In an effort to make my exhaust system easy to build and reliable I bought a set of slip on circle track collectors to go from the shorty headers to the side pipes, and it looks pretty sweet IMO. I could not make full length headers because they will not fit in the car without a joint. Currently both stainless shorty headers are completly welded and the sidepipes and also completed, so I am kind of commited to the setup.

Only now do I realize the slip on collectors might play havoc with the O2. The headers are 1-5/8" and slip into the 1-7/8" collectors nice and snug, but there is small gaps in some places. As I built these I was not really worried about small exhaust leaks cause it will probibly be very loud, and drowned out the leaks. So, will any small leaks cause the O2 to read incorrectly? any ideas for preventing leaks?

I am going to put the O2 bung in the passenger side sidepipe right at the collector. Currentylthe megasquirt is running with no feedback, but I would like to add a wideband this spring.

any help would be great!!!

thanks,

matt

before welding:

 

my bad, the slip-ons are 1-3/4"
http://www.speedwaymotors.com/p/3567...ollectors.html

 

if they fit tightly, gobs and gobs of ultra copper... lol Any exhaust leak near an O2 sensor will cause sampling contamination during closed loop operation. The workaround if you can't do any better with the hardware is to run open loop, but dialing in the setup would still be just as "in the dark" as your wideband would see the same contamination as a narrow.

 

Use of any sealer not "sensor safe", will put the hurt on the O2...

 

agreed, most permatex silicones are sensor safe

 

I have had a lot of O2 tuning trouble with slip-ons, even with sealer because with heat it eventually leaks due to slippage caused by exhaust system contraction/expansion. There is a lot of exhaust scavenging of outside air thru leaks trailing each high velocity exhaust pulse.

 

I accept it is doubtful that I will be able to seal the slip ons, so I think I have a new idea.

Since I am running bank fire with the megasquirt, every cyclinder in theory should be running the same afr. So what if I put the O2 sensor in the #2 primary tube a couple inches prior to the slip on? I know dynos run O2's in every primary, so it should work, right? Would the O2 in that primary cause a problem with the flow of the exhaust gases?

any ideas?

 

It will likely still suffer some ill effect from any leaks, even pre-slip connector, though maybe the velocity in the primary will be enough to keep your flow downstream past the slip. On the other hand, you don't want the O2 too close to the cylinder discharge either. There's no way you can rework the exhaust? I know you're "committed" to the setup, but it just seems like you're asking for trouble in the long run.

 

my only other option would be to build flanges and bolt the header to the collector, but then where am I going to get gasket? bahhh I really screwed myself on this. How about I put the O2 in the #2 primary (the longest one) about 5" up from the slip on and about 12" from the head? The factory put there O2 in the manifold if I am not mistaken.

I dont know