Tim, it's interesting that the design even on turbo cars is still such that it allows straight pulses across. The picture was part of another post and it was meant to show how all the F6's turbo or not come with it. As of yet, there is no independent test showing an improvement and many knowledgeable people who say it does not show any improvement aside from seat of the pants. And others have felt a loss. If you have independent proof otherwise, cool. But all I have heard about is seat of the pants feel and that is all.

I know a few who build these engines that will disagree with you. So until people show proof there is none to show improvement.

John, in that thread of yours, after you fixed the leak, you indicated better feel and performance and after looking at your dyno, it does look to me like the IPD did indeed give you a slight gain at the top end. Maybe not the dramatic gain as expected, but after you replaced everything you did have a leak and this could have accounted for the loss. I also now remember BBI having done dyno with more impressive results on this plenum.

Hi, Others also say the same thing about a leak??I did state these below facts in my thread and I guess other people miss that part too?? :confused:
I said when I got home from the dealer'AFTER'the dyno test the idle went to a steady 1200rpm..
I also said it was a hot day and I took the highway home from the dealer and just ran it hard on Highway,probably when the hose came off,so I couldnt tell how it was in the other ranges.
It did idle perfect, 750 rpm after the install and on the dyno..I made sure everything checked out before the dyno pulls..I would never do a test if something was not right...One of the those 3 front left had side hoses popped off...I know it was put on during the install ..
Also remember the switch from a 68 mm to 74 mm TB in this..:)

Ok, but even you noticed more responsiveness and your dyno shows an improvement ever so slight. I may include this in my dyno tests to come

Not really.. the N/A motors have large cross overs with a valve. the turbo motor only crosses through the plenum.

There seems to be two sides to this story and there seems to be some proof on both as well. I don't think anyone in here sets out to prove that it doesn't work. However, one common denominator that all have stated is that there is definitely more responsiveness and feels like more power. So there has to be some improvement however so slight. I looked up BBI's thread and I fully believe they saw results. Also looking closer at the plenum, if it is like the one pictured, there is a line of sight from one side to the other.

I am going to be hitting the drag strip and the dyno, so I may get one and compare before and after.

The dimples actually create lift which in turn give longer distances, if the Cd is decreased, it would be minimal on that shape object.

Greg, do you have dynos or other comparable data sheets for the claimed 35-40whp/tq gains with just an IPD Plenum? These are indeed impressive numbers.

While intake flow is important (especially on NA cars), the combustion and expulsion efficiency would have the greatest gains, I've seen as much as 20-25hp max from a high quality, port matched headers/exhaust combo on the 996tt. I'd guess you could use that patented Y design in the header collectors and make mad power increases as well.

Btw, for conversation, what is the patent number of your Y design? I am interested in reading how this design is generating that much power.

Good points and I have heard from others privately that they lost power when the TB was the same size. The plenum that BBI tested had a 74-75mm TB versus the std 68mm TB, I can totally see the reason for the gain in power in the version, since that is a major difference in TB's, but this one listed above uses the stock TB.

Dimples or sandpaper will trip a turbulent boundary layer on a relatively smooth surface sooner.

The turbulent boundary layer has more energy and MORE surface drag, but it also keeps the flow outside of the boundary layer attached longer around the curvature on the back side of the golf ball (or whatever changing surface your trying to get flow to bend around).

The pressure drag reduction from delaying flow separation can outweigh the increased skin friction drag from the longer turbulent BL (in the case of the golf ball, it does).

Total drag drops, L/D goes up, ball goes further (or the intake du jour has less pressure loss, etc)

/aero eng rant off/

no comment

I am sure that losses in a 5 ft distance will be negligible with rough or smooth pipe. I don't think this is where the argument lies on either side. Do any of you wish to show psi losses for a 15 psi, 5 ft, 2.5-3 inch diameter pipe. You wanna bet that it will be low enough not to matter. The y-design from ipd makes sense to me, but the counter argument about bellows t-type system from people that know these engines better than I do is hard to counter.

Even the new GT2RS uses a T-type plenum instead of a y-plenum. Porsche knows it's stuff and they did not switch to a y, why?

Earl,

You are quite knowledgeable and apply it correctly. The vacuum test before the turbo... Intercooler testing... Reps to you.

I agree with you on the loss on pipe. I do not disagree with your last statement but if the power increases do not warrant the extra cost of manufacturing that design then the Value Engineer will put a stop to it. Like bolts instead of studs or gluing the coolant fittings

That last statement has a quantifiable value. We are talking about a limited production car with a sticker of 300k. I think that if there was any way that porsche could make the power delivery better, they would have modified that one simple piece. To date, not one factory flat 6 porsche, neither race nor street has it, not even the 956/962's. Just sayin. ;)

Hello,
The first day i installed the plenum and the 74mmTB,everything was fine but the second day i had an issue:when i start the car the rpm goes to 1000 then drop to 800 after 20 seconds which is normal,but just after running the car 15 to 20min the rpm become 1200 ,i checked all vacuum lines and did pressure test,didnt find any leak,Do you think there is a problem with the new TB?at partial and wot the car is running well.
Thanks.