What does a trigger wheel do?
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Joined: Dec 2013
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From: Yuma AZ
What does a trigger wheel do?
So what exactly does a trigger wheel do and how does it work? Saw that full function made one on their website and looked some stuff up on google but still a little confused about it. Also why would you need to upgrade to one like the full function, whats the difference over stock? Thanks!
talking head
Joined: Apr 2008
Posts: 2,775
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From: Perth, WA, OZ
stock = 12/1 signal.. from a reluctor transducer ..one event every 30 degrees
.. the ecu uses an algorithm that calculates the acceleration between each of the 12 events per rev and thus can "guess" the angle from TDC in degrees
the full function wheel is capable of using hall effect trigger .. no smudging of the trigger point as is inherent in a reluctor trigger system
and has much more events per revolution so the window of its "guess" is much narrower
add to it ,, if using an FC CAS ( 24/2 events )
.. it has the accuracy of the FD at 12/1
.. but adds to it the backlash slack that is in the cogs that drive the dizzy
.,. and any wobble in the crank snout ..
which makes for a least a few degrees of "vagueness" to the "guess"
when you is searching past 400 rwhp.. every degree of timing pushes you closer and closer to the sharp edge of your safety envelope for controlled ignition and combustion
so it is a smart move to remove that few degrees of "slop" in the CAS drive system ( FC ) and narrow the window of the "guess" for the crank angle
and a smarter move again to move away from "zero crossing analysis" error inherent in reluctor signal based signals
.. the ecu uses an algorithm that calculates the acceleration between each of the 12 events per rev and thus can "guess" the angle from TDC in degrees
the full function wheel is capable of using hall effect trigger .. no smudging of the trigger point as is inherent in a reluctor trigger system
and has much more events per revolution so the window of its "guess" is much narrower
add to it ,, if using an FC CAS ( 24/2 events )
.. it has the accuracy of the FD at 12/1
.. but adds to it the backlash slack that is in the cogs that drive the dizzy
.,. and any wobble in the crank snout ..
which makes for a least a few degrees of "vagueness" to the "guess"
when you is searching past 400 rwhp.. every degree of timing pushes you closer and closer to the sharp edge of your safety envelope for controlled ignition and combustion
so it is a smart move to remove that few degrees of "slop" in the CAS drive system ( FC ) and narrow the window of the "guess" for the crank angle
and a smarter move again to move away from "zero crossing analysis" error inherent in reluctor signal based signals
I suggest you read this PDF from the FFE site if you haven't already, it has some good info http://fullfunctioneng.com/info/Hall%20vs%20VR.pdf
The trigger wheel and its sensors basically tell the ECU the angle/position and rotational speed of the eccentric shaft and then the ECU uses this info to control ignition timing and other stuff...you can find much more info on how they work if you google or youtube crankshaft position sensors, obviously we dont have crankshafts in our rotary engines but the idea is the same
The PDF above gives a great explanation how they work...
I'm not an expert and I probably shouldn't be posting info in the tech support section, but I hope this helps
The trigger wheel and its sensors basically tell the ECU the angle/position and rotational speed of the eccentric shaft and then the ECU uses this info to control ignition timing and other stuff...you can find much more info on how they work if you google or youtube crankshaft position sensors, obviously we dont have crankshafts in our rotary engines but the idea is the same
The PDF above gives a great explanation how they work...
I'm not an expert and I probably shouldn't be posting info in the tech support section, but I hope this helps
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