924Board.org

[jseabolt]

Still thinking about this 924 purchase but just out of interest.

I have turbocharged two of my Fiats. One is a 1980 Fiat Spider w/L-jet and the other one is a 1987 Yugo with a Fiat 1500 engine, blown through a Weber 32 DFTA.

Here's the master directory:

http://s222.photobucket.com/albums/dd148/turbofiat/

Both cars have stock engines and drivetrains. The Spider is a 2 liter twin cam with 8:1 C/R running 7 lbs of boost. The Yugo has an 8.5:1 C/R and struggles to make 6 lbs of boost. Probably because the turbo was sourced from a Saab 9000 2.1 liter and is too large for this engine. Also still working on the primary jetting.

Both cars are non-intercooled and both systems were built from scratch by me. Except for the exhaust manifold on my Spider.

I have found these cars to be very reliable at 7 lbs.

The question is what sort of C/R would a 1977 924 have? Would it hold up to a 50% increase in HP (7 lbs of boost) like my Fiats?

If I were to to this all I would really need was the exhaust manfiold and turbo. Any other plumbing would be icing on the cake.

With L-jet the trick is to use a Malpassi rising rate fuel pressure regulator. These work up to about 7 lbs of boost. After that the mixture starts to lean out a bit.

I also placed a pressure switch between the O2 sensor and ECU so it disrupts the signal when the turbo kicks in. Otherwise the O2 sensor picks up on the extra fuel and tries leaning the fuel mixture out. PING!

The ignition trick is to use a GM 5 pin control module from a 78 to 81 Olds or Pontiac to provide 5 degrees retard under boost. These work with any distributor that uses a magnetic trigger. Here is one I retrofitted to a Bosch distributor on my Yugo turbo:

http://s222.photobucket.com/albums/dd148/turbofiat/GM%205%20PIN%20HEI%20module/

Could you use the same trick (boost the fuel pressure up) on a K-jet system as you could on an L-jet system?

[fiat22turbo]

8.5:1 for most of the US I believe. The others are 9:1.

Aside from the headgasket, and some cooling upgrades that might be needed, you should be fine.

http://www.connact.com/~kgross/FAQ/944faq02.html
_________________
Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[Khal]

[ideola]

^+1

The turbo exhaust mani will not bolt up to the NA head, at least not without modifications to one or the other. Essentially, the entire top end of the 931 is different than the NA. About the only thing in common is the camshaft. Head casting, valves, exhaust mani, dizzy (same body but different ignition curve), intake mani, throttle body, CIS, are ALL different.

I've stated such many times before, and will do so again here. I personally believe the quickest and easiest way to boost the NA is with a belt-driven centrifugal SC mounted in the spot where the 931 alternator is mounted. You'd have to move the CIS in order to make this work, but for this kind of project, that would be the least of the efforts.

Turbocharging is a lot harder to accomplish because of the challenges of adapting the NA exhaust manifold or replacing it. There are some old BAE ex manifolds floating around on cars and abandoned projects, but they're really hard to find.
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erstwhile owner of just about every 924 variant ever made

[ideola]

As for US-spec CR, early 77 had 8:1; 77.5-79 had 8.5:1, 80-onward had 9:1. All Euro spec had 9.3:1.
_________________
erstwhile owner of just about every 924 variant ever made

[fiat22turbo]

Check out the thread by DutchPug on mounting the turbo on the driver's side using the stock exhaust manifold ala Porsche 944 Turbo.

Not saying its ideal, but it's better than the crack prone stock manifold and opens the possibility of turbos other than factory.
_________________
Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[Raceboy]

[jseabolt]

Thanks for the info guys.

I still do not have this car in my posession. I've been having trouble getting the guy to return my phonecalls. He finally returned my phonecalls today and apologized and said he had been ill so we agreed we would try next week.

Getting back to turbocharging. I did not realize the N/A and turbo engines were different.

Most factory turbocharged engines are built that way. All I've had experience with are turbocharging N/A Fiat engines by building my own parts.

I got lucky and found an aftermarket turbo manifold for my Fiat Spider but had to modify a 4-1 Fiat F.I. manifold for my Yugo. Luckily the casting was good enough to where a SS exhaust flange could be welded to the cast iron manifold using a welding rod high in nickel content.

If I am determined to turbocharge this engine, then looks like I may have to do the same. Hopefully once I buy the car, I'll be able to see how the engine is laid out.

Also like I said I'm not that knowledgable on K-jet. L-jet can easily cope with forced induction with a rising rate fuel pressure regulator. I was hoping I might be able to do the same the K-jet.

[ideola]

Word of warning. Throw out everything you know from other cars, as most of it will not be applicable to the 924.

While you're awaiting the outcome of your pending purchase, might I humbly suggest some recommended reading on performance upgrades? This thread will provide you with 80-90% of what you'll need to learn to make an educated decision about whether or not to proceed with an attempt to turbocharge the NA. See particularly the forced induction section. It provides many links to other threads with details on how others have approached this unique problem on the 924 NA platform.
_________________
erstwhile owner of just about every 924 variant ever made

[jseabolt]

[Khal]

[ideola]

[jseabolt]

We will see. I guess it just depends upon how much work I want to put toward building another turbo system. I can see this being an expensive system if I had to hire out the work but like I said this would be the fourth turbo system I have built.

The K-jet system is my main concern because I know little about how to troubleshoot it much less modify it.

If this engine has a C/R of 8:1 and the engine is built strong then I can easily run 7 lbs of boost.

As far as turbocharging VS supercharging goes. I would not even consider supercharging a four banger. Superchargers are better suited for V8s and engines already making ober 200 BHP because they require power to make power where turbos used wasted power to make power.

I would supercharge my 08 Mustang GT before I would turbocharge it but would turbocharge a four banger before superchrging one.

Supercharged are expensive by the way. The cheapest system I've found for my Mustang GT is over $3000.

[fiat22turbo]

From what I understand, the K-jet system is similar to a carb in how it meters fuel. More air being pulled past the flapper valve, the more fuel, etc.

You can adjust the base pressure fairly easily to compensate a little bit. Ideally you'd need an adjustable WUR (whether electronic or manual) to fine tune the fuel further.

On one of the factory racing efforts they used a 928 distributor with two fuel lines per injector, if that gives you any ideas.

With a wideband 02 and a set of CIS gauges you can probably get it close enough to survive just fine at 7psi. Add an intercooler (or water/methanol injection) and you could probably get it to 12 or so without to much hassle. I can't say the same about the Automatic, but not many have done much with those other than use them as parts cars.

There is a guy in Australia (RC is his username?) that has a supercharged 924 auto that's he's made some changes to his automatic to improve its capabilities. I think he's posted some of his mods in the How-to section, might be useful to you. The blower install was home made and seems to work well.
_________________
Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[ideola]