9x8

That's what I'm aiming for, actually.
Completely stripped down with zero sound insulation, rollcaged and so on.
Will be used as a weekend summer-only car, which can also work for track days and DE's.
I do have other cars to use them as DD.

And yea, it's not like I have $100 to spend on the whole car, I just don't want to spend too much on any individual component.

danglerb

Ah, the mythical "cheap" track car, usually not too much more expensive in actual practice than the cheap nice 928, money is just spent in different spots. Except for the bone stock, buy it in nice condition, put on race tires and go (see the "brown car") a track car is worth maybe twice as much as a same model street car. OTOH much of that worth is from the labor to strip out the car, and fiddle with all the bits that make it go a bit faster on the track.

I've got the same basic plan, but with a more modest HP goal. Once you strip a 928 down to the bare bones the weight drops down to the 2800 lb area with rollcage and racing seats, and it doesn't take that much power to go pretty fast (see 928 estate lemons car). I plan to use a Euro hybrid NA motor, Euro S2 heads, US S3 short block, hot rod higher lift welded cams with 951 valve springs, and expect to have enough HP and torque that big cheap tires will be spinning too much.

Iwanna928

Danglerb that would be a lot of fun!

Build a hybrid. Is it CIS? You mentioned stand alone. Could look into unwired tools. Controls CIS for boost up to a bar. 911 guy's have had success with it. Mid mount the turbo, nothing fancy in regards to manifolds and might just not get as hot!

Very doable!

Alan

I think the problem here is the idea of a budget turbo system - home made out of readily available parts...

Available from where?

The issue with a 928 is not so much performance though that costs more money - the biggest issue is space and construction challenges. no bolt together system can fit - so you are talking custom made to very tight tolerances... this will never be inexpensive due to trial and error and materials and much worse if you have to pay anyone else to make it for you.

I'd say go with a proven system... considering all this $11K is inexpensive (just not cheap). I don't think you will be able to save much money and may end up just creating lots of very large paperweights.

I know this isn't what you want to hear - but I think its the truth.. as borne out by real life experiencves here on rennlist.

Alan

mark kibort

just go NOS. you can get a real nice 100hp adder system for just around 5-700. put the button on the dead pedal and you are all set. no moving parts, just power when you need it. bottles cost $40 to refil and give you about 14 x 12 second WOT runs. I used to use it at the track and it would last 10 laps by using it only on the straights.

ptuomov

This was when racing your "stock" 928? Did you ever get caught? ;-)

ptuomov

...and my crystal ball shows a hefty price increase to the flagship twin-turbo system.

Roy928tt

From my perspective, and remember I've done it.

If you can fabricate or get someone to do it for you for free, you could create a tubo system for less cost than Johns. However if you have to pay anyone to do things for you, Johns is the way to go.

By the time I was 'finished', parts plus my labour @$45/ hrwas well in excess of what I could have bought a kit from John.

Would I buy a kit ? probably no, it was a personal challenge and an engineering exercise I set myself.

I have learnt from what I did and would do it differently, were I to do another.Study carefully what people have done and learn from this. This means using 4 valve heads because they make heaps more power!

Good Luck, Best Wishes Roy

9x8

Guys, thanks for all the input.

Guess I have to think about it some more. Will prolly consult some of the local "turbo-guys" to get an estimate of what fabrication costs will look like.

Bart-Jan

Nice to see everybody’s opinion! I’ve also thought about a DIY turbo set-up for my 928. The cheapest and probably easiest option I could think of is to build a rear mounted turbo, at the space where the rear muffler used to be. There are some guys that have done it before…


Expected disadvantage: turbo-lag; however, this is said not to be much of a problem, as an intercooler is not really needed, when the compressed air in the long inlet tube under the car is made from aluminum and can cool the air.

Biggest advantage: due to the cooler exhaust gasses, it would probably be possible to use a turbo from a big turbo diesel engine, or maybe two of them (reduces lag even more). These turbos are much cheaper to get secondhand, since there are much, much more nowadays.
Do a search on PPCmagazine to find out more; they did a few items about this a few years back.

danglerb

I will use a US 85/86 set of LHjet 2.2 brains at least to start with. Its the easiest path with a Euro S2 intake and MAF, and the Sharktuner works with it, which I think is essential to accommodate serious change. No boost planned, just motor and cam.

ptuomov

Actually, you could use variable geometry diesel turbos that nearly completely eliminate lag. Diesels have those, only one production gasoline engine so far. The reason being that the mechanisms can't take the heat of gasoline engine exhaust. But that's not a problem in the rear.

The "cold" side pipe under the car could also have cooling fins, which would make it like an inercooler.

9x8

Rear (or maybe mid) mounted turbo is not out of consideration yet either.

But the main question remains: is the whole initial idea of hybrid engine (euS top end + S4 bottom) impractical?
Colin recommends just using stock S4 engine, but do we have any different opinions on this subject? I've seen SC'ed S4 engines reliably function under ~0.6-0.7 bar boost, but will it survive the same amount of boost from turbos, not supercharger?

The idea of lowering the compression by building hybrid - I want to be on safer side when tuning the engine, and to have some potential head room for increasing the boost.

Darklands

Using a cayenne turbo engine and after market ecu is maybe the easier approach .
You need a new oil pan , that´s for sure .

9x8

Or, using Panamera engine instead!
AFAIK, Cayenne's engine won't fit in 928.