Coil per cylinder 4.3?

[Skinny Pedal]

A 3x crank wheel does not have the resolution to control individual coils. Look at the 5.7 which is a 4x. You don't get individual control until you hit 24x. Thats 6 times the resolution. Yeah you could say that each 3x signal will be good for one cylinder each rev but you only have that one pulse then the timing would have to be figured with rpm in mind through a timing formula. With more resolution you are getting those extra pulses in between to help trigger timing events without a complex calculation that would take more time to calculate than the event window is long.

Thats my take on it anyway

[ericjon262]

A 3x crank wheel does not have the resolution to control individual coils. Look at the 5.7 which is a 4x. You don't get individual control until you hit 24x. Thats 6 times the resolution. Yeah you could say that each 3x signal will be good for one cylinder each rev but you only have that one pulse then the timing would have to be figured with rpm in mind through a timing formula. With more resolution you are getting those extra pulses in between to help trigger timing events without a complex calculation that would take more time to calculate than the event window is long.

Thats my take on it anyway

what's to say you don't swap the trigger wheel? I guess I should have said coil per cylinder V6/0411 too, because that's what I'd be more interested in.

[RobertISaar]

i don't see why it can't be done with a 3X signal. less interrupts gives the processor more time to do other work rather than service an interrupt.

in fact, the less pulses there are, the more accurate you can get. compare 3 notches on a wheel vs 6, the timer will get reset twice as often with the 6 pulse. at 6000RPM, with 6 pulses per rev, that is a frequency of 600Hz. assuming the timer ran at 65,536Hz(that way it will fill up a 16 bit counter once per second), then we're looking at a period of 1.66666mS and a timer value of 109.22(which will get rounded down to 109). with a 3 pulse, it's a rate of 300Hz at 6000RPM. period of 3.3333333mS and a timer value of 218.45(which will get rounded down to 218). that makes the error with a 6 pulse .2%. with the 3 pulse the same .2% error.

with 12: 6000RPM = 1200Hz, .833333333mS period, counter value of 54.6(which will likely get rounded down due to timing logic accumulating). so 54. an error of 1.14%
with 24: 6000RPM = 2400Hz, .416666666mS period, counter value of 27.3(round down to 27), error of 1.14%
with 48: 6000RPM = 4800Hz, .208333333mS period, counter value of 13.65(round down to 13), error of 5.03%

GM started adding more notches into the reluctors for the same reason that the single injector TBI 1.0 geo metro gained a cam sensor in 1996: misfire detection. it's a lot easier to track crankshaft acceleration and deceleration when you have multiple reference points to measure during a revolution.

[S10LS]

2007 up lu3 is 58x. Didnt see that posted yet.

[ericjon262]

2007 up lu3 is 58x. Didnt see that posted yet.

I think most everything GM is 58x now, I'm pretty sure that happened around 2007. I'm mainly looking at 24x, specifically the 0411 because it is so well supported, and because I don't care for DBW throttle. Something someone with a test bench may be able to try is just changing the cylinder count on an LS1 file and seeing if it still fires.

[JeepsAndGuns]

Well the V8's use a 24x wheel, that 8x3. So could you do the same with a 6 cyl? 6x3=18. Could a 18x trigger wheel be made, and possiably a V8 file be modded to use it? It seems to me this would give the same resolution for a V6 as it has for a V8.

Or, if all the newer engines use the same 58x wheel, weather they are 6 or 8 cylinder, then could the 411 code simply be re written to use the same 24x wheel it uses on the V8's, but just run 6 injectors and coils instead of 8?

[RobertISaar]

GM made a V6 application with an 18X signal... roughly 87 and up 3800s. they have both a 3X and 18X output. PCM only uses the 18X signal up to about 1200RPM and then switches to using the 3X due to better accuracy above that threshold. both signals are created by the 18 equal sized notches in the reluctor, but the 3X signal is created internally from the 18X signal after being passed through a /6 operation.

there is also a 3X reluctor on the same pulley/ring, each has a different width of notch to indicate to the ICM which cylinder pair is coming up on TDC. the ICM NEEDS both of these signals to operate. if either is gone, no fuel or spark.