Which is the Best Engine Valvetrain Design? OHV, SOHC, DOHC or Flathead | Pros and Cons
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- Опубликовано: 6 июн 2024
- Valvetrain: OHV, SOHC, DOHC & Flathead | Explained
Valvetrain:
The valvetrain is a mechanical system in an internal combustion engine that manages the opening and closing of the intake and exhaust valves. Its purpose is to regulate the timing of these valve operations to allow the intake of air/fuel mixture into the combustion chamber and the expulsion of exhaust gases.
The intake valves are responsible for controlling the flow of the air/fuel mixture into the combustion chamber during the intake stroke. On the other hand, the exhaust valves regulate the flow of spent exhaust gases out of the combustion chamber during the exhaust stroke. By coordinating the timing of valve openings and closings, the valvetrain ensures efficient combustion and optimal engine performance.
Types of valve train
Different engines may utilize variations in valvetrain designs, such as an overhead valve (OHV), overhead camshaft (OHC), or dual overhead camshaft (DOHC) configurations.
Advanced technologies like variable valve timing (VVT) and variable valve lift (VVL) allow for even greater control over valve operation, optimizing engine performance across various operating conditions.
--- Time Stamp --
00:00 - Introduction
00:40 - Parts
04:16 - Types of Valvetrain
04:42 - Overhead Valve (OHV)
06:25 - Overhead Camshaft (OHC)
07:03 - Single Overhead Camshaft (SOHC)
08:38 - Dual Overhead Camshaft (DOHC)
11:07 - Flathead Engine
16:39 - Thanks For Watching
#ohv #sohc #dohc
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Worth mentioning that flat head designs were still very common in small engines until recently. (Such as in lawn mowers and generators)
And I don't miss them one bit! I went from a 4 hp. side valve Briggs and Stratten powered lawn mower to a 5hp Honda OHV and I couldn't believe the difference. The Honda uses about half the fuel and, to the nose, emits about half of the unburnt petrol. That said, I'd rather a '32 Ford V8 was sitting in my driveway than my Civic!
@@davidbrayshaw3529 Actually it took Ford a year to sort out the V8 Flathead motor. Very few 32's with original motors.
Soviet T-34 tank. all aluminum V-12 DOHC diesel 4v per cyl, shaft driven valve train 85 years ago
The video says this at 11:25
There's a new light aviation flathead engine (d-motor). Air engines run at low rpm's (max 2500) so that's not an issue. The compact engine without the valve gear on top of the opposed cylinders is good aerodynamically. And the overall weight is a bit reduced.
@2:07 valve springs do not exert downward pressure on valves, they exert upward pressure on them, which is how they are closed.
Nope. The springs exert downward pressure. Down is not relative to earth and sky. But relative to the valve seat. Down is with the valve seated (closed).
For instance, a lawnmower engine with a vertical crankshaft and horizontal stroke. The valves move (open and close) horizontally also. What is "down"? Down is valve closed. Thus, the spring exerts downward pressure on the valves.
Thats what he said. But he forgot to mention the camshaft
Valve springs only close the valves, that's it. Desomodromic valve train that's a different story
They're basically there to make sure the valvetrain has no slack. If you're getting floating valves at high RPM, there's obviously clearance in the system because the rocker has stopped pushing on the valve stem because the height of the lobe is decreasing and the spring is still trying to pull the valve back tight against it's seat. You must get valves out of the way of the pistons in an interference engine. You also must have both valves closed by the time the power stroke starts or you're going to burn your valves.
@@galaxiedance3135 Float at high rpm is the result of the cam cycling faster than the valve spring can match with resistance. The remedy is proper spring rate.
This video helped explain to my son what is going on with my truck.
