If you've been following my posts, you know that one of my chief concerns in installing a Y-pipe has been the potential for long-term engine damage. It's been postulated that damage may occur from an exhaust flow inbalance between cylinder banks caused by removing just one of the pre-cats. I posed this issue to Dave at Random Technology and he responded as follows:

"An engine doesn't really care if exhaust flow is unbalanced from side to side. The only potential damage could come from the air/fuel ratio being dramatically different from side to side, but most late model "V" engines have dual oxygen sensors, so the computer will automatically compensate for differences in air flow and keep fuel flow at the proper levels."

Thought you guys might find Dave's response useful.

 

Dan 93 SE here. My main computer is down. This post supports my theory that the 3rd Gen Maxima (which has only 1 02 sensor) is at risk if you have a dented anterior down pipe, causing the front bank of cylinders to run rich, so the 02 sensor appropriatly leans down the fuel mixture, causing the rear bank to run too lean. This happened to me, thank God it didn't do any permanent damage. It sure burnt up my plantinum plugs.If my car had a dented pipe, I would at least pull the plugs and compare front to rear. Thanks for the info.
Dan WSP

 

Interesting info Bruce... thanks.

 

So it sounds like the only reason we would need to remove the front pre-cat is to increase flow and power and not to balance exhaust flow. Therefore, we WILL NOT increase the potential for engine damage if we leave the front pre-cat on? The next question would be, "how much power can we gain by removing the front pre-cat?

 

Unfortunately, the question is moot. Removing the front pre-cat will generate a check engine light and place the ECU in safe mode. To the best of my knowledge, no-one has figured out how to get around that yet.

 

I realize this thread is old, but since y2kse just gave a link to it in another thread and it might see some action, I felt I should refer people to my site on how I removed the front precat and also dyno results to show my gains. Just click on the site in my sig and follow the links.