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Megasquirt help pwm threshold settings
Mj2326 - 6/8/15 at 11:38 PM

The engine tries but fails to start it's close reading the notes I give a touch of throttle and the engine briefly started. From what the notes say that it's getting too much fuel my settings are as follows


Injector dead time 1.0ms

Battery voltage correction 0.2

Pwm current limiting on

Pwm current limit 100%

Pwm time threshold 25.4ms

Injector pwm period 66

Different bank settings off.


I have gsxr throttlebodies and injectors measuring 19 ohms so set the pwm time to 25.4 as instructions for high impedence.


I took a data log of the start with a touch of throttle and the pw time dropped to 8ms so do I need to adjust my pwm threshold time down? If so what would be a good starting point and what increments should I try 0.2ms?


Thanks


Mike

r1_pete - 7/8/15 at 09:08 AM

Are your throttle butterflies just off closed with no pressure on the throttle?

You need a small opening to allow air in at tickover, otherwise you just starve the motor of air.

Mj2326 - 7/8/15 at 09:34 AM

Not sure gonna whip filter off how much of an opening are we talking about a mm?

dave_424 - 7/8/15 at 09:43 AM

You have fuel settings for cranking the motor over and when it fires it switches to another set of fuel settings.

Cranking settings should be set so that the cranking RPM doesn't exceed the idle RPM, something around 300-500rpm is good. Once it fires and the RPM goes above your cranking RPM, then it switches the fuel over to your VE table.

So if it isn't firing at all, play with the cranking settings. If it fires all the time and then dies straight away, then play with the VE table and your ignition table

Mj2326 - 7/8/15 at 09:47 AM

Yea it's the cranking settings I need to play with the ve table doesn't come in till its fired up gonna check my throttle opening then play with fuel setting at cranking

MikeRJ - 7/8/15 at 03:11 PM

quote:
Originally posted by Mj2326
Not sure gonna whip filter off how much of an opening are we talking about a mm?


Less than that by quite a bit, a mm of throttle opening will have the engine revving very high with no load on it.

If you can regularly get it to fire but then it dies straight away, then you may want to look at the after-start enrichment. This provides additional enrichment for a number of ignition cycles after a start, too much or too little and it won't run.

Mj2326 - 7/8/15 at 03:22 PM

Yea as I tweeked them thought a mm was quite a lot did them to .3 mm still wouldn't start so changed ignition from table to fixed 10 degrees and it started and ran rough but it ran time to give it some 1 who knows how to get it going any recommendations in manchester?