OHV engines are ideal in countries that dont tax displacement. They make most of their power in usable revs, are light, compact, very fuel efficient and have very low service costs. The only drawback is that you need to give them a bit more displacement. The market needs another Buick 3800 V6. That engine made the same power (205HP) as most 3.0L DOHC V6s of its time, was smaller, lighter and got 31MPG highway moving large cars around the highway and are extremely reliable. I had a 2005 Mazda 6 and that car was smaller than something like a Pontiac Bonneville and only got 29 highway from a 2.3L DOHC 4 making 160HP.
Definitely agree the family of engines is great and easy to work on
The 3800 series II is an awesome engine, my kid is still driving my old Buick that is 23 years old and no issues.
Very comprehensive and clearly explained. Thanks!
One type you missed is the "F"-head, where the inlet valve is push-rod operated in the head and the exhaust valve is [as a side valve engine] in the block. This allows for two things. Smooth power and a huge inlet valve for good breathing. They were used by Rolls Royce and Rover from the early 1945 era until the late fifties in Royces, and right into the 1970s in Land Rovers.
They are famously quiet, smooth [especially in in line six form], and robust. Neither Royce nor Rover really made performance cars, but they did build cars to last and be comfortable.
Several Bentley variants of the Royces appeared that showed that such an engine could really perform in the grand tourer segment of the luxury are market, such as the Bentley Mark Six and the earlier Continentals, before Royce's own new V8 was adopted across the Royce and Bentley models.
Nice video. Thanks from George [in UK].
A "Flathead" with a correctly sized turbo would be ideal.
don't forget the Atmospheric IOE.....hey, it worked anyhow...
I've never worked on such an engine but from what I heard the were somewhat inefficient and not as reliable as they wanted it to be hence why it did not catch on.
Hi George, in the late 70's my brother had a Land Rover with that style engine.
At 90mph, the 'aerodynamics worse than a house brick' meant the door tops got sucked out about an inch.
You could also watch the fuel gauge dropping like the second hand of a watch!
Video also missed out on Ducati with desmodromic valve operation (I don't think anyone else uses it?)
The head shown around 7 minutes looks like a Triumph Dolomite, direct operation bucket one side and rocker for the other?
Kaiser/Jeep used a F head design in the mid 50's the 134CID engine and the 161CID engine.
Amazing video. Good pictures as well as good explanations of advantages and disadvantages as well as history. Perfect
Just subscribed excellent video packed with historical and useful information. Thanks for sharing. 👍
I really grateful with all this videos, they`re been helpful for me to learn all this car items. Thank`s again. Congrats, great videos.
Excellent, well presented and very educational. Thank You and Best Regards.
Triumph had a lovely Sprint engine that was 16 valve straight 4 engine. One cam, with one set of valves under it and the other side working off rockers but on the same cam! It was a lovely neat design that kept the engine quite compact.
I always wondered why this configuration was never used more.
I wonder too.
Sounds like the Alfa Romeo "Busso" V6 ("Busso" is the italian word for "Bullshit"):
- In 2.0TB it's quite a pointless design, really..
derivating from 4v/cyl. where they made 2v/cyl version - but still on twin-row, cross-flow valve-design:
- The intake valve is driven, directly by the cam, with a rotating cup (tapper).
I see some logic here.. Not the best, but quite simple. Classic design. Me - okay here.
- For the exhaust
- the cam's profile is offsetted on 90 deg. next to the intake - because the movement is picked up by a horisontal tapper
- then, a push-rod - which drives the rocker;
- the rocker, itself - hinges on a rocker-axle which is placed, where the exhaust-cam would stay if it was 4v/cyl. (WHY?! Why not go JUST with a second cam? Who does that!? And if "Nobody" - why?!?!)
On the other side of the rocker is the adjustment screw for valve-clearance, and this drives the exhaust valve.. :D
How stupid is that?!? - twice more complex design, with 3-4 more weakpoints, heavier - in order to LOSE power!
Not like the 24v was something impressive, but 12v - blew my buttcrack, really. This is simply - combining weaknesses of DOHC's & OHV's. With none of the profits.
