WTB: Cat Bypass 993

[only993]

Looking for a cat bypass for sale.

[993inNC]

Allow me to introduce you to DACH Perfomance Systems cat bypass pipes. Hand made 304 SS Tig, welded and will fit like a glove. Do a search for DACH on Rennlist.com to see the many threads (including positive response) on us.

We can do bypass pipes or 200 cell cat pipes (in the "X")

PM me for details

[Bill Verburg]

IMO you will be better of w/ Fabspeed's version of the cat bypass pipes.

[only993]

does anyonje have a used set?

[993inNC]

Dependant on the year of the car, I know someone that has a set of bishoff style X-pipes of mine used and for sale. He bought the wrong ones used from another customer of mine and is looking to move them. PM me and I'll give you his email

I still don't understand Bill's oversion to my stuff even after having posted positive hp (20 hp by another customers tests) and torque increases (2 lbs). But if you'd like a piece of art on your car that sounds great to boot, buy the used set if you can, otherwise I'd be happy to build you a set (yes mine are all hand made to order)

Once again Bill, and with all due respect, thanks for not supporting US

[Bill Verburg]

Don't, won't or can't?? Other opinions apparently aren't tolerated in your world even when founded in known science

Now we're claiming 20hp from your pipes? Don't make me laugh.

I have spent way to much time explaining what is wrong w/ your pipes, short version for anyone new,

a design feature of any non scavenging exhaust such as used on a 993 is to separate the exhaust pulses as far apart as possible to facilitate their evolution down the pipe to atmosphere(it's just like a highway, to keep traffic flowing, keep the individual cars separated, on straight flat paths and interchange free), and when merging pipes to have as smooth a transition w/ as few changes in gas velocity vectors as possible to limit turbulence and promote smooth flow(again like a highway, a roundabout will inhibit flow). Stock 993 has an even fire engine w/ the pulses 240 crankshaft&deg apart on each side, and relatively benign merges where the pipes do come together, keeping the sides separate w/ long runs conserves gas momenta and promotes flow and decrease back pressure.

Joining in the manner you do promotes turbulence and a gas traffic jam at the merge. Never seen your pipes but I will bet that they show signs of heat distress at the merge.

The pipes can properly be merged in a tri-y set up like this, the lengths of the primary and secondary segments are not arbitrarily chosen, but rather chosen to take advantage of acoustic signals that are reflected back up the pipes to place a neg pressure region at the exhaust port at the desired time to enhance charge flow into the cylinder, while keeping the other 2 principles of gas flow in mind(minimize D flow vectors, smooth convergance at intersections)

[993inNC]

First of all, opinions are fine in my world, but you made an absolute statement, I'm just responding. I'm not claiming anything in that 20 hp, I said it was a customers car that got dyno'd not anything we have done. On the other hand our 200 cell cat pipes have also been tested and garnered 8 hp and 4 ft lbs, so they apparently do something......like it or not Bill. My claim has always been that these are for amazing sound and an alternative that is a piece to be proud to have on your car nothing more!

As far as your theory about heat stress at the merge, we have tested for that and there was no higher heat value there then there was at the flange from heat exchanger to bypass pipe, mainly we believe because the pipe diameter is larger than it normally would at that location, allow for the heat to either exhaust or disperse before causing an overheating situation.
And really, that factory cat is not much different in design. Its nothing more than a collection chamber with a cat at either end.

I've said it before and its worth repeating, until you try and test it, stop knocking it. To say that going with a Fabspeed piece is a "better" alternative is a load of crap. I make no outrageous claims and then disappear off a board when asked to back up claims. I have never been shunned because of those claims. Those who have ought my parts (30 + in the first year) have had nothing but the best to say about the product, how we treat people, our support after the sale........none of which unfortunately I can say about your choice of referral (stating facts, not flaming).
What really bothers me the most (I think) is that you put your name up for them ....for what? the point of just knocking my stuff? Because you can't wrap your engineer mind around something that may not make sense to you? What Bill? You're probably a really nice guy ......and probably smarter than me, but I have something that works and being hard headed isn't going to change anything. Try a set, hell buy a used set, then once you have concrete evidence that they aren't anything I've ever claimed......we'll have something to agree on.

.........until then

[Bill Verburg]

And really, that factory cat is not much different in design. Its nothing more than a collection chamber with a cat at either end.

Not so, here is an illustration from Porsche's patent application for the 993 exhaust


Not all of the features were implemented in all years and markets for final production but the key feature of the diffusion chamber was. It is designed for emissions, not performance. The exhaust gas flow was optimized to enhance the performance of the cats by increasing the exhaust gas residence time in the converter. The most efficient way to do that while retaining the necessary heat in the gas was the diffusion chamber illustrated above. There is no merge, the gas is stopped and diffused laterally, the volume of the cat included an oversize chamber to keep exhaust back pressure and acoustic effects to a minimum.

[only993]

well thanks for all the info, but to be frank this was not the question being asked. Apparently you guys have a beef with each other and if I had the money i would go with the Dach system hands down. the quality seems great! personal opinion.

[993inNC]

Sorry, ONLY, its not a beef, more like a complete disagreement between 2 enthusiasts......one knows to much, the other knows just enough to be ..........well anyway
Like I said, PM me and I'll get you the email of the guy with the used X-pipe.
Oh and thanks for the public support, I appreciate the gesture. I go by the same screen name on Rennlist (993 board)if you get over there.....hope to see ya.

[onefstm]

Only,

You may want to seriously consider Bill's opinion and knowledge base around this subject (and virtually everything else regarding 993's). Before purchasing my Fabspeed bypasses, I read many threads on Rennlist around this subject where Bill posted detailed information about the advantages of Fabspeed/Dansk type bypasses vs. Dach.

While I do agree that the Dach pipes are a beautiful work of art with what appears to be top notch quality, you may want to pay more merit to the best performing system for your 993.

[993inNC]

How do you gauge best performing? What they claim and what the reality is, are apparently two different things according to plenty of info I've seen in the past both public threads and private PM's to me. We are finally getting ready to do our own dyno runs, but from 2 customers of mine (on opposite ends of the country), both test they did (on their own, not on by our request) produced positive gains with my pipes and no other mods. Fabspeed's "system" produced losses from one of the two customers of mine that has now dyno'd both pipes.

I thank you for the kind words about quality, but would urge you to not jump on the B.V. band wagon because he posts pics from early 90's technology engineering. Ask F.S. to post any recent dyno #'s for anything they do........hasn't happened yet (check the post on Renn about their "GB" for 200 cell sport cat pipes). All I'm saying is, just like to Bill, don't discount what you haven't experienced.....you'll never know what you're missing