epbrown01

Seeing John's "Goldmember" got the wheels turning in my brain. Take a 1980-1984 project car, rebuild the motor with 8.0:1 pistons like in the first 944 turbos, and add the turbocharger kit. The 944 turbo - stock - is good for 220 hp or so, and upgradeable fairly cheaply to 400 hp. A turbocharged 928 with similar pistons should be good for 450-800 hp, right? (Excellence has an article on a twin-turbo 928 motor used in a speedboat with 750 hp, iirc). Has anyone done this, and have a site where I can read about it? Searching for turbocharging on this forum comes up with John and little else. I'm not planning on doing it (maybe...yet), I'm just wondering about the capacity and feasibility of it - how you'd go about it, what it would cost.

Emanuel

Jim @ EuroWerks

Be sure and approch it thinking it's going to be expensive as hell and take alot of pics because I want to see it

Andrew Schauer

I've often wondered whether anyone has used two turbos from a 944 to boost a 928? From what I remember hearing, the 944 engine was mostly "half" of a 928 block and ancillaries. Fuel injectors, blow-off valve, etc, would be approximately the right size if you use twice as many for the increased number of cylinders. I'm sure someone has tried this already, but I've never seen anything like it in my 'net travels. Or, maybe I'm smokin' crack, and that's why it's never been done.
A big to all the fellows who have taken the massive amounts of time to boost 928's, both turboed and supercharged.

SilverSFR

The choice of turbo or turbos, new technology versus old technology is the easy part of the equation. The difficult and expensive part is how and where to run the intake and exaust tubing. With the 928, you have very, very little room to work with. The higher the boost presure the more important fuel and cooling play a part of adding to the expense. In 1986 to have mine produced, it cost @12,000 dollars. Now in 2004, what that amount of initial expence has given me is 40,000 miles of problem free driving. If you choose to under take the journey of boosting your 928, either turbo or blown, the money you spend will be in direct proportion to the amount of problems you will have in the future.

SilverSFR

Kaz

Three years ago at a Phoenix Porsche meet I spoke to the guys at PowerHaus about such a project. They didn't think it'd be too big a deal to do long as I supplied the car and the checks to make it happen.

ViribusUnits

This has been discussed to death. Maybe 3 or 4 times.

Bascily, it can be done, but there are so many details that are diffrent between the 928 and the 951 that you can't use the same bits. This means most everything is special purpose.

For example, the pistions are diffrent diameters. The 944 engines are all 100 mm, but the 4.5 or 4.7l 928s use like 95 or 97, IIRC. The exauste and intake plumbing are all diffrent. There is far less open space in general. Not to mention, the L-jet fuel system is not exactly all that helpful. Do a quick search, just about all the issues have been disscussed.

It can be done, no question about it. This isn't a new feild like it was in the 30s, but to do it right, you've gotta lay down some cash.

epbrown01

VU - Yeah, I read some of that in my searches, didn't seem like a lot of detail (though I got a laugh from a 2001 post by John saying he was done with turbo projects!).

My solution to the piston problem would be to bore the cylinders out to match the 944 engine, giving you a 5.0 liter. (I'd think the '86 pistons would be best, being forged instead of cast like the later ones.) A 5.0 would also give you better performance for low rpm driving, as you'd have more torque even before the turbo's spooled up.I think the space considerations would be reduced a bit with a twin setup as the two turbos would be smaller - ideally, I'd want little, efficient turbos to reduce lag at the expense of some top-end power. But again, just idle speculation.

ViribusUnits

If your going to do that, why don't you just use a 5l block?

And if your going to use a 5l block, why don't you just get your hands on a 5l doaner motor. And if your going to do that, why not get the 32v heads too, they should come with the doaner motor. They hold off detonation better, and flow better too.

And if your going to ue the 5l heads, you need the 5l intake, or a coustom made peice.

But to do that, your going to need the later engine computers, or a aftermarket unit. Eighter of which would probably be a good idea, because the L-jet system isn't exactly modern. It's pretty decent, but deffently late 70s technology.

Anyways, thats the way I see the problem.

James-man

Maybe a stupid question but what the hey...

If treating the 5L like 2 951 engines and doing 951 turbos on it, couldn't you just install 2 951 computers to manage electronics and fuel to get things right?

I ask because I understand that it can be tricky getting fuel tuned right on boosted engines.

sweanders

I think it would still be to far away from a 951 motor, probably easier to use some sort of stand alone management.

The question is why anyone would prefer to turbocharge a 928 when there alreay are SC installation kits that run really well readily available.

Drewster67

Times change I guess.

6 months ago I approached powerhaus - they said - NO. Not enough "interest" to warrant development. Not even a maybe ...........

Kaz

Wow, bummer. Well it wouldn't be the first time a business missed the boat on something for 928's would it?

chris0626

A standalone EMS is absolutely the way to go. You cannot, with any degree of certainty, make a computer that was designed for another car (951) work on a boosted 928.

All the standalones I've reviewed will let you control fuel, timing, boost, literally anything that can be computer controlled to begin with, as well as provide inputs for other related items (NOS, water injection, etc.). Prices can range from $1500 to over $4000, depending on who you go with.

Sounds like a 5.0l 32v motor is the best place to start. 2 smaller turbos will provide a lower boost threshold than a single larger one and you won't necessarily sacrifice top-end either... if they're properly sized. And, since the engine isn't revving into the stratosphere, the top end will be reached rather quickly.

Another note on turbo selection... you'll read a lot about the dual ball-bearing units now available which 'claim' to offer the best of all worlds (super fast spool with amazing top-end)... well, they don't. The boost threshold IS in fact quite low (more to do with sizing than anything else) but not supercharger-like (which is what some manufacturers claim). Their real benefit is boost transition. Once they start making boost, they SCREAM to the wastegate set-point (whatever that happens to be...). Shifting from one gear to the next, the turbo is right back at it, much quicker than a 'standard' bearing turbo.

Hope some of this helps!

Chris

ViribusUnits

And since your redueing the running gear of the engine anyways, why not think about a stroker crank?

Your probably redueing the conning rods anyways, so you can be sure you've got forged components. In that case, if your not starting out with a forged crank, or conning rods, you may as well call up the folks at 928intl or Devek, and get a stroker set for your car. If your not starting with forged components, your going to need to spend the money to replace them anyways, right?

The devek crank is suppost to bump it up to 6l, so that can't be a bad thing right?

Eh, it's just an idea, may not be a good one. More than a few rennlisters have though about what it would take to make the "ultimate 928." For the ultamate n/a 928, talk to Sterling.

chris0626

I don't think you'd need to stroke it if your boosting it. And if you keep your boost 'relatively' low, you shouldn't need to change pistons, con-rods, crank or anything else... this of course providing that you have your EMS correctly set up.

The hardest thing about turbocharging the 928 is the space for the exhaust manifolds/turbo's themselves (as someone previously suggested).