928S4 Twin Turbo Final Design and Results

[Herr-Kuhn]

I figured some people over here might want to see the results of the latest 928S4 Twin Turbo system. This engine is built with Carrillo rods, Mahle pistons, Nikasil plated block, Elgin 65-6 reground S3 cams, PAS 1223L Beehive springs, Siemens 80 lbm/hr injectors, stock Bosch LH2.3 and EZK ECUs, Garrett GTX3576R turbos with 45mm Turbosmart remote wastegates. The engine produces over 900 flywheel HP on 93 octane pump gasoline with 21 psig manifold pressure.

[stepson]

Very Nice, John!!

[Herr-Kuhn]

Thanks, now my big push has to be to reproduce these items for my own personal car.

[stepson]

Originally Posted by Herr-Kuhn

Thanks, now my big push has to be to reproduce these items for my own personal car.

Hopefully, you will so busy recreating this for customers that you won't have time to do your own personal car.

[beran earms]

This is beautiful!!! The best would be in my car, second best go for a ride, third, I would settle for a video, hint hint.

[Herr-Kuhn]

Well, there is still interest in these systems, but the pricing is pretty steep to play all the way at this level. We now are doing the manifolds as castings and as well the turbos are GTX with remote waste gates, then the engine build on top of all of that. Still, at the end of the day, it's well worth it. Still cheaper than buying an 800+ RWHP 911 turbo that runs on pump gas (maybe someone can show me one because I think to get to that power level you need to be on race gas or E85..perhaps not with a 991 basis for the build?). Right now I have two more systems to build, one is a hybrid (old+new stuff) and the 2nd is likely all new stuff. Plus two 16V cars to upgrade to modern hardware (in-house catch-up projects).

The owner now has this car back in Boston. All I can say is with it floor-boarded on 18 psig at the top of third gear, it's sort of frightening... to say the least. It's a real monster of a car. It's not a car I'd want to ride shotgun in, that's for sure. The "low power" setting on this car is 625-640 RWHP on 12 psig, and these are all straight pump gasoline numbers, no spray, no water-meth, no octane boosters, etc. Also, these are just massaged setting on the stock ECUs, no stand alone or anything fancy past a custom MAF setup to work with the LH 2.3. That power will be adequate to outrun most new performance cars. All in all it's a pretty efficient system, considering the age of the engine itself.

We're waiting on some Dynojet numbers on the car. I've found my machine tends to run 6-8 percent off (lower) of what a Dynojet reads. My local guy here with the Dynojet was tied up when I wanted to run the car on there. With all of that said, it should be able to post around 900 RWHP on the high boost setting. I have a couple of data points on other cars between my machine and Dynojet that confirm that 6-8% difference. It's moot anyway, the car is bloody insanely fast on the road regardless of the power numbers.

Best of all, the thing still has air conditioning and cruise control!

Here's a video:

https://www.youtube.com/watch?v=38TwqSXIvb0&t=725s

[harborman]

Looks like quite a project from both engineering and building/testing. I am sure it cost plenty to do. I don't know what I would do with all that power except get in a whole lot of trouble. Guess I will just enjoy my 288 HP and be happy. I will say that installation looks very professional.

[JK McDonald]

Hey Herr Kuhn – Very professional twin turbo installation. I’m not sure what I’d do with a 900 HP setup but it would sure come in handy to have tucked under the hood at times…..

My wife and I just returned from a couple of weeks down in the Texas Hill Country. Spent most of our travels visiting back road attractions including an overnight stay at the old Presidio La Bahia Fort down near Goliad. As always Miss Purdy was well behaved and mingled well amongst the highway traffic, but it seemed like as soon as some road warrior came up from behind and saw the “Porsche” lettering along my rear hatch, we suddenly had a pickup blowing smoke and trying to pass. Yep, I agree with Harborman, even at 90 mph a 900 HP power plant on tap when coming out of a curve and onto a long straightaway would be handy.......

Michael

[Herr-Kuhn]

Thanks for the feedback on the build.

The owner reported back yesterday saying that he was able to hit 90 MPH in 2nd gear with it hitting the rev limiter at 8,000 RPM. Mind you, I'm not saying that I endorse this type of behaviour

The best thing about turbos is the Dr. Jeckyl/Mr. Hyde personality of the car. In cruise, it really is so docile that your grandmother could drive the car, assuming she can shift a manual with a slightly difficult clutch. On boost, it's a whole different animal. It's not a car for an inexperienced driver. My personal car makes 535 RWHP on the same dyno and it's fast, but not on the same plateau as this one.

This build isn't so much about 0-60 MPH, but more about 0-160 MPH. In the upper 1/3 of the engine's speed range the car is really incredibly fast.

The only real issue we've had with the car is keeping an A/C belt on the darned thing. Probably ultimately will need deeper pulley for the A/C pump and the stack.

[XLR8928]

Wow! those are some impressive Power levels, truly impressive engineering. I wish I had the time and gumption to do a turbo set up on my car. I just got lazy and bought a 'Vette.... but... there is still no substitute for my old 928.

[Herr-Kuhn]

Thanks. It's a decent spend to make this engine push these numbers...but then again it is on any engine so it's all the same in the end. Hard to argue with reasonably efficient displacement.