Engine/Transmission (1998.5 - 2002) Quesion Regarding Defueling/Overboost

[kdw75]

Ok, well unless I am missing something here the trucks ECM should defuel when boost exceeds 21 psi or something close to that right? Well, I have posted several times and I have been having trouble with surging and the dealer said I had a bad ECM so I replaced it with one I bought from Cummins which cost $1150 after they flashed it for $250. Tonight I totally romoved the Powermax2 and all of it's wiring since I am trying to find out why it is getting surges of fuel and wanted to eliminate that as a possibility. I still have in my DD stage III injectors but the truck is otherwise stock except the waste gate doesn't open until it hits 44psi. I expected my truck to do something strange when I hit 21 psi of boost but it did absolutely nothing unusual. It just kept climbing and topped out at 32 PSI of boost. First of all I was surprised that just the injectors would build that much, but secondly I couldn't understand why the ECM didn't mind it going that high.



Keith



'98. 5 2500 QC LB, PMax2, DDIII injectors, Used to have TST reflashed ECM

 

[KLockliear]

You may not feel it pulling the power back, especially with Stage 3's in it. Get it on a dyno and you will see it in the graph.



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[TractorNut]

I had my DD-UFM off the truck for a few weeks. . but didn't remove the elbow... I was expecting the same. . but it still devoloped about 25-26 psi. . and no light. . (I didnt check to see if it set a code. . ) It seemed OK. . until I put a tailer on. . it woud go great until it went over about 20-22 psi. . and then. . that was it... it was like there was a wall. . I just learned to keep it in the stock boost range. . until the box was back in... (stock injectors. )

(Keith's graph shows it the best. . )

Good Luck

Bryan

 

[kdw75]

Well, I guess there is a difference but from seat of the pants before and after removing the PMax wiring I can't tell a bit of a difference and the boost levels are identical. Just thought that was strange.



Keith

 

[TBrown]

Keith, how do you like the way your truck is set up. I have close to the same as you except for stock injectors and am thinking about going to DDII's or DDIII's. Any suggestions? You have your stock turbo? Thanks, anyone else have any advice?

Tony

 

[kdw75]

Well, I think it runs pretty good but I sure miss the extra power of my old ECM. Everything else on the truck is stock except I redid all the fuel lines and got rid of the banjo bolts. It runs about 41 lbs of boost wide open. I am really surprised by the lack of smoke. With my old ECM if you would step into it people could see the smoke cloud for several blocks and you couldn't hardly see any cars behind you. Now though I hardly get more than a faint trail of smoke. And to be honest I don't think all that smoke made much more power. I guess if you can't burn it then you aren't going to get any power out of it. I am going to upgrade mine though to a Powermax 3 or one for off road since I couldn't care less about smoke and intend to upgrade to a bigger turbo before too long. I do really like to DDIIIs to answer your question.



Keith

 

[TBrown]

Keith, what do you see for egt's? I have a pm2 and am plan on upgrading it to a pm3 adjustable by adding the remote. This way I think I will be able to tow by setting it down to a lower level. With my pm2 I can make some smoke if I really get on it above 2500 rpm's. I run around 38 psi now, but think I should set it back to around 36 or so. One other question, does your boost LED light up when your truck is idling? Mine is on all the time, not sure anymore if that is what it is supposed to be doing.

Thanks,

Tony

 

[kdw75]

Yeah, my boost light glow fairly bright all the time. I thought this was odd too but it has done it since new. I have a K&N filter and straight exhaust without any resonator or muffler and I never have any trouble with temperatures while towning. I don't tow anything super heavy. I tow about 12,000 lbs usually and never have any trouble with EGTs on the highway doing 75 or 80. Of course I live in Missouri and don't have any real mountains or anything. If I pull quickly onto a highway sometimes my temps will get up there but it is very easy to back off just a bit and continue on. I am amazed at how cool it seems to stay.



Keith