okay im getting ready to port out my intake manifold, i have the stock H22A Intake manifold.

Reading through the threads on here im getting mixed thoughts...

Some people are saying that you want ~130% of your displacement in your plenum volume, and others say you want ~50-60% of displacement in plenum.....

which one of these is more correct? Im wanting to run a high compression (~12.5:1) na H22 with BC Stage 3 Cams.

My idea is to port out the upper part of the manifold as much as i can and port match the intake to match 68mm throttle body, port out the runners a little bit, and take the Butterfly bypass valve and port match it to the runners....

Ideas? Thoughts? Criticism?
anything is welcome

 

i thought it was %100 plenum volume as far as working efficiently but maybe some engines are designed to work with plenums with %130 of their engine displacement. im sure it varies based on the engine design and setup

 

Thats what i originally thought until i started reading through past threads.
Thats what im shooting for is a 1:1 ratio for plenum volume vs displacement.
Just wondering what everyone else thought on it

 

http://theoldone.com/articles/h22a_head/

 

Very nice link! Thanks for that.
The only with it is it doesn't show anything for the butterfly bypass and the upper part of the intake mani.... Did they just leave those as is?

 

I didnt touch the top part and just left the butterflies out and it is making good hp looks like this.

 

thats the idea i wanna go with mine only port out the butterflys the same way as that. making the runners that much longer.

What kind of setup do you have? High comp? do you think you would see any gains in porting the top half? what size throttle body do you have?

 

Stock throttle body 12.3 and its making 252 with skunk 2 stage 2 cams.

 

Awesome you have been a great help! Thank you

 

Plenum volume depends on the style of intake manifold. I just read up on this last night actually; How to tune and modify engine managment systems, for refurrance. For manifolds with no tuned length runners and with air flow restrictions; 1 to 2 times the engine displacment is ideal. If you have a Hemholtz resonator type, for a 4 cylinder, plenum volume should be 50-60% of engine desplacment.

The Hemholts resonator design uses pressure waves, while the latter uses a big plenum to make sure their's enough air per cylinder, other wise the engine would choke itself.

I'm assuming the modified OEM manifold wouldn't be a Hemholts resonator design, so the plenum design should be 1-2 times the engine displacment.

 

Thats the main thing i was wondering
thank you!

 

Great info on this thread. I have been looking for this information for a while.

 

I agree good stuff mine turned out good but i would have loved to had this information before i did it maybe ill do another one now.

 

So do you guys think i would benefit at all by extending the runners out via the butterfly valve? or should i just empty it out for more volume in the plenum?

 

What kind of motor are you building? In theory longer runners will give you better torque down low, whereas shorter runners will help out on the top end. The Blacktrax spacers extend the runner length/volume and their graphs show gains just about everywhere, so don't know if that helps you any.

 

Exactly what i needed! thank you
so i will extend my runners out and see how much it iproved it