seaeagle

Your dog has red spots on his nose and if your wife thinks a flat 6 purrs - well its very hard to find a woman like that!

I am so confused. When my 964 hits the wall well it is time for a good hard lash at a GT3 I say.

Still looking for a 94/95 928 GTS manual

Sea Eagle

hdemas

Bill answered most the questions here, but I figured I'd chime in for completeness. My 964 has a 993 motor that my brother and I installed. The swap is not for amateurs, but it isn't too difficult either for someone who knows what they are doing. Some special electrical wiring and oil line routing required, and reprogramming of 993 ECU needed to remove driveblock for the varioram cars. 964 and 993 C2 engines and transmissions can be freely used with each other. 993 headers and cat fit in 964 just fine, but mufflers don't fit so you need something smaller...I just used the Fabspeed supercups for the 993 which fit fine. 964 headers and exhaust system in general is very inefficient, which is why Bill didn't recommend using them. Custom heating tubes need to be fabricated if you use the 993 headers.

In the final analysis, though, buying a 993 motor and paying for the significant amount of labor required to do the swap and make it a clean, professional install is a significantly larger amount of $$$ than simply rebuilding a 964 motor, and the difference in power is really not enough to justify it. If you have the ability to do it yourself, then it isn't bad, but I wouldn't suggest it to anyone who is paying a shop to do it as at that point it would probably be cheaper to just sell the 964 and buy a 993.

Red rooster

hdems,
You made the comment that the 964 header exhaust system is very inefficient .For interest ,do you know where there are any power plots comparing a 993 header /exhaust with a 964 set up with cup pipe ?

The work I have seen done over the years doesnt seem to support your view but I do have a 993 system that could go on if there is any real benifit !

Thanks

Geoff

Bill Verburg

It would, but the nice thing is a 993 motor and trans will bolt into a 964 as well.

Most of the incresaed hp that the '95 993 has over the 964 comes from the exhaust system.

Stummel

You can get those at many places over here.
For example Mr. Freisinger in the city Karlsruhe has a lot of engines. He also has tuned and race engines if you want more power.
He is not exactly cheap as I recall but good quality:
Phone ++49 0721 5549-26 or 27.

Perhaps try: http://www.elferteile.de/

Here you get the most crazy parts and cars: http://www.niederhof.com/

Look under "KFZ-Boerse" and then "Biete" (i.e. for sale)
A complete engine is "motor" or "komplettmotor".
They have a lot of CF parts for every 911.

Red rooster

Bill,
Your comment that the 993 extra power is due to the exhaust , do you know where there is any back to back evidence of this ?
I always thought that the MAF system + extra ignition timing were the major contributors.
Certainly, a 964 with the same timing + cup pipe makes 272 bhp. The 964 primary muffler is a disaster .

Thanks

Geoff

hdemas

Geoff:

I haven't seen any specific data on the efficiency of the exhaust, but was drawing the conclusion from a few observations:

1) 964s that are used in racing often seem to be able to get very close to 993s in power, but the ones that do seem to always have much more open, custom headers that are equal length and symmetrical (more closely resembling the configuration of the 993s headers), while in contrast some of the most competitive 993s still run stock headers and I've been told by people who should know there is little to be gained by replacing the 993 headers with aftermarket ones.

2) The 964 headers just look incredibly inefficient...small diameter tubing, assymetrical design (exhaust path of the right bank is significantly longer than the exhaust path for the left bank), and the exhaust path of the right bank gets pinched where it crosses the left bank's tubing. Contrast this to the 993s exhaust, which is symmetrical, has larger diameter tubing and has no choke points.

3) There are only a few differences between the 993 and 964 engines that could affect performance...MAF in 993, slightly larger valves in 993, different ECUs and very different exhaust systems. Figuring both have generally well-optimized ECUs, the difference in power is probably not from that. The difference in valve sizes is deminimus, and not enough to explain the significant power increase. This leaves the MAF and the exhaust. The MAF no-doubt helps some, but when you look at the huge difference in the exhaust designs I would have to guess that the MAF is responsible for less of the gain than the exhaust. The 993's exhaust is just able to flow a significantly larger amount of air than that of the 964.

