Author Topic: Crankshaft and Camshaft Sensors (Read 4514 times)

mrjezza · « **on:** June 06, 2006, 06:54:59 AM »

Hi guys,

Can someone give me some info about these sensors? - info on the trigger discs, pulse generators, whatever.

zerofreez · « **Reply #1 on:** June 06, 2006, 07:18:57 PM »

VRS sensors

They work off of AC voltage and use magnitisim.

It works a lot like an abs sensor, it "sees" teeth in whatever its sensing and creates a wave form based on whats moving past the sensor. The computer interperites the wave form according to the program.

This is pretty much just a generalization of a VRS sensor, I havnt had any first hand experience with one in a 318is except for just seeing it was there and what type it is.

mrjezza · « **Reply #2 on:** June 06, 2006, 07:49:37 PM »

Thanks zerofreez

bmwman91 · « **Reply #3 on:** June 07, 2006, 10:31:14 PM »

Zerofreeze knows his stuff. Anyone who knows what a VR (Variable Reluctance) sensor is probably does.

The upper sensor detects the one peg on the exhaust cam sprocket. It is used for cylinder identification (the computer uses it to determine the phasing of the cylinders...when cylinder 1 is TDC for an intake stroke, and when it is TDC for a power stroke...I am guessing about cylinder 1 BTW).

The lower one is for crank position, and AFAIK for computing RPM (I do not believe the cam one is used for that). It is a 60-2 tooth wheel (has 58 teeth, and a 2-tooth-wide blank spot). The teeth are used for ignition advance computations (60 teeth gives a spark resolution of 6 degrees). I BELIEVE the second blank spot is aligned with the sensor when cylinder one is 60deg BTDC.

Aah, the joys of learning about this (frustrating) junk from my MegaSquirt days.....

tim_s · « **Reply #4 on:** June 08, 2006, 04:28:26 AM »

Quote from: bmwman91

Aah, the joys of learning about this (frustrating) junk from my MegaSquirt days.....

haha, yeha i've been there... i thought the cam sensor was a hall effect? i haven't been using it with MS so haven't paid much attention to it.

318-is · « **Reply #5 on:** June 08, 2006, 05:15:21 AM »

Quote from: bmwman91

Zerofreeze knows his stuff. Anyone who knows what a VR (Variable Reluctance) sensor is probably does.

The upper sensor detects the one peg on the exhaust cam sprocket. It is used for cylinder identification (the computer uses it to determine the phasing of the cylinders...when cylinder 1 is TDC for an intake stroke, and when it is TDC for a power stroke...I am guessing about cylinder 1 BTW).

The lower one is for crank position, and AFAIK for computing RPM (I do not believe the cam one is used for that). It is a 60-2 tooth wheel (has 58 teeth, and a 2-tooth-wide blank spot). The teeth are used for ignition advance computations (60 teeth gives a spark resolution of 6 degrees). I BELIEVE the second blank spot is aligned with the sensor when cylinder one is 60deg BTDC.

Ah, the joys of learning about this (frustrating) junk from my MegaSquirt days.....

One of the best explanations iv seen; A simpler way of looking at it is that the crank sensor tells the ECU the position of cylinder one, and the camshaft sensor tells the ECU which stroke its on. Without a crank sensor the engine shouldnt start

zerofreez · « **Reply #6 on:** June 08, 2006, 06:36:06 AM »

If you want to get even more technical, the cam sensor tells the engine what cylinder to fire.

bmwman91 · « **Reply #7 on:** June 08, 2006, 11:07:22 PM »

Haha, excellent. A waaaaay too-in-depth explanation sequence has been started. Well, that's the best way to have it!

318-is, you have prolly the best concise explanation of the roles of the sensors I have yet seen.

318-is · « **Reply #8 on:** June 22, 2006, 06:06:00 AM »

Quote from: bmwman91

Haha, excellent. A waaaaay too-in-depth explanation sequence has been started. Well, that's the best way to have it!

318-is, you have prolly the best concise explanation of the roles of the sensors I have yet seen.