Fabspeed Motorsports Sportcats/Catbypass Pipes
01-17-2008, 11:29 AM
#46
Porsche racing, Ninemeister, Fabspeed and you all agree that for max top end power, split flow is best. Consider it settled, then.
But how many of these bypasses, sport cats and X pipes are sold for pure track cars, vs street cars where 10hp at 4000 rpm is a much greater benefit than 10hp at 6500 rpm? So, as you say:Seems like that would be important to about 90% of the end users. What IS a properly designed merge x- over for our engines?
But how many of these bypasses, sport cats and X pipes are sold for pure track cars, vs street cars where 10hp at 4000 rpm is a much greater benefit than 10hp at 6500 rpm? So, as you say:Seems like that would be important to about 90% of the end users. What IS a properly designed merge x- over for our engines?
01-17-2008, 11:50 AM
#48
Bill,
Thanks for posting those exhaust systems photos. Question; I'm assuming that there is no good/easy way to have a proper higher performance exhaust system for the 993, And retain the heat exchanger, And have streetable sound levels (muffler), And keep the EPA happy (cats) ? (I'm also guessing that Porsche did the best they could with the stock system with all these other concerns it had to deal with.)
Thanks again,
Glenn
Thanks for posting those exhaust systems photos. Question; I'm assuming that there is no good/easy way to have a proper higher performance exhaust system for the 993, And retain the heat exchanger, And have streetable sound levels (muffler), And keep the EPA happy (cats) ? (I'm also guessing that Porsche did the best they could with the stock system with all these other concerns it had to deal with.)
Thanks again,
Glenn
01-17-2008, 11:51 AM
#49
Weathergirl
Rennlist Member
Rennlist Member
Perfect for the street, Bill! 
BTW, did anyone else notice the phrasing slight of hand in the initial post:
Not compared to stock, compared to the Fabspeed bypasses. So, the Fabspeed bypasses made 12hp and the hacked together X pipe made for comparison purposes made 9.5hp. Not much of a difference at all. Gotta wonder what the curves look like.
BTW, did anyone else notice the phrasing slight of hand in the initial post:
Our catbypass pipes increase performance by +12HP and save around 45 lbs. from the rear of the car. We designed and tested a crossover/X-style catbypass system which lost 2.5HP as compared to the Fabspeed straight pipes systems.
01-17-2008, 12:01 PM
#50
Rennlist Member
From what I have learned on this thread I have gone from a "little information being a dangerous thing" to I know enough now to know that I know very little. Better said, from unconscious incompetance to conscious incompetance.
01-17-2008, 12:07 PM
#51
01-17-2008, 12:25 PM
#52
Burning Brakes
Ok. So through all this fancy *** talk....still haven't figured out if I got f---- on buying my new DACH-X w/200 cell cats? 
P.S. Chris...I STILL WANT THEM!
P.S. Chris...I STILL WANT THEM!
Last edited by melman911; 01-17-2008 at 01:53 PM.
01-17-2008, 12:59 PM
#53
Perfect for the street, Bill!
BTW, did anyone else notice the phrasing slight of hand in the initial post:Not compared to stock, compared to the Fabspeed bypasses. So, the Fabspeed bypasses made 12hp and the hacked together X pipe made for comparison purposes made 9.5hp. Not much of a difference at all. Gotta wonder what the curves look like.
BTW, did anyone else notice the phrasing slight of hand in the initial post:Not compared to stock, compared to the Fabspeed bypasses. So, the Fabspeed bypasses made 12hp and the hacked together X pipe made for comparison purposes made 9.5hp. Not much of a difference at all. Gotta wonder what the curves look like.
01-17-2008, 01:35 PM
#54
Nordschleife Master
So, are you saying that I should not have any lean combustion issues if I run a cat? One of my track buddies thinks he burned a cylinder in his 964 because of a lean issue due to cats. I'm planning on trying to tune the potential lessened backpressure(?)/higher horsepower-lower torque issues from the DACH X pipes by adjusting the timing and by playing with my first gen Fabspeed Supercups and the Car Chemistry muffler discs, utilizing a G Timer to assess accleration times. I'm hoping to take the increased peak HP and see what I can do to tune torque. I'm not sure how sound this is and am not sure if I'll actually have time to do all of this, but I'm willing to try.
Can you please clarify? I have no idea what "potential acoustic scavanging effects" means.
Can you please clarify? I have no idea what "potential acoustic scavanging effects" means.
My point was that if you keep the flow rate the same & not change the pipe diameter. You can really compare a 50mm pip to a 100mm pipe with flow rates.
First the 993 MAF is more resposive than the 964 barndoor, second perhaps w/ an open exhaust but even then i'm doubtful, third it's always best to check anyway wideband O sensors are widely available
No, you shouldn't have any lean issues even without a cat. How are you going to adjust timing? All fuel and timing parameters are totally controlled by the chip in the DME. I haven't installed my Car chemistry disks, I bought them to control noise but they will certainly raise back pressure and slow flow rate.
As noted in post 28 & 36 A correctly sized and constructed equal length header system w/ properly sized and constructed collector used w/ cams that have a fair amount of overlap can use the acoustic echos in the pipes to put a negative pressure signal at the exhaust port at the right time to suck additional charge into the combustion chamber. The pipes are like organ pipes, width and length resonate at different frequencies This is sometimes referred to as "the 5th cycle" or "exhaust scavenging". I've dynoed 3.0, 3.6 & 3.8 w/ stock and sport cams w/ stock and various aftermarket exhausts. It works best on open exhaust b w/ cams w/ a button up exhaust and stock cams the effect is greatly muted. The resonance effect only happens at 1 frequency range, w/ 31" true headers that is ~6500 for our engines, the down side is that way down the rev range the headers put a positive signal the reduces flow. You can both hear and feel both of these effects when driving.
