John..

The header is somewhat over rated for forced induction. Sure, there are 951s making over 400 rear wheel, but how much boost are these cars running? 18-21 lbs is my guess, and probably like 6,800 RPM to make it. Keep in mind, the Callaway I upgraded made 360+ RWHP at a very low RPM with moderate boost. It will make more once I install better cams, I'm projecting another 40-45 HP. As for dyno sheets, check the Bastard's. I expect this car is well within the ball park and to be honest it is a lot more fun to drive since the turbines are smaller with a tighter A/R. Keep in mind I am starting with the lowest HP 928s ever built, with the worst camshaft profiles. If I do another project, it will be 32V S4 based.

Why more for the turbo? In my mind it is a more desirable package, docile and quiet when you want it to be and on full tilt when you need it to be. And, able to pin the boost gauge at 3000 RPM in high gears. How about dialing in the boost from the cockpit? Turn it up on the race gas, turn it down on the pump fuel. Turn it way down for valet parking. Look at the success of the 917 and R8. Both wear turbos.

Richard, why don't you call Reeves, he now lives in Laguna Beach and I'm sure he is living quite a nice life after building 500 some odd Callaway TT Vettes. Let me tell you, Mr. Callaway is quite an interesting man and has made some very interesting automobiles. I get it straight from a very reliable source that he was on a team of people that VW gathered to discuss getting into F1 quite some time ago. This is fact, Reeves was and is highly respected. He is also one hell of a business man, to work the deals with Alfa Romeo and Chevrolet when he did it was amazing. Chevy contacted him after one of Reeves' GTV6 Alfas chewed up a stock Vette during Chevy's testing and the rest is history. Do a search on the Sledgehammer Vette. I'm not saying my car setup was perfect, but for 1983 it was one nice ride. My work just updated it to year 2000+ technology.

Chris, I totally agree with your comments. I did not set out to build a track car to make the absolute most peak HP, as this is self defeating. Like you, I live in the real world where the car has to perform on a day to day basis. It is not a trailer car, but a nice driver. The goal was a sleeper system that could be easily installed without cutting the car to pieces to do it. Aesthetics was also important and there is not one forced induction system for the 928 out there that looks as stock as mine when you lift the lid. I looked into Garretts, but decided to go triple K to save some money. If I do an S4, it will have Garretts for sure.

Richard, I will work on getting you the dyno charts as soon as I can get to it, but this car might go on a load dyno instead of Dynojet so comparisons might be hard to make.

Somebody please show me where I can get a full MAF conversion for $200. The sensor alone costs that much the last time I looked.

Jim bailey - 928 International

The words Porsche and Turbo have a long history and in many circles if you said, I got a Turbo it was understood that it was a 911/930. The fact that a new 996 twin turbo sold for about $120,000 plus might add some value to being able to mention having a Porsche "twin turbo"...........There is the perception that turbo boost is "free", capturing energy otherwise "wasted "as exhaust which has a lot of appeal .

blau928

John,

Don't take it to heart, but I know quite a bit about Mr. Callaway, ever since he started making 2002 BMW kits in his garage in Old Lyme CT.... to past his design of the Aston Martin 5.3L V8, and other projects that you mentioned..

I am not putting your system down, just asking a fair question... Granted, I am not a certified engineer as yourself, I'm just a guy with a barn, some "excess parts" and too little spare time.

Anyway, enough said, this is getting way out of proportion, just because I asked you for a dyno sheet. A simple no, I don't have one would have sufficed. If you and others have something to prove, then be my guest. From now on, I will refrain from asking questions of those who IMHO are in this "mindset."

Enough said Cheers,

chris0626

Tim,
I don't think a sequential-type system would be possible on a v-type engine (without some SERIOUS plumbing and its associated lag). The only sequential-type systems in recent memory are from the Mazda RX-7 and the Toyota Supra. A smaller turbo spools first, starting the boost 'wave', the added pressure then spools the larger which adds more pressure, etc... With the turbo's on seperate sides of the engine bay, 'feeding' one from the other is almost an impossiblity. FWIW, most 'upgrades' for either of the above-mentioned cars do-away with the sequential-system in favor of a larger single setup (FAR less complex).

