BAM! Twin Turbo S4 557 RWHP, 540 RW ft-lbs
 

I've been working out the tune on the 928 S4 Twin Turbo over the last several weeks. We strapped her down this morning back to the same dynojet that was used back in September. I could not be happier with the results:

557 Rear wheel horsepower
540 Rear wheel torque (in ft-lbs)
Manifold Pressure: 0.8 BAR (11.8 psig)

The uncorrected numbers were 565 HP/548 ft-lbs (I'll post both sheets)

I made it a point to make certain where the boost was hitting on the car...just a tick under 12 psig (my boost gauge is calibrated in BAR and the car was hitting 0.8 BAR).

Here's the list of essentials:

Again I want to be very clear here... no internal engine work was done on this engine whatsoever and it now has logged over 177,000 miles since it left the factory with the last 7,000 of that being under twin turbo power. The valve covers were not even lifted to install the twin turbo system. The engine has never been rebuilt or opened up.

Engine: Stock 928S4, 1988
Transmission: Stock 5-Spd with Limited Slip Differential
Cams: Stock 1988 928S4
Turbochargers: Garrett GT2871R Ball Bearing 0.86 A/R hotside, ceramic coated
Manifolds: Kuhn Performance Technologies, header style, ceramic coated
Intercooling: Kuhn Performance Technologies, Twin Bar and Plate Air to Air units
Fuel Management: JDS Porsche "Shark-Tuned"
Ignition Management: JDS Porsche "Shark-Tuned"
Mass Airflow Sensor: JDS Porsche "Super-MAF", blow through setup
Injectors: Bosch 42 lb/hr
Fuel Pump: Bosch "044"
Fuel lines, rails, etc.: Stock 928
Air Filters: K&N RU1500 breathing on Kuhn Performance Technologies Air Snout System
Exhuast: Dual 3" with Borla XR Race Mufflers (divorced wastegate pipes at Turbochargers)
Clutch: Spec Stage 3 Street Clutch..no stock single disc 928 clutch will hold this level of torque.
Turbo Lag: Yeah, right... ;)

The pulls were made with the car on the Dynojet Dyno with the exhaust on the car and air filtration system hooked up as designed. No "tricks" were done to inflate the actual horsepower or torque numbers. All pulls were made in 4th gear and only 4th gear.
Fuel is 93 Octane Mobil "Pump Gas", No Octane booster was used.

It would appear that 600 Rear Wheel HP is 2 to 3 psig away. She needs a tiny bit more fuel tuning at 3,700. We simply had to roll the car off the dyno due to time constraints at the shop.

One of the big benifits you get with turbocharging the engine is a very docile and mannerly "gentleman's car" when you want it. Stick you foot into it and you are rewarded with over 500 ft-lbs of torque by 3000 RPM which holds there all the way out past 5,500 RPM. It's a very rewarding car to drive because you can just hammer down to 1/4 throttle and the car takes off like a cannon shot.

These systems will be reproduced and will be for sale this coming spring. I've not yet decided on the exact manifold pressure but I'm thinking around 10 psig.

The turbocharger is the king of the forced induction jungle! Working hard, staying the course and being dedicated to this technology has paid off.


http://forums.pelicanparts.com/uploa...1196534108.jpg

http://forums.pelicanparts.com/uploa...1196534594.jpg

Great numbers John !

Here is a shot of the car on the dyno from earlier today...as you can see it is hard to get a lot of airflow through the charge coolers when you are using a fan on the dyno.

Thanks to Ken at Modular Depot here in town for the dyno services.

http://forums.pelicanparts.com/uploa...1196540818.jpg

What´s with the dip in power around 3700rpm?

OH my god are you going to get attacked over at Rennlist!

Don't worry- Randy V will be right there on the spot to protect you and your achievements.

Anyway, good work! Question: What is the lag like? My brother has a 2002 Jetta with the 1.8t, and the lag on that car is noticeable, but in the end the engine response is not much different from my own 1997 Jetta GLX with its' cammy VR6 engine.

Keep up the good work!

Awesome job!

I might have to get in line behind Hans for one of these systems.

