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Inconsistent dwell? see attached logs

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I have trouble with what I believe is some sort of electrical interference.

The engine won't rev above 6000 rpm but I doesn't get any trigger errors in the Link. Just feels like a soft rpm cut.

Checking the logs from a WOT run in 2nd and 3rd reveiled some strange and inconsistant dwell.

What could cause this behaviour?

First, this is the dwell settings in the map:

http://www.revline.se/cars/RRXXX/2008/link_dwellsettings.jpg

I took the interesting values of from the log file:

http://www.revline.se/cars/RRXXX/2008/link_inconsistent_dwell.jpg

First, notice that the dwell is well below the specified dwell in the map.

Second, notice that on some occasions the dwell drops significally!

Third, notice that on 3 occasions the rpm falls, even though the TP is 100%.

Throughtout the logfile this happens a lot. The dwell is down to 0,36 v at some points. But also up to 5+v at some places even though the battery voltage is steady as shown in the log file.

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The engine is running a 60-2 trigger at the flywheel with an inductive sensor

Picked up a lot of interference with the stock Porsche 944 sensors at the flywheel.

The 60-2 trigger at the front reduced that a lot but still problems above 6000 rpm.

I'm confident it's not a problem in the PCL file but I'll mail it to you later on.

Also tried to add a suplementary ground to the engine ground point (to which the EMS is grounded) but not change.

Disconected the alternator, no change.. changed the ems, harness, sensors, ignition, coil pack, ign. wires etc. no change..

No voltage drop either. But next thing is to change all the battery cables. Perhaps there's a problem there.

Thanks,

Gustaf

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Regarding the polarity - the signal shows correct on the scope so it should be OK.

I need to understand the logic behind the dwell time showed in PCLink. It would be great if someone at Link actually read these forums........

What could cause the dwell to be inconsistent like this? A spikey rpm signal?

The question is... if the rpm signal goes way up for a fraction of a second (too short to show up in the log file) the coil would fire directly before the correct dwell has been reached?

But in that case, why doesn't the trigger error show up in the counter?

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I had the exact same problem and eventually my fully built engine was destroyed.... no mechanical indication of what would happen.... weird dwell log , rpm dropping than only rising at 100% open throttle , melt spark plugs on bank 1-4 coil even though i changed 4 coils on that bank , 3 igniters and many different types of spark plugs , i even calibrated my trigger sensor at +180deg and used wasted spark coil no 2-3 on 1-4 and even then the same results , tha car was running fine untill 4000-5000 rpm when the dwell started to jump around with NO trigger errors at all.... Should i go shoot the guy who installed the ecu ? the guy who built the engine ? the guy who programmed it ? me for buying LINK than another ecu ?

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i had this exact same problem recently with a vauxhall 60-2 using the original sensor we could not rev over 5500rpm. tried 10k resistor inline with sensor smoothed rpm log but not cured.. ended up using a late model Digital(hall effect) sensor.. cured it straight away..  never got to the bottom of why it did it either

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Hi Gustaf.

I know you have this working for you currently, but if you were wanting to remove that Autronic reluctor adapter, I believe lowerering your arming thresholds at that RPM by about 1v could help. 

Ensure you have only level 1 trigger filters applied to these trigger inputs as anything higher than this could also be causing issues for you at that RPM.  If your keen on trying that, give it a go and let us know how you get on.

Jurgen

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Hi Jurgen,

thanks for the reply but I tried every possible combination of settings and the setting that worked best was with arming threshold at a minumum, 0.2 volt, and level 1 filtering. That setting generated the results in my first post. Any higher threshold or filtering than that gave worse results.

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