[Diy_efi] Why TWO cam position sensors

Torbjörn Forsman torbjorn.forsman
Sun Mar 26 20:42:33 UTC 2006

If there were only one cam position sensor and the engine happens to 
stay just after that TDC when it is about to be started, then it would 
be necessary to crank the engine two full turns before the first spark 
can be given. With two sensors, one full turn of "dead cranking" will be 
the worst case.
Probably, they want to treat the cylinders individually for some reason 
(perhaps sequential injection, or an ignition system with one coil per 
cylinder, or individual knock regulation for each cylinder). Otherwise, 
a TDC sensor at the crankshaft or a cam sensor that gives signal att 180 
? intervalls would suffice.

Best regards

Torbj?rn Forsman

Chris Wilson wrote:
>   26/03/2006 21:08
> Can someone explain why Toyota use a crank position sensor and also TWO
> cam position sensors on the Supra 2JZ-GTE engines? A page detailing this
> in the factory manual is at:
> ftp://ftp.chriswilson.tv/cam_position/
> Is it for better accuracy than just one cam position sensor, i can't
> understand why they use 2. Thanks.

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