Intake Manifold Design

[twilightprotege]

Hey guys,

here's a question that'll get your brain ticking....but does anyone know the mathematical formulas etc do design intake manifold diameters, lengths etc???

I've done the good old google search and found numerous ideas, but all of them dont go into great details about how they came to certain figures.

one thing that i did see a few times is that the intake manifold runner area should be 80% of the area of the valve faces (both valves).

a theory on length is using ram air...that's where the "pulse" of air goes into the valve at the point of where it opens are you selected "power-band" range.....but the fomulas were like

L = 90000 / RPM

so if you wanted a peak power range at 6000rpm, you'd have a runner 15inches long.....that doesnt sound right.....

anyway, anyone have any ideas on this?????

 

[kcbhiw]

There was an excellent article posted on protegeclub.com by PseudoRealityX on this topic. But I'll be damned if pclub hasn't yet again failed. If I can find the info, I'll post it here.

 

[twilightprotege]

yeah i think i saw that, but it was one of those articles like what i kept on finding....if didnt give as specific as what i want, it was generalisations. if memory serves me correctly, that was the first one i found and that's what got me trying to find more! i like inforation!!! hehehe

 

[70]

Hmmm...

 

[twilightprotege]

anyone know the formulas????

 

[Installshield 2]

I have never heard of general formulas for every engine...There are certain variables that apply to different engines, but I don't think there is a single formula that can lump everything into one engine...

Some generalizations are things like short runners for highend power, long runners for lowend torque, etc...

the shittiest part, especially with the racing teams, is that it is mostly trial and error...the best part would probably to figure out the specs of the stock intake manifold and go from there...I am working on that as we speak...You then need to figure out your finitive amount of mods that will be done to the engine, and figure out about where you want the powerband...

More importantly no significant gains can be had without a new engine controller...GreenMP3 knifed the s*** out of the stock intake manifold, then polished it along with adding intake valves the size of silver dollars...He claimed way too much air was getting into the engine, and that it was running too lean and he was loosing power...I am no expert but to me that sounds a little strange...The stock ECU runs the mixture extremely rich at open loop, in which case the fuel delivery is good for around 5-6psi of boost...The tuning isn't, but there is enough fuel for it...I don't see how his intake manifold is allowing enough air into the chambers for it to lean out at open loop, especially with MAF input allowing even more fuel in...My guess is that he either is experiencing massive turbulence that is gutting power and making the engine feel lathargic, or that simply the ignition timing and fuel delivery needs to be adjusted by a proper standalone...actually it could be a combination of both...

 

[twilightprotege]

yeah i've found a few sites that talk about actually making the IM. i was going to attempt to try and make my own one of these days....i'd probably make a few i guess. 1 for drag, 1 for circuit and 1 for street....

i was going to attemp to expand on mazda's VICS idea and take it 1 step further for the street....

 

[p5sundevil]

well doesnt the Jspec manifold use long and short runners as described above to allow a smoother power band?

What I would do is find the tech specs of our mani, the specs of the Jspec mani, and then maybe make one with specs a little stronger than that of the Jspec. for comparison purposes that could work.

Also the race p5 that was featured in SCC a long time ago use a tubular intake mani that supposedly made huge power gains for that car, as in they designed the strut bar and other items around being able to make the mani fit since it was so crucial to making big N/A numbers.

Maybe try to find some info on those race p5 and see if they have specs about what they did and why for those custom ones.

Other than that I really wouldnt have an idea for an equation, as said each engine Should have a different one for different displacement, rev range, initial power capabilities, valve design and everything else.

Good luck I look forward to more info on this.

 

[twilightprotege]

i'll probably just end up running a single runner design.

the problem is that there is so so so many ideas on the subject around i have no idea which is right and which is wrong...

trial and error looks to be the way unfortunately

 

[Installshield 2]

where did you get that formual in your initial post? Maybe the length measurement is in metric, in which case it may be 15cm...I don't know...it still sounds to general to apply to any engine...

