VR2+ sensitivity

[24c]

Based on my previous experiences with GTS1000s using a cased MicroSquirt, I get no cranking rpms in TS using a good battery on my red GTS1000 now, so I suspect the cam sensor to cam lobe clearance on this engine is greater 0.5mm, and it's outside the limit of the starter motor cranking rpms.

Turns out it the same issue as the black GTS1000. Cover to cam lobe 27.42mm, sensor body to cover 25.4mm and tip protrudes 1.1mm, that's 26.5mm in total...so the cam lobe to sensor clearance is 0.92mm. The crank generates a good pulse on VR1+ from a slightly bigger gap, but the cam sensor VR2+ doesn't. On my other engines I have had to skim the cam sensor flange and reduce it down to about 0.3mm to get cranking rpms to register under closed throttle, about 240 rpm.

So this seems to be a lack of sensitivity issue on VR2+ circuit, as VR1+ picks up a more than adequate signal from a virtually identical sensor. As I want to use the Module board soon, I am wondering whether the VR2+ circuit is the same, and can it be modded easily if not, to make it more sensitive, so I don't have to keep skimming my cam covers?

[Matt Cramer]

The VR2 circuit has a bit of an offset, around 1.8 volts, built in. This offset can be raised or lowered on the module board by adding pull down or pull up resistors to ALT_CAM.

[24c]

Brilliant, thanks for that bit of info Matt.

[chango de naranjito]

did the Vr inpus work fine in the stock CAS of tha 88' turbo II rx7? did you have to do any mod?

thanks,Frank

[Matt Cramer]

did the Vr inpus work fine in the stock CAS of tha 88' turbo II rx7? did you have to do any mod?

thanks,Frank

IIRC, they worked OK on our RX-7, although I can't remember what year its CAS is from. Worst case is you may need a 51K resistor between Alt_Cam and ground.

[24c]

The VR2 circuit has a bit of an offset, around 1.8 volts, built in.

Is there any way to mod a cased MicroSquirt? I have just discovered a problem with my GTS1000, in that there was no fixing screw in the cam sensor. It was just a push fit in the cam cover, but when it gets warm, the cam lobe hits the sensor, I can feel it with my finger (no damage yet though). If I adjust it so it doesn't, I get no cranking RPMs

I realise I could use an amplifier/conditioner of sorts, and I have purchased them, but had no success at all using them. If I understand correctly, if I reduce the 1.8V offset, by say increasing R48 maybe by using a pot/bigger resistor etc this would enable the MicroSquirt to see enough VR2+ voltage at cranking rpms ? ....any suggestions?

Threshold voltage

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[24c]

I am going to mod a cased MicroSquirt to lower the offset voltage, but the component markings are "smudged" on my board. Are these R48 & R55?