Rev pulse at 2000 rpm

[les]

When trying to bleed the system I noticed that as I raise the revs to 2000 and try and hold it there, they automatically drop to 1200, climb back to 2000 and the cycle repeats. I've turned off idle control on the emerald but its still occurring. Has anyone seen this happen before? I was wondering if it was the MAP kicking in and trying to do something. Obviously with installation of the D2HTB's I no longer have the IACV, could that be the reason. Suggestions greatly accepted

[robin]

If you are using a Emerald then the MAP will be ignored in all probability. The emerald uses so-called alpha-N mapping, meaning that it determines load from the throttle position sensor. The MEMS used the MAP sensor as the primary load indicator and then you could perhaps get the behaviour you describe, but it won't happen with an Emerald.

It is possible that what you are seeing is it dropping in and out of idle which would happen if the throttle position sensor was just on the cusp of the idle.

Or it could be flip flopping between three neighbouring fuel/ignition cells that have very different mapping characteristics, such that it's not possible to hold the revs in the middle.

If you can attach the emerald software and look at the live data page (the one with the dart board in the top right corner), hold the throttle steady and see what's changing in the display ... in particular you want to look at load site, fuel, ignition and towards the bottom left there's a "mode" - from memory it'll say either crank, idle or run - in your case you want to see if it's flipping between idle/run.

Cheers,
Robin

[les]

Robin, Its jumping between Running and Over run before it appears to cut the injectors

[robin]

Over run is when it thinks that you're off the throttle and engine RPM > some configurable threshold. In this scenario it cuts the fuelling until engine RPM drops below the threshold OR you re-apply the throttle. Chances are that the throttle pot is out of calibration or dodgy giving you values that jump around all over the place. Did you run the throttle pot calibration since installing the jenveys?

[les]

Thanks Robin, Yes thethrottle pot calibration was done (a couple of times). I've still got a TPS that you gave me a few years ago so will swap it out, recalibrate and give it a shot tonight

[robin]

If you turn on data logging in the emerald you should be able to plot a chart of throttle pot, RPM, injector pulse width. If you see sharp drops in the throttle pot around the RPM drops then you know the ECU is seeing throttle movement - that'll either be a throttle pot failure, a cable failure or actual throttle movement.

Cheers,
Robin

[les]

Robin, swapped out the TPS and recalibrated. Similar figures were listed during calibration. The pulse still occurs around 2000 rpm . Plotting of the graph (will upload when I get back to the house) adidn't show me to much but I'm not sure I'm reading the graph properly. I'm assuming that injector pulse width is IPW?? I should also say that I can push through the 'dead zone' of rpm as well so that I'm assuming rules out throttle movement??

[les]

Robin, thanks for your help. It turns out that the fuel cut off TPS value on the event tab was set to TPS < 160 and revs 2000 then cut fuel. Disabled the option and the car runs again. Yippee!!

[campbell]

Fab-u-lous!!

When's the shakedown?

[les]

Campbell, its long overdue just got to change the brown temp sensor, but the current one has been siliconed in and it isn't wanting to move, but move it will

[campbell]

Well you do have until, oh, 13 Aug, I suppose

[robin]

Don't remove it if siliconed it - I'll bet that's because the thread has been stripped on the coolant elbow. I have a spare elbow here no doubt - can post or you can collect - FOC to you Les.

It's probably a scunner to replace in situ ..

Cheers,
Robin

[les]

its an elise after all RObin, thanks that would be fantastic

[campbell]

Les, I can only marvel at your sense of humour in withstanding all that this project has thrown at you!