2006 CM870 high EGTs

[JBaird]

I have a 2006 CM870 in a Kenworth. I’m on the 4th head, and 2nd bottom end in 425,000 miles. This engine has been worked on by 4 different shops, including Rush Peterbilt the last time. Every tuning result and rebuild still ends with high EGTs. I have 2500 miles on the current inframe with new liners, rods, pistons, oil pump, rebuilt oil cooler, rod and main bearings, and head. We did not change the turbo (still stock VGT rebuilt 150,000 miles ago) we reused both cams (injection cam has approx (175,000) miles, and reused rocker arm assemblies. The truck was remandated by Rush Peterbilt on the last head replacement. They couldn’t get rid of a shutter in the 1200 to 1400 rpm range. If you fall into that rpm range under a load the EGTs would skyrocket. With the current build the truck is not mandated. The truck with an empty trailer will run between 850 and 1000 degrees. The EGT actually seems to run cooler while loaded unless you are on a long pull, then I have to be soft on the petal to keep the temps under a 1000 degrees. I think sometimes the truck may be boosting at idle, the exhaust temps at idle won’t come under 500 degs. The truck is tuned at a 530 that is what it came stock at from the factory. The exhaust only has a small resonator. This truck does about 75 miles a day off pavement, and also somewhere around 350 red lights a day and is mostly over gross with a permit. The shop that worked on the truck are good folks and has bent over backwards trying to help me solve this, and I think they are at a loss and I know they have lost money on this rebuild. So I’m reaching out to this group with my hat in my hands to try and figure this out. Thanks