(Let's say it's an Alfa-thing)
Yes the dolly sprint engine was the first mass produced 4 valve per cylinder engine.
@@grebo121 I had an Alfa 33 for many years, it ran like a train doing 200+ kph from a 1.6 litre engine, problemfree for more than 300.000 km. Lovely little car.
honda d series and mitsubishi 4g92 has also 16V sohc, very compact but still allowing high performance for its size
It sounds and looks great. Thanks for your efforts
What an easy explanation... The best ever video i have seen ever😊
There never is a best, always an engineering compromise. It is all about the initial design criteria.
I'd say that's incorrect. The overhead valve is much better in regards to efficiency than a flathead. The same goes for overhead cam vs cam in block, have more options for size of valves, number of valves, and chamber design, not to mention intake and exhaust port design and size. Dual vs single overhead design means you can more specifically tailor valve timing, geometry, and again number of valves per cylinder. You don't really want to control four valves per cylinder on one cam.
Weight and packaging are a determining factor. So you are wrong. Corvettes get the same gas mileage as Civics. How is that for your efficiency.
I agree, a compromise.
Flathead is out of date, but has the advantage of liquid cooling the exhaust improving durability.
Inlet over exhaust also has this benefit.
OHV has a place in low Octane environments (as does the above )
OHC does make the most *of 87+ octane economically. But that wasn't always the case with gasoline.
DOHC is great for high Octane fuel, 89+
@@drtracernum20 I think their point is that if you have limited space, you may need an OHV design to maximize the available room. Likewise for reliability, required maintenance, etc.
Flexibility is best. Variable intake, variable timing, variable compression, variable displacement. Direct injection is best til the intake gets carboned up. Turbo beats supercharger though. C4s made 250-275 horses until DOHC LT5 came out. 50% more power, 200% the price for the car. Chevy should've stuck it out with that setup and learned to build the engines themselves. Develop improvements along the way. The ZR-1 was the only interesting C4.
The valves in an Overhead Valve engine are not in the block, they are in the head. Flathead engines have the valves in the block.
You got that right. Even the diagram they used pictures the valves in the head.
Ohv engine are also known as cam in block engine.
Dohc sohc ohv
Terima kasih telah berbagi ilmu, smoga bermanfaat.
Overhead Valve design does not automatically mean more low end, rather OHC allows higher revs with lighter valve springs due to the lighter valvetrain. Camming an engine for higher revs takes away low RPM torque. That is the reason Overhead engines tend to have more low end- OHC engines tend to have aggressive camshafts and therefore have weak low end.
Thats not the reason at all
@@wiktorjachyra1869 Ok, I will say it differently then: Pushrod overhead valve engines do not have more low end torque than OHC engines just because they are pushrod engines, but rather OHC engines have a light-weight valve train that allows the use of relatively soft valve springs. so those engines can use a more aggressive cam shaft without having to resort to the super-stiff valve springs that a push rod engine would require. That more aggressive cam shaft means less low end torque but more high end horsepower, and the fact that it doesn't need super-stiff valve springs also means less internal friction and freer-revving characteristics. This assumes everything else being equal.
You're right. NASCAR uses ohv engines and they rev over 9k rpm.
Why does the 2020 Corvette make 30 hp more than the 2019 Corvette?
@@Tom-xd4ct In contrast, the Merlin engine in Spitfires during WW2 was a SOHC 4-valve per cylinder unit V-12. Peak power was at a mere 3,000 rpm.
Thank you for posting this. It was very effective in communicating the differences in the configurations.
Some single camshaft engines had the cams directly mounted over the tops of the inlet and exhaust valve’s leaving space for spark plug; for example the Coventry Climax racing engine which was also used in Hillman Imps and fire engine portable water pumps.
Love these videos!
Very useful. Thanks for sharing
OHV / center cam. Used for decades and time tested.
Over head cam is even older.
It’s ok for small application, terrible for high horsepower
@@2seep I think there have been one or two pushrod engines that were actually pretty big and made some decent power.
