Here's a thread I also posted on Rennlist earlier today.

I've been following the various threads on the 993 forum for a few years now, with a particular interest in discussions around increasing power and torque from the normally aspirated engine without resorting to major internal work. Overall, it seemed to me that there was a lot of subjectivity out there, with little or no factual information available. So I set about conducting my own experiments on my 1995 non-varioram 993 and this is what I found out.

All tests were conducted on the same Dynojet machine at ProTechnik Racing in Houston by shop owner and 993-racer Sam Shalala (thanks also to Steve, Dick and Rob). I attempted to test in similar climatic conditions where possible and all tests were conducted using 93 octane gas and with the car in third gear between 2500 rpm and the rev-limiter. Reasonable periods of time (and the odd track day) elapsed between tests to allow the chip(s) to adapt to the other modifications.

Here's a key to the graph attached and description of the modifications:
1) stock is fully stock !
2) Supercup exhausts (from Fabspeed), stock chip, stock airfilter and lid.
3) Supercup exhausts, Supercup airbox lid, BMC airfilter and '95 chip (again all from Fabspeed).

Observations:
- there are a lot of dips and bumps in the stock trace, probably due to the intake and outlet sides of the engine conflicting with each other.
- above 3500 rpm there is a discernable increase in power and torque over stock, except for a small area around 5000 rpm where it's about the same. The maximum increase over stock is about 15 - 16 bhp at 5900 rpm (less backpressure ?).
- adding the chip, BMC airfilter and open airbox lid produces a much more consistent increase in power and torque across the entire rev range. Max numbers are now 257 bhp at 6100 rpm and 234 lb/ft at 5300 rpm (this equates to 298 bhp and 271 lb/ft at the flywheel using a multiplier of 1.16).

The car is now also fitted with cat-bypass pipes (if you think the Supercups are loud you should hear these !!) and has tested in excess of 260 bhp (~302 bhp at the FW) during preliminary tests (but before the chip has fully adapted). Next I'll be fitting a bored-out throttle body, as I believe there is still room for improvement on the intake side, and then I'll re-run the dyno tests. I'll post the results back here when I'm done.

It appears therefore that I've got close to 300 bhp with relatively simple modifications, and with the added bonus of a great sounding car (too loud for some !!). No doubt you will have had or seen different results to mine, but I'm happy with what I've done (for now) and have learned a great deal about what is a very fine motor car, even in stock spec, during the process.

 

It appears the dyno graph attachment was too big to be included here. Please see it on the Rennlist 993 Forum. Apologies.

 

Dave, I'd love to hear your car if you're out at TWS any time soon. I have Supercups with the stock cats currently.

 

Hey Matt. I have a vid clip of my car with B&B bypasses and RSR mufflers. Its not at full song but you can get an idea of the sound.

Email me at nota_troll@yahoo.com