V2Rocket

Not trying to make it complicated.
Just want to know if putting the air in like the LR intake or like Duke's intake gets air more evenly to all 4 cylinders.

Runner length and plenum volume are sort of secondary considerations vs overall packaging.

I understand a larger plenum is a sort of bandaid for distribution but I don't want a huge one because I don't have the space and I don't want bad throttle response.

Paulyy

Straight up. They'd be the same unless there's a bottle neck inside the plenum. as it's under pressure, and not all valves are open at once. I have done CFD on a few designs years ago. minimal difference.

User 41221

^+1

Unless your design is flowing so poorly that the engine isn't getting enough air to feed the cylinders, which means mostly that the plenum is probably inappropriately sized rather than configured wrong. Feel free to correct me on this, but isn't the plenum really acting as a holding tank in this situation? There should be an overabundance of air with either design, and then when the valve opens, it rushes in to full the void. Its not meant to be a continuous flow per se like the intercooler or the pipe leading to the intake.

refresh951

My experience is that plenum size and runner length are the key variables. Unless you have very good CFD, which no one has, the rest just does not matter much and opinions are a dime a dozen. An automotive design engineer told me that my intake would not work but after 5 years the motor begs to differ. Certainly no authority but this is my experience. Long runner, smaller plenum for a responsive mid range and large plenum, short runner for top end power. Many of the OE designs you see around are more focused on fuel economy and emissions. Those are things I cannot speak to as I really do not care about either.

Tom M'Guinn

Clearly you need to make one of each, then flow test and dyno both and let us all know.

V2Rocket

i've had so much fun in this process, that i think once will be enough

Nowanker

Re: GM LS intake manifolds....
They do have possible issues with airflow. High HP N/A engines sometimes run hot on the rear 2 cylinders.
Some say it's due to the cooling system design, but others say it's from lean mixture, caused by the inertia of the air.
I suspect #2....
Probably neither design is ideal. Maybe center inlet minimizes the variance.
How about an intake manifold that looks like a set of headers?

PaulD_944S2

ITBs for the win....

Noahs944

V2,
Got any pics of your project ?

Voith

Most inline 4 turbos in wrc use double plenum style like that audi so there has to be some benefit to it.

This is interesting read on the topic:

https://www.bufkinengineering.com/in...0manifolds.htm

V2Rocket

I hesitate to post my in progress work... while all the metal is in place there's still plenty of mock up tape and wood

the absurdly low 944 hood line will shave years off my life, due to stress of trying to package stuff under it.
Have seen those over the years but seems nobody out in the real world really knows if they work, at least any better than a more conventional design.

i know peep has done them on both of his cars and they work for him.

funny thing is that every discussion you find online about that intake references the bufkin Audi site but there are no secondary sources... lots of photos of rally stuff so it must do something. I don't think i have the space to package one of those though (maybe)

Voith

Here you go.

Humboldtgrin

V2Rocket

Goran,
that article was very interesting but nothing like the Audi manifolds.

George,
did you ever get your one off 928 intake from Tim? Or are you just going to use a normal 16v 944 piece and 'make it work' despite port size differences?

Noahs944

V2, What are your powerplant output goals?
Is this going to basically be a forced induction S engine? Why not use the OEM intake?