Thanks a lot 4 the video, it's really very interesting.
A fantastic video with one error. At 11:12 the labels for the graphics are mismatched. The OHC label should be on the left, and the OHV label should be on the right.
Thank you so much for teaching
Awesome video, thanks.
Super! Thank you so much for it.
Very good info
🎉Enjoyed a lot . Thanks.
Great video. I learned.
now i understand so much of valve train i mean those pictures tells you everything
DOHC does not imply 4 valves per cylinder, although it makes it easier. There are many DOHC engines with 2 or 3 valves per cylinder (for instance the classic Alfa Romeo engines) and there are also 4 valve per cylinder designs with only 1 camshaft (such as the Triumph Dolomite Sprint, as someone else mentions). The main advantages of DOHC are certain kind of simplicity and lightness of the moving parts + ability to regulate the position of the both camshafts individually when you are going for adjustable timing arrangements.
In what timing situation would you want the valves opening up unsynchronized on the 2 cylinder banks?
Because of you guys i know everything about V6 engine and combustion engine how it's work. Thanks for you guys
Great appreciation👏
good video. thank you.
I like the Detroit Diesel setup that has the cam gear driven just below the head, with the rollers mounted to the head. It gives all the advantages of OHC without the extra complication (labor cost) of dealing with chains and cams and all that when doing a head job. (EDIT: Talking about the 71/92 series, I don't know anything about the later model stuff)
Amazing😊👍
My 89 Mazda 323 has the very reliable B6 series engine.
It has a single overhead cam and 8 valves. The peak torque comes low at 2500rpm and you feel it. High end power is low however and you feel that also. It behaves more like an OHV motor.
GM engine X16SZ is same.
Thanks alot man.
Many thanks...
The Honda CX500/CX650 and various diesel engines use pushrods and 4 valves. Done correctly, this setup has the obvious advantages of each design.
The combustion chambers in a flathead are in the head. It is the valves that are in the block.
Very nice
You are a very good RUclipsr. ❤
Thanks
".....Which is the Best Engine Valvetrain Design? OHV, SOHC, DOHC or Flathead?....."
Depends upon the application, the budget, and the fuel.
Everything I Always Wanted to Know About Valves (But Were Afraid to Ask)!
I want to know more about the other types of valves. sleaved and rotary
If the flathead valve it's in the cylinder, how is the carburetor or injectors works and how can you mount it in the cylinder which is close to the crank shaft
I always thought OHV naming instead of calling it pushrod was a 80s way improving pushrod's PR problem during the Japanese flood of overhead cam and DOHC offerings. After all, they all have valves up top.
OHV 😊
I just love chains, belts, and tensioners that fail causing massive damage when the piston repeatedly smashes into the valves 😈
The answer to the question in the title depends on whether best actually means in terms of power, torque, speed, or reliability or durability, or all. My considered opinion, and taking life experiences into consideration; If the quality of materials for all designs are high and equal for all configurations, of course the dual overhead cam gives the highest volumetric efficiency, power and speed, especially if more than two valves per cylinder are present. That said, the drive linkage for the multiple cam shafts is more complicated than the other designs, with many more moving parts , and can be prone to more instances of wear and catastrophic failure.
As for reliability and durability, the flat head valve train is the simplest, and least prone to failure, with no rocker arms, or push rods and either a gear or chain drive for the camshaft. Bottom line for the flat head is that the design is dependable, but efficiency is not very good compared to the others partly because the fuel/air mixture has to be lifted up, against gravity, into the combustion chamber.
To me, the push rod, overhead valve, and single overhead cam engines, strike a happy medium between the two extremes I have referred to, with reliability and efficiency both taken into account.
I will add that any interference engine, with a fabric timing belt, is asking for catastrophic trouble, I don't care how efficient and powerful it is.