This being said, just bolting on a 993 exhaust on a 964 may not necessarily give a performance increase (and may even result in a performance decrease) as it may be necessary for the ECU to be properly tuned to this new configuration to take advantage of the more open exhaust and different exhaust length.

Harry

N51

Bill,

After an extensive search on the PCA website, Joel Reiser gives the same analysis. I've yet to find someone who has quantified this.

Noah

Chris M.

I read the previous posts but tell us more. We've already had at least one person on this board who put a dual-exhaust system on his 964 that made less power than stock. Maybe they didn't retool his ECU. I'd say if a bolt-on 22hp were available for the 964 then everyone would have it.

c

Red rooster

Harry ,
I am at a loss to understand this big difference between 964 and 993 headers.
They both run pretty well the same size / length pipework to the collectors.

The 964 RH pipework is longer but not constrictive ( Larger area than the 993 bit ! ).
The flow cababilities are pretty well matched as the 964 uses larger diameter pipework that pretty well matches the 993 flow capability.
The 993 design came about because two seperate exhaust paths are needed for OBDII , dual lamda operation .
We are discussing street motors with relatively mild cams , so "tuned " exhausts are not really part of the equation.

Fitting a 993 exhaust system to a 964 is a PIA with oil / heater pipe complications so I am reluctant to do this job until I can see some substantial proof rather than speculation and hersay.

I know that the factory hid behind BS about the exhaust rather than say that the 964 could have had 270 bhp as standard , running on on the same higher octane gas as the 993.( The RS made it to 260 with almost no effort )

Maybe someone out there has done the exhaust swap with no other changes and can tell us what happened.

Sorry to keep on this but I have the parts to do the job IF it will bring RESULTS.

All the best

Geoff

Bill Verburg

First you cannot compare dyno #s from the factory w/ those from an individual.

The dual exhaust on the 993 has nothing to do w/ OBD2, all '95s and all n/a ROW are OBD1.

The 964 exhaust is restrictive in the sense that it all dumps into the single x-over and the wildly divergant paths that the flow takes




Compare the above to these



The 993 airflow meter and valves etc are marginally better than the 964.

The factiory #s show a jump from 250 to 270 when going form 964 to 993, this comes from the meter, the valves and the exhaust. The 964 RS @260 has the same exhust w/ a chip. They also hand selected them, normal production line variance will yield a range of power levels, the RS was selected from the top of that range.

The same can be said of 993 there is a range if you drive a # of cars this can be very noticable, but I digress.

chris walrod

Just about all of the major differences between the 964 and 993 engines have been covered already. Another source of power gains in the 993 is not only from larger valves, but smaller valve stems and lighter internals.

I feel a 993 3.6 swapped into a 964 is a great option to those who are facing rebuilds. Even the higher mileage 964 3.6l engines sell for over $4500. It completes the trickle-down engine upgrade food chain. 2L cars become 2.2L, 2.2L cars become 2.4 or 2.7L, 2.7L cars become 3.0L, then 3.2 and 3.6 blah blah blah...

Now what does the 993 crowd get?

Bill Verburg

The lighter recipricating assembly won't show up in a steady state dyno run which is what the factrory #s represent.

993 guys get the GT3RS crank and oil pump

pete000

Why did Porsche reverse the mounting flanges on the 993 right side bank?

I see there are guys who reverse them and mount them on the 964. Would the 993 exhaust fit the 964 including the cats once the flanges were reversed? The conversions I see out there don't seem to use cats.

I like this aftermarket design, but it has no heat and no cat.

Second photo is another aftermarket design which has optional duel cats. I see where they are similar to the 993 system.

Adding heat really makes it a bit more complicated.

I like the 993 design best, but retrofitting looks a bit tricky...

Third photo is a 993 header with modified muffler and heat ducting. No cat. I don't really see any way to mount a cat on 933 headers?? other than the way the factory did it...

JasonAndreas

The patent covering the 993 exhaust system doesn't tell you much but its still interesting.