333pg333

Not necessarily trying to re-invent the wheel, but sounding out ideas and options for further down the track. Currently the motor in question has a stock intake on it although it was extruded honed. It also had some deflectors put in it to help equalise flow. However there were some issues experienced on the engine dyno in vacuum or low throttle angles so I believe the deflectors maybe reduced or removed by now. With the LINK ecu able to trim individual cylinders it is hoped that the best tune can be found without too much of a compromise. Therefore I'm thinking about a different intake should the need arise...or even not a need as such but perhaps a preference for a more ideal setup. This is on a racebuilt 3L motor so I'm thinking the extra cc's will give a bunch more tq and the large cam, race head, big headers/exhaust, larger t-body, front mount i/c w larger pipes etc...might respond more to a different intake?

George D

Patrick,

John Milledge Engineering may have been the last company to actually do more R&D than just flow bench testing for intakes for the 951. I am using the SFR intake. Chris White uses these, or used to. Seems like Tim has gone AWOL.

Garrity did change the internal runners slightly, but Chris tells me the SFR intake does flow better than the stock intake when you are flowing air to support the HP of motors like ours.

Patrick, I think we've come to the end of these cars truly competing against modern engineering. Yes, having 500WHP is fun, and driving our expensive 951's against many rivals with a win brings some gratification.

In the end, know the money you spend attempting to be front of pack in any unlimited division race is not worth the effort, and will continue to wring funds from your wallet with gains that can't compete against what I'm seeing come from Ford, BMW, Mercedes, and the supercharged motors from Ford. Ford is using supercharging on their V8 motors, but trust me, those V6 twin turbo motors will eventually be part of their smaller, fuel efficient V8 motors that are now in R&D.

You will be able to purchase a 2012 800hp Shelby Super Snake Mustang with a warranty from the dealer soon. The new stock Mustang GT is competing very well against the new stock M3. There is a 20K difference in price, and know 20K put into a stock GT Mustang will get the checkered flag with similar drivers.

My build has been difficult, and after many years of intent, money, and issues, we are still working out issues that come up during dyno sessions. I do enjoy my car, and we will have a 500whp 951 using 91 fuel. We are still working out the issues that modern manufacturers spend MILLIONS to make right.

I miss just having my old 350whp and tq 2.5 951's with few issues.

My EVO could take 30psi on 91 fuel. Really, did this daily with ZERO issues. Faster than my current 951, no, but add some rain, dirt, or tight corners, the EVO was much faster.

Once my current 951 build shakes out, I'm keeping the boost low, and will enjoy some USA SCCA time trials, PCA events, and fun drives to my mountain home, and great drives here in AZ. It will be street legal.

The 951 is my favorite Porsche, but Porsche has much better cars for competitive racing venues.

I know if I turn up the boost for a brag dyno, that may be fun to share here, but these motors can't take the boost like modern day turbo motors.

The new Porsche, BMW, and Ford motors have the best direct injection turbo motors on the planet. These engine management systems as delivered have more tuning hours paid to engineers than this whole list can pay with a $10,000 donation per member.

Once my car is done, I'll enjoy it for what it is.

If you want a killer track car running against modern technology, your money is better spent on a newer platform.

This should be a PM to you, but maybe I'll learn something by hitting the "Post Quick Reply". I mean no harm, we've both been through a great deal making our 951 cars one of the best examples in the world.

I'll drive mine for many years with a grin every time I'm at the wheel.

Regards,

George

67King

Didn't mean to come across in an insulting manner, sorry about that. I meant it in terms of changing an intake from another application, not in terms of messing with the Porsche engine.

The key to the intake, or rather its largest potential, likes with runner design, and tuning it. Nothing to do with flow. The plenum volume may make a little bit of difference, but nowhere near what the runner design will give you the potential to do. You want your throttle body sized to the rest of your piping system. The larger pipes will cut down a little bit on losses, but changing sizes is the bigger problem. If you think about it, you are only capable of filling one cylinder at a time, and an intake valve is a WHOLE lot smaller than an intake. Not saying you can go that small, but people often put way too much thought into the throttle body. And going bigger will give you less control as you are trying to feather the throttle.

Quick note on plenums. THe Brits call them "surge tanks." THink about it, it makes sense. Just mention that to frame the purpose of it in your head, so you don't get too focused on thinking that the plenum is a really big **** you can turn.

Gotta run, cool to see the interest here.

Scott H

Given your background maybe you could help design a performance aftermarket intake for our cars in conjunction with one of the performance suppliers?

Whats the most economical way to make small-run manifolds? I realize "economical" is relative in this regard, but what's the point where metal/sand casting breakseven with hand welding pieces of tubing?

