Cat ECM: Lower Exhaust Backpressure - Truckers' Trucking Forum | Message Board

dcw · **^ Top** #1 07.14.2008

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

550hpW900L · **^ Top** #2 07.14.2008

I dont think you will see as much back pressure from a C12 as a 3406E, being almost 3 liters smaller. Yes the ecm's are mapped for it, the C12 has a "wacky" program in it, responds to some mods very well where a 3406E, C15, C16 wont.

Same goes for the ACERT's, but with the ACERT your mufflers dont cause that much back pressure comparing them to the turbos. The exhaust housings really choke this engine down, so even if you get rid of the catalytic converters you still have LOTS of back pressure from the turbos, couple that with 18:1 compression and 50+psi of boost, that engine wont breathe well untill you get rid of the twins. The ecm also really retards the timing once it sees that you got rid of the catalytic converters, it might take a few days for it to learn, but once it does ,the timing is retarded and the motor is so sluggish it just sucks fuel and has a lot of turbo lag.

dcw · **^ Top** #3 07.14.2008

Thanks for The reply.

"The ecm also really retards 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.

550hpW900L · **^ Top** #4 07.14.2008

It will see the exhaust temps drop, and i guess thats a tip off, when they drop to much it will retard the timing after a while to get them back up, CATs theory is higher exhaust temps means lower emissions

Yes the new CAT flash files are better than what they had before and flashed every ecm in 2002-2007 with those crappy files. Now the new files are designed for better throttle response and better millage.

Typical CAT everything is hush hush, you wont get a word out of them.
Now if you have a 99 and older CAT with the 40 pin ecm they will even give you a special puller program for sled pulling, but you have to sign a piece of paper saying you wont use it on the street. These programs are very clean, get good millage on the street, and run very cool on the exhaust, i know a guy with a 1LW 3406E 550hp with one of those programs and he did 660hp to the tires.

dcw · **^ Top** #5 07.15.2008

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!

550hpW900L · **^ Top** #6 07.15.2008

Quote:

Originally Posted by dcw

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!

Yeah i hod those CC mufflers on my bridge, they sucked. Yes you will see a mpg gain and power gain with muffler removal, but it wont be a enormous difference since the motor will still be corked up. Yes if you can get the ecm to see "normal" exhaust temps, by rigging a resistor in the harness somehow, then it wont retard timing.

There are ways to convert a ACERT back to single turbo but its quite a bit of $$$, to some people not worth the hassle, but if i owned one i would do it in a heartbeat.

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