Has been a while since I last posted, however I have mustered another tedious question.
What is the consensus for the best position, rotationally relative to TDC, for the tooth gap of a trigger wheel?
And which edge, rising or falling; I guess this depends on whether the answer to the question above is ATDC or BTDC?
It's not especially critical on a 36-1 or 60-2 setup. However the relative position of the cam position can be critical if you're using a "keyed by single cam" setup as you don't want the trigger edge to be very close to a crank trigger edge (so that it might be either side of it in some conditions). For a "single gap single cam" setup like you would find with a 36-1 the cam position just needs to be well defined and a safe distance from TDC so it can't swing from say 358 degrees in phase one to 2 degrees in phase two.
There is of course a very slight lossing in accuracy at the point of the gap, and you might want to put the gap somewhere where there is unlikely to be an ignition even at full power, but really I wouldn't worry as it's going to be very small, worst case equivalent of an 18th tooth non gapped wheel, and the "preferred" motec setup is 12tooth anyway!
Edge wise you probably want to use falling, but this is often more to do with the sensor type and output. If you're using a hall sensor they will have a sharper fall as they often exhibit some damping and slight "rounding" at the top of the rising edge, and a reluctor sensor has a steep well defined drop in voltage through zero volts again a falling edge is required. Most crank wheels will have an even spacing so you get nicely defined pulses at the ECU. A quick look at the sync scope will tell you what you need to know as far as this goes, as there can be some oddities (like flipped output from subaru hall effect cam sensors).
Thanks for the reply Pavlo.
The trigger is a 36-2 wheel. http://bagpuss.swan.ac.uk/200sx/evo-swa ... rigger.JPG
The cam trigger is most likely to be the std 4G63 trigger which has an assymetric pattern, Pat previousy advised to use the Manual Cam Checklist option in another thread.
I'll set the gap up to be 30-40deg ATDC, there shouldn't be any ignition events going on there.
That sounds fine. You'll need to remember that the definition for the gap position is effectively in degrees ATDC, and the reference angle refers to the tooth after the gap, rather than the tooth that concludes the gap.
The manual cam checklist is certainly the way to do it, but it's a pain to set up if you lots of cam events! Essentially you're looking for something unique angle wise between events in each phase. I'll have to come up with a methodology for working that out because the camRAW info does change depending on how the checklist setup, which isn't very intuitive as you would like to be able to just use that info to define the checklist. I have some log files that go with a GTR I setup with 36-1 and OEM phase sensor which can be used to make sense of how to sort it out.
