JohnA944

Ok, I've read about this test pipe and the pros and cons of putting one on your car. The price if i am not mistaken is around $200 correct? Well, wouldn't it be more financially sound to remove the cat and weld the same diameter pipe in its place? I mean cmon its a pipe for petes sake. If I were to do it I would probably fabricate a single pipe to run from the manifold/header to the resonator. Wouldn't this be the same?

streckfu's

Don't forget that the wastegate dumps into that pipe as well which would make more difficult fabricate. It is worth the $250 to avoid that headache. The real advantage cna be seen in increased flow resulting in quicker spool times and a small power gain.

The advantage of the test pipe is the loss of the restrictive cat. If you have inspections in your state, it's illegal to have the test pipe (keep your stock exhaust for inspection time).

The pipes in the $250 are usually mild steel (not stainless) and are not as durable. Plan to replace it every few years or so do to rust and cracks.

The stainless pipes sold by many vendors (SFR,etc) are probably worth the extra $ for their longevity. If you buy the mild steel unit, you can have coated with Jet-Hot ti increase it's life.

Just my thoughts.....

<img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />

Chris_924s

The weld in front of the cat is notorious for failing.. Mine completely went on Friday on the way to Hershey. Cost 40$ for a reweld- Its looks simple enough to just cut the cat out and weld a straight tube in its place.
Is there really a power benefit from removing the cat? I will be replacing the entire tailpipe from the header back soon, as I now have a few small holes in the cat- and my muffler is basically shot..
I was looking for a larger diameter pipe- anyone know of a good supplier for a stainless piece- how difficult is it to replace the header pipe-The drawbacks? I heard the header is a real time consuming process (Engine lift??)
What are the sensors in the header before the cat? Is it safe to omit these?

TIA- Chris

streckfu's

The power benifit will be more noticable in the turbos. However, if your cat gets clogged, you'll notice a difference with it removed.

ringo951

Yes it is definitely worth it. I noticed a difference right away. Quicker spool, for sure. I have the B&B testpipe, great quality and very light. I do think it makes the most difference with the turbos. I see no reason why you cannot just cut the cat out and weld in a solid pipe in it's place. Others here have done just that. The problem is if you have inspections in your state, you cannot swap the cat back in for the test then swap back. Also if your state is strict you will probably need to know someone personally to cut that cat out.

Perry 951

If you can weld, get a section of stainless pipe, 4 flanges, and make one up. Cut the converter off at the neck, weld a flange on both ends. Cut the pipe and weld in the flanges.

Badda bing, you have a test pipe.

Porsh-uh

Hey John,
I just put a test pipe on my 16v'er. I had to cut the stock down pipe from the original piece and cut the down pipe off the test pipe and weld the stock 16v down pipe (exhaust flanges are turned in a different direction as compared to the 8v manifold flanges) to the test pipe section. Let me tell ya... it was a PITA. I not only had to measure several times with both pieces under the car, one in place and holding the other up with my foot and hand (all while the car was on jackstands- so very little clearence) but I had to make sure the angles were all just right because it's a bent piece of pipe in several places. So yeah... you could fashion one yourself, but in the end... it seems like it really would be worth it just to pipe the piece pre-manufactured. I thought I was doing that until I realized the exhaust manifold flanges were turned in different directions. Long story short, buy it.

ninefiveone

Lets all note that JohnA944 has a N/A. The results will be different for an N/A as opposed to a turbo. Anyone with experience with a testpipe on a 944N/A care to comment? Exhaust tuning on N/A cars is different from turbo cars. Backpressure plays an important role in producing power for an N/A car. 968's, for example, are well known for having a well tuned exhaust from the factory which aftermarket exhausts and testpipes have not been able to improve on.

Porsh-uh

I had a blocked cat on mine, so after I did all the headwork to mine, it was moving a significantly higher amout of air and melting the pipe in front of the cat. So I don't know how much gain I would have seen from stock, but I do know that the gain was tremendous from the way my car was. And I'll tell ya this also. For a time I just simply cut out the cat and ran an open pipe (Man it was freakin' loud!) and then installed the testpipe and the difference was stark. The whole thing ran smoother (not to mention quieter) and the power delivery was much better in the low end and slightly better in the high end. It has been the most satisfying work I have done on my car.

JohnA944

Hey ninefiveone,
thanx for noticing that little bit of info. I have a place that told me thay would weld a pipe in place of the cat for $25, but I have to cut the cat out myself. They will not cut it. said if he cuts it he has to put a cat back in its place. But no we do not have emmissions where I live. There are alot of open exhausted cars riding around!

M758

I ran with a stock cat and muffler on my race car for some time. I do not drive it on the street nor is it registerd.

I cracked the fwd weld as chris said on the track once. I replaced it with a complete cat pipe from my 924S parts car. I did this since I cracked it at race and this was the quickest fix. I then ran that for while then completly broke it at another race. There I just pulled the rest of the exaust and ran open from the break. It was loud and lots of vibration in the car. Some noticable prower improvement.
I then had the brokend pipe cut and simple pipe welded in is place. I ran a straight through pipe for a little while(no cat or muffler). It was ok, but a little loud. Later I learned that the difference between open and a stock muffler w/ no cat was nothing on the Dyno. So I figured I'd at the stock muffler back on. I have been runing that way ever since. Sound is pleasant, but slightly louder than stock. Power is very good as well as trottle response. I can't say it makes anything more than 2-3 hp over having the CAT installed. In my racing 2-3hp and not worrying about the cat weld breaking is big deal and I will never reinstall the stock unit.
For a street car??? I'd guess it would work, but you would need to reinstall a cat for emissions time.

M758

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Chris_924s:
<strong>I was looking for a larger diameter pipe- anyone know of a good supplier for a stainless piece- how difficult is it to replace the header pipe-The drawbacks? I heard the header is a real time consuming process (Engine lift??)
What are the sensors in the header before the cat? Is it safe to omit these?

TIA- Chris</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Personaly I like the stock tubular headers. They are light and work nicely. They also make good solid power. Most 944-spec guys run these. A few run MSDS headers, but don't seem any faster

There is an O2 sensor port on the cat pipe. It is before the cat and not in the headers. There are no other ports (except for the test port next to the O2 which you can ditch).
You will want to keep the O2 sensor since it makes the car idle more smoothly when hot. I disconnected mine for a while, but reinstalled after I got tired of the rolling warm idle. Cold idle was fine since the computer was in open loop mode anyway.