Intake Manifold Boosted flow comparison GM 60°V6’s
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- Опубликовано: 16 окт 2023
- After blowing up the 3.1 turbo engine, I figured it’s a good time to compare the intake manifolds I’ve collected and see which flows best when boosted.
Thanks for watching! 
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Awesome, I always have read online that the 3.1 manifold was really air flow restrictive, so increasing the air flow to the pistons will indeed increase the HP on these great little V6 60 degree motors.
So I am an engineer… and I can explain a little of what is going on here.
First, this is uncharacteristic of the flow provided by a running engine. So apples to oranges first off. The reason is that an engine running causes distributed vacuum from each opening valve event, and the summation of all events over a period of time gives you the intake vacuum. The airflow through the port will ultimately be determined by the valve event and available air volume ant whatever pressure or vacuum within the plenum. This is a basic running engine.
Whereas your test is using a constant air source, which is forcing air through the throttle body and into the plenum and distributing it to the runners. While this test kind of makes sense in our heads, it is not how an engine operates.
And this is important for this fact, the air is not distributed from the throttle body to the runners… it is a vacuum that pulls from the supply of the plenum, provided from the runners.
Analogy time;
Do you breathe based on the air flow into your mouth, or based on what your lungs draw in? If you forced air into your mouth and said that your left lung was distributed more air than your right lung, therefore your throat was at fault for poor airflow to your right lung… would that statement mean anything?
The other part to take into account is how air flows. As we said, it is a valve
event. And each event (starting with opening) causes a drop in pressure, which causes air to flow from a high pressure region (plenum) into a lower pressure region (cylinder). The beginning of this event sets off a pressure wave that starts at the back of the valve and moves into the plenum, where it is reflected back into the valve where it carries some air and reflects back into the plenum. This happens until the pressure wave losses its power, and each reflection is weaker than the last. This waves speed is based on the characteristics of the air as the density changes with pressure and temperature (boyles ideal gas law) and the speed of sound at the gas state.
All this is taken into to effect when the valve opens, PLUS the available air within the plenum, which is replaced when depleted by the opening in the throttle body. This wave can move faster than the speed of sound and have more force behind than the vacuum of the cylinder that is drawing in the air based on the characteristics of the port. Meaning, at certain speeds, you can have a supercharging effect where more air flows into the cylinder than the vacuum draws in by itself. This is what “tuned port intakes” do, by utilizing the helmholtz resonance theory, you can “tune” a runner and intake system to flow more air than it can statically.
Back to your test, which only shows how the intake would flow if all cylinder were drawing air at the same time.
To get a realistic idea of the air available to each cylinder, you would have to measure the differential pressure from the back of the valve to the opening in the plenum, temperature correct for the density of air, humidity correct, and DA correct for altitude. Then you can quantify flow for each port for each valve event. You would obviously have to plot this over the RPM range and for each quantifiable point of valve lift. This would be able to show you how much air the plenum was able to provide for each cylinder based on the conditions of the engine for each RPM.
I do this kind of stuff at work for much larger systems. And the data is worth its weight in gold!
Thanks for that!
I’m happy to hear from someone that knows more than I do on these subjects because through my own research there’s tons of misinformation out there and I’m always trying to educate myself more.
I’m aware that this test doesn’t accurately reflect an engine under NA vacuum conditions and I mention in the video that this is “simulated boost”.
I also blocked off each port to show “boosted” airflow going to each port separately.
My goal was really to just show which intake would work better than the others, including my home built version.
My intake was designed with 14.5” “tuned” runners based on my camshaft specs to have an increase at approximately 4500 rpm.
I was quite happy to see actual results on my data logs showing boosted pressure spikes between 4300-4600 rpm.
I am working on a video on intake manifold design as well so if you have any suggestions feel free to let me know.
Thanks!
@@xlr8ing_zgarage absolutely. I have a few formulas and spreadsheets I have developed over the years that I can send you. As well as a wealth of information.
I too have developed several intake manifolds for many different purposes. I geek out on this kind of thing.
its a turbocharged car are you missing chromosomes or something? forced induction is not how you breathe.
@@chehystpewpur4754 the phrase is having an extra chromosome. Missing one is turner syndrome. I hope you never have the misfortune of either in your family.
And if you truly understood how forced induction works, you wouldnt have made this comment. Says a lot about what you understand.
I can help though. Forced induction doesnt “blow air” into the engine. It pressurizes the air that is in the plenum. The valve opening allows the air to flow. The only way you create boost is by having a restriction. The exact same way as breathing.
so basically i was right for using the 3400 intakes years ago.
the 3.5 and 3.9l have some great tech in them too if your 3100 dies. the 3.9l is the crown jewel for small gm v6 powerhouses.
super freeking cool always liked this body style , love the custom intake too . every time i look at my intake on my 535i i wonder how much better it could be flow wise ! you seem to have broken youtube most of the comments here are gold either helpful or just cool and encouraging i will be subbed after this comment and back for more . cheers , keep your stick on the ice
Thanks!! Appreciate the kind words!!
