CM570 Reman Issues

[Rawze]

(10-26-2022 )hhow55 Wrote:  When Mr Hagg looked at mine, he told me max boost is about 20. I do my best to keep it at 10 when running for good fuel mileage. And yes it is cm570

The max boost for a CM570 is about 35-36 psi (37 max) at 600HP.

in the service manuals.. it generally says to refer to the specific engine make/model data-sheets...

(just an example.. not engine specific)...


However ... those are not so easily obtained.

CM570: To be even more precise, most of the old Engine performance datasheets (from cummins) for them (CPL 2442 = Sig. 600) used to show "Prime (optimal) power production" is a minimum of 33 psi as achieving the highest efficiency before any power loss occurs when turning 1750 RPM. <- only issue with making one run this low of boost levels is that the exhaust runs a bit too hot long term for most waste-gated turbochargers .. hence,.. the 35-36 PSI rating after considering the turbochargers needs as well.


On slightly newer model engines like the CM870 and the CM871, they used to always list the pressures that include controlling exhaust temp considerations due to the VGT turbocharger and its temperature ratings. Sig-600 CM870's and for most CM871's above 515HP, they all show that "Prime (optimal) power production" is now at 37.4 psi as achieving the highest efficiency before any power loss occurs when turning 1750 RPM. This number also does not consider the inflated boost value due to added 'EGR' pressures either... so it infers that it is still 35-36 PSI on those model engines?, but I doubt it. - Much dyno testing however has been done over the years and we know what a de-mandated CM870 or CM871 engine needs about 36-37~ish PSI optimally, 38 max.

On a non-deleted engine, this should be be about 38-39~psi or so due to EGR gas artificially raising the intake pressures. This has been observed time and again by testing and during troubleshooting of these engines. This clearly shows that up to about about 2 psi of intake pressure is the EGR gas itself, and NOT due to only the turbocharger.

On the CM2250 and newer model common rail engines, it gets murky. They seemed to have stopped making/providing detailed datasheets and Prime Power production publications for these engines that included all the extra info. Details like compression ratio, intake boost, and the other things that they used to list are now missing. Finding those specs is difficult and obscure.. though there have been a few advertisements running around the interwebs that have show some of this data here and there in the past.


In any event.. on ALL MODEL ISX engines, assuming that it has been de-mandated (no more egr gas) ... the proper boost level can be actually determined by measuring the post-turbo EGT's. Assuming for a moment that the injection timing + all other settings have been corrected 100% properly for that type of operation (as 90% of all programs are not ) .. and ...

assuming there is 100% absolutely nothing wrong with the engine including boost leaks, restrictions, any engine issues, etc...

At a sustained 100% throttle position, and at an RPM of 1650 - 1750 ... the EGT's should be about 1050 - 1100.F.

If it is very much out of this range (POST TURBO) .. then the boost level for the engine is either too high (lower then normal EGT's, like only ever able to get to about 900~ish) or too low (higher than normal EGT's, like say can get to 1200+).

Again though.. out of bounds EGT's does not mean your turbo is adjusted improperly.. maybe someone has engine or other issues.. as most engine should be adjusted properly to begin with .. but it is one consideration when someone just does not know the answers.

This is why we know what the boost levels should be for the various ISX models out there.. much testing has gotten that proper information... so here it is (roughly) again ...
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(Since all 570 overhaul kits are now 17.6(tier2) or 17.1(tier1) ratio .. ) CM570, Waste-gate at 35-36 psi for most and max is 37-PSI for a 600HP model on the intake at full operating load.

CM870, 871... 36-37 PSI for most engines, and 37~ish, 38 max for a 600HP model.

CM2250, no more than 36 PSI at 600HP+.

CM2350, no more than 33-34~psi at 600HP.

CM2350-X15, Not more than about 32~33PSI at 600HP.

The pressures keep dropping off from one model to the next because they keep raising compression ratio of these engines from one model the the next. This also shows up when testing them.

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The trouble is that too many people have bad/improper delete programming, so this info is mostly useless for the 90% of people who would read this that are running around out there with deleted engines.


In the case of the CM570... these same numbers should also hold true.

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Maybe Mr. Hag was referring to how someone should be driving it for optimal fuel mileage?>..

It is mentioned many times on this forum for people, if they can manage to drive it and keep the boost down to 20 or so by controlling their right foot, .. it will fair much better in fuel mileage.