hmmm...may look into that, as I am planning on keeping this car for a long while.

You ran it from the check valve that is "above" the SAI valve?

 

Great solution! I had this same idea - bypass the ports entirely, but maintain the SAI functionality. I'm not sure, but technically I think modification of the emissions system is illegal even though you improved it. Any issues passing the visual smog inspection?

 

Massachusetts, for one, doesn't have a visual inspection on an OBD2 car, they let the computer do the talking. This is a really interesting solution, as I'm considering a 97 C2 with clogged ports at a decent price.

 

"Rather than performing a whole top end rebuild on an otherwise perfectly good engine,"

That should ALWAYS be the last approach, especially if the oil consumption is less than
a quart every 1200-1500 miles. Many independents have good success cleaning the passages,
so when a DIY effort fails, have it done by a shop. It's not that expensive, i.e. about 10%
or less than having a valve job.

 

do you have a pic?

 

I don't think the NYS emissions inspection has a visual inspection aspect, so it passed with no issues, since it performs the same function the factory intended.
OBD-II cars here are no longer subject to the tailpipe sniffer - if the OBD reports that the car is clean, that's enough.
BTW - someone mentioned resetting, etc. That will not work, since the OBD system has to go through the readiness codes. There are a few (4, as I remember) that come after the SAI check. So, you can never get beyond that without triggering the dreaded CEL.
Removing the CEL bulb is not a solution either. At least not in the NY metro area - part of the test is confirming that turning the key to the "on" position lights all the appropriate dash warning lights.

 

This was all done at a P-shop owned by a friend and they weren't able to clear any more than I had already done. I actually had the whole thing on the ground for a LWF install when I managed to clear out one side. I probably just opened up a single passage on that bank, but it was enough to allow some flow through. However, since the other bank would have triggered the CEL anyway, I had to take the next logical step.

 

I didn't take any pictures, but the plumbing is pretty straightforward. I removed and discarded the manifold that distributes the air pump flow to each bank and ran a line, with a "T", to a bung welded just before each catalyst. I also plugged the SAI openings on both heads. Everything else is still there and the system still works as intended. Just not as pretty.

 

since i can't visualize this set-up, i will simply ask: would a state emissions inspector be able to see that something was modified? here in CA they visually inspect as well as sniff as well as connect your car to the computer...

 

Damn, that is good.....any pics of that?

 

I'd assume you could put the ports into the exhaust on the top or side of the pipe where it would be relatively hidden; the air cleaner should hide the check valve. I wouldn't think there would be much for them to notice since they are probably just looking to see if the cats are there.

 

Loren -- outstanding write up on this issue. Bottom line, the issue is caused by Porsche engine engineers and there's no easy fix. I hold Porsche responsible -- they've never lifted a finger to help us out.

 

Marco,

Any chance you can take a few pictures to show us your work? In particular I would like to see the check valve and the size of the hoses.

GREAT WORK!

 

I'm not sure how competent the inspectors are in CA and other states, but here in Ohio they could not tell you the first thing about a 993, nor it's emission system.

Oh, they do know the car has a catalytic convertor, and have to verify it's in place. You can see them checking for it when they slide the mirror under the door and look. It's happened the last two times I was there... mirror goes under the door, a 3 minute look to verify it's there, and then I get checked off for it being in place.

I'm not sure what they saw while they were looking, but I'm absolutely certain it wasn't a catalytic convertor. They never asked me one question about it...

 

Sorry. I've been away, so no responses to the above questions.
I didn't take any pictures, but I'll try and get some soon.

In response the "will an emissions inspector see that somehting is not OEM". In short - yes. It's hard to hide, since there's a bung welded into the exhaust just before each cat. I don't think there's any way to truly hide that.
As far as hiding the check valve - no need. I'm still using the stock unit and even though I replaced the distribution manifold with my own "T", all of this is above the engine tray toward the front of the car. Which is to say, it might as well be invisible.
The tubing runs through a hole I drilled in the tray, back to the catalytic converters. Most of this run can be hidden pretty well. I used high temp "rubber" and ran it where there was plenty of room. If you run a hard line instead, it will blend in much better, but you still have the problem of tapping into the exhaust where it's not obvious. I suppose you could just inject the air into the exhaust farther back (the OEM system does). I didn't do it that way, only because this way was neater.