Jim,
All other things being equal, I would agree that turbo boost is, in fact, free. Plus, saying you have a twin-turbo Porsche is definitely WAAY cool!
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A supercharger requires a direct connection to the engine (pulley & belt). So even when you're not boosting, your motor is still spinning that extra accessory... a price you pay in mileage via parasitic losses. Granted, technology has come a long way, but the losses are still there. Turbo's, on the other hand, suffer from none of that.
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Richard,
Relax We all need to ask questions and find out what works and what doesn't. It's all for the good of this community of 'ours'.

Callaway isn't the only turbocharging resource around. There is no 'be all and end all' of this kind of information.

Jim bailey - 928 International

Chris..."All other things being equal, I would agree that turbo boost is, in fact, free." The point is all other things are NOT equal with the added back pressure and greatly increased heat forced back into the heads and exhaust valves. There is no free lunch except at the Sharktoberfest Sat Oct 23rd .

chris0626

Jim,
The cats and mufflers are more restrictive than a turbocharger. Often you can run an exhaust system that is so free-flowing (non-restrictive) that the turbo being in the exhaust stream isn't an issue at all. Why would you go to all the trouble of adding turbos and not change the exhaust?

As for the added heat, yup, absolutely. But that's why we have intercoolers. Water injection is another a great way to combat detonation (in ANY boosted application--especially if you've also got a high compression ratio).

Unfortunately, I won't be able to attend the 'Fest' this year. Hopefully by next year, things will turn around a bit

Red UFO

John,

I certainly couldn't afford a turbo now. But down the road I would go for one. You might consider makings extras and shelfing them, or having 928int, devek and others help market them. I'd like to be able to get one later on, and hope they don't become to rare. Make 100 plus and the sharks will come and bite when the time is right for them.

Jim bailey - 928 International

Let's see 100 turbo kits at $9,280 retail equals $928,000 just to test "Build it and they will come" even if the cost is far less it is a major investment. Many, many people want a super,turbo ,stroker, GTS .......... that is the easy part ,wanting !

M Danger

as far as exhaust you'd definately want the most free flowing you can get. With stock 2.5 in tubing you certainly dont need a muffler. And many people pass emissions with OUT a cat.
I dont use a muffler, ive replaced it with a straight pipe and a megaphone(no not a rice boy part) to give sort of a venturi effect.

besides you can get a 500hp NA, for all that work, i want alot more.
Oh and yes 951s have good area under the curve, and no peak hp is NOT a 6800 rpms.

John..

Rich...I will get you the results. You started the mud slinging on this one. I'm just stating my side.

heinrich

I've not seen 500bhp n/a anywhere. Stroked 928's make somewhere near 450 or so. IIRC. Supercharged 928's make 500+.

blau928

Heinrich,

I have seen a 565 RWHP 6.5L 928 measured on a Dynojet. I drove in the same car when it had 500 RWHP Laguna Seca, and Thunderhill.

heinrich

Richard, I am impressed.

blau928

Heinrich,

It is the DEVEK car, and the 565 NA Hp was with Louie Ott's Individual Throttle body intakes. Some very well engineered and finished parts.

Prior to that, it was with a stock TB/Intake, using a stock air filter....

It is an insanely fast car, and I think anyone who has been in it would attest the same.


John,

As I said yesterday, I consider this matter closed, and will not discuss it any further with you.

John..

Re on the oiling. Oil is taken from the thermostat plug for the oil cooler and runs through two braided oil lines to each turbocharger. The oil then is drained out of each turbo and collects in a small sump. Finally it is pumped back into the engine with an electric gear pump. Pretty simple actually. Unfortunately, the pump is necessary, but the sump is a nice place to collect blow-by vapors off the case. All in all it works pretty well.

Whatever...., all this talk about stroking to 500 HP would have to be done to a 32 valver or big vlave 16 vlaver. I selected the 4.5 liter US because it is the 928 that needs the most help. 375-400 HP from 220 is a very healthy gain. My design concept applied to a 5.0 liter S4 will be a healthy force and just might become a reality next year. Who knows, I might even design it with an air to water intercooler!

Gotta run I have a short block to build this weekend! Pictures to follow...