i am going to M11 this weekend and was thinking about running open headers at the track. The main reason is that i have a broken plate inside my muffler and it seems to be blocking off the drivers side exhaust. Would it be better to run open headers or with a y-pipe in place?

Scott

O and i am trailering it there

 

id say open headers if you take all that exhaust off it will save you a decent amount of weight
if i were going to do it id prolly throw some turn downs on there but othere than that id say go open with no y

 

I dont see no problems going open.

 

Are you running a closed loop tune? If so, where are the O2 sensors, with reference to the open collectors?

 

I'd be careful about open headers, depending where the 02's are, they could read outside air and throw off your O2 readings big time.

 

that was my concern and why i thought about leaving the y pipe on because they are close to the collector and i dont want it to falsely richen the car up. Does the PCM read the O2s at full throttle though?

Scott

 

It reads the O2 sensors all the time, but it doesn't use them to control anything at WOT.

Where it hurts you is the fact that it does use the O2 sensors in closed loop to adjust the fueling. It does that by reading the sensors and adding or cutting fuel with the BLM's. If you have open headers, and the O2 sensors are being backwashed with air, the PCM will see "lean" and add fuel using the BLM's. When yuo go WOT, the PCM uses the BLM's from Cell 15 (if the BLM's were adding fuel) and you end up running excessively rich at WOT.

If you drop the pipe when you get to the track, and don't drive it very much, particularly in the high load/high RPM cells, its not going to have a chance to mess with the BLM's. But there's always the chance the PCM will start to alter the BLM's and it can screw up your WOT A/F ratio. It a lot safer to keep the Y-pipe there.... how much are you possibly going to lose with an open Y-pipe compared to open headers?