MicroSquirt.com read only forum (Jan.15,2018)

Hi all

OK, I am having a little trouble sorting my ignition settings. The engine is an SR20 nissan motor with optical pickup. I had to install a 1K pullup resistor on its output as the output get pulled low when the optical holes align. ECU is MSII, I am using the IGBT to fire an external Bosch driver.

2 Problems are -

1. Coil and driver getting very hot. Coil is a 1ohm Bosch T-coil. Had to install a ballast resistor to tame it a bit. Ballast coil glows dull red while idling!

2. Had to keep ignition map flat at 10 degrees or the engine start backfiring.

I Tried playing with the dwell and spark duration last night. Adding more dwell (8ms) made it idle faster for some reason, yet this morning when I went to leave for work it would not go past 2000rpm without faltering. I set it back down to 3ms and all was OK again. Spark duration was set at 3ms. What gives with this? Coil output is set to inverted and trigger is falling edge.

Now the second of the two I suspect is due to me having too much offset at 63 degrees and I most likely have bad rotor button alignment. But here is the thing...how much offset do you need? If I am running say 35 degrees advance under some conditions, does this not mean I will need at least 35 offset? Or does the ECU not work like this? Can it count backwards? Or does it count forwards?

Thanks fellas

Pete

Pete,

It depends what Bosch module you are using and whether it is 'smart' (does dwell control) or 'dumb' (relies on MS-II for coil control). If you mismatch a smart module to the wrong coil, you will have problems. With a dumb module you can adjust the dwell to compensate for different coils.

Coil and driver getting very hot. Coil is a 1ohm Bosch T-coil. Had to install a ballast resistor to tame it a bit. Ballast coil glows dull red while idling!

Use the dwell control to limit the current, you shouldn't need a ballast resistor. You might need to use dwell at less than 3.0 milliseconds, try moving it down in 0.1 jmillisecond increments until you notice misfires, then up it 0.2 or so.

Had to keep ignition map flat at 10 degrees or the engine start backfiring.

It's likely the trigger offset is incorrectly set - have you checked the timing with atiming light?

If I am running say 35 degrees advance under some conditions, does this not mean I will need at least 35 offset?

MS-II doesn't work like that. However, you should try to keep the trigger value outside the normal operating range (there may be some interference in the timing due to the tach interrupt being called). If you are using 'trigger rise' cranking timing, then you should set the trigger up so that it physically triggers between 0°BTDC and 8°BTDC.

Lance.

Err, no it is not a smart module. Input is on, its output is on.

So yes I have been trying to use dwell to control its current but what is with the idle rise and fall when I change dwell? Even at 1ms dwell, the ballast still glows red.

What is a typical spark duration going to be?

It would be nice to have an oscilloscope!

I will reign back that offset and make sure to get the rotor alligned with the segments better. I am sure it is way out.

The timing is checked and verified at 10degrees on the crank with 10 degrees on the MSII. Offset is set at 63

I should mention, the reason I went with an external ignitor was because of how roasting hot the IGBT was getting in such short time.

Something is not quite right here I think.

zymodude,

Yeah, something's not right. It is possible that the module is inverting the signal. So you might try changing your 'Spark Output' setting.

If it's currently set to 'going high (inverted)', change it to 'going low (normal)' (or vice versa) to see if that helps.

The safest way to test this is to replace the coil with a test light, and use the setting the keeps the light off when the engine isn't running (and the coil is powered). Then check it to see that it flashes when you crank.

Let us know how it goes.

Lance.

I was thinking about that yes. The inversion thing I mean. I actually have the coil powered off the fuel pump relay to avoid the possibility of the coil being powered when the engine is not running.

Pete

Hi all

OK, so after much head scratching, swearing and many ciggies, I managed to sort out the ignition issues on the SR20DE motor.

First up I set the rotor button to be centered on cyl 1 plug segment. At this point the closest optical 'window' was about 90 degrees away. I rotated the optical chopper disk so it sat 10degBTDC and set the trigger wizzard accordingly.

Then I tested the optical pickup to see what it was doing in relation to the optical trigger windows in the disk. When the windows are opened, the output of the pickup goes high to 3 volts and gets pulled low to zero when over the blank section of the trigger disk.

Next then, set

Ignition Input Capture = falling edge
Crankning Trigger = Trigger Rise
Coil Charging Scheme = Standard
Spark Output = Going high

Hit the key and it started. Tweak the trigger wizzard to get it exact and its all looking good. IGBT is not getting hot and neither is the coil. No need for the ballast anymore!!

Dwell is set at 4ms and max spark duration is set at 2ms. I can now rev the snotter out of the motor without misfires! I can adjust dwell without it totally changing the timing!

So all good with one exception......it is now a SOB to start!! It will crank and crank and finally sputter as it tries to start. Release the starter key and it may or may not keep going after sputtering away for a few seconds. If it does keep going, it will just suddenly spring into full life as if something just came good all of a sudden. I was thinking that maybe the dwell is not high enough during crank and until the alternator starts charging. I guess maybe some logging might show that, at least the batt voltage anyway.

For those interested, it is not injected but running an LPG carburettor with a turbo.

http://zymo.homemail.com.au/bmw2.htm

Pete