870 boost

[Rawze]

(08-11-2022 )Kbarnes0 Wrote:  Under a hard pull 100% throttle, should boost maintain at peak level, until rpm slows due to the grade?

My boost varys quite a bit. Rarely do I see 35-36psi. Typically pulls at 32/33. Seems like it should hold 36+ consistently.

What you are describing is the most common derate that CM870 engines get. It is very well known.

If the CM870 goes into a boost derate then the boost will typically jump up to about 36 psi in a pull, then fall on its face back to 30-32 psi. It is the most common derate those things will do.

This can happen because someone unplugged the egr valve or has defeated the egr in some way. EGT's also will skyrocket and this is very hard on the turbo.

Like I said.. It is a very well known condition with CM870's, and a person would think that after 15+ years of them being out there in trucks.. that some of the complete morons who are half-arsse making de-mandate (delete) programs for them would know this by now.. but that is not the case at all.

-= Someone's half-arssed delete programming that makes the check engine lights go away cannot fix that derate, but instead, typically only makes things worse by shortening the life of the engine due to garbage settings.

The problem is in the ram memory of the ecm, and not even in the programming itself. CM870's are special that way, and very few people understand them properly.

-=============

Forum member 'running rough' here on the forum knows how to program them and adjust those ram memory settings properly .. I trained him myself on handling this issue. I only do things thru e-mail (files only) and don't mess with CM870's, as they require someone to remote desktop to them.. and i do not do remoter desktop work. 'running Rough' does most of the CM870 engines for people on here instead. - Maybe PM him for some advice, etc.

If you have a de-mandate program in it then I would also suggest that you. or someone copies it from the ecm and e-mail a copy to me for a proper review so that you can find out if it was harming your engine internally.

Most de-mandate program are very harmful, all while the truck owner swearing it seems to run ok. Bad programming can shorten the engine life by as much as 75% and the truck owner never know it until it is far too late.