I am about to install a 36-1 ring to my Ford cosworth crank pulley and need your confirmation whether the position of the ring is correct.
I was advised to set the engine 90 deg BTDC than position the ring such that the trailing edge of the 1st tooth after the gap is in the centre of the crank sensor.
The pulley has 4 teeth now so was quite easy to set it at 90 deg BTDC:
stevieturbo wrote:That air gap looks quite large, and depending on what ecu you are using, position may not matter.
But if you're happy with the position of the trailing edge of the tooth after the gap 90deg before TDC, then that's fine
S series can go anywhere, older EX48 or P8 you'd still be within range.
I only hold the ring with my hand in the picture, it will be in the inner side of the pulley and gapped properly. I just made this photo for illustration only.
Low compression engines like yours is fairly irrelevant.
With high compression engines, and especially very light bike engines, it's important to make sure the gap in the crank trigger gap passes the sensor as piston 1 rises to TDC. This ensures the crank is slowing down, and ensures the crank signal is strong enough.
Yes I believe the converse is true. But at cranking speed the rpm is very erratic and I think that's the point and 90deg is the recommended and you can do that then that's fine.
Just make sure you check with a timing light as it won't be exactly 90deg
A slowing crank doesn't produce a stronger signal from the sensor, that is constant. It's the way the ECU processes that signal.
The ECU looks for the gap by measuring the time seen between each tooth. If the gap passes the sensor on the down stroke of a piston, the time seen between successive teeth is less than it would be on the upward stroke.
On very light, high compression engines, this acceleration can be enough that the gap passes the sensor so quickly relative to the previous teeth, that it doesn't appear as a gap.