Bigfoot928

Great thread. I went through a lot of this years ago.... ask me why I remember the stock intake is 9300cc in volume... btdt You are breaking new ground and making good progress. 3 things will make the S4 intake flow much better. 1st. Bigger bore throttle plate. Done. I did it... 2nd... Divider in the lower plenum as posted here by others.... If you really wanted to make good power I would do this digitize the lower plenum and put a 90mm throttle plate on it, with a divider in the center to drive the air upwards. Add that to your upper intake mods and you will be there.... if you could digitize the upper intake and increase the runner size in addition to what you have done, have them printed in 3d... done... don't let the naysayers get you down... and don't forget the kibort effect..... he is actually living in a different dimension so our laws of flow, gravity and most of all... our GLADIATOR rules don't apply.... if the last one escapes you google kibort and gladiator... but I warn you... you can't unsee him in tights.... IJS

ptuomov

Sterling -- What's the evidence that a larger throttle plate makes the S4 intake make more power? Or if not power, that it makes the whole manifold flow significantly more CFM? Not saying you are wrong, just trying to figure out exactly what we know for sure.

mark kibort

I think the throttle body might make some good gains, as that usually is the largest pressure drop in the system. however, I seemed to remember Anderson hogging out the throttle body and intake and not see any gains at all. so, I think the manifold mods listed here is a good start. maybe all above can make more sizable gains... larger throttle body with the intake runner horn mods.

UpFixenDerPorsche

Spot on on both counts Mike.

UpFixenDerPorsche

Mark, go back to https://rennlist.com/forums/928-foru...iced-this.html #11 #13.

In there I describe how the splitter plate is attached. The pics show the plate only resting in position. I also dished each side a little, which gives it double radius curvature = very rigid.

But you haven't seen the last mod. Need some more dyno work yet.

BTW I'm suspecting there is a flow restriction upstream of and maybe even including the TB.

More stuff to "futz" with.

UpFixenDerPorsche

Thanks SG. I'm not worried abt the naysayers as I already have a sharper performing car as a result.

The Kibort and I seem to be getting along OK so far. Not sure I want to risk the effects of the tights image.


Not bigger runners. Not getting enough air into the ones there now.

PorKen is doing some fascinating stuff with ignition timing maps for different runner pairs. His input to this would be great.

ptuomov

Why would the 74mm throttle body not be enough for 350 or so hp?

I get it that the turn after the throttle plate is hard to navigate. However, didn't someone post some flow bench results saying that the manifold flows just 10 or so CFM more with the side plenum plates off vs thru the whole throttle body? If so, doesn't this mean that all the easy gains for the first ten improvements come from improving the runner inlets, unshrouding the inlets relative to the plenum, port matching the manifold, and doing something magical to the runner #5 turn short side radius?

Edit: Here's yet one more source saying that the flow doesn't go up that much even if the plenum covers are taken completely off. Those numbers most likely aren't flow thru the throttle body, however:

mark kibort

good stuff.. I agree... as long as you can keep that piece from coming apart, I think it would provide some good flow eff gains.

Now you wait a min..... ive talked about pressure drop across the throttle body several times ..... ahechem......... pressure drop across a throttle body = venturi (almost)

UpFixenDerPorsche

About bellmouth intake flow:

Did someone say bellmouth?

Yikes !!!!




To get a feel for air flowing into a bellmouth, watch the flow animation of this pic at:





Shape of an intake and resistance to flow: self explanatory I hope.




Basic bellmouth intake/runner shapes:

- parallel tube and tapered (see pic above).

The S4 uses the parallel tube type. Easy to spot 'in the flesh'.

The tapered bells follow an elliptical profile, and so they have definite proportions re intake diameter, lip radius and so on.




In my mods I tried to emulate these proportions, BUT, in 90F heat I had about 6 minutes working time with the epoxy so had to estimate by eye. LOL. Later corrected by our friend Mr. Dremel.

Word of WARNING

Those seemingly bulbous bellmouth lips are there FOR THAT VERY REASON: BETTER FLOW.

So if you decide to copy my mods but decide "let's get rid of that big lump of stuff in the way", then you're on the wrong track and so don't come griping that "I copied your changes and they didn't work". OK. Got it?

I will happily work with anyone to help them do what I've done. It may not be optimal but the dyno and my Seat of the Pants feel says it works.

Don't forget that the S4 manifold has so many airflow problems that impoving it's flow is like trying to turn an elephant into a cheetah.

Out of time now. Will post more soon.

Strosek Ultra

This is the bellmouth I have fabricated for the flow testing of 928 heads.
Åke

mark kibort

after all these years, WHY doesn't someone make an adapter plate (we have one) that can be set up to mate to a really efficient intake sytem, like the V8 M3???? whyyyyyyyyy??????????
just something that bolts up, and the MAF and some filter set up can be adapted to it!!!!

UpFixenDerPorsche

Was my concern too Mark, as it was for the epoxy filler sections in the upper plenum.

Firstly the splitter: I was fortunate in that during my engineering degree studies that my 'stress design' professor was a a senior ex-rocket design engineer (no kidding) overseeing 1960's satellite launch programs.

To minimise launch weight they designed components with a fatigue life of 20 minutes: a few minutes longer than needed for critical components to reach orbit. How good is that. :-D

I gained both a mathematical and intuitive understanding of thin walled structural failure as well as metal fatigue failures.

To allay your concerns why not reproduce my splitter to give you a hands-on feel for its rigidity, then follow that using my fixing method ?

As for me, I've backed myself in that my splitter design/fixing is already inside my engine.

UpFixenDerPorsche

Looks perfect.

But the problem lay well before the ports.

UpFixenDerPorsche

Everyone thought you were going to do that Mark. Arrrrrrrrrr haaarrrrrrrrrrrrrrr harr harrr ... well we were ... really... chuckle ... larf ... giggle ... no, really ...

ReDesign by FEATHER

I wonder why all of this seems to ignore the coriolis effect. Or maybe it just doesn't matter.