heinrich

Ceedee, may I recommend you read a few turbo books. Corky Bell (I loaned mine to someone or I'd loan it to you) wrote a LOT on the topic. All your questions will be answered and THEN if you come here, you can talk the talk. I don't think many here (myself included) know a whole lot about turbo's. Like Fabio says, many of the turbo guys FOR SOME REASON were a little harsh and so got run off the list. Certainly not by me.

Abby Normal

One of those guy's (Kuhn) left on their own accord. Mark R. being gone is entirely against his will, and I have no idea what M21 has done to FI the 928 or if/why he is banned, so really can't comment on him. And because of some recent incidents, I likely will not be sharing much info on my car here either... A dyno sheet/timeslip will probably be about the only info I post. You'll have to look elsewhere to get detailed info..

heinrich

Abby my brother, you are among friends. Say your say, post as you want. I don't respond to baiting etc. it really has helped me

hans14914

The only "problem" with an twin charged system, is that you need a roots or preferably twin-screw super to make it work. There is not a lot of space on the 928 for a large format super like this. DR has made this format work very well, but it would not be practical to add turbos to his system, as they would provide limited assistance without opening the motor... the 928 engine cant even handle the full boost of a smaller twinscrew without dropping the cr. Plus I doubt the plumbing could be made to fit. I have been goofing around with twincharging for several years. To be honest, its really generally better to just have a well designed single forced induction option. My twincharging experience is with audis, as they have a strait-5 motor, and tons of space for both. They area also built for boost, and the small displacement makes it easier to match turbos and supers appropriately. I would love to see someone try to do a twincharge system, because all 928 development is good development at this point, but in my experience, creating a twincharge system would cost at least $12k in parts & labor & tuning, even if you did most of the work. That said, if you want to give it a try, I have the right superchargers lying around for the job: IHI twinscrews from the 32 series amg... they have native outputs of up to 14lbs, very efficient, and clutched which is necessary for twin charging. They are also fairly small.
Hans

RyanPerrella

Nicole,

I know it wasnt a production engine, they used it for hil climb cars or early rally efforts.

Its too complicated to sell in a production car, I thought i made that point.

TAREK

Again, with enough time and money, nothing is impossible, although the whole effort may be pointless. Physically speaking, it is possible to relocate everything forward of the timing belt covers to the rear of the car which would leave plenty of room for a turbo system. You can also eliminate the power steering pump and air pumps. I installed an electric power steering pump in the rear of the car, but did not replace the air pump. This allows for even more room for plumbing. In fact, there is so much room, I thought of installing a second engine in there, coupled to the first one at the crank !!!

Again, it's all about time and money available - and some compromises here and there. Anyone expecting substancial more horsepower than stock at low budget is setting themselves up for disappointment

123quattro

I'm big into turbos. I just don't have one on my 928 yet. I can give rides in a 500 hp 20vt Audi though.

Courtshark

As a Saab tuner, I'm very familiar with HO turbo set ups (my 88 SPG flies on 25 psi of boost from a custom turbo). Any 928 is a prime candidate for turbo charging given the strength of the engines and transmissions. This company seems to have the right idea:

http://www.928turbosports.com/index.php

I'd add water injection to the stage 2 kit, blowing the mist right into the IC outlet. For those figures they claim (see dyno sheets and 1/4 mi runs) that's an exellent value over supercharging.

Doing both a supercharger and a turbo is overkill. You'd be better off coming up with a twin turbo system with staggered size turbos, like 300ZX turbos. There's also new variable compressor wheel turbos, where the blades expand after a certain RPM level is reached. Lastly, Saab has worked on an electrically pre-spooled turbo to eliminate turbo lag. All of this could be worked into a 928...

Fabio421

The staggered turbo setups seem to never be enough for their owners. Most speed freaks replace them with a larger single turbo.

I have never heard about the electricly spooled turbo. That sounds interesting. Tell us more. I don't see where its really necessary with a properly sized turbo. Especially now with the full ball bearing turbo's and lightweight ceramic impellers.

Courtshark

Bigger turbos tend to have more lag; the bigger the wheel the harder it is to spool up, generally. I would think a staggered system set up properly would be more effective and powerful than a single, unless the single is a massive turbo.

I can't seem to find a detailed link with info on the electrically spooled turbo. I learned about it from one of the engineers at the 9-3 Sport Sedan launch in Washington, DC. (That day, became one of the first people in the US to drive a 9-3 SS Aero. 6 speed... joy. Loved that car. Might buy one here soon... Anyway, that car is a "drive by wire" throttle set up, and the turbo is hooked up to a small electric motor to that is connected through the engine management system. Pretty ingenious design. Wish I could find a link... odd that I can't. The engineer was pretty excited about it. Maybe they couldn't get it into the production cars. The cars we drove that day were all factory direct, and in some cases, not yet finished! I'll keep hunting for a factory link.

sweanders

Come on now, how hard can it be to spool a turbo with the exhaust from a big V8 spooling it.

FlyingDog

If you're talking about twin turbos, each one is like a 951. Ask the 951 guys about spooling up their turbos. If you're going with a single, that would be one massive turbo to spool up to supply enough air for the 'big V8'. I think asymmetric turbos is the way to go. The problem is mangaging the changover.

Most sequential (symmetric or assymetric) production turbo systems use extremely small turbos and small piping to spool up as fast as possible. There isn't much leftover room for bumping up the power. People go to huge single systems either because they just want to brag about peak dyno numbers or they're drag racing. Either way, a complicated dual system doesn't help them.

sweanders

No need to ask the 951 guys.. I've got two of them..

FlyingDog

D'oh. I knew you had a 4-banger, but thought it was non-turbo. I was too lazy to scroll to your sig while replying. Feel free to talk to yourself about spooling.

sweanders

Ok, spooling is not an issue on a 2.5 liter 8 valve 4 cylinder with a stock turbo. It will be even less of an issue on a 5 liter 32 valve 8 cylinder. If I were to turbo a 928 I would contact Herr-Kuhn since his setup is very attractive.