fast_freddy

lol... Oh, I remember. It's funny, if I post numbers to my prospects/clients that arent AIMR/CFA Institute compliant, I run the risk of spending time in a federal pound me in the *** prison. They fork out a couple of "g's" to sponsor this forum and they can falsely infer all they want and get away with it. If they are "sponsoring" a web forum that is with the explicit intent of advertising their products and services and there are laws that protect the consumer from that. They constantly try to diffuse a bomb that has already gone of. If they came out with the truth, they would be pleasantly surprised at the positive results.

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...

Mark in Baltimore

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

Stealth 993

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.

Caveman

I'm always wary of a company that feels it needs to trash its competitors in order to encourage sales of its goods...

Bill Verburg

Doesn't look like a big issue to me

Bill Verburg

Such venom
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

Bill Verburg

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

FLA997

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:

Bill Verburg

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,

Bill Verburg

i'm not generally on my belly when I look at them.

FLA997

LOL...touche! :-)

Stealth 993

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!

eclou

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.

hutch

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.

Mark in Baltimore

I thought you might take issue with my guarded assumption. This is what another Rennlister posted in the thread I started on the racing board:

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.