaries have two spark plugs if I'm not mistaken
@@bababence The 26B have three
@@bababence They do. The four-rotor engines in the LeMans cars had three per rotor, which was supposed to improve the combustion characteristics.
Looking at some peripheral-ported, four-rotor projects online with just two spark plugs per rotor shows a HP figure somewhere around the 500HP figure mark. For context, the 26B in the 787B could reach 900HP peak, and even the “detuned” version have 700HP.
By this example, I’m intrigued on just how much an extra spark plug could really change the performance of a Wankel rotary engine.
First car, 1989 4 cylinder mustang. I called it "four angry cylinders" 8 spark plugs, 88 horse power. I genuinely cannot fathom how they managed to make such an anemic engine from 2.4 liters of displacement. I wish I still had the car, would have loved to swap a mid 2000's SVT focus motor into it.
The Alfetta 159i had variable cam timing (though very simple) before Alfa introduced twin sparks - done for performance. Later twin sparks in these engines (hemi heads - long flame front) was just cheaper than designing new heads, and was done for emission reduction. Any performance advantage after that was just a bonus.
I forgot to mention, the aviator genius glenn Curtis in the very early 1900s when airplanes had radial engines and airplanes had double wings, had to overcome the problem of planes taking off from muddy Fields which requires more horsepower than if the runway is paved.. Glenn Curtis is the one we all need to thank for coming up with the idea of dual spark plugs oer cylinder.. that gave airplanes the increase in power needed for planes to take off from muddy fields..
curtis also came up with the idea of adding a second cylinder to a motorcycle single cylinder engine, creating the V twin engine because that configuration would fit neatly into a bicycle frame, which is what motorcycles were in the early 1900s.. Indian stole that idea from him, and Harley stole that idea from Indian..
Glenn Curtis in 1907 also went 136 miles an hour in his V8 powered motorcycle..
dual spark plugs cut down the lead time required for ignition to occur completely, greatly reducing the chances of detonation .. you don’t have to light a spark plug at 30° BTDC with the dual plugs.. you cut down the leadtime by half. Also, you’re not trying to compress a mixture that’s trying to expand because you lit a spark plug so far in advance.
Vance and Hines when they were actually in the early years of their drag racing which gave them their big name that they still have today because of their success. They actually had a motorcycle engine that was four-cylinder and it had three spark plugs per cylinder..
gasoline burns very slowly in the open atmosphere. You could pour a stream of gasoline 50 feet long on the ground, stand beside it at the beginning, light it at one end, and you can walk to the other end of that stream of gasoline before the flame will get there. For an engine to run, you have to speed up combustion buy as much as 200 times the speed that it burns in the open atmosphere.Lighting the mixture with two spark plugs cuts that time in half. Especially with dome shaped pistons, which in my opinion is the worst shape for a piston/combustion chamber because, it takes longer relatively common for the complete combustion chamber to ignite if you have a single spark plug on the east side of the combustion chamber, by the time the west side of the combustion chamber catches fire, you have a high probability of detonation occurring.. dual spark plugs reduces that problem. Dual spark plugs also reduces the amount of the cylinder that is exposed to flame of combustion, lowering engine temperature, making it possible to have a higher compression ratio, which will equal more power if you can control the combustion chamber. It’s a win, win, win to have dual spark plugs..
of course the ignition system has to be adjusted to back the timing off by half with dual plugs vs a single plug for the benefits.. you can’t just drill a second hole and add a space second spark plug and keep the same ignition curve that the engine was designed to have with a single plug. That would be worse than having a single plug because the mixture would ignite completely as the engine was trying to compress.. if the engine came from the factory with two spark plugs. I’m sure that the factory has already calculated the correct ignition timing curve.
I knew a mechanic specialized in dual plugging Air cooled BMW motorcycles. He explained The benefits of dual spark plugs.. I watched him do it to a set of heads. He had jigs rigged up so that he would attach the jig and drill and tap the hole for the second spark plug, then he had to adjust the ignition timing advance by backing it off halfway..
he also pointed out to me that the great aviation/motorcycle inventor in the early 1900s, Glen Curtis solved the problem of airplanes having trouble getting airborne when taking off from muddy Fields. The solution was to dual spark plug every cylinder on those airplane engines..
in case you never heard of glenn Curtis. He actually made a V-8 motorcycle in the early 1900s went well over 100 miles an hour. He also is the inventor of the V twin engine for motorcycles. Motorcycles in those days were nothing more than bicycles with engines on them. Glenn decided, and rightly so, that it would be easy to add a second cylinder to an engine that fits in the V of the frame of a bicycle. Of course Indian copied that design from glenn Curtis, then Harley Davidson copied that design from Indian..
of course that narrow V design does not have perfect primary or secondary balance. BMW with the boxer twin has perfect primary balance.Moto Guzzi engines with thier 90° V twin have perfect primary and secondary balance..My last 2 Moto Guzzi’s both had two spark plugs per cylinder from the factory..
