TT Oversteer

What is a reasonable increase in hp and general performance one could expect by installing a performance chip with a cat bypass on a 3.2? How well does the stock airbox and filter flow? I am personally not a big fan of K&N filters.

Amber Gramps

you can probebly find my post on what I have done to my car and see that I am a huge fan of the chip/bypass/airbox set of mods. It works. It's worth it. It sounds great. It runs great.

My chip is a MAXHP

My bypass I believe is a Shnell or a Fabspeed

My airbox cover is a Fabspeed

My filter is K&N

All the above is pointless without correct valve adjustment, new plugs, wires, rotor, distributor cap, and the all mighty octane.

MIK911

Close to euro hp (230ish). But the real (noticable) increase will be increased torque at lower rpm.

KC911

The chip (I've had one of Steve Wong's for several years) along with a euro premuffler and sport muffler are a nice upgrade (part throttle performance, sound , etc.), but imo don't expect a "night & day" boost in hp. Other's have differing results, but I dyno'd my car (GHL sport muffler & Fabspeed premuffler) while alternating back & forth between the SW chip and the stock chips (three runs each in 4th gear at WOT), and found no significant difference between the torque/hp curves between the two chips. Now if you have a stock 84-86 chip, you should easily see the 10 hp that the factory gave us in 87-89. I love my combo! Forget the K&N, as the factory airbox is not a limiting factor, and the K&N actually allow more tiny particles into the motor from what I've read...I have cut my cover off (a spare), or some drill holes for the sound effects.

Keith
'88 CE coupe

911vet

I'm considering removing my cat but not upgrading my chip.
Any problems associated with that?

And as I understand it, the cat acts as a pre-muffler. So does cat elimination greatly increase the decibels? I like performance mufflers but I don't want "loud."

KC911

When I installed the GHL 1/1 replacing the stock muffler, my car became a "sports car" in terms of sound (loud, but not TOO loud). Later, when I replaced the cat with a Fabspeed premuffler, I personally could not detect any change in the sound at all. Drilling the air box will change the "sound", but will not add hp.

84_Carrera

1984 Porsche 911, stock engine, cone filter, Weltmeister Chip, Fabspeed Premuffler, Fabspeed Muffler Bypass, DME Fuel Setting 2 (+6% Fuel, no timing changes) for the newest (green) run.

Original (Red) run was stock cat, stock muffler, Welt chip, stock fuel setting, MTBE-added Super Gasoline, 50k miles.

Middle run (Blue) was fabspeed premuffler, forget which muffler (maybe Bursch), but same config made similar numbers on the dyno as compared to stock. 3% Power loss attributed to 10% Ethanol-added Super Gasoline.

Looking at the numbers, assuming 15% driveline losses, current setup looks to be making about 250 crank hp, 227 crank lb-ft. Most of the latest gains are up top, and I don't spend a lot of time up there.

old man neri

I did this. I replaced the cat with a fabspeed premuffler thingy. It is more than just a bypass pipe, it's got an expansion and some perforated stuff in there. The sound didn't really get louder but it just got deeper. I really like it. I noticed a bit more 'umph' but I think that was due to the fact my cat was finally beginning to clog up. The smell will also change.

You can pick them up used in the for sale section on pelican. They pop up and usually sell pretty quickly. And if you don't like it you can always put your stock cat back in and sell the pipe, at most you will lose your shipping costs.

-matt

KC911

Just my .02, but unless the dyno runs are "back-to-back" (same day, same dyno), and only one variable is changed (i.e. chip), then any conclusions are "suspect" particularly based upon a sample size of one run (each). Some dynos aren't "that consistent" even if no variables are changed, hence a sample size of "one" just isn't adequate enough to reach a "valid" conclusion imo. Some dynos are more consistent between runs (i.e. Mustang) and lend themselves to "performance tweaking", yet the "reported numbers" will not necessarily equate to what say a Dynojet produces. The number is just that, a calculated algorithm and should be take with a big 'ole grain of salt. I do like my SW chip, but HUGE hp increases aren't the reason !!!

Keith
'88 CE coupe

KeithC2Turto

I agree that getting all maintance stuff taken car of. If one has a dirty air filter a new one can add power.

I suspect that a lot of our old cats are getting a bit restrictive just from age. This is on top of there restrictive nature.

When I replaced my cat with a bursh style bypass, I felt a differance in performance. In my case the sound did not change or get louder.

I think I noteiced a differance with a change to a chip.

I dynoed my car w the chip and bypass and got 217rwhp. That is over 250fwhp. Yes, dynos vary but I have at least what a euro car has. I can still add a sport muffler for more.

However, a dyno test proved I was running to lean up top which can be part of the gain. I belive part of the gain tuners get from chips on a 3.2 is from leaning the A/F ratios above 5k. I think the factory had built in extra richness up top for safety as the flaper valve basicaly stalls about then and can no longer mesure changes in air flow. Thus the chip has to be pre set with how much fuel just bassed on rpm input.

This gives room for some mods on the stock chip which seems to be a bit rich with out risk of running lean. It also helps explane how just a simple exaust change can have a significant effect on power on a 3.2 as it may alow freer flow and get us to a more powerfull A/F. A bit of synergy.

I am a big belever in the SW 'custom' chip option and dynoing ones car to verfy a A/F ratios. Cars can go out of spec or just differ and if the chip tuners are cutting the line closer to get power, one could be over the line depending on the car.

We do not seem to expect any gain over stock on the air fulter unless one is really effective at improving high rpm operation. If it is a 3.4 or has C2 cams or some such, then just cutting off or holeing the prefilter opotion may help.

There has been mixed results on a 3.2 from nothing to 3 Hp. Makes it sound better though.

I am not an expert, just my opinion.