Crank Angle Sensor type question

[Jon]

Ben,

Hall sensors use the Hall Effect, VR are variable reluctance, and the 
optical is teeth chopping a light beam. They are three different sensor 
types. If you are really interested you can look up Hall effect and 
variable reluctance on Wikipedia, I'm sure they do a better job 
explaining than me. The optical isn't Nissan specific, but it doesn't 
seem to be as common as the others.

The angle sensor on the SR20 is 2 optical sensors in 1 (crank+cam) and 
is in the distributor. It is very similar to the GM Opti-Spark. It has 
360 pulses per cam revolution for 2 degrees of crank resolution (180 
pulses). There is a second set of cam pulses that vary in pulse width 
depending on what cylinder is up. You can tell when cylinder 1 is up by 
counting crank pulses while the cam signal is high. I have some scope 
caps of the trigger wheel at different rpms showing the different pulse 
widths of the cam signal at different rpms etc. Email me privately if 
you want me to send them to you. They are jpegs about 60k zipped.

If you are using a distributor or wasted spark ignition, you don't need 
the cam signal, but you still need the crank signal. On the SR20 there 
is no good way to ignore the cam signal... the crank signal is just a 
stream of pulses with no way to tell TDC unless you look at the cam 
signal too. Some other methods that don't need a cam signal have either 
missing or added teeth on the crank wheel for TDC. If you wanted to get 
creative with some digital logic, I'm sure you could make a 60-2 
crank-only signal (popular GM) out of the Nissan signal.

Hope that helps,

Jon Davis

Ben Fenner wrote:
> degrees of resolution. So, that's the cam angle sensor. Awesome. But is 
> it a VR type, or Hall type? Wikipedia says:
> 
> So... our optical sensors are not Hall type. I guess. But are they the 
> VR type? Or something Nissan specific? I only ask because MegaTune has a 
> specific setting for Nissan type sensors... =/
> 
> After reading quite a bit about distributor and distributorless 
> ignitions, it seems there's no need for a crank angle sensor if you're 
> running a distributor. I plan on going to passive coil-on-plug ignition