👏👏👏👏👏👏
I used to rally a Nissan Bluebird from the early 80s, I ran it with the Z18ET 1.8lt turbo engine.
It had the 'NAPS' twin plug cylinder head but on those engines, the exhaust side plugs were disabled at high rpm and heavy throttle to prevent knock from two flame fronts.
I not now that Beta has just released their 2024 range which includes a twin plug cylinder head for the 250/300 2 stroke models.
Miki...you are correct. I have an '02 CLK55 and '04 CLK500 and both engines have dual spark plugs. A mechanic told me that the dual spark plug design of MB engines fire one spark plug and then on the next power stroke, the other spark plug fires. What I was told, is this has the effect of spreading the heat more evenly across the piston. I'm just repeating what a seemingly qualified mechanic told me. I'd be interested to know what the official answer is. I do know that Aston Marten's racing engines of the 60's had dual spark plugs.
The 5.7 in my Ram has 2 spark plugs per cylinder.
All modern hemis have twin plugs
The most common use for them now has to be the Modern Hemis.
The most common use is aviation, there is definitely a performance improvement and adds needed redundancy
I owned a small 150cc motorbike manufactured by a company from India called Bajaj. It sported a technology they called DTSi which implied two spark plugs for that small single-cylinder engine. I don't know that benefited the performance, reliability, or efficiency of the engine but, to their credit, the engine never failed to start and that's not a small feat for a carburated engine. Today I own another similar bike and I have disassemble the carburetor whenever I spend 2 weeks without starting the engine.
Good explanation but for the details you need to search more deep in the technology , especially Mercedes with the 3 valve V6 and V8 have twin spark and fires the sparc plugs up to 5 times each per combustion cycle because in some situation the engine runs very lean to save fuel. Also for the Hemi, the 6.4l is available with an intake system that variates the intake air mass and speed. Always enjoy to watch your videos.
A *good* combustion chamber design for most passenger car size engines doesn't need dual plugs. Poor chambers may benefit. So may engines with a bore greater than about 100mm. A good example of "if you can't hide it, make a feature of it."
you're so full of crap. it all depends on what a person wants from their vehicle. take your patronizing crap elsewhere.
Happy D4A Sunday, all. Wishing you the best from sunny California!
With regards to aeronautical engines, older designs use twin magnetos rather than coil type ignition systems found in automotive applications. One of the pre and post flight checks is to test these by switching off one bank of plugs.
There is a noticeable reduction of RPM and consequentially power when one bank is switched off.
Not only are two plugs used for redundancy in aeronautical engines, the cylinder sizes are big. I'm of the understanding that this is a consideration for engineers with respect to flame propagation.
Another insightful and well-presented video. Your manor and demeanor add to the learning experience.
My bmw motorcycle had twin tipped sp plugs. But had some idling roughness issues. On advice from other owners I changed them to single tipped ones. And yes, that made a noticable differance.
I was just about to comment about aircraft engines, and then you mentioned them too :)
Aircraft also use Nickel-Cadmium batteries which allow a lot of drain at one time. As it takes a lot of power to start an aircraft engine. Lead batteries would just fry at that load.
This may be my favorite video you've done so far. Thank you.
I have a Kawasaki kle 500 parallel twin that revs to 9.5k rpm and I've seen examples of the gpz 500 that has the same engine but differently tuned, revving to 11k rpm with a single spark on each cylinder. I don't know the point I'm trying to make,I'm just mentioning the fact. Great information btw,great video.
My 2013 Ducati 1200 Multistrada has 2 spark plugs per cylinder.
Some time ago I came across a recount by an owner of the same bike, who had engine roughness which took some time to diagnose. In the end it was one spark plug (just one) not firing reliably - they replaced the spark plug and the engine ran perfectly.
What this tells me is that the twin spark ignition must serve a very real purpose, otherwise the remaining spark plug would have done the job adequately.
A good explanation. The initial concept of twin plugs was to allow constant ignition on aero engines because early plugs were very temperamental and would often fail on take off or over enemy territory. The advance of flame front on early engines was little understood as these averaged between 1200 and 2000 rpm. Post First War research by K lee Guinness KLG proved the validity of his mica plugs and manufacturers research developed flame front technology and raised rev limits. These were usually magneto operated and there were safety limits on the drops allowed. This was 400 rpm on the Rolls Meteor which initially were lifed out Merlin engines but later were made in their own right.
