Open Downpipe Problems

[White1GST]

The other day I installed my Punishment Racing downpipe. I was going to install my 3" exhaust but I have to wait about a week so right now the car is open downpipe. I went to take it out for a drive and it wasn't too loud but when I'm slowing down to come to a stop the car will shutoff. If I'm sitting there idling or driving its fine but it turns off just about every time I slow down to stop.

I found a small leak between the downpipe and o2 housing that I'll be fixing today, could that be causing the problem? My only other engine mods are a 3" intake, k&n filter, and a boost gauge. Could my car be running lean because I have no fuel mods running open downpipe. If so would rewiring the fuel pump help this?

I'm not planning on driving the car much until I get the exhaust on anyway but it would be nice to know I have a car to drive that will get me where I need to go just in case. Thanks for any help.

 

[Rob10_99]

Not that loud compared to a ### ridin' a harley?
Geezuz when I had a side exit it was annoyingly loud, maby it was because of the tube thickness.

Yes your issue is most likely from the exhaust leak pre02 sensor.

 

[White1GST]

Noise in a car just doesn't really bother me I guess. Its not any louder than my buddies old SRT-4. As for the leak wouldn't that be post O2 sensor since its where the downpipe connects to the housing?
I cranked the bolts down a few minutes ago and it definitely helped the leak but theres still a leak. Could the O2 housing be warped because of its age? What size are the stock nuts that connect the downpipe to the housing supposed to be? I've been using a 19mm ratchet but it feels loose on the nut, an 18mm doesn't want to go on the nut though.

 

[tscook3]

Wouldn't think that the leak would have anything to do with it if it is where the downpipe connects to the o2. Not positive what it could be. I'm guessing that it didn't do it until you disconnected it? Might be another issue that arose. I don't think that the fuel system would have any effect on running open downpipe. On my old o2, as far as I remember, I think the bolts connecting it to the turbo were either a 15mm or 17mm, might be different for you though. Good luck figuring out what it is, sorry for the limited help.

 

[ineedagsx]

how big is the pipe? u do need SOME kind of back pressure... and does ### really get blurted out? it doesnt mean ### it means idiot riding a harley that is loud and obnoxios... hasnt anyone seen the new dictionary meaning

 

[Hubbell91Tsi]

how big is the pipe? u do need SOME kind of back pressure... and does ### really get blurted out? it doesnt mean ### it means idiot riding a harley that is loud and obnoxios... hasnt anyone seen the new dictionary meaning

wrong, no back pressure is needed.

 

[Rob10_99]

It's not 'real' backpressure you need for a correct 02 reading, its more like 2 feet of pipe estimation.
Yes that leak on the dp/02housing could cause an off 02 reading.

Anyone else find a good deal on the new dictionary yet?

 

[White1GST]

Got an update. I used Ultra Copper RTV on the downpipe gasket and reattached it yesterday. I cranked down the bolts and theres no leaking now but I'm still having the same problem. I took it out and it was still turning off when I would come to a stop. It's not as bad as it was before so fixing the leaked helped but what else could be the problem? It does it more often if I'm going faster or if I floor it and then come to a stop.

 

[supersplat310]

A buddy of mine was having the same problem with his 95 GST. Turns out his MAF sensor was blown because of his exhaust. Try cleaning it and see if it helps any. I hope it works out for you.

 

[falcon8r]

I don't want to rain on your parade but the RTV and the O2 sensor do not play well together. The RTV fumes as it evaporates/reacts will plug up the o2's operation. Way meaner than race gas. Can you look at the o2 sensor output for proper switching? You have to rule out the o2 sensor. Tres...

 

[talon913]

seems like to much airflow.or you gettting a major back spin especially if you still have the 14b..i was have problems with open down pipe with my 16g..it may sound ok but your probly gettin alot of knock up in high rpms

 

[White1GST]

I don't want to rain on your parade but the RTV and the O2 sensor do not play well together. The RTV fumes as it evaporates/reacts will plug up the o2's operation. Way meaner than race gas. Can you look at the o2 sensor output for proper switching? You have to rule out the o2 sensor. Tres...

Well it says its O2 sensor safe and from what I've read quite a few people use it. How would I do that?

seems like to much airflow.or you gettting a major back spin especially if you still have the 14b..i was have problems with open down pipe with my 16g..it may sound ok but your probly gettin alot of knock up in high rpms

Well I'm just going to keep the car off the road and do some work I want to get done on it anyway until the test pipe gets here. Once that gets here I'll put the exhaust on and see if the problem continues.

 

[400hp93talon]

Are you sure the wastegate isnt sticking open? Just an idea and Im pretty sure running an open downpipe does mess with the o2 sensors reading. Like when some cars are tuned on dynos and they dont have a wide band so they run the o2 sensor that reads at the very tip of your exhaust for the computer they are using. Then later they put wide bands in and it has a completely different reading(more accurate) being closer to the motor. So only having 2 feet of exhaust has to mess with it some how unless it has been tuned with it. I guess you will find out when you put the rest of the exhaust on!!

 

[ThatGS-T]

Old thread but incas someone has the same issue try disconnecting the battery and letting the computer reset and relearn