Fabspeed Motorsports Sportcats/Catbypass Pipes
#16
Rennlist Member
The funny thing about this is that do people really believe that a guy from Philly with a fabricating shop has found "horsepower" that the most revered automotive engineers in the world "left on the table" without compromise? Save a few pounds? Absolutely. Eliminate a cat and free up a few hp? Absolutley. According to them if you utilized their maxflo exhaust, cat bypass and air intake you would add 34hp. Porsche engineers could only squeeze out an extra 18hp with wholesale mods to the engine, ecu and exhaust. Hmmmmmmm lets go over that trust equation again...
#17
Rennlist Member
One thing to consider is that the lower flow of the X pipes may, I repeat, may increase backpressure which is not necessarily a bad thing. If there's too little backpressure, the engine can run too leanly and burn up cylinders. This situation may be present with the X pipes; I am not certain.
I started a thread on the racing board that degenerated into a ton of static with regard to torque and horsepower: https://rennlist.com/forums/racing-and-drivers-education-forum/400250-another-torque-versus-horsepower-question-for-a-track-car.html
I started a thread on the racing board that degenerated into a ton of static with regard to torque and horsepower: https://rennlist.com/forums/racing-and-drivers-education-forum/400250-another-torque-versus-horsepower-question-for-a-track-car.html
#18
Nordschleife Master
Dam I just spent money on the Dash X!
Ok, now isn't the stock system a X pipe type? Both pipes share a common chamber. I think Porsche did this for low end torque & better exhaust pulse tuning.
How did you see a -.25hp with the X pipe with no cats? Can you run all 3 setups on the same dyno & let us see the charts?
Personally I would sacrifice a few HP up top for a much more brood & flat torque curve.
I'll Dyno my Dash setup when I get it, & compare it to my stock Dyno graph.
#20
#21
It's amazing that you're still trying to peddle this bull****. I have Fabspeed bypass pipes on my car. I weighed the stock cat on a digital scale and it weighs 24 pounds. I didn't weigh your pipes on a scale, but I'd guess they weigh a little under 10 pounds -- let's say 8. That's a 16 pound weight savings, NOT 45. Every other person I know who's weighed the stock cats has come up with a number between 23 and 25 pounds. Where in the world did you come up with 45 pounds? I'd really love to know.
You're dealing with an intelligent audience here, not a bunch of pimply-faced teenagers reading muscle car magazines who'll believe anything.
Rant off.
BTW nice photo of the Dach X-pipes. I personally don't think the X-pipe design is a good one, but really -- could you have made your competitor's product look a little worse?
You're dealing with an intelligent audience here, not a bunch of pimply-faced teenagers reading muscle car magazines who'll believe anything.
Rant off.
BTW nice photo of the Dach X-pipes. I personally don't think the X-pipe design is a good one, but really -- could you have made your competitor's product look a little worse?
You'll notice muffler by pass as well as cat by pass?
Yes, the single O sensor cat weighs ~ 21# w/o sensor, I never weighed the cat by pass by 8-10# sounds resonable
#22
One thing to consider is that the lower flow of the X pipes may, I repeat, may increase backpressure which is not necessarily a bad thing. If there's too little backpressure, the engine can run too leanly and burn up cylinders. This situation may be present with the X pipes; I am not certain.
I started a thread on the racing board that degenerated into a ton of static with regard to torque and horsepower: https://rennlist.com/forums/showthread.php?t=400250
I started a thread on the racing board that degenerated into a ton of static with regard to torque and horsepower: https://rennlist.com/forums/showthread.php?t=400250
w/ smog cams and especially w/ mufflers any potential acoustic scavanging effects are largly obviated.
The torque thread debate was mostly a matter of semantics, one of the posters didn't/ doesn't understand the use of standard engineering metrics.
Motronic is self adaptive wrt fuel/air ratios w/i the regimes determined by simple exhaust mods
#23
Drifting
In fairness, I think these pics give a more accurate representation of how the Fabspeeds fit. I'm not starting a pissing match with Bill V by any means, but I know I would be (and WAS) upset if I purchased a set of these only to find they fit like this:
#24
The torque curve of a stock 993 is already pretty wide and flat,
#25
i'm not generally on my belly when I look at them.
#27
Nordschleife Master
No, the stock setup is designed to increase operating temp andn residence time of the exhaust gases in the cat. It consists of a mixing chamber, the gas enters the chaber in || perforated pipes caped at the end. The gas comes to a very abrupt halt and is forced to ooze out laterally into the active l/r sections. From a gas dynamics perspective it is a very poor design, from an emissions perspective it is brilliant.
The torque curve of a stock 993 is already pretty wide and flat,
The torque curve of a stock 993 is already pretty wide and flat,
Interesting, so it goes into the big part, & hangs out pre cat. It is a common chamber. So, this "should' create a lot of back pressure? So, wouldn't anything that speeds up exhaust flow there increase HP a bit given same flow rates?
Thanks, I learned something new today!
#28
Addict
Rennlist Member
Rennlist Member
While backpressure itself is never going to help power gains, resonance tuning of the exhaust can. The length of the primary runners of the exhaust manifold/header is often "tuned' to a length to increase exhaust scavenging out of the combustion chamber. Depending on length the the gains will be seen as added torque at certain ranges in the rpms. That is why racing exhaust manifolds don't just dump freely into the open air before merging at the collector.
#29
I had a set of the Fabspeed cat bypass pipes, I replaced them with Cargraphic cat bypass pipes. Much better fit and they didn't hang down and look like the bad design they are. Even if I don't spend much time on my belly looking at the back of my car I still know if something isn't correct.
#30
Rennlist Member
That's a myth, pack pressure is never a good thing, it leads to increased pumping losses. An exhaust is designed to do one thing let the gas out at maximum speed, too big slows gas down, too small slows gas down, all exhaust is a compromise between high and low rpm unless there is a mechanism to alter the configuration of the exhaust dynamicly(I know Audi has used that on S models and I believe that Porsche may also use it on GT3, but not sure on that), bends slow gas down, turbulence slows gas down, sharp stepped transitions slow gas down, improperly implemented merges slow gas down.
w/ smog cams and especially w/ mufflers any potential acoustic scavanging effects are largly obviated.
The torque thread debate was mostly a matter of semantics, one of the posters didn't/ doesn't understand the use of standard engineering metrics.
Motronic is self adaptive wrt fuel/air ratios w/i the regimes determined by simple exhaust mods
w/ smog cams and especially w/ mufflers any potential acoustic scavanging effects are largly obviated.
The torque thread debate was mostly a matter of semantics, one of the posters didn't/ doesn't understand the use of standard engineering metrics.
Motronic is self adaptive wrt fuel/air ratios w/i the regimes determined by simple exhaust mods
Can you please clarify? I have no idea what "potential acoustic scavanging effects" means.
Last edited by Mark in Baltimore; 01-17-2008 at 12:43 AM.