Looking for fabspeed catbypass dyno results
 

Hi, there I'm trying to find if someone has dyno results showing that fabspeeds catbypass get you any Hp. Ive read lots of oppinions on what fabspeed offers but what I want is proof of any gains. In particular an 79SC (my car :) ) I just want to know if its worth the $$ or not for the catbypass or exhaust. I just got the smog done on the car so I don't have to worry for another 2yrs. So If anyone can help me out I would gladly appreciate it.

a cat bypass pipe most definitely gives you at least 8bhp. No need for a dyno sheet. Great cheap, bolt-on bhp. go for it.

After a lot of research on this including quotes from B. Anderson...it appears that a Euro pre-muffler does indeed give you some extra HP...maybe 6-8...but similar reports indicate a "cat by-pass"..if it's simply a length of pipe...might offer as little as "0" increase...

The design and internal geometries seem to be important, not just the "low restriction" aspect of a straight pipe.

- Wil

Here are my dyno sheets before and after fabspeed. Both were with stock chip. I think 8-10HP is expected with a cat bypass alone. To compare, the last sheet is with a cat bypass, Autothority MAF and a custom chip from Steve Wong.

Stock: 186.6 RWHP (219 FWHP running too lean) 217 rated HP
http://forums.pelicanparts.com/uploa...1136684783.jpg

Fabspeed bypass: 193.4 RWHP (227 FWHP)
http://forums.pelicanparts.com/uploa...1136684805.jpg

cat bypas/MAF/Steve W chip: 213.7 RWHP (251 FWHP) plush nicer torque curve
http://forums.pelicanparts.com/uploa...1136684869.jpg

Thanks every one for all your help, Ill give fabspeed's catbypass a shot
Don911 thx for the sheets

Don, Are those the only modifications you did to get 213.7? Reason I ask is I just had my car dyno done today. SAE peaked at 210.4 at the rear wheels and 218.2 actual at 76F. (I tossed in the 76 degrees 'cause everyone knows it sucks her in the summer but is sure nice right now.) I thought I was doing great until I saw your results since I have 964 grind cams in addition to the Authority MAF, cat bypass and a dual out modified stock muffler. Your test and mine were both done on a Dyno Jet and the curves look similar. The shop (Motorsport Technologies) can't do an air fuel mix test without drilling a test hole in the exhaust system. This is probably because they do Vettes and did comment about getting the test plug upstream on the exhaust pipe. I told them the 911 is a little shorter than the Vette but still couldn't get the A/F data without the $180 hole drilled. One thing I do see missing from my car versus yours is the Stev Wong chip. Mine has the Authority chip which is designed for the MAF but not the cams and exhaust. Its also set back or adjusted for Houston summer temps which I get the impression Steve can design for without lossing power during the rest of the year. I'll post the chart tomorrow when I figure out how to scan the darn thing and then upload it.

Tom,
My motor is stock with the exception of the MAF and a cat bypass pipe. I have the stock muffler with single outlet.

Sounds odd about the AF. The place I go to sticks a probe in the tail pipe. With the AutoT chip, the motor dyno'd at 204.7 at the wheels. The AF mixture was my main reason for having Steve do a custom chip. Better power and torque was a nice bonus.

The AutoT chip seems to run pretty rich. Car ran pretty good but not as smooth as I wanted in the daily driving rpm ranges. On the dyno at WOT, it never did blow out all the crap so I think it was loading it up pretty good. There are two dips on the chart whick was the crap blowing out. I sent Steve the AutoT dyno sheets and he said the richness is typical. After his first chip, he tweeked it a little to get a flatter AF mixture. Also gained a few ponies. Car runs awesome now and is smooth all the way to redline.

Here are the AutoT charts including AF.
http://forums.pelicanparts.com/uploa...1136698449.jpg
http://forums.pelicanparts.com/uploa...1136698468.jpg

Seve W chip (Red line: initial chip Blue line: tweeked chip) Also, the blue line was done in mid 40 temp. Everyone was showing lean. Don't know if the HP number were affected but it ran pretty good that day.
http://forums.pelicanparts.com/uploa...1136698645.jpg
http://forums.pelicanparts.com/uploa...1136698663.jpg

Don by any chance did you try Dansk's catbypass?

I actually switched to the Dansk cat by pass and that is what is on the car now. The early dyno sheet with the cat by pass only was with the fabspeed installed.
I doubt that there's much, if any performance difference between the two.

Don, Thanks for the info. I stopped by a friends house this afternoon that was a serious 911 owner before buying a continuation series Ford GT40 (original frame with a repro body, interior and engine). His comment was the Dyno's could have been the differance even though they were both Dyno Jet. I'm thinking its my chip that was programed for the hot wire MAF but not the cams and exhaust. I'll get an AF test this week and send everything to Steve Wong for a new chip. Let you how it all comes out in a month or so. And BTW I agree there's prbably not much differance between the Fabspeed and the Bursch cat bypass except for the fabspeed is stainless which is nice. I painted mine with high temp heat paint and it seemes to be holding up.

Re: Looking for fabspeed catbypass dyno results
 

Call Joe Fabiani at Fabspeed and ask him to send you data.

Tom,
Do you have the Bursch straight pipe? As Wil F indicated above, the straight pipe may not provide HP gains. I've heard this before but have no idea if it's true. I've never seen any dyno sheets with just a straight pipe.

BTW, what do the cams do for you?

Don,
I got the cheapee Bursch pipe for several reasons. First its cheap. Second, using one takes a lot of cat heat off that side of the engine and in Texas we have lots of that in the summer. Actually its even hot in the winter now with near 80 Monday. Other reasons are the exhaust note is deeper, its lighter than the cat and now I can save the cat for the yearly smog test which I used to pass without it until the city added a test for NOx. Attached is a pic of it (cause we all like Porsche pics) painted with high temp paint. Heat exchangers and cross over pipe are also painted. I'd like to see a dyno comparison of the Bursch vs the Fabspeed. I'd guess the Fabspeed is worth the extra simply because its stainless but for $100 the Bursch is fine. I did not research the choices when I got mine otherwise I might have gotten the Fabspeed for the stainless.

The cams are my originals sent to John Daugherty in California and ground to 964 specs. Great guy and am very pleased with the results. Nice gain over the MAF and cat bypass. Plus they sound cool at idle. Real lumpy idle now like I remember 1955 Chevys with 283's and roller cams when I was a teenager.
http://forums.pelicanparts.com/uploa...1136782793.jpg