Anir

Thanks for the update, Scott. I really want to do this mod - for the track only, of course. Like you said, "some people...".

Bill and Jeff,

Here is some helpful info from Rick in Portland that may answer your earlier questions:

"There is a different way to accomplish this. There is a guy in Scottsdale, Az. that can take your CATS and modify them with some pretty cool flanges so you can remove just the CATS and slip in some bypass pipes. Then when you need to smog the car, you can remove the bypass pipes and slide the CATS back in. Both the CATS and the CAT bypass pipes have the same flange fittings. So, it's a matter of removing 3 bolts per end to slide them in or out. I understand that it takes about 30 minutes to make the switch. A very cool idea and setup.

His name is Bob Holcomb, and he owns a shop by the name of Motor Designs of Scottsdale. Bob is a master machinist and does unbelievable work. Bob's number is 480-483-9514. It was about 1 1/2 years ago when I talked with him."

Greg Fishman

Anir,
Get the stuff from Bob, I have seen some of his engine work and if that is any indicator, you will be more than happy.
If I was to ever build a serious hi hp turbo motor I would have this guy do it. I know of several guys with 700hp motors that he built that are very reliable.

Anir

Greg,

Thanks for the rec. I plan to give Bob a call. How much weight do you think can be saved just by replacing the cat canisters with straight pipes (leaving everything else the same).

Is it hard to remove the cats? A lot of the exhaust system bolts looked pretty rusted when we were under there this weekend.

Greg Fishman

I think the cats weigh around 28lbs on my car. I have them in the garage if you want to see them.
The first time we will need to remove the bumper cover (not a big deal) and just spray the bolts with some liquid wrench. I would say it is a 2-3 hour job max.

4flynlow

I am running the FVD cat bypass pipes and had them on when my car was smoged.The P-car dealer did the smog check and I was given a certificate.I hope that will be the case next time.
Jeffry Brusseau

David in LA

What about 100-cell cats? Are the performance gains meaningful? Or are they not worth the price compared to cat by-pass pipes?

johnfm

I'm with TB993 - I don't think the turbo cars have varioram.

PorschePhD

No varioram has ever been installed on the 993TT. Sorry that is probably some lag you are feeling As far as gutting the cats. I have a buddy that just drilled a hole and did that. You can always use a plasma cutter and knock them open and then clean them out.

Interesting the light comes on. I guess they changed something as all the units I have ever sold actually had the light disabled. The computer new it too because the OBDII would actually give you a code for a light not working, DOH. Great to see they turned that back on. It should always be functional so you know if any problems occur.

Anir

Greg,

OK, this will be the next project following the coilovers.

Speedraser

How much extra power/torque does bypassing the cats on a TT generate?

Ian964

I'd like to install a cat bypass on my 964 Turbo. Will it still pass inspection? And how much HP can I gain?

David in LA

Todd / Ian

I think the gains are not so much addtinal hp and torque, but less turbo lag from quicker and earlier spool up of the turboes as there is less restriction to impede exhaust gas flow.

Rick in Portland

David,

It's a combination of spooling up faster / much less turbo lag / and an increase in HP. There is much more torque in the lower RPM region.

100 Cell CATS - I paid a bunch of $$ and bought the FVD sport CATs a couple of years ago, and it was a waste of money. Steve Weiner, at Rennsport Systems, put them on a flow-bench and found that the volume was exactly the same as the stock CATS. For me, they were a waste of money.

Rick
<a href="http://www.993tt.com" target="_blank">www.993tt.com</a>

David in LA

Rick - Thanks for the correction. So to answer Todd's and Ian's question - what was the approx hp and torque gain?

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

Ian964

I read that its illegal to run without a CAT, do you put it back in right before inspection and then take it out?