 

[twilightprotege]

it was from a university site. a guy was studying engineering for cars and had a suzuki swift or whatever you guys in america call them. he was testing the theory of ram air intake manifolds. it was a line of formulas which measured the length of time it took the air wave to first hit the valve when it closed, back to the plenum (or whatever that things is called), back to the valve, back to the plenum and then hopefully as it then next hits the valve, the valve would be open, hence creating the ram air effect.

i dont have the formula here with me (i'm at work) but i've got it saved as a fav at home. i'll post it here tonight when i get home.

i think the theory behind intake manifold runner length is the same for all cars and engines, it's the diameter that is the variable depending on the size of the engine, cylinders etc etc etc.

 

[PaulMP3]

Wagnermotorsports is making me a mani this jan/feb if i can give him the car for a while. Im not sure of his plan/design yet, but i would love to find the best design for a turbo protege. I dont think many have been made except for the JIC drag protege. Anybody know of any links to info on this car

 

[twilightprotege]

hey see if you can get wagner to tell us their secrets!!!!!

 

[Installshield 2]

Wagnermotorsports is making me a mani this jan/feb if i can give him the car for a while. Im not sure of his plan/design yet, but i would love to find the best design for a turbo protege. I dont think many have been made except for the JIC drag protege. Anybody know of any links to info on this car

I will try to dig up the site with info on that Ziel Motorsports/JIC drag car...

From what I remember none of the SCC cars use the stock intake manifolds or even casts,...contacting sunbelt might help with some more info on what was done...

 

[Mike R]

Installshield2, one of the problems with huge runners and big valves is that the port velocity will drop causing problems with power loss and a/f. I bet extrude honing would be good for the intake/head, but it's too much $$.

 

[twilightprotege]

extrude honing isnt as good for heads as people think. the problem is that it takes out more metal where the area is the smallest (that's where the greatest pressure is), so it is actually worse for flow than just making the standard bigger but keeping the same size....but extrude honing is best for intake manifolds...where normal tools cant get to

 

[green MP3]

good one !!!

__________________
More importantly no significant gains can be had without a new engine controller...GreenMP3 knifed the s*** out of the stock intake manifold, then polished it along with adding intake valves the size of silver dollars...He claimed way too much air was getting into the engine, and that it was running too lean and he was loosing power...I am no expert but to me that sounds a little strange...The stock ECU runs the mixture extremely rich at open loop, in which case the fuel delivery is good for around 5-6psi of boost...The tuning isn't, but there is enough fuel for it...I don't see how his intake manifold is allowing enough air into the chambers for it to lean out at open loop, especially with MAF input allowing even more fuel in...My guess is that he either is experiencing massive turbulence that is gutting power and making the engine feel lathargic, or that simply the ignition timing and fuel delivery needs to be adjusted by a proper standalone...actually it could be a combination of both...

good one man!! but you missed something. My cars runs great on open loop,after 4500 rpms it just takes off. it is before that when the cars goes lean then a bit rich then lean and so forth.
i have been working on it , so i borrowed a fuel pressure regulator and the car got much better; then i changed the injectors to toyota ones and after 4500 rpm the car flew big time, i was very impressed. our injectors suckkkkkkkkkkk.... the fuel delivery was good on low and high. the rpm when from 4500 to 7500 in secs, it was a great feeling.
i am still tuning and finding ways to get our freaking computer to work better and well i guess it's just a matter of time.
i won't tell you which injectors i am using cause i want to test everything and get the "errors "out of the way so all of you won't go to the first junkyard and get them then bith at me
if you were to run in to trouble.....

but i can tell you this.!the electronics on our cars suck but can be modified with other automobile brands that use denso so take it from there......

Green


(greenpro)

 

[twilightprotege]

I thought of another way to keep the VICS in play, but make it work better. (green, check to see if this is right)

currently at low rpm it's open i beleive and that keeps the little chamber there so that gives the car the impression of a longer runner, then at high rpm it closes it off so the runners are in theory shorter.

an idea would be to drill round holes though the bottom of the what i'm going to call the VICS chamber and at low rpm have the butterflys closed. it will still give the same effect as having them open without the holes drilled. then at rpm, the butterflys open so you then have air going through both chambers.....

waddia think???

 

[green MP3]

Which Victs Butterflyies??

the ones by the head ports ot the ones in the middle????


Green

 

[twilightprotege]

VICS is the one in the middle of the intake manifold - just above where the TB is - the ones i think from memory you cut right out??