If you have to watch the video you are big learning curve ❤
OHV owner here. :D
Great 🎉
To jsou takzvané spodové motory, kde jsou ventily vedle válce ovládané spodem od vačky.🤔🤩
I think an interesting topic would be discussing Coates spherical rotary valves. They're simple and efficient
And with the doubling of the power output from the Coates heads negates the use of forced induction set ups.
And for the low end pockets that most of us have, Rhoades lifters does away with trying to pay for roller rockers
@@jamesharrison6201Exactly. Keeping things mechanical while improving overall performance and efficiency
One advantage mentioned on DOHC is the 4 valve per cylinder. But there are SOHC engines with 4 valves per cylinder, many Mitsubishi' since the 90's and 2000's had SOHC with 4 valves per cylinder. I had a few and even today I have a 2.4 SOHC Outlander, discontinued in the last redesign.
What about desmodromic valve systems? Used mainly by Ducati, but I assume by others.
I have been studying Diesel & Petrol Engines or Fuel Injector Engines & Spark Plug Engines for 15 Years now and will continue to Automobile Engines also.Studies are way ahead....Still studying to Master the Application on Engines..Anthony Anakapu.
Bro honestly no one gives a fuck
15 years is almost half the career time of an engineer in any profession.
I will take OHV any time
I think reliability n efficiency durability is best for everyone to transport from work family travel n people that are not mechanically incline, it would be best for the world to all ideas to built that one engine , even old inventions work , as a realist
Judging by the simplicity, reliability and superior power output of the Chevrolet LS pushrod engine compared to the double overhead cam Ford stuff, I say you have your answer.
@the engineers post do you have pdf for this.
I love thisi
Based on my long long experience, OHV , is the best valve -train design. Period. Thanks
It's good in tractors.
Said no one ever!
The Renault 16TS had an OHV engine and dominated many races at the time
Must be true as you used ' period '.
@@alstoundSaid everyone, LS is the most swapped engine in the world. Cry more, DOHC is slow ☠️
Define the parameters of "best". The context and especially the timeline plays a major part, thus the question is as ill-defined as when asking which snake is the biggest. Considering length or weight?
Muito bom.
Video seems to think OHV engines cannot have four valves per cylinder. This is incorrect. See Ford diesel, for example.
The low compression of a flathead shouldn't matter if it's force induced, and I could of swore 4 strokes have a dedicated intake stroke and that scavenging was more of a 2 stroke problem. The float could be solved with a desmodromic cam, which would never have a problem with lubrication in the crankcase and does not need springs.
Push rod OHV for me please.
Push Rod Engines are the most practical engines. BMW Boxer Oil Head 4 Valve Engines used in R1100, 1150 & 1200 RT & GS are good examples.
You are so correct. Working on push rod engines is so much less hassle.
I like the high revving Japanese engines so timing chain for life🎉❤
The "oil-head" boxer twins from BMW are technically "in-head cam" engines (with very short pushrods). The oil-head engines have two camshafts (one in each head), unlike the older "air head" engines that had only one (centrally located) camshaft.
Desmo system of Ducati?
What is the engine designed to do? What RPM range is it expected to operate in. Lower RPM OHV is perfectly acceptable. High output low displacement. DOHC w/4 valves per cylinder.
It depends for longevity go with KISS ! Which would be over head valves with push rods. Fewer moving parts.
All things being equal, rpm determines power. The higher you can rev, the more juice you get. Obviously DOHC engines are best for high-end power. I stipulate that Chevy has done a fine fine making their ancient OHV designs perform well.
This is true. For the mundane duties we perform every day, the OHV 2 valve engines work just fine, plus it's smaller, lighter, and cheaper than an OHC engine. So many people believe they need a DOHC engine with VVT, V-Tech, and all the other fancy crap when all they do is sit in traffic on their way to work.
I do love my Toyota V8, but I dread the day something goes wrong. An old Vortec or LS is a much more user-friendly engine.
👍
pushrod v8 lowend rumble is music to my ears..
Uuu... Bagus.
