jeffnudd

Ive been doing some hunting recently because i have the engine out of my 964 and i came across a bit that mentioned putting on a plastic manifold apparently from a 993 which fits directly onto the 964 motors.

Questions:

Does it increase power if so how much?
Does it really make the engine sound better?
Are they available reasonably cheaply in the UK?

I have a alloy inlet at the moment whitch is part of the cars originality and wondered if it was really worth changing?

When i changed the heat exchangers recently that changed the note of the engine completely i was really surprised.

1990-964

I thought about doing this as bench racing legend has it that the plastic intake makes more power. This is actually a 964 intake from I believe 92' on, not a 993 part. that is a whole different setup. As I inquired about the value of doing this I came to realize that it may flow a bit better due to a smoother inner passage surface but the trouble and expense would not be worth it. Now converting to a 993 Varioram, that is something that seems worthwhile.

joey bagadonuts

I run with a number of 993's and they don't seem to deliver a whole lot more with regards to straight-line acceleration. These are stock class race cars, so mods are limited to intake and exhaust (chips, too, for the prepped 964's) and the difference in hp is negligible.

An exhaust swap--maybe to 993 heat exchangers--is probably a better route for more power. What did you say you switched to, Jeff?

1990-964

Joey,
Do you have more insight on the conversion to 993 heat exchangers? I have heard both great and no real gain. Was about to make the swap a while back but got steered away from it because of dubious power gains. Sorry to the OP for hijacking this thread.

joey bagadonuts

No firsthand insights but I am aware that the 993 racers I know use stock heat exchangers along with cat bypasses and Fabspeed Supercups, i.e. straight pipes all the way through. As you probably, this "upgrade" is recommended by Steve Weiner and Bruce Anderson and there's also an RSA equipped with 993 exhaust putting down 273 rwhp with SW chip (dyno info at bottom of page):
http://www.911chips.com/c2chips.html

For a street or dual-purpose car, I'm inclined to believe that this may be a worthwhile swap. What was the push back you heard?

PS: For track cars, that Supercup set up puts out a sound that is simply hard to beat.
Fabspeed 993 Supercup and Cat Bypass Pipes (takes a minute to load but well worth it)

race911

Love how an exhaust change and a chip on an otherwise stock 3.6L can be within sniffing distance of the 3.8L Steve built for the yellow car..............

Another data point, anyone remember Cervelli's yellow 993 he club raced in the early part of the decade? At Laguna, he could pull me by less than two car lengths versus my RSA that was factory stock down to still racing with the cat in place.

Ditto my observation from two weeks ago, again at Laguna, where I could only pull my current 140K factory stock RSA by a similar distance with the yellow car.

These are all 45-115mph runs.

Geoffrey

The 1995 993 uses essentially the same plastic intake as the 964. This may be what you are thinking about. FWIW, all of the stock 964s we've had on the dyno fit within a 5-7hp range.

1990-964

I would not so much call it pushback but more a lack of any quantifiable results. I had a conversation with Bruce on this very subject and while he was sure it was a source of increased power for the 964 engine he had not really found anyone to do the conversion. I also talked to Joel Reiser about this and don't remember getting a definitive answer either. I remember a few other skeptical opinions from sources I can't recall anymore, but there was enough doubt to keep me from investing the money in a swap that may not yield any substantial results. If I knew that it would provide the lions share of the increase in power between the 993 and 964 I would be more likely to do it but I am not sure if it is really worth the effort and cost. I have even spoken with Steve Timmins at Instant G, and while he makes the typical horsepower claims, it is still a fair bit of money for something that may just be bench racing legend.

Geoffrey

THe 1995 993 found 25hp through lighter recpricating mass of the engine internals, camshaft profile, free flowing exhaust, less restrictive MAF (vs AFM of the 964), and engine mapping. Judging from the difference between the 964 street and 964 RS, 1/2 (or 13hp) came from just the engine mapping. I suspect the majority of the rest comes from the better 993 exhaust system.

jimq

My 91 built 09/90 has the plastic intake.

joey bagadonuts

Did you not find the 273 rwhp somewhat compelling? That's over 300hp at the crank, right? And, as Geoffrey suggested, it seems unlikely that the SW chip, alone, was responsible for that kind of power.

As Ken mentioned, these cars in stock form are very formidable. Last Summer, I instructed a PCA member in his bone stock (except for g pipe) 964 at Road America and was amazed at the top speeds this novice reached. He was just a few mph slower than the race cars (I was actually a little scared going into the braking zones).

I'm not sure there's much gain from the intake side without going with a MoTec or similar upgrade. I've had an Autothority MAF on my car and was completely underwhelmed. The exhaust changes, however, definitely "do something" for these cars. Whether it's a cat bypass (yes!), cup/g pipe or high-quality headers, the improved power delivery and responsiveness is noticeable.

YMMV. Have fun and be safe!

jeffnudd

I sounds like i should be going the cat bypass route as there seems to be a lack of evidence or very little HP on the plastic intakes like someone mentioned is it really worth the investment, and how much can it cost?
For the lucky ones who already have the plastic intake when they were built at the factory i'm assuming they are still 250hp stock which makes me think there could be no difference at all?

When i changed the heat exchangers i replaced them with the original Porsche set as i was in the middle of solving a problem and didn't think of using 993 exchangers. (more interested in solving the gas in cabin problem)

NineMeister

Jeff, didn't I read a thread where you were asking about rebuilding your engine? The bottom line is that a fresh rebuild with a face skim & proper valve job on the heads will easily make more power than changing the intake manifolds.

As for fitting the 993 exhaust onto a 964, the problem that you have is with the opposite hand exhaust flange alignment of the RHS 993 heat exchanger to the 964 head, so without cutting and re-welding the flanges in the 964 position they will not fit. Furthermore, even if you do get them to fit I doubt that they will yield any more power than stock even with a live remap because your fuel injectors will be running flat out to keep up with the demand....

Hope this helps.