GM EFI system on a Air Cooled beetle

[ggenovez]

Thanks Robert.

WOuld I not be able to use a GM one? I figured a knock sensor is a knock sensor...

[RobertISaar]

Thanks Robert.

WOuld I not be able to use a GM one? I figured a knock sensor is a knock sensor...

not quite.....a narrowband knock sensor has about a 1KHz bandwidth where it reliably picks up on the frequency that a given engine will generate knock at(which is determined by bore size). i can't think of many/any GM engines off-hand that have a similar bore size to the VW(which one is it, BTW?), maybe the 1.8/2.0 four-cylinder engines of the late 80s might match up well enough?

the reason i'm mentioning GM is that you'll need to match sensor impedance as well, generally with GM there are two setups there, a ~4K one and a ~100K one. there is also the oddball dual knock sensor stuff that i believe are 8K, but they're so far out of the range of what you'll need that it won't be relevant.

4K vs 100K comes down to which ECM you plan on using. most, if not all of the C3 ECMs use an external knock filtering module with a 100K sensor. the P4/P6/P66 models tend to use an internal filter with a 4K sensor, but some can be modified to use a 100K/external filtering module.