High compression ISX

[Truckdriven]

In my area there is a strong prevailing reputation that the low HP/higher compression ISX is worthless junk, they will randomly window the block at randomly 850k for no reason, etc. I know there is a popular shop saying this but I always had my doubts, Is there actually more problems with these models weather it be minor or major? Do they need to be maintained in any different way than the higher HP models to keep reliable and long lasting???

[tree98]

(01-20-2023 )Truckdriven Wrote:  In my area there is a strong prevailing reputation that the low HP/higher compression ISX is worthless junk

What exactly are you referring to? Are you talking about an X15 that's set to a low HP?

I'm sure you'll window the block if you use a demandate from whoever these guys are (judging by your location i think i know) that are saying that. Sounds like a sad excuse used by idiots who don't understand how to tune these high compression engines that are designed entirely around the use of EGR gas.

I haven't heard of these things happening to anyone that has good programming. If I were you I would stay far far away from that place and lose there phone number.

This video Rawze made might help you understand

https://youtu.be/sQESWU3_wAI

[Rawze]

(01-20-2023 )Truckdriven Wrote:  In my area there is a strong prevailing reputation that the low HP/higher compression ISX is worthless junk, they will randomly window the block at randomly 850k for no reason, etc. I know there is a popular shop saying this but I always had my doubts, Is there actually more problems with these models weather it be minor or major? Do they need to be maintained in any different way than the higher HP models to keep reliable and long lasting???

Your post describes the outcomes of the bad delete scene, and abuse/ neglect, etc.. all in a nutshell.

It is just as much a plague of bad information that people who are quick to complain about the design of the engine and to make convoluted theories/excuses up.. then let them echo around in a circle until everyone believes it, rather than actually investigate the underlying causes .. of which will always be an abuse of some sort (bad delete, neglect, etc.) at the end of the day.


DON'T get caught up in that garbage mess of convoluted theories...

These same type of miscomceptions are all over the place. A few years back it was the excuse of "softer engine blocks" .. and before that.. "metal not designed for non-egr exhaust temperatures"... and all sorts of other garbage-can theories.

At the end of the day.. it is these clowns who hang out on social medai and at shops who do horrible deletes and under-par work that are clammering at straws all the time rather than own up to the fact that it is the very abuse of the engine that they, and about 90% of others have created, that cause all those kinds of common failures.


NO... I have not seen this as a trend for anyone who properly cared for their engine.. and also did not have a bad de-mandate program shoved into it.


besides that ... the higher asperated compression ratio would have nothing much whatsoever to do with enigne longevity once a turbocharger is introduced into the mix. -= The whole premace of a turbocharger is to "Dynamicly Raise the comporession ratio" of an enigne.. and that is its primary purpose.... SO....

Also ... A naturally higher compression engine of the same design .. simply needs "LESS turbocharging" to get it to its older cousins same compression ratio under full operating load to make the same HP output. It is as simple as that. The final cylinder pressures are going to BE THE SAME under operating loads as they are with the same exact engine that has a lower compression ratio.

THE FAILURES that you describe as being a "plague"... are in fact due to some complete moron trying to put 38-psi (the boost level used by the older cousin engine to get to 600HP for example) into an engine that only needs 31-psi to achieve the same 600HP, ... and then wonder why it failed with a piston thru the block after a few hundred thousand miles.


THIS IS WHY...

* The CM870/871 = takes (36-37 optimally), and 37,38 psi boost MAX to get to 600HP.. any more boost than this destroys the engine at some point... even at lower HP numbers.


* The CM2250 = takes (35 optimally), and 34,36 psi boost MAX to get to 600HP.. any more boost than this destroys the engine at some point... even at lower HP numbers.

* The CM2350-X101 = takes (33.5 optimally), and 33,34 psi boost MAX to get to 600HP.. any more boost than this destroys the engine at some point... even at lower HP numbers.

* The X15-CM2350 = takes (31.5~ish, 32 optimally), and 30,33 psi boost MAX to get to 600HP.. any more boost than this destroys the engine at some point... even at lower HP numbers.



I.E>. The higher the compression engines .. need LESS BOOST to get them back to the same exact final cylinder pressures, to get back to the same HP output to the flywheel. -= IF THE FINAL CYLINDER PRESSURES WERE ACTUALLY HIGHER >>> THEN THE HP OUTPUT TO THE FLYWHEEL WOULD BE HIGHER TOO, BECAUSE IT WOULD DRIVE THE PISTONS DOWN HARDER!>>>

It is only when someone over-boosts an engine vs the power level generated, do you get the same (sometimes less) output to the flywheel, because it causes the engine to labor against its own exhaust gasses all day long .. (typical bad delete) ... trapping excessive heat and creating a ton more friction in the cylinders, .. then wondered why it sent a piston thru the block due to all the excess friction generated in the cylinders. This BEFORE EVEN ADDING ANY POWER!.

-====

So, the most common cause of this type of failure is actually ... Some idiot who takes that new X15 and shoves a bad delete in it + puts it to 36, or even 38+ psi boost to it like a fool + has it running in the wrong engine mode permanently, .. and then blames it all on "compression ratio", or "weaker metal" and all sorts of garbage when it windows the block, instead of looking in the mirror.

I have also seen it on non-deleted engines.. when some idiot lets is get carbon packed so incredibly bad, that it eats the rings out of it and sends a piston thru the block when one of the rings finally snaps.
here is a fine example: http://rawze.com/forums/showthread.php?t...4#pid74364

[tree98]

I remember guys claiming the 870 blocks were made from harder steel than the 871. 870's typically go longer than 871's before dropping a liner.

The actual reason for that is the difference in response time between an air actuated turbo and an electronic actuated one.

These bullshit rumors spread like wild fire though.

[SquareOne]

(01-21-2023 )tree98 Wrote:  ...These bullshit rumors spread like wild fire though.

Misinformation is a damn plague...

[Truckdriven]

Thanks for all the responses on this. Based on what I read on this forum I had pretty well come to the conclusion it was bad programming, lack of maintenance as was pointed out but I wanted to hear it from the legend himself, Rawze, and he delivered! Thanks for the detailed explanation on cylinder pressures boost Etc!