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Greenday694

E36 3000rpm at start up

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93 325is 3 l m 50 Stroker Eaton m122h supercharger . Problem = slight prolonged cranking, then jumps to 3000 RPMs. Cold or hot start up. Then very quickly comes down to 900 RPMs. Max clamp is set to 60. Although it shows 80% during cranking?

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6 hours ago, Greenday694 said:

Max clamp is set to 60. Although it shows 80% during cranking?

I believe the cranking position is hardcoded.

There was another post on here somewhere (cant find it now) where someone else with a supercharger had a similar problem.  I assume it is because you've got a really large volume of air in the plenum and superchager case that takes a bit longer than normal to evacuate once the engine starts?  If you want to see how much effect the idle valve has just try it with it unplugged.

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4 hours ago, Adamw said:

I believe the cranking position is hardcoded.

This is what I thought too. I did not have this problem with the 413 dme, modified 623 bin , ostrich 2 emulator, pmas hpx-e mas and 42lb injectors. The problem with that set-up, was the dme didn't have the broad range needed with large injectors. -60% for idle then try to add 110 at 16 lb boost. The injectors were maxed out. And since -60% was already pushing the dme limit I knew it would not work with the needed 60lb. 

I mite try to restrict airflow from the ISC.?

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Try unplugging or blocking the ISC valve temporarily just to prove it is the startup DC causing the problem, then once we know for sure we can see what options we have to improve it.

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Can you attach your map and a log of a start up (with ISC working), I have a couple of thoughts on how we might workaround this but I want to first see what is going on with the DC in your log.  When I test on the bench the hardcoded 80% is only applied below 400RPM, above 400 it then jumps to base position + the startup step.  So you would think that wouldnt have much effect by the time it started.

My thoughts are we could possibly close the throttle blade a little more so that the normal idle valve position is not as far away from the 80% - maybe say 50 or 60% (our help file suggest the bosch valves should be near 50% at normal idle).  If the throttle blade is already in its most closed position then that idea wont work.   Another option may be to use another aux output to switch the power off to the idle valve until about 400RPM so it bypasses the 80% step.

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