Jeff Curtis

CATalytic converter, that is!

I've owned my 964 for just shy of a year now...and have often pondered what I might do for bolt on HP mods. So far, I have installed a Fabspeed sport muffler, lightened "Cup" flywheel/clutch assembly, modified the airbox and installed an underdriven pulley/single "V"-belt component that's found on the RSR cars.

I have been hesitant to do much more, as my car produces lots of low end torque...and I feared that opening up the exhaust anymore or adding a chip would "borrow" from this treasure chest of torque. <img src="graemlins/nono.gif" border="0" alt="[nono]" />

Recently I've decided to "test" one of the aforementioned "upgrades", just to see what would happen.

Last week, I acquired a Fabspeed "European Premuffler"...this piece of fabricated wonder is designed to be a bypass for your catalytic converter.

I must say, it's not your average bypass as it has a resonator/baffle type setup instead of the "straight-thru" styled ones that are usually found on the market...so it's supposed to be quieter. It also has a threaded "boss" that accepts your O2 sensor.

You gotta admit - it looks pretty snazzy too!

I plan to install it tonight, and after driving it to work and such, I will give my opinions on sound quality and if there's any increase of HP via the "butt dyno"...do you think I can sense a predicted 12HP? We'll find out. <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

Here's a pic:



Let me know if you are interested in my findings, I plan to post another pic of it installed.

Christer

Jeff

I would be interested in getting soem feedback from your butt(dyno)

johnfm

Why not use the stopwatch dyno??? If your engine puts out more HP, it will accelerate your car more quickly (or Newton was a lying bas@£!d).

I know there may be variations re temp, air pressure etc, but f you find a flat straight run and measure a few 0-60s or whatever and then compare,you will have your answer.

However, if the power increase is small, it probably won't register in 0-60 times OR top speed. Small gains will be lost in the "noise" of your dtat.

jonfkaminsky

Jeff-
why not a dyno-dyno? We've a good start elsewhere with data from performance enhancements and this would be a nice addition.

Jon

Jeff Curtis

"Why not a dyno-dyno?"

Simple...I'm not going to waste my $$$$$ on a dyno session to find out if I've gained 12HP...I would guess that most manufacturers of bolt-on modifications have taken some measurements, and this is probably the MAXIMUM gain they ever achieved.

Let's say they achieved that on a nice cool day? Well, then I go in on a nice warm day and only gain 3HP, while disappointing that would be, it would also cost me @ $100...even more disappointing. <img src="graemlins/cussing.gif" border="0" alt="[grrrrrrr]" />

***Not very many dyno operations are environmentally controlled.*** ..at least they're not around here!

I want to keep this fun, not necessarily technical down to a gnats a$$. I doubt I could even feel 12HP if it DID increase by 12HP. As for an decrease in 0-60 times, I doubt that would measure a difference as well.

What I do think will decrease times and provide a nice sensation to the "butt-dyno" is a combination of mods. I do plan on plugging in a chip someday, just being very picky about who's chip I use...as everybody seems to have a different idea of how to program theirs.

About the only improvement I think I will feel is the car "breathing" better at higher RPMs...which of course would indicate a HP increase??

I am in a position where I can spend a little money to "test" out things...if I don't like it, there's always somebody else that wants to try it. <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

That's what the classifieds are for!

Bill Gregory

Joe Fabiani at Fabspeed said "the catbypass pipe will lose low end & midrange torque but get it back ONLY after 5000 rpms. TOP end power is the only advantage." I've opted to leave the cat on. Three reasons, first, if the factory left them on their cup cars, there probably isn't any real magic there. Second, it saves me having to put it back on for emissions testing. Lastly, as a dual purpose street/track C2, losing low-mid torque isn't attractive.

Joe@Fabspeed

Hi Bill
yes as I mentioned to you before the "standard type 3.0"/ 76mm catbypass pipes are just straight pipe and offered by B&B Triflo, GHL and others.

These "straight tubular catbypass pipes will lose torque in the low and midrange and on the 1989-1994 3.6liter cars are extremely loud to many 964 car owners. These parts were the only choice a 964 owner had until recently.

What Fabspeed Motorsport has elected to do is make a "European premuffler style" catbypass pipe that reduces backpressure for more performance.... BUT has the proper internal design to maintain maximum torque and control sound, sound quality, and not be too loud.

The 964 Europremuffler "bolts-on" directly replacing the stock catalytic converter. The 964 Fabspeed European premuffler/catbypass means that the Porcshe owner can still can roll a "golf ball" through the 964 pipe and can see daylight as there are no obstructions or baffles inside like a straight pipe.

However, with a premuffler you keep the torque and midrange to TOP end horsepower gains without a sacrifice in driveability.