For some slow speed applications an L head (valve in block) is a better option. The old flat head Ford 8N tractor can, in some cases, out work it's modern cousins. Outwork here is defined as plowing more acres with the same sized plow on less fuel burned.
A flathead, with it's simple light weight valvetrain, has less internal friction, everything else being the same. That gives it an edge in mechanical efficiency.
3:07 you had OHV & OHC back to front!
That's right, he labeled the OHC diagram as OHV, and the OHV diagram as OHC. It's been two weeks since he uploaded the video, I wonder if he is aware of the error. I hope he reads these comments and will make the necessary correction. Otherwise it's a decent educational video for newbies.
I came here to say that too. Wanted to see if anyone else noticed that.
I noticed that too. Had to back it up to make I saw what I thought I saw.
Thank 💡💡💡💡💗💗😎😎👍👍🎈🎈
Opposed piston engine ?
The video was really helpful visually but the clicking and typing sound effects were distracting for listening.
What about a boxer engine like Subaru ?
What about them?
sleeve valve engine?
Can you make a video, Some Manufacturers says 24.31PS@6500RPM & Some says 43.5PS@9000RPM and 32Nm@4000-4500RPM & 35Nm@7000RPM. Can you explain or make a video please.
We use Brake Horsepower @RPM, and Lbs. Ft. of torque @RPM.
@@michaelbenardo5695 ... I think you meant to say, "In the United States, we use...". Germany historically used PS as a measure of power. Most of the rest of the world now lists engine power in KW (KiloWatts).
Here are the conversion: 1 BHP = 1.014 PS; 1 BHP = 0.746 KW. BHP, PS and KW are all valid measures of power, just using different units.
There’s no question about the overhead valve. Much lower center of gravity, lighter engine, and infinitely simpler, and the parts that typically fail on dual overhead cams and such as chains and chains guides are eliminated.
OHV is the best when working on a engine.
Rica etsem altyazı seçeneklerine Türkçe dil seçeneği ekleyebilir misiniz ? Sizi anlamak ve takip etmek istiyorum !!!
altyazı ayarlarına gitmeyi denesen görürsün
The Flat head was more of FORD able!
GM has proven with the LS engine you can have an old fashioned OHV cam in block and still keep up with and exceed the other guys with any other valve system. To say it limits performance is BS, and it's less complicated to less parts to break.
You just need large displacement cylinders to compete.
@@billymania11 OHV 520cc singgle cylinder can produce 33 HP,
seem win win for me, actualy for motorbike that need bigger CC, but still love fuel economy and high low torq and small gear usage with CVT, it's would be just fine, cause actualy CVT make torq more exist with OVH engine set up,
It would make more sense if the flathead valvetrain was explained first.
My honda CX500 was a V twin with 4 valve heads. The heads are just behind the riders' knees, but heres where it gets weird. The heads are twisted by 22 degrees so the carburettors are tucked in and exhausts splay out. This cant use an overhead cam so its pushrod. Each pushrod works a rocker that opens two valves. There are lower finger followers too. Mine was nicknamed "The Knocker" by my friends as all this valve gear makes a racket. 4valve OHV. A picture tells a thousand words. Look up a Honda CX500.
7:59. Did the author have a stroke? "More the power more is full consumption"??
God, I want to get a project car. Gotta get some land first.
What about free valve or camless engine?
Free valve has not been in mass production yet. It is a vapourware. It is good for billionaire who drives their hypercar as toy and does not rack up mileage. There is a China car manufacturer that has licensed the Freevalve tech. They make a prototype to demonstrate in a China carshow. Nothing heard since there. They silently drop the project. Thus Freevalve is not the real deal. If you have billion, you can ask fancy hypercar maker to make you one. That's it.
Depends on how fast u want to rev.
What happened to CIH engines?
I take it you mean the ones like Opel used to build. I had a Renault that was OHV but had the cam placed so high in the block the tappets were in the head. Plus it was a hemi.
no pneumatic valve?