pbs911

I am installing a 964 motor in my 78SC and using the 993 exhaust manifolds. A switch-stud adapter is being made by a gentle in Germany that allows the 993 exhaust to bolt right up to the 964 motor. This would allow you to run the 993 cat and and possbily mod some mufflers or run just the cat. The I am going is to have pipes welded up from the 993 heat exchangers to a Factory two out early muffler. Even with the early muffler the oil line will be too close for comfort so I am using the pre-74 "question mark" oil line.

Ruairidh

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by johnfm:
<strong>Is the 993 twin outlet exhaust any better than a 964 system with cat bypass and primary bypass??</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Exactly the question I was going to ask....

Kevin

Yes, the 993 exhaust will out perform a Cat bypass and muffler bypass pipe. The reason is the tuned collector, or header system. The 993 system is not a equal length system that many tuners offer. Instead it is a factory designed system that on a 993 it offered a 27HP increase over or 964's. Yes, one has to give some merit to the hot film mass sensor, but all in all for a Cat system it's hard to be for a minimal investment.

Kevin

pbs911;

I would caution the use of a bolt on adapter. It is safer and easier to cut, flip, and weld the ears. It is very simple. If you have paid for them your stuck, I'd rethink the process.

Kevin

With the emails that I have received, there seems to be alot of interest in this conversion. I am putting a DYI together. I will also extend the offer to LOAN-LEND my jig, to people that take on this little endeavor. It is a small contribution to further our cause.

Ruairidh

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by Kevin:
<strong>Yes, the 993 exhaust will out perform a Cat bypass and muffler bypass pipe. The reason is the tuned collector, or header system. The 993 system is not a equal length system that many tuners offer. Instead it is a factory designed system that on a 993 it offered a 27HP increase over or 964's. Yes, one has to give some merit to the hot film mass sensor, but all in all for a Cat system it's hard to be for a minimal investment.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Thanks for this Kevin, you've now really caught my attention and if you are able to put together a DYI that would be great!

RSAErick

<img border="0" alt="[thumbsup]" title="" src="graemlins/bigok.gif" />

Jeff Curtis

Kevin, you took the words right out of my mouth!! ...I was going to ask you if you'd loan your jig, way cool!

I am soon to undertake this task, when I'm ready to go - hopefully you have the jig on hand to loan.

Kevin

Jeff;

Have you started to collect your parts? Are you going to use the CAT? Email me when you need the jig. Also, guys I have the fiberglass molds that I made for the left side extension. That was a project, but it was fun doing it.

Christer

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by Kevin:
<strong>Yes, the 993 exhaust will out perform a Cat bypass and muffler bypass pipe. The reason is the tuned collector, or header system. The 993 system is not a equal length system that many tuners offer. Instead it is a factory designed system that on a 993 it offered a 27HP increase over or 964's. Yes, one has to give some merit to the hot film mass sensor, but all in all for a Cat system it's hard to be for a minimal investment.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Kevin, there were other changes in the 993 engine department that may contribute to the slight gain in power over the 964. What makes you think it is all down to the exhaust?

Jeff Curtis

Kevin, I haven't started as of yet, but if you know of a good source...turn me on to it! Thanks for the offer, will certainly take you up on it...when I get my act together!

It would be cool if I could just send the right-side heat exchanger to YOU and have to modify it!

My main issue right now is getting the car back on track...OOPS! <img border="0" alt="[icon501]" title="" src="graemlins/icon501.gif" /> ...I mean the road. <img border="0" title="" alt="[Wink]" src="wink.gif" />

Once I achieve that, and get my cage/safety equipment sorted (crazy East Coast drivers ya know), I'll be ready to "fenagle" a 993 exhaust system up there.

Can't wait to have those cool tips sticking out...LOVE the way it looks on your car...and have seen a setup "in the flesh" while at a track event last November. A guy showed up with a C4 that had the modification, he bought it that way.

Christer, the 993 makes it's additional power via the Varioram (and Hotfilm system) intake AND the tuned exhaust.

I've heard from a few sources, including ones on Rennlist that the exhaust mod is well worth it.

tonytaylor

The original 993 had only 12 bhp more than the 964 so, considering the other changes mentioned, I`m not that convinced that all the increase in power is due to exhaust differences.
Better headers will improve HP in a 964 but to me the gains are small for the costs involved cf other enhancements.

johnfm

Power increases from 964 to 993 are always difficult to attribute - I don't think it can be pinned down to one particular thing. I expect, ultimately, for a higher PEAK HP figure, it either flowed more air (& thus more fuel) for a bigger bang OR revved higher (more RPMs will generally give more RPM if the engine is able to shift enough air) OR higher compression ratio.

What I would like to try is the 993 sytem WITHOUT the cats!

Still, where do you stop?? I'm sure we could used higher C/R (especially now that in the UK, at least, 97/98 RON fuel is pretty readily available, re-time or re-profile the cam, etc etc ....how deep is the wallet??..

Bill Gregory

Bruce Anderson said that most of the 964 to 993 22 hp difference was due to the headers. A factory engineer in Germany said the new exhaust system contributed around 6 hp, with the mass flow air system and larger intake ports contributing the remainder. Sounds like a before and after dyno is needed to clarify the 993 exhaust benefit.

tonytaylor

I suggest that there is only 12 bhp difference between the964 and 993(non-varioram)