tkerrmd

Since I have taken off my 100 cell cats and gone to a straight pipe from the turbo to the tips car seems to stall out easily. dealer says it is most likely the combination of the LWFW and no back pressure.
Well I certainly am not a porsche mechanic but I didnt make the correlation myself.
So I throw myself on the mercy of the court here and hopefully someone knows something about this combination that I dont?
Any insight would be greatly appreciated

tom

GTi35R

what did you do with the 02 sensors that were there? Did you make provisions in the test pipe for them?

99firehawk

light weight flywheel is definatly a contributier....but as for back pressure im gonna say no. With a straigt test pipe on a turbo there is only 12 or so inchs of piping from o2 sensor to tip, on decel and at rest thats not enough pipe to prevent the back flow of fresh air into the pipe and making the car dump fuel to cominsate the lean condtion it is seeing. Ive alwaysheard and lived by the ruel that 18 inchs as the minumum from front o2 senor to end of exhuast pipe on efi cars. Now a talanted tuner could likely adjust the maps to give you a richer idel but then it will smell stinky like my car

tkerrmd

The sensors are in approx the same location on the straight pipes as the cats had them. Thanks GTi. firehawk I was hoping you would chime in, thanks. I'm going to ask them about that tomorrow!

thanks again

tom

Dock

It doesn't seem to me that there would be any back pressure issue with the Turbo in an off-throttle situation, regardless of what exhaust system is present.

99firehawk

i understand that but maybe the cats are enough of a restriction (also esentialy a heating element) that the back flow (not back pressure) is negligent. Some thig you could wtach with a scanner and see if the o2s are going very lean on decel and at rest

tkerrmd

thanks Dock, that's what I thought but now not sure?
Firehawk, again I'm going to get at these guys tomorrow to see what they say, thanks

Wachuko

Tom, let me know if you want to try with the cats again... I have them on the car but it is easy to take them off if you want to test back with them installed.

tkerrmd

Jaime, nice offer, I appreciate it, but I would leave your car alone, its perfect!! I'll get this sorted out, I think it is down to a software issue.

Oak

tom, curous, did you ever resolve the cut-out issue with the clutch pedal?

Woodster

Tom,
why not run a good exhaust system (of your choice) with cats (high flow 100 cell/in.), and then
you will be able to converse while in your car, use your cell phone, and get your beautiful Turbo
back to proper running condition. I feel your pain. Maybe try new exhaust and new programming?

good luck!

MK

Dock

Tom - I still think it's the combination of the LWFW and your current tuning.

Oak

HELLO! tom, don't you have the EVO LWFW and tuning? If so, this would be the first I have heard of this problem. I know the 993tt has some issues with the LWFW coming off throttle and dieing.

Dock

I have the LWFW, and if the AC is on, there are times when the engine will drop below idle rpm and stop running following a throttle release from higher rpm. I remember sitting at a stop light when a guy pulls up and asks to hear my exhaust. I throttle blip (AC is on) and the engine drops down sub-idle after the blip..and quits running. No problems if the AC is off.

mdrums

Tom, get that car fixed...Sebring in November is coming up! Dinner soon OK?