36-1 Trigger wheel fitting

stevieturbo
Posts: 898
Joined: Sun Dec 07, 2008 2:04 pm

Re: 36-1 Trigger wheel fitting

Post by stevieturbo »

pretty sure keyed by single cam is for crank trigger patterns where there are no identifying teeth. ie, 24 teeth, 36 teeth...

Not for 24-1, 36-1, or similar.

So if you were to ignore the indexing which would be the camshaft....any small errors with the main trigger could not be recognised which could lead to problems.

With say a 36-1, even with no phase ID once running.....it's still repeatedly counting each TDC event accurately anyway. With no ID teeth this is impossible.

Trickster
Posts: 45
Joined: Mon Nov 28, 2016 6:09 pm

Re: 36-1 Trigger wheel fitting

Post by Trickster »

That what I was thinking, I never noticed before as I have never really looked into engine configuration too much, but mine is set to ignore cam after 720, on stock dizzy pickup 24teeth and single cam tooth. Its always been OK, just got me curious.

I did assume the engine would only need to know its phase position once.

How does the ecu calculate precise ignition when it only has say 35 teeth, it can physically see every 10 degrees, is it simply a calculation of the speed the teeth pass by with the amount teeth/degrees per cycle and the more teeth the more accurate it can be? If an engine is accelerating it must always be playing catch up to an extent?

Not that any of that matters, just find it interesting haha

Graeme
MR2 Turbo 5sgte 750hp 527ft/lb Syvecs S6

stevieturbo
Posts: 898
Joined: Sun Dec 07, 2008 2:04 pm

Re: 36-1 Trigger wheel fitting

Post by stevieturbo »

As the instructions suggest.....ignoring cam with such a setup seems a very bad idea.

If the engine only read and accepted phase/TDC ID once.....that might be after one or two revolutions at startup.

How many hundreds of thousands of revolutions might it run for thereafter....and how much chance is there of some small errors creeping in ?

If you've ignored any means of identifying errors, or re-indexing as it runs.....that is a bad idea.

Catch up....maybe, but not really.

Your ecu could be going and watching a movie in between it detecting each of the 35/36 teeth. You might think an engine turns fast...and it does. But when a processor is doing a few million things per second, a trigger passing a wheel at a few thousand turns a minute really isnt fast at all.

Trickster
Posts: 45
Joined: Mon Nov 28, 2016 6:09 pm

Re: 36-1 Trigger wheel fitting

Post by Trickster »

Yeh I understand the processing power, 100mhz as an example does make the trigger pickup seem walk in the park material!

I am setting up my crank pickup sensor today, fabricating a bracket should be fun, but looking forward to escaping that stock pickup!

Graeme
MR2 Turbo 5sgte 750hp 527ft/lb Syvecs S6

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