911 cis vs 930 cis
 

Is there a difference between a 911 cis and a 903 cis?

Yes. I happen to have both. The fuel distributor for the SC will run you a few hundred bucks used, for the Turbo a grand.
Turbo injectors are screw in, (early) SC are pressed in.
Turbo runs dual fuel pumps, SC single.
The two systems components are physically in different places, probably for turbo and intercooler placement issues.
SC uses individual cylinder runners, turbo has one manifold for all.
No air box for the turbo, only a very large air filter housing.
I'm sure there are more differences, this is off the top of my head.

I have owned and worked on a '78SC and a 930.
In principel they work the same but mechanically they are very different. The SC is an updraft system and the 930 is a down draft system. Warm up regulater and auxillary air regulater appear identical.
Bob W.

So my point is, if I install a turbo in a 3.O CIS, the system will manage well the .5 boost I want to use?

You can't install a turbo on a 3.0 CIS system. Maybe with some(lots) of custom fabrication you can use the 3.0 CIS system as part of a butchered injection system that you might get to work. It would be easyer and cheaper to use the complete turbo iduction system already designed to flow properly with a turbo.
Also, turbo heads are made of different material to withstand the higher temperatures of boost. So...think carefully about boosting a non-turbo engine.
Bob W.

I don't know the limits of the SC CIS system, but 0.5 bar does not seem too radical. The 3.3T CIS system is overdesigned for racing, longevity, and modifications up to around 400HP.
This type of conversion or modification has been done. I have seen pix and articles from the early 80's on the subject.

I have also seen an article that shows a turbo installed on a 3.0 CIS engine. I think it was a stock engine running low boost. I think it was producing around 300 hp.
What I should have said was, it's not a bolt on installation unless you use stock Porsche turbo parts. It could be a bolt on with an after market turbo kit that has all the pieces that you need in the kit(the pieces are already fabricated).
Bob W.

[This message has been edited by Bob W. (edited 06-08-2001).]

Marcello - have you considered a supercharger? That kit is available and close to a "bolt on". I don't know of any turbo kits available for the SC engine.
More options become available if you are willing to give up your CIS for some type of EFI.

Is this true on the 964s and the 993s as well? The reason I ask is because a lot of big name tuners base their 650+hp turbo engines on the NA engines. Apparently the head design is more efficient on the NA models or something like that but if they are made of different material then it doesn't sound very smart.

0.5 boost would give you about 33% more horsepower. This works out to about 60hp more for a 180Hp engine (total of 240hp).This assumes no intercooling. Temperature after compressor would be 36C higher than ambient at 0.5 boost.

The compressor would have to be slipped in between the fuel meter plate and the throttle body. You would have to cut the boot between the two and duct in the compressor.

I have thought of this. I have a turbo I got for free from a jetta diesel. I'm sure it could give me 0.5 boost.

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Tony
'78 911SC

Hey Rarly, how much HP do u get out of a supercharger?