G4+ vs G4X start

[MarcusP]

I have a G4+ and it hates to start.  Its on an odd fire 2cyl and from what I'm told it is looking for a vacuum signal to start firing, does the G4X need the same thing or will it fire from a tach signal? or other reference?

[Vaughan]

G4+ shouldn't need the MAP pressure to drop before starting, if you have a copy of your tune and a log of you starting it we might be able to diagnose why it is having issues

[MarcusP]

On 2/13/2022 at 1:12 PM, Vaughan said:

G4+ shouldn't need the MAP pressure to drop before starting, if you have a copy of your tune and a log of you starting it we might be able to diagnose why it is having issues

So I key on and it will crank and eventually backfire, key off then back on and it will fire 50% of the time.  Thats what it did in both logs

 

[Vaughan]

Those logs do show that it is happy with the triggers and trying to fire (dwell value is changing and injector pw runtimes are non zero).

The Polaris RZR Trigger pattern does actually appear to be a special one which has a missing tooth crank trigger but looks at the MAP value for a pressure dip to determine which half of the engine cycle it is in, given that it isn't starting 50% of the time this would indicate that the MAP sync setup isn't happy for some reason.

G4X does have the same built in trigger mode but also has a user configurable MAP sync setup and includes An Volt 1 on the trigger scope to make this setup easier.

Your tacho signal will most likely come from your coils which are ECU controlled and so cannot be used as an ecu trigger signal. You could theoretically fit a single tooth and sensor to a cam, wire it up to Trigger 2 and use that to tell the ecu which half of the engine cycle it is in.

[Adamw]

I would say the problem is possibly how much you are opening the throttle during craning, obviously the more that you have the throttle open the less vacuum it will be able to make at cranking speed. 

It might be better to get rid of that start up step and instead manipulate the E-throttle target table so that at less than say 300RPM the throttle is more closed so good vacuum is produced to allow sync, then above 300RPM open the throttle more to allow enough air to start.   

Also, is it the stock MAP sensor?  Im not sure if G4+ looks for a specific pressure drop or voltage drop on the MAP signal.

[MarcusP]

14 minutes ago, Vaughan said:

Those logs do show that it is happy with the triggers and trying to fire (dwell value is changing and injector pw runtimes are non zero).

The Polaris RZR Trigger pattern does actually appear to be a special one which has a missing tooth crank trigger but looks at the MAP value for a pressure dip to determine which half of the engine cycle it is in, given that it isn't starting 50% of the time this would indicate that the MAP sync setup isn't happy for some reason.

G4X does have the same built in trigger mode but also has a user configurable MAP sync setup and includes An Volt 1 on the trigger scope to make this setup easier.

Your tacho signal will most likely come from your coils which are ECU controlled and so cannot be used as an ecu trigger signal. You could theoretically fit a single tooth and sensor to a cam, wire it up to Trigger 2 and use that to tell the ecu which half of the engine cycle it is in.

Thank you for the help,  its been frustrating for sure..  maybe the second trigger is the answer, just a bit out of my wheelhouse.  Ill have to find someone that could fab up a holder etc.

 

2 minutes ago, Adamw said:

I would say the problem is possibly how much you are opening the throttle during craning, obviously the more that you have the throttle open the less vacuum it will be able to make at cranking speed. 

It might be better to get rid of that start up step and instead manipulate the E-throttle target table so that at less than say 300RPM the throttle is more closed so good vacuum is produced to allow sync, then above 300RPM open the throttle more to allow enough air to start.   

Also, is it the stock MAP sensor?  Im not sure if G4+ looks for a specific pressure drop or voltage drop on the MAP signal.

I have tried that, there is a very fine line between too much air and not enough.  at 500rpm I have the ethrottle map at 2.0, that helped but still not consistent. . Ill try playing with the start up step and see if that helps.

 

Its a link 4 bar map sensor.

 

[Adamw]

11 minutes ago, MarcusP said:

I have the ethrottle map at 2.0, that helped but still not consistent.

If you look at the "hot" log though it is cranking at 13% TP.  I doubt there will be any depression at all with that.  

[MarcusP]

34 minutes ago, Adamw said:

If you look at the "hot" log though it is cranking at 13% TP.  I doubt there will be any depression at all with that.  

Agreed. I didn’t think about the startup step. I turned it off and it definitely helped. I’ll try again in the morning from cold and see how it does. The startup step was a 6.0 when warm. 

[MarcusP]

21 hours ago, Adamw said:

If you look at the "hot" log though it is cranking at 13% TP.  I doubt there will be any depression at all with that.  

Taking the startup step to 0 definitely helped thank you.