low vr trigger input

[Denmark]

Hi All,

I need some help to get my own subaru running, it´s runing a trigger setup that i think is not supported in the dropdown trigger menus ,
its a 36-2-2-2 lvr on the crank and 4tooth vr trigger on both inlet cams

the setup that is supported in the dropdown menu in vemstune is 36-2-2-2 with hall cam sensores running a 4-1 on both inlet cams.

I have scoped the signals from the engines as shown on the bottum of this page:

http://www.vems.hu/wiki/index.php?page=InputTrigger%2FSubaruThirtySixMinusTwoMinusTwoMinusTwo

As you can see the cam signals are very low , just about +200mv and -300mv peak-peak,
and apparently there  is not gettin any signals throug the lm1815 , thats connected on both secondary and 3rd trigger,as the triggerlog only shows the cranksignal.
Do any of you have suggestions to make the vr signals better or higher, there is currently on the 18kohm inline resistor ,and no pulldown or pullup on the signals
config file :

http://www.2shared.com/file/ookjAFv2/v33_u004656-A-20120422-114234.html   

Thanks
Skassa

 

[rob@vems.co.uk]

Have you measured the resistance of the VR sensor's coil?  Just to check that the sensor itself is not at fault.
Can you measure the voltage between the LM1815 and the 18K resistor?  IIRC although the LM1815 is a zero crossing detector it's not triggered until something like 120mV is seen at the input pin, so it may be that you have to reduce the value of that inline resistor.
But first check that things are as they should be with the cam sensor.

[Denmark]

Hi Rob,

I have measured the resistence, and its like all other Subaru´s at 1.9kohm,
and the voltage at the sensor is very low on both cams, 0.1mv,
were its 490mv on the crank sensor,
and the cranksignal is the only one shown in the triggerlog.


Thanks,
Skassa

[rob@vems.co.uk]

Thats extremely high, I'm used to seeing 600ohm as a rule.
The LM1815 will not trigger below 120mV so you wont be seeing anything other than noise.
You could by-pass that 18K inline resistor - this may inject noise, so maybe stepping the value down by half might get you a little better result.

You may find that the GT101 Hall sensor has the result you want.

[Denmark]

Sorry , i have just been away at the nürburgring since thursday
I Will try to half the resistor to see if that Will work ,
But i dont Think it Will be before the weekend as i have to pull and split a engine so i Can get it bored to resive new pistons

Thanks
Skassa