And just another question that has always stuck out in my mind. I once read that if you polish the inside of intake runners (or that area of the head) it will flow less than if you give the interior surface a certain amount of roughness. From what I remember the little bits of turbulence nearer to the surface effectively allowed more air to pass through. Any credibility to this?

Thom

I know it's a cliché but this is how sharkskin is and the reason similar surfacing has been extensively used in aeronautics.
Not sure to which extent it applies to intake design.

67King

I don't know that the market size would justify the cost, and you'd probably be really surprised at the lack of engineering a lot of them are interested in. Certainly can't speak for all, but the performance industry still seems to prefer to do things with trial and error.

When Ford did the Cobra R back in 2000, I think they made 300 of them? They outsourced the cylinder head casting to a small operations shop, but they still made them with sand casting. With teh emergence of rapid prototyping, making the positives for the sand molds would probably not be all that tough if the CAD work were done. So I would say if there was enough interest, a small batch of sand cast ones would be the ticket. But I don't know if there would be enough. You have to consider that there is probably a greater number of people in the market who would be as or more interested in the shiny parts/bling look of a fabbed intake than a more mundane but functional sand cast one.

You certainly can make a surface too smooth. The trick, though, is that really only applies to bends. What happens is that when air flows over a surface, a "boundary layer" of stagnant air forms. The smoother that surface, the thinner that layer. But when air needs to go around a bend, the thin boundary layer can't hold the air as well as a thicker one, and instead of following the curve, the air separates from the surface, and creates a large pocket of stagnant air. That serves to reduce teh cross sectional area available for airflow, which chokes the flow. Note, though, that it doesn't take much textures to give you a good surface. And teh less sharp the bend, the less of an issue. A lot of nicer heads will have CNC's ports, which is pretty smooth.

ehall

Great thread!

Paulyy

it's like a golf ball,

mythbusters tested the differences with the smooth vs rough surfaces.

had a golf ball and a smooth ball (same weight and size) and hit them at the driving range, the golf ball obviously flew and the smooth ball didn't get far at all, it just floated and droped.

obviously theres more to it but it has been explained here already.

333pg333

67k, no offense taken whatsoever, more, I just wanted to clarify my particular situation.

As you state, the issue is with the runners and tuning them. Unfortunately tuning is pretty much out of most of our realms so it winds up being a bit slap dash, or compromise with the stock intake. To clarify further, I don't have any empirical evidence as to the faults of the stock intake, but lots of anecdotal. Eventually you have to concede where there's smoke...

Just looking at the thread that Chris linked to, showing all the CFD modelling, makes me think that this would be the best way to pursue this. Not sure who has access to this level of software/hardware. Do you?
If this proves too elusive then just have something built that follows the greatest body of evidence and hope for the best. I might have some better options with all the brake booster etc removed now which opens up that side of the engine bay. If nothing else, it certainly gives greater access to the turbo!

I'd certainly be interested in being involved in having something made. Not sure what numbers you'd need to even begin to contemplate this exercise? Be great to get some feedback from someone that actually has the JME setup. Seems as if they're sighted once every Unicorn!

333pg333

George,

I hear you loud and clear. Watching road going EVOs on road tyres run times that are as fast as JET's times in his 3L 16v on full slicks is scary. To be honest, it's like cheating when you see these funny looking 4 door sedans wobble and wrinkle their way around the track but somehow seem to keep moving forwards very quickly. Not a lot of finesse but nobody gets style points against the clock!

Sorry to hear that you are still having problems with yours. Hopefully it's not too much longer. I've been off the road/track for a year and it's still only 85% done. These things always take up much more time and money than we ever imagine. What were we thinking.....

schip43

If it's not going terribly off topic.. How does an ITB setup fit in? Plenum would need to be made for a turbo application but aren't the runners usually really short on ITB setup's?

Rogue_Ant

Hrmm, I second the notion of 67King designed an intake manifold for the 944/951

333pg333

Good question.

George D

Thanks for the response. You know I love these cars, and my intent. The issues with my car is me wanting a reliable "perfectly" tuned car with no issues that can handle the power as easily as the original design.

Regards,

George

67King

ITB systems usually give the benefit of more streetability with a radical cam. The reason you think the runners are short is that the throttle bodies are right up agains the head to keep reversion from getting into the plenum. But, the runners extend beyond the throttle bodies and into the plenum. The ITB discussion has come up here before, as it was being worked on. While you do reduce the losses a little, I think it is, for the most part, a waste of money. You can reduce the losses a little more if you use barrels or sliders instead of butterflies in the setup, as you eliminate the plate and rod in the middle.

Here's a shot of an M5 intake that shows the longer runners going into the plenum.