High rpm cut-out

[Stephen Dean]

Hi John,

The threshold noise that is coming up does not appear to be the cause of the issue, if you change the Engine Speed Pin Threshold and Engine Synchronisation Pin Threshold values to 0.1V this error should clear, if it is being caused by the signal floating around 0.0V. If it is a wiring issue, then this change will not make a difference.

[parsonsj]

Hi Stephen,

Thanks -- that's an easy change to make. I was just looking at those parameters.

Any other ideas what might be causing this?

[parsonsj]

More review of the data shows that the Fuel Mixture Aim goes from .87 to .92LA as the rpm passes 8k on its way to 9k. (you can see it in the posted log)

I can't even begin to find a reason for that. The main table is set to .87 for the entire region, but for some reason the ECU has picked another table and is leaning the fuel mixture as the engine approaches redline...

[Stephen Dean]

I had seen that as well, but hadn't been able to work out the cause.

[parsonsj]

Mea culpa: I think I've sorted the cut out: I'm using a PMU now, and the coil circuit limit was set to 5A. By my calculations, based on idle current draw, the PMU would "see" about 5A somewhere around 9000 rpm. And the break strategy was set to "retry", so as soon as the rpm dropped a bit, it would recover. An old-fashioned fuse would have blown, and I would have figured this last week. Gotta get used to the new way of doing things. Many thanks to all for helping on this issue.

However, the rise in Mixture Aim from .87 to .92 remains unexplained. I run Sunoco GT 260 Plus gasoline, which has a US octane rating of 104, so .92 will be fine if it continues to happen. I'm logging Fuel Mixture Aim State, so I should get some better data on the problem on Friday.

[Stephen Dean]

Hi John,

That lean spike may have been caused by the coils not firing and no combustion occurring thus affecting the lambda reading.

[parsonsj]

The weekend report is that the engine ran nicely all the way to redline . No high rpm cutout, no weird Mixture Aim movement. Seems like this issue is sorted. MoTeC's recommended ITB tuning method worked great.

Again, many thanks.

Wing mirrors, front tire puncture, shifter valves... that's another story.

[Stephen Dean]