Thanks guys...

It just needs a little more tuning in that area...the car likes a lot of fuel when the turbos light up.

Normy, let them attack. I don't need to justify myself or my work to those who have set out to destroy my reputation. It's really that bottom line simple.

If you look at the torque curve....you can see the turbos have reached full boost by 3,300 RPM. Lag is a relative term. The delay in the onset of boost is a very desirable feature that allows the car to be driven effortlessly around town....boost is just a throttle stab away. If I am cruising in 3rd at like 2,500 and drop the throttle open I have very appriciable boost before 3,200 RPM. There is not much that can hang with the car out on the street. If I was to give you a ride in the car you would not walk away saying "this feels laggy". The throttle response is excellent and the boost rolls on when you call it online. It's very balanced.

Holy smokes, 400HP at 2600 rpm and 500HP at a hair over 3000. Nice

Wrong line, thats torque I am pretty sure. ;)

Yep, your right.

To put things into perspective...the car is making as much RWHP as a stock 928S4 can make upstairs, but it does it at just 3000 RPM.

The one thing you really have to look at when you make comparisons is the overall powerband width. Nobody drives their car around hammered up on the rev limiter, therefore midrange and top end power are very desirable. You always have to select the next higher gear once you run out of gear...so where you drop back down on the torque curve tells a lot about how the car will drive out on the road. With this system you can just short shift the car and it is still wickedly fast.

Compared to the claimed "top-dog 928 HP" belt driven 928 boosting system, the twin turbo system is up an average of over 50 HP across the entire RPM band and up an average of nearly 70 HP when averaged over the "race" powerband (4000-6000 RPM). In some areas the twin turbo system is producing nearly 100 extra HP. On torque the story is the same, the twin turbo is making, on average, over 60 more ft-lbs across the entire powerband with an additional 70 ft-lbs when averaged over the race powerband (4000 -6000 RPM). In some areas there is in excess of 120 additional ft-lbs compared to the belt driven system. There is little doubt that the twin turbo equipped 928S4 can easily motor away from its belt-boosted competition in just about any situation. The above numbers are pure and simple fact and can be confirmed by the math. :D

With turbochargers you can be cruising in the vacuum and nail it and you've got all the boost you could ever wish for in a VERY short period of time. This is not a vehicle you let your friends borrow for the day...I'm very cautious with who I'll let drive the car.

I expect to release pricing sometime in January of 2008.http://forums.pelicanparts.com/suppo...eys/gitaar.gif

Way to go Herr-Kuhn.

I've been following your turbo projects for quite a while now and knew it was only a matter of time until you put up numbers like this.

Now you need to build a car that uses your new system, but with custom internals. Then you can really turn up the boost and put up some numbers never seen on a 928:eek::eek:.

Again, congratulations. The only problem I can see with your system is that I can not afford it currently. I still have a few more grand to spend on getting my mechanicals where I want them.

Do you have a website?

You should go to the drag strip and break 12s in the 1/4 mile to be the fastest drag 928 ever. It should be pretty easy to do with that kind of HP and torque.

Dragstrip launches do nothing but break drive train parts. I would be interested in knowing what the top speed would be in the 1/4 mile though.

I'm designing the website over the next several weeks and hope to have it up and going in January. Just a matter of time. I'll be sure to post a link here when it is ready to go. There is lots going on here right now...getting the workshop setup, new TIG and Plasma cutter arrive this week, working on the website, etc. I enjoy it, it's a lot of fun to think what it might turn into some day.

Actually, I was going to go on and strip this engine down to turn it up to 16 psig or so. That would be well over 600 WHP at that point, but I can't do that and build the business too. Still though, the attraction of 8.5:1 pistons, 16 psig and a few more degrees of timing is VERY attractive right now.

I talked with the dyno operator about the accelleration times yesterday...he tells me by the book my car should be able to go low to mid 11s in a 1/4 mile assuming it could hook up properly. I'm not a big fan of drags myself but it would be fun to find out someday.

So fabio when are you going to twin turbo your car!

It will be done in 2008. One way or another, it will be done.

Well triplet t is runing well.