exhaust system performance on 3.2/3.4L engine

[pojefferson1]

Hi Steve -
I would like to get your point of view on a decision I was about to make, as I am receiving conflicting opinions on; i.e. between 2 Porsche shops and Steve Wong (911 Chips).

I have a 1988 911 Carrera with the following modified exhaust set up:

- heat exchangers; from Automotion; part #911829
- Dansk Premuffler; from Automotion; part #914366
- Dansk Sport Muffler, 1 in/1 out, 84mm outlet; from Automotion; part #900130
- Porsche Cross-Over Pipe; from Porsche; part #930 111 169 05

I recently (last summer) had the 3.2L engine rebuilt; top and bottom; and "... while we were in there..." changed it as follows:

- converted 3.2L to 3.4L via 98mm pistons (LN Engineering)
- 9.8:1 compression
- twin-ignition
- 964 grind cam shaft
- Steve Wong (911 Chips) custom chip stage II (corresponding to this set-up)

The 2 Porsche shops (plus my interpretation of what Bruce Anderson says) lead me to believe I could achieve additional gain in HP with a less-restrictive exhaust configuration. To do that, I was planning to change over to this exhaust set up:

- SSI heat exchangers; thick-flange, for 3.2L engine
- M&K Sport Muffler; 2 in/1 out
- Steve Wong (911 Chips) custom chip stage II (corresponding to this set-up)

However, I was just told (by Steve Wong) that this new set-up would not actually be better; i.e. ".... because the SSIs are smaller in diameter than the stock heat exchangers, you actually would be loosing at least 10 if not 15 hp with your new exhaust setup over what you had before."

Can you help me reconcile these different point of view? Perhaps I am misinterpreting the various sources of information I have.

~ Philip

[Steve]

Hi Phillip,

True enough, the SSI's have smaller tubes than the factory HE's do, however that crossover design which merges the right into the left side is FAR from ideal, too.

In the perfect world, one would like to have had 1 5/8" SSI's, however that never did happen. Given your modest camshaft profiles, SSI's won't hurt your power until above 6K and they will boost performance below that.

Mufflers are not all the same and there are definitive differences in power & sound between them. Like people, some do a better job than others,..

Call me for more details.