The picture Jeff posted is of the new part we just released in polished T304SS and its has 2 Oxygen sensor bungs. One O2 for the Porsche stock Oxygen sensor so the engine runs great. The 2nd is there for racers/street enthusiasts that want to "hook up" a LED "air-fuel metter" to actively monitor their airfuel ratio. Both Oxygen sensor bungs are threaded so you just unscrew your stock O2 sensor and thread it into the new hole. The 2nd O2 sensor has a nut to seal the hole incase you dont have an airfuel monitor.

Also Fabspeed made a hitech Europremuffler/catbypass pipe for the 964 that "looks just like a stock catalytic converter" so that if anyone asks..... its looks like a stock cat for emissions reasons, visual exams, SCCA scrutineers, and yada yada!
best regards
joe<a href="http://www.fabspeed.com" target="_blank">Performance for the Next Millenium</a> <img src="graemlins/bigok.gif" border="0" alt="[thumbsup]" />

David K.

You can gain good power by removing the cat and opening up the air box, but you must have the car retuned on a dyno. When you remove the Cat the car will run lean do to the reduction in backpressure. Without the retune you will lose low end torque and gain some power above 5000 rpm.

There is a lot of power bottled up in the 964 3.6 motor by the intake and exhaust. I have a mass flow system, S-Car-Go headers with a Fabspeed duel in and out muffler. My '93 RSA was retuned by Paul at Cyntex in PA (610-738-8804) the Power at the Wheel is 237hp @ 6000rpm & 228 ft-lbs @ 4750. A stock RSA has 200 HP at the rear wheels.

The headers broaden up the torque a lot and moved the max down 500 rpm.

My car out pulled 964 Euro CupCar all day long a Lime Rock last week. The CupCar must weight 150 to 200 lbs less then my lighted RSA.

I have the dyno charts if any one is interested.

David K.

Jeff Curtis

Whoah! ...the King himself speaks! <img src="graemlins/r.gif" border="0" alt="[king]" />

Thanks for your input Joe, everything you said sounds very reasonable...and it seems truthful as I have installed the premuffler and it sounds great.

I mentioned that I already had a Fabspeed sport muffler, which is basically a factory Primary with a Fabspeed tip, highly polished and eliminates the Secondary muffler. So, essentially, this would be the same as having a Secondary bypass.

The sound level on my 964 yields many compliments from other P-Car owners, as well as other car enthusiasts. The addition of the European Premuffler doesn't seem that it increased the sound level significantly, although, there is a difference.

I installed a "straight-thru" cat-bypass for one weekend at the track last Summer...and promptly removed it once I returned from the track, it sounded NASTY!

Overall, my predictions of what I would gain out of installing this premuffler rang true:

1) the Premuffler weighs quite a bit less than the factory catalytic converter - a "bonus" not thought of until installation.

2) the Premuffler adds a lower, but not annoying tone to the exhaust note.

3) the "butt-dyno" says "Otay!" ...as the car does seem to breathe better at higher RPMs.

Considering all that, I will further test it at a three day track event over this next weekend, Kershaw, S.C. (CMP) - here I come!

Thanks for the advice David K. - I will consider that as good advice, seeing that you've been there, done that...with positive results. <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

SuperCarrera

Joe,

How does this new Euro premuffler compare to a performance-type catalytic converter as far as exhaust flow restriction is concerned?

I have one of your standard cat bypass pipes on my supercharged C4 and would like to quiet it down just a shade so I'm currently looking into my options.

FYI -- this standard Fabspeed cat bypass pipe is also a very nicely made exhaust component and does look like a stock catalytic converter.

Thanks..

johnfm

Dave K

you say the stock RSA made 200 HP at the wheels!?? Thats just 235 flywheel HP. I assume the RSA was a 3.6 litre 964 (excuse my ignorance, I'm from the UK!!).

I expect my stock 92 C2 has 212 at the rear wheels?

Where did your figure of 200 Hp come from?

Christer

John

Your 92 C2 would have had around 212rwhp when it was new and assuming 15% drivetrain loss. After 10 years it may be a bit much to expect optimum performance still available. Besides, the 15% I believe is a best guess figure. The only way for you to make sure is to take it to a rolling road.

Christer

johnfm

Christer,

you know my doubts re: rolling roads! I think I'll stick to level tarmac, known mass, Cd & frontal area and a couple of Newton's ideas on force, mass and acceleration!!

Christer

John

I would have thought that it would be less accurate to use that method. You can't know mass accurately, rolling resistance will depend on tyres, is the tarmac 100% level? and all the rest of it. How did you arrive at 212rwhp with your method?

Christer

GP964

Hi Everyone,

I have a 90 C2, dynoed on a Mustang Dyno at 3000 elevation level, pushed out 237hp at the rear wheels.

GP