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Unusual behavior while tuning on dyno with Motec M150.

Practical Diesel Tuning

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I finally managed to get my hilux on the Dyno today but ended up having some strange behavior with the power output.

We were staring the runs at 1250rpm and ending at 4000. At the 40 second mark in the log you can see the dyno start the run. Just after the 2200 rpm mark and right at full boost the rpm drops a bit before carrying on with the run. I tried getting the boost to come on sooner and added more fuel but it leaned over every time in that spot. It was making 630NM at the flywheel when the rpm dropped back. Unfortunately i ran out of time to look into the issue further.

Im still working on my tuning skill set but im pretty happy with the results so far.

I have attached a log file for one of the runs which clearly shows what i describe.

Thanks John.

Attached Files


I'm trying to get a copy of Motec software to use to analyse your log.


Thanks Nick,

Its free to download from there web site.

Cheers John.

Looking at your logfile, I notice that this happens when the Boost Pressure is within 10 kPa of the Boost Aim. That is the piont when the Boost Servo Actuator Position is 36%, and the acceleration doesn't continue until the actuator reaches 48% (even when Boost hits the target with the Actuator at 42%)

Perhaps you need to tune the Boost Servo Linearisation -- add more boost control points, and perhaps modify the Engine Speed Points to match your needs.

Hope that helps!

Thanks for the reply David,

I had an opportunity to do another couple of quick runs again in the weekend I took some fuel out down low and it flattened out the curve a bit. Im in the process of installing a larger VNT turbo and i will be fitting a EMAP sensor when i do this. I suspect that some of the issue is excessive back pressure. I may be able to open up the VNT earlier while maintaining the same boost response but allowing the engine to breathe. I have attached the log file for the better run.



Attached Files

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