What you have to remember is that in 1914 the only reliable magneto was made by Bosch. So at the end of the war all the magnetos made by the Allied powers that used Bosch principals of design had to make a payment to Bosch. This happened in WWII as well as all the French factories bombed by the RAF and the American Air Force as well as American factories in Germany were given financial compensation. The factories here that created the magnetos and other instruments of war were taxed very heavily for excess profits from government contracts.
First time I heard about twin spark was on a Mercedes M class SUV. I thought it was a standard thing for Mercs.
Hey, suggestion for your “What Makes It Great” series. The Ford Taurus SHO had, in my opinion, one of the best V6’s ever made. That car outclassed the BMW M5 and the Ferrari Mondial the year it came out and took the late 80’s by total surprise. Nobody thought an American car company could make anything that wasn’t a plodding snore fest. I’d love to hear what you thought of the Vulcan DOHC V6 that Yamaha built for Ford from 88-95.
Kao i uvek - vrhunski urađeno, samo napred i dalje!
Excellent video! Very Informative and thorough, as always!
I wasn't wondering this question but I'm glad you asked and made a video about it, very interesting cheers 👍
Legacy aircraft piston engines also have 2 spark plugs that have their own ignition system, called magneto's. You can run them on both, during the start you have to run them both and each independent to verify if both systems are working properly.
If you run one system you have a rpm drop between 50 and 100 rpm at 2000 rpm (= +/- 50% power, you have propeller up front that needs power to be able to reach 2000 rpm.
I never get tired watching your videos !!
I initially think about Mercedes M112, M113 and 137 V6 V8 and V12 engines. They have a 3 valve per cylinder design, which makes twin Spark quite logical.
I had one of those Ford Rangers with a 4 cyl, 8 spark plug engine. I called it my gutless wondertruck. I'm sure it was because the engine was just so old and tired but in order to get pretty much anywhere you had to put your foot to the floor. It was a 5 speed manual. Come up to any kind of a hill and you can pretty much count on downshifting to at least 4th, if not 3rd.
I had a 89 Ranger with the 2.3 twin plug, it was only 4 years old and gutless. A trip through the mountains wasn't fun, only had decent acceleration going downhill.
@@abpsd73 mine was a 92.
My last truck was in 96 with a 4.0 and when I looked at replacing clutch slave cylinder, it turns out they used what they call a concentric slave cylinder in those years. It fits around the input shaft of the transmission so in order to replace it you either have to pull the engine or the transmission out.
At least this 2000 Ranger I have now with a 4.0 doesn't seem too awfully bad to work on. I replaced the spark plugs and routinely change my own oil in it.
My father has a newer F-150 with a Triton 5.7 V8 in it. He asked if I would change the spark plugs in it and without knowing any better I said yeah sure. I took one look at the top of the engine and then Googled how the heck to do it, and it turns out you have to take half the intake apart, and take the fuel injector rails off in order to get the tank spark plugs out because they go straight down to the through the top of the valve covers. I had to tell him I'm sorry pops, but I don't think that's in my wheelhouse.
I think we need to make the engineers that design this stuff come out to the shop and service it, and then go back to the drawing board because I know they will have some things to change lol
Either that or they're just truly sadistic and enjoy turning what should be half an hour to an hour job into something that's going to take you all day long and need professional training and specialty tools to do :(
Still have a 94 Mazda B2300 that has the same engine as your Ranger. You are spot on having to put your foot on the floor to run it on the highway.
on the KTM 1190 motorcycle, there are 2 plugs per cyclinder (one large, one small) the dealer claims one plug for low speed & smoother running... the second plug for higher speed running...
it is possible to verify this claim ?
thank you for the content produced .... always engaging to listen !
The boss 6.2 from Ford produced from 2010-2022 also had two spark plugs per cyl. :) I own that and, ironically, a 91 Ranger. One benefit of the dual plugs not mentioned in the video, is great cold-start performance. Those two vehicles seem to start no matter how cold it gets!
When my grandad was a 15 year old apprentice mechanic in England in the early 50's, he told me of a 1911 Isotta Fraschini Prevesi Creps chassis touring car. Black, 16 gauge aluminum body. The straight 8 had duel distributor and magnito ignition.
I love how clear and simple the diagrams are, if you don't get it at 5:21 pause the video for 3s and look at how the diagram perfectly illustrates pre-ignition- the flame front reaching the upward-moving piston while the other half of the cylinder is unignited!