I’m working on a video about intake manifold designs but it’s not ready yet. A lot of information to try to cover. Thanks!!
Curtis Walker used a modified rear wheel drive 3.4L intake from a Camaro on his infamous turbocharged Z24. He had to cut off the back corner of the intake in order to clear the alternator. Even at 20 psi with a HUGE turbo, he never had a problem with cylinders running lean.
GREAT video BTW!!!
Thanks! I know Curtis and his build on the Z24. Met him and the car in person one time in Bowling Green many years ago.
That’s another intake I’ve never looked into closely because it’s only for iron head engine which I’ve never used.
Thanks for watching!
@@xlr8ing_zgarage I lived in the Dallas area where Curtis lived 20+ years ago. Got to work with him on the car. Went with him and a few other guys to a J Body bash back in the day too. That car was crazy, and it was crazy at how many different GM parts fit on other cars, but also different parts fit on different engines. At one point I owned a 91 Cavalier and did a TBI to MPFI swap on the 2.2L motor. Later I owned Wagonstein, a 1991 Cavalier wagon with a mild 3.1L turbo under the hood. There will always be a place for old school J bodies in my heart! Love your videos!
@@91CavGT5 I think I remember Curtis talking about putting a TGP setup in a Cavalier wagon. But I’m getting older and might be confused…🧐
Big difference when only using ONE port vs ALL ports at once.
MUCH more uniform! Even for the 3.1 intake!
Great video. Pretty surprising results from the 3400 intake. Curious to see how each flows on a flow bench under vacuum situations. Also curious to see if manifold actually had a positive pressure using the leaf blower. Plug a boost gauge into one of the vacuum ports.
Didn’t even think about that! I bet the stock 3.1 would have had positive pressure considering how much lower the flow numbers were.
I still doubt it with a leaf blower. They aren't really made to compress air, just move it. Ever watch the leaf blower supercharger roadkill episode? Took half a dozen gas leaf blowers to make boost lol.
@@danscustomprojects4486 nope haven’t seen it but I know they don’t put out much volume of air, just velocity. Like the pool toy inflators but they can’t blow up a car tire.
Science! I would love to test your custom intake on the flow bench and maybe compare it to an extrude honed 3.1 intake...🤔
That would be awesome!!
@@xlr8ing_zgarage I'm sure we can arrange something over the next couple of months!
Glad you got some tape on there;) I want to see what you get with the 3500 upper intake on the 3400 lower. The 3400 is the best distribution for sure on a flowbench. What you are testing is how boost could be distributed since its being forced through rather than drawn through.
Thanks! I’d like to see how the 3500 compares as well but don’t have one here.
Very interesting, I'd love to see you do a 3500 and even a 3900 intake in comparison.
If I can get my hands on them I will do! Thanks!!
3400 is what’s in my Pontiac Montana. Guess I need to turbo it. ;)
DO IT!!! My wife has had numerous 3400 Montanas and would’ve liked to do that but I’m afraid the 4T65 transmission would be toast almost instantly!!
@@xlr8ing_zgarage Try to figure out how to swap the 4T65E for an HD model! I THINK they were not only used in the 3800 SC cars, but the 3900 cars too.
Not sure if they were used with the LS4 in the W-Bodies or if they used another, such as the 4T80E (I THINK the '80E was only used in Northstar cars?)
@@mstover2809 I believe the HD was only with the 4T80 transmission and GM even had a race version for sale at one point.
Not really worth it but would be fun to make one of those AWD Montana vans turbo as well!
Will a 3400 upper plenum fit on a 3100 lower intake?
If it’s a later model, after 1999 i think, I believe it’s the same. Just different numbers on top. Likely not worth swapping.
The first 3100 SFI in 1994 had the same style intake but smaller ports and are not interchangeable without changing cylinder heads as well. Thanks!
Interesting now I wounder if the 2.8 style is same port size and everything as the 3.1 . Does the 2.8 and 3.1 have same size and it's just stamped 3.1 on it
I plan on swapping 3.1 from my Lumina to my celebrity Eurosport and just curious about that part but I doubt there's a difference tho but never know
Thanks!! I believe port sizes are the same for both 2.8 and 3.1 MPFI engines. I know there was a change on the 3.1 version at some point but it was just a bolt size change if I remember correctly. Basically you can’t use the newer upper plenum on the older lower intake because the bolt size was different.
@xlr8ing_zgarage main difference that I remember was the pcv location, 3.1 went into the plenum and the 2.8s went in the lower intake manifold.
@@modeverything1 Yes That is True
Ahh forgot about that!!