No, you shouldn't have any lean issues even without a cat. How are you going to adjust timing? All fuel and timing parameters are totally controlled by the chip in the DME. I haven't installed my Car chemistry disks, I bought them to control noise but they will certainly raise back pressure and slow flow rate.
As noted in post 28 & 36 A correctly sized and constructed equal length header system w/ properly sized and constructed collector used w/ cams that have a fair amount of overlap can use the acoustic echos in the pipes to put a negative pressure signal at the exhaust port at the right time to suck additional charge into the combustion chamber. The pipes are like organ pipes, width and length resonate at different frequencies This is sometimes referred to as "the 5th cycle" or "exhaust scavenging". I've dynoed 3.0, 3.6 & 3.8 w/ stock and sport cams w/ stock and various aftermarket exhausts. It works best on open exhaust b w/ cams w/ a button up exhaust and stock cams the effect is greatly muted. The resonance effect only happens at 1 frequency range, w/ 31" true headers that is ~6500 for our engines, the down side is that way down the rev range the headers put a positive signal the reduces flow. You can both hear and feel both of these effects when driving.
If you are running out of fuel, then all you really need to do, is put in an adjustable FPR & tun the fuel pressure with a WBO2, it's real easy & only takes about 20min on a Dyno.
Can we all agree that all aftermarket designs will flow more then the stock system? Maybe the X pipe my flow less at peak it will broaden the power curve & a separated exhaust will flatten the curve a bit, but give more at top end?
01-17-2008, 01:46 PM
#55
Rennlist Member
There is obviously a lot of animosity toward Fabspeed here that must have been generated by incidents before I've been on the forum. I, for one, have been very happy with my Fabspeed Supercups that came with my car. They appear to be first generation versions with non-removable baffles. They've been on this car for more than 10 years and there is no rust, fitment looks good, the sound is great (perhaps a bit loud for most) and not too much resonance that I've seen written about from others. I've also had very pleasant and informative interractions on the phone with these folks regarding their strut brace and other items that I've been scouting.
I'd be interested to see the links to the prior incidents that seam to have people up-in-arms about Fabspeed. The attacks here must have some roots in incidents passed. To be fair to the newer members, can someone post links or give a reader's digest version of what went wrong? I'd also welcome a response from Fabspeed too.
I'd be interested to see the links to the prior incidents that seam to have people up-in-arms about Fabspeed. The attacks here must have some roots in incidents passed. To be fair to the newer members, can someone post links or give a reader's digest version of what went wrong? I'd also welcome a response from Fabspeed too.
01-17-2008, 02:10 PM
#57
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WOW..........I was and am in the market for a new exhaust system and was thinking of the Fabspeed system.....high flow cats with the their maxflo mufflers......is their anything else out there that is comparable? It is a street car, so no wide open stuff, but I don't mind louder either....
Or is all this just some people like this, some people don't?
Or is all this just some people like this, some people don't?
01-17-2008, 02:19 PM
#58
Addict
Rennlist Member
Rennlist Member
I'd be interested to see the links to the prior incidents that seam to have people up-in-arms about Fabspeed. The attacks here must have some roots in incidents passed. To be fair to the newer members, can someone post links or give a reader's digest version of what went wrong? I'd also welcome a response from Fabspeed too.
01-17-2008, 02:23 PM
#59
Rennlist Member
There is obviously a lot of animosity toward Fabspeed here that must have been generated by incidents before I've been on the forum. I, for one, have been very happy with my Fabspeed Supercups that came with my car. They appear to be first generation versions with non-removable baffles. They've been on this car for more than 10 years and there is no rust, fitment looks good, the sound is great (perhaps a bit loud for most) and not too much resonance that I've seen written about from others. I've also had very pleasant and informative interractions on the phone with these folks regarding their strut brace and other items that I've been scouting.
I'd be interested to see the links to the prior incidents that seam to have people up-in-arms about Fabspeed. The attacks here must have some roots in incidents passed. To be fair to the newer members, can someone post links or give a reader's digest version of what went wrong? I'd also welcome a response from Fabspeed too.
I'd be interested to see the links to the prior incidents that seam to have people up-in-arms about Fabspeed. The attacks here must have some roots in incidents passed. To be fair to the newer members, can someone post links or give a reader's digest version of what went wrong? I'd also welcome a response from Fabspeed too.
IIRC, Joe spoke disparagingly of Robin's mufflers and did it under a pseudonym. I believe he was banned at one point, maybe two, and then tried to reregister and post under a new name but can't find the records to support that belief . Also, some of the less-than-conservative claims he makes about his exhaust products did not endear him to the board. I seem to recall John D. having some harsh words for him, but it seems as if things have gotten better(?).
https://rennlist.com/forums/993-forum/118422-a-lilttle-confused-about-some-of-the-fabspeed-animosity.html
Didn't the old website state that the products were made in the US of A? The new website makes no mention of where the products are manufactured.
01-17-2008, 02:35 PM
#60
Rennlist Member
I don't see much point dredging up the past. Sure they've made some power claims that may be questionable, but we're not dummies. Just look past the hype and consider their products for weight reduction purposes. They certainly work in that regard.