He is actually describing detonation, not pre-ignition. Detonation after spark fires, pre is before.
Aaahh yes. Quality content for us Alfisti! Thanks a lot mate
Most engines with twin plugs are use a hemi or heli inspired combustion chamber. With the lack of quence areas these chambers NEEDED twin plus for combustion efficiency and effectiveness. A wedge or twisted wedge chamber doesn't need two plugs as it has a quence area that forces the AF mixture towards the plug. This also helps reduce knock sensitivity in moderate compression ratio naturally, aspirated engines. As boost is added or increased or compression is increased for racing performance, we "soften" the chamber or even reduce the quence area(s).
Mercedes AMG engines also have twin sparks... at least mine (SLK 55, 2007). They ignite in sequence and at every ignition the PCM changes the sequence, in order to consume the electrodes evenly (1-2 / 2-1 / 1-2 and so on). Not sure if newer engines have the same. My engine has 3 valves / cylinder, variable intake runners and a fixed cam timing.
There seems to be an upper limit for bore diameter relating to efficiency. The main reason we are able to make so much power nowadays is all about OEMs being forced to comply with emissions restrictions. All of the manufacturers are using similar bore sizes now. 83mm seems to be the most efficient size with diameter rarely exceeding 95mm.
Efficiency is directly related to emissions and power comes from efficiency. Motorcycles use even smaller bores for high rpm in the 60-70mm range as you said. Big twins need dual plugs for high rpm. It would be much easier for manufacturers to make larger bores for efficiency and higher RPM but complexity for multiple plugs is extremely expensive. Not only plugs and coils but the wiring, drivers, ecm, and so on adds huge cost in production.
The Mopar Hemi is an exception due to the marketing strength behind it's return. With it's bore over 100mm there's no way to reduce the timing advance enough to meet emissions targets with a single spark plug. The concept was to run a single plug but the hemispherical combustion chamber is not as efficient as the heart shaped chamber in a two valve chamber with offset spark plugs. The cool thing about the modern Hemi is that it's extremely efficient with the dual plugs. A GM LS3 compared to a Mopar Gen3 Hemi with identical bore and stroke run very different spark advance timing. The LS runs around 35 degrees of timing while the dual plug Hemi runs around 23 degrees of timing. The closer you can get to zero advance, the more efficient and powerful it is.
Here's the main thing, with advance you are making a trade off. Even though you don't reach maximum efficiency instantly, the cylinder pressure starts spiking immediately upon plug fire. This is using rotational force to finish the move to TDC. Waiting as long as possible to create the spike in cylinder pressure puts more of the total combustion force after TDC pushing down increasing power. On a dyno when you creep up the advance to maximize power, you are optimizing the trade off between trying to stop the piston from coming up and the part used to push the piston on it's way down. When you add a little too much advance the balance is off exerting more pressure on the rising piston than necessary. The explosion happens to early and it makes more heat due to resistance to motion. Detonation or preignition happens before the plug fires. Adding boost or nitrous increases cylinder pressure which is why higher octane fuel is needed to stop the fuel from lighting before the spark plug fires. Also the higher the cylinder pressure, the faster the flame will propagate across the bore. That's why you have to reduce timing with boost. The combustion is identical to a 5 pound sledge hammer 🔨 with a 1/4 inch or 6mm rubber pad punching the piston. Detonation is that hammer punching the piston too early. Tries to stop the engine instantly, the rod punches the crankshaft against rotation and the piston rattles because you just rung it's bell. Everything superheats in an instant from the opposing forces.
This is just for you D4A, I love your channel and the work you put in every time. Thanks again.
Ford ranger 2.3 dual plug and just started work on several vintage Nissan datsuns with dual plug heads. The Harlry Davidson shovelhead sportsters also benefit from this upgrade.
The Mazda rotary had two plugs because the combustion chamber location actually moved. I have antique boats with flat heads notorious for skipping at low speeds. I use MSD dual spark ignition on these to insure it finally does fire. At river events I can run the engine down to 250 rpm for hours without fouling the plugs.
Hello, I must comment on the alfa romeo CF1 and CF2 twin spark delivery....on research you will find the coil on each spark plug delivers spark to the firing cylinder and the opposing exhaust stroke cylinder.....just look at the spark plug leads....both at the same time.....this was done for emissions by burning residual fuel in the mixture about to become exhaust gases.....also allowed for a richer mixture whenever needed, by being corrected on the exhaust stroke for emission clean up....
Alfa mechanic for 50 years, stefan.