RobM626 Posted November 2, 2018 Share Posted November 2, 2018 Hey guys. How much boost is the mp8 supposed to push? 2012 mp8 with Allison auto. My my 08 mp7 is getting up to 39-40 psi... I’m lucky if i can get 28-29 with the mp8 fully loaded up hill. I can’t even hold it at 28. It will start to drop to 25-26 with WOT... Quote Link to comment https://www.bigmacktrucks.com/topic/54728-mp8-boost-question/ Share on other sites More sharing options...
steeler Posted November 4, 2018 Share Posted November 4, 2018 Not sure of the exact spec, but should be higher. What hp mp8 is it? Can you hear any squealing noises or anything abnormal? Quote Link to comment https://www.bigmacktrucks.com/topic/54728-mp8-boost-question/#findComment-408861 Share on other sites More sharing options...
RobM626 Posted November 4, 2018 Author Share Posted November 4, 2018 42 minutes ago, steeler said: Not sure of the exact spec, but should be higher. What hp mp8 is it? Can you hear any squealing noises or anything abnormal? Ita either 445 or 425 I can’t recall 100%, I gotta check valve cover... the fan clutch has been stuck on for a while and I can’t get it to go off. I changed the fan clutch assembly and nothing changed. I scanned it with computer and had some dpf codes. Had to do a forced regen. Also had a code for engine brake module. So I changed that out but still don’t have much engine braking power. I think that’s related to the low boost... this truck just feels like it has no balls anymore. It used to be a nice pulling truck and now I can barely go 30-35 mph. I’m thinking injectors. I gotta check for a boost leak though as well Quote Link to comment https://www.bigmacktrucks.com/topic/54728-mp8-boost-question/#findComment-408864 Share on other sites More sharing options...
Dirtymilkman Posted November 4, 2018 Share Posted November 4, 2018 Sounds like turbo actuator Quote Link to comment https://www.bigmacktrucks.com/topic/54728-mp8-boost-question/#findComment-408869 Share on other sites More sharing options...
steeler Posted November 4, 2018 Share Posted November 4, 2018 Do you still have active dpf codes? Could be derated causing your low power? Quote Link to comment https://www.bigmacktrucks.com/topic/54728-mp8-boost-question/#findComment-408877 Share on other sites More sharing options...
RobM626 Posted November 4, 2018 Author Share Posted November 4, 2018 10 hours ago, Dirtymilkman said: Sounds like turbo actuator That was a thought as well. Quote Link to comment https://www.bigmacktrucks.com/topic/54728-mp8-boost-question/#findComment-408890 Share on other sites More sharing options...
RobM626 Posted November 4, 2018 Author Share Posted November 4, 2018 7 hours ago, steeler said: Do you still have active dpf codes? Could be derated causing your low power? No. dpf codes are gone after I did forced regen. Quote Link to comment https://www.bigmacktrucks.com/topic/54728-mp8-boost-question/#findComment-408891 Share on other sites More sharing options...
Dirtymilkman Posted November 4, 2018 Share Posted November 4, 2018 My bad actuator never gave any bad codes. Quote Link to comment https://www.bigmacktrucks.com/topic/54728-mp8-boost-question/#findComment-408895 Share on other sites More sharing options...
RobM626 Posted November 4, 2018 Author Share Posted November 4, 2018 11 minutes ago, Dirtymilkman said: My bad actuator never gave any bad codes. If the vanes are dirty or clogged will t give codes? Same goes for egr.will it always give a code if it’s dirty? Quote Link to comment https://www.bigmacktrucks.com/topic/54728-mp8-boost-question/#findComment-408897 Share on other sites More sharing options...
Dirtymilkman Posted November 4, 2018 Share Posted November 4, 2018 2 hours ago, RobM626 said: If the vanes are dirty or clogged will t give codes? Same goes for egr.will it always give a code if it’s dirty? The codes will never tell you specifically what is wrong. They just tell you if something is out of it's normal operating limits. You then have to diagnose it from there. I had a bad scr for quite awhile and the fault codes kept leading us back to the egr. Finally they replaced the scr and all gas been good for months. Quote Link to comment https://www.bigmacktrucks.com/topic/54728-mp8-boost-question/#findComment-408906 Share on other sites More sharing options...
RobM626 Posted November 4, 2018 Author Share Posted November 4, 2018 26 minutes ago, Dirtymilkman said: The codes will never tell you specifically what is wrong. They just tell you if something is out of it's normal operating limits. You then have to diagnose it from there. I had a bad scr for quite awhile and the fault codes kept leading us back to the egr. Finally they replaced the scr and all gas been good for months. I went they 3 sets of nox sensors. Had the dpf baked like 3 times. Def dosers. It makes me think a fuel problem causing it to get so dirty faster than usual. I gotta start taking stuff apart. Before doing that I was just trying to figure out where to look first Quote Link to comment https://www.bigmacktrucks.com/topic/54728-mp8-boost-question/#findComment-408907 Share on other sites More sharing options...
Kbt mud carter Posted June 13, 2020 Share Posted June 13, 2020 I had a problem we’re I was lossing boost intermittent. There was no fault codes. The problem was the wiring in the front of the motor had rubbed through and was grounding on the block Quote Link to comment https://www.bigmacktrucks.com/topic/54728-mp8-boost-question/#findComment-453272 Share on other sites More sharing options...
Mark T Posted June 13, 2020 Share Posted June 13, 2020 Fan is stuck on ???? Air clutch ? I've found when a fan stays on and the engine doesn't run at the right temperature it never gets all the condensation out of the EGR cooler.....which makes it try to open the EGR valve more (and bleed off manifold pressure) Temperature is critical to everything working and if it's too cool it won't really think it has anything wrong with it. (no codes) If it is an air fan clutch ?? often the out of tank regulator (cut off) can be malfunctioning ....again, no codes. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/54728-mp8-boost-question/#findComment-453274 Share on other sites More sharing options...
Mark T Posted June 13, 2020 Share Posted June 13, 2020 Also, I'd imagine a fan on that no matter what type can draw 50+ HP if it's full on. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/54728-mp8-boost-question/#findComment-453276 Share on other sites More sharing options...
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