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KWT880 · 07-09-2019, **(Subject: X15 turbo pressure )**

What is everyone seeing for turbo pressure under acceleration and when using the engine brake on a X15 performance motor?

I'm having a low turbo pressure issue on my truck when using the engine brake. I am getting 28psi at 15-1600 rpm and then after 1700 it will drop to 22psi at 1900. A couple others guys I haul with get 35+psi to 1900 rpm.

I get about 30psi under acceleration.

2018 KW T880, 565/2050 X15, 63,500kg/140,000lbs

Thanks!

Rawze · 07-09-2019, **(Subject: X15 turbo pressure )**

Not sure what it is "supposed to be", as I don't own one,.. but what you describe for boost during engine braking is spot on for most of the older model ISX's.

Next, if the jake boost did not drop off with high rpm's, it can cause the engine to drop a valve and destroy itself. Again, what you describe with the pressure falling off sounds like the engine is properly protecting itself.

Just make sure your exhaust gas pressure sensor is accurate and that the feed-piping is not blocked up. As well, verify the barometric sensor to ensure it does not think it is at high altitudes incorrectly and running in the wrong engine mode(s).

Some over-view,.. opinion...

As far as boost pressure goes, that engine does not need very much boost at all to produce full power because the compression ratio is so high. - Even the CM2350 (2017 engine) with its lower compression ratio than the X15, if you go much above about 32-33 psi (no egr), or about 36-psi or so (with egr), then you have high potential for engine damage.

If the "couple guys you haul with" are not running the same exact X15, make/model/year engine with the same exact calibration/programming, then there is no basis for comparison at all.

Also,.. the ISX with its emissions systems uses the turbo to make exhaust heat,.. (or not) to regulate the temperature exhaust canisters, DOC, DPF, SCR, etc.. so from one truck to the next, you could be getting totally different results depending on what is going on at any given moment.

The ISX has been developing and changing at a rapid rate. From one program to the next,.. one application to the next,.. from one model to the next, they are drastically different in how they operate.

If you think the engine is not as efficient as it should be, then pressurize the engine up and check it for boost and other air/egr/exhaust related leaks. I.E.> do proper tests.

Lastly, if you value the lifespan of the engine, you will get that 2050 torque (that is only between the engine killing 1100 and 1300 rpm range) out of it and set it at 1850 or less, keeping the HP level so you can haul heavy.

Has your truck been de-mandated or custom tuned? -- and if so, who did it? <- this could be a factor as well.

Lonestar10 · 07-09-2019, **(Subject: X15 turbo pressure )**

X15 performance vs x15 efficiency is also a compression difference efficiency is lower and will probably run higher boost on long pulls vs a performance model

03maxpower · 07-10-2019, **(Subject: X15 turbo pressure )**

I have a performance and get 30 pulling and jaking

Bsmith106 · 07-18-2019, **(Subject: X15 turbo pressure )**

It seems like the the Performance series would have a lower compression ratio than the efficiency series? Does anyone know the Actual compression numbers?

Rawze · 07-18-2019, **(Subject: X15 turbo pressure )**

(07-18-2019 )Bsmith106 Wrote: It seems like the the Performance series would have a lower compression ratio than the efficiency series? Does anyone know the Actual compression numbers?

the mid-tier is 19.1:1 and the performance series is 19.3:1 from my understanding,... that is high enough that the engine should produce a few hundred HP without even a turbo mounted on it.

Just some cautionary words for those who are thinking about de-mandatng one ...

I think a of of people trying to del these things don't realize that due to the small, somewhat restrictive turbo that normally would have a high AR ratio at higher power levels, the AR ratio is very heavily influenced and lowered/kept in check by the egr circuit itself. - Take that away and AR is going to be the determining factor first and foremost at those abnormally high compression ratios. This leads directly to...

(rough speculation) ... Theoretically, at that compression ratio, it should only take about 26-28 psi (give or take a psi or 2) or so to make 600HP with it with the EGR out of the way. This also means that much more than about 30 psi or so would likely severely shorten engine life on one without egr gas to keep it in check.