Cat ECM: Lower Exhaust Backpressure

Hey folks..

We are testing a reduced backpressure muffler with some pretty high tech data collection gear. We are getting phenomenal mpg and torque results on a 1999 Peterbilt 3406E engine [dual stacks] but when we go to a 2002 Peterbilt C-12 [single stack and without our data collection gear] we are marginal. We experienced similar flat to marginal results on ACERTS [C15 2003-2006] but we always attributed that to additional emission parameters programmed in for the ACERTS and the fact that the ACERT catalytic converter muffler [which must have huge backpressure] being mapped into the ECM. But the 2002 Peterbilt with C12 would not have those emission standards.

We have even checked for reversion pulses and the particular muffler we are testing not only reduces backpressure but also seems to eliminate reversion pulses. [We are strapping mufflers on a sister straight stack to fully determine the elimination of reversion pulses]. So it is not a case of backpressure not being reduced by this product.

We believe the difference is ECM related.

We hope to transfer our data collection system to a C12 to see what is happening but in the interim…. Any ideas out there as to why the difference?? We are still testing to try to diagnose but any thoughts as to what happened between 1999 and 2002 would be appreciated.

Thanks

 

Thanks for The reply.

"The ecm also really ####### the timing once it sees that you got rid of the catalytic converters..."

How does it "see" the CC mufflers are no longer there since there is no backpressure sensor?? From the turbo??? Any other sensors picking up the change??

Also, we had a guy in 2005 International with C13 remove his CC muffler and replace with a backpressure reducing muffler. He had marginal improvement in mpg. Then he had a service bulletin to have the C13 ecm flashed. Post flash the mpg jumped to 10-12% better. Would the flash coupled with the reduced backpressure muffler being installed when flashed have an impact?

[We tried to have the Cat dealer tell us what parameters were changed with the flash. That was a"top secrect" no go.]

I appreciate the feedback.

 

Thanks for the info.

We are going to test on an ACERT C15 with our data collection gear. You have given us some areas for us to drop our sensor package into that we may not have thought of for readings before and after.

This muffler does result in lower exhaust temperatures so if the ECM is reading that after the instal that could be part of the problem.

Do you think if we can intercept the exhaust temperature signal and let the ECM thinks everything is OK we would see any difference?? Or are the turbos just too much of a constipator to be effected by post turbo backpressure improvement?? [By the by... we cut open a CC muffler and it is also a huge constipator. About 8 inch honey comb topped off with a reverse flow muffler.]

Much appreciated!