The size of the runners should be the same size as the intake port mate and the volume should be around 100% of what your cylinder displaces ..the actual plenum size is the same as the total engine displacement..

 

If my memory serves me correct its 1 1/2 times a runner volume. And thats the total runner not just the head

 

bttt for escosracer

 

The length of the runners is dictated largely by the RPM range you want them to be most effective at.

Optimum plenum volume is almost never the same as engine volume.

Corky Bell recomends around 50-70% of displacement.

Its quite obvious why it doesnt need to be as much as the engine volume really when you think that on a 4 cylinder engine, only 1/4 of the volume at a time is required from the plenum during an induction stroke.


Can you tell us a bit more about the engine you have, what you are using it for etc?

Ultimately though, its going to be trial and error to get the perfect volume.

Reality is, even if you get it very wrong, it dont drive *much* different, plenum volume is far less important than a lot of people give it credit for (thats not to say it doesnt matter, but its certainly not going to make huge differences that ruin the car if you get it a bit wrong)

 

Helmholtz’s Theory

This is a vast vast subject which cannot be covered in a simple thread, if you read through the folowing link......this will help in your undrstanding and also hopefully help in your design.

http://www.grapeaperacing.com/tech/inductionsystems.pdf

this expalins all your need to know

and as for boschdealer , why waste your time go polish that amg

 

Its referring to N/A engines, although some of the principles are similar.

I think he enjoys making random guesses or kind of half remembering something he read/heard somewhere and pretending its accurate.

 

..my answer is very accurate thanks...something i have studied.

 

I would be surprised if the standard volvo plenum doesnt work quite well from what I remember of it.

Can you post a picture of it so others see what I mean?

 

Your answer is accurate for which engine? on what camshafts? with what turbo? and at what RPM?

Or are you under the impression its the same for all engines?

What institution did you study at? play school?

Was this your course text?

 

...he asked how to calculate plenum size and runner length and i am talking on a 2.3lt engine,as i dont know what he is using but volvo's are general 2.3 aint they?

edit just saw its a 1.7

 

A 2.3 volvo engine optimised for what point in the rev range, and using what camshaft? What turbo did you assume in your "calculation"


Seriously Phil, you know NOTHING about how to work it out, so dont try and pretend you do, it leads to you giving misleading advice and trying to pretend that its gospel, its not a simple subject at all.


So now you know its a 1.7 engine, what changes will that have to your guesses?

 

Hark hark the dogs do bark
The beggars are coming to town
Some in rags and some in jags
And one in a velvet gown.

this being his favourite

 

Pimping aint easy some would claim, but in reality its a doddle compared to plenum design

 

just getting comfy