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Thread: Coil per cylinder 4.3?

  1. #16
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    interestingly enough, most GM obd2 PCMs can support DBW throttle bodies. the 0411 does it with the corvettes, and the PCM's used on most of the V6 cars do it on the later V6 4th gen F-bodies. I also don't see why the V6 PCM couldn't support a returnless fuel rail too with the right tuning. I think many of the 3800's use a returnless rail. I'm pretty sure the 0411 does out of the box.

  2. #17
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    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
    Last edited by Skinny Pedal; 08-11-2013 at 02:08 PM.

  3. #18
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    Quote Originally Posted by Skinny Pedal View Post
    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.

  4. #19
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    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.
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  5. #20
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    2007 up lu3 is 58x. Didnt see that posted yet.

  6. #21
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    Quote Originally Posted by S10LS View Post
    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.

  7. #22
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    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?
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  8. #23
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    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.
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  9. #24
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    I'm starting to think the crank sensor wouldn't be as big a deal, I'd bet a 24x would run it, if not the real trick would be figuring out the pattern, because it doesn't appear to be simple. keep in mind, 24/6=4, so it's still an even number of notched per cylinder, whatever that's worth.

  10. #25
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    Quote Originally Posted by ericjon262 View Post
    I'm starting to think the crank sensor wouldn't be as big a deal, I'd bet a 24x would run it, if not the real trick would be figuring out the pattern, because it doesn't appear to be simple. keep in mind, 24/6=4, so it's still an even number of notched per cylinder, whatever that's worth.

    maybe it wouldn't be so hard though, there's always the short*, it had coil per cylinder, and a single dual pattern crank trigger much like the LSx engines, but I'm unsure of the trigger tooth count or spacing.
    Last edited by ericjon262; 08-14-2013 at 08:40 AM.

  11. #26
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    without knowing the accuracy of this diagram, the shortstar APPEARS to also use a 24x crank trigger.

    http://www.tonkinonlineparts.com/sho...category=22670

  12. #27
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    Looking at that picture it looks to be part of the crank like the northstar. I guess you would just have to find a picture of the crank out of one of those engines. I tried google searching, but came up empty handed.
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 99+ intake, SS header, dynomax exhaust, 5 speed, 8.8 rear, WJ front brakes, hydroboost, P-pump conversion, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

  13. #28
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    I have the original gm training literature from 99 on the shortstar, its a 24x crank reluctor and 1x cam reluctor. It uses a dual pickup crank sensor so if one side fails the engine keeps running. Cool project!

  14. #29
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    Quote Originally Posted by mecanicman View Post
    I have the original gm training literature from 99 on the shortstar, its a 24x crank reluctor and 1x cam reluctor. It uses a dual pickup crank sensor so if one side fails the engine keeps running. Cool project!
    !! !

    are there any detail specs on the trigger? is it the same as the LS1 trigger?if it is, that makes my converions plans much easier! do you have any detail pictures of the crank trigger, and the pickup angle?

    Thanks-

    Eric

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    Camshaft Position (CMP) Sensor

    The camshaft position (CMP) sensor is also a magneto resistive sensor, with the same type of circuits as the crankshaft position (CKP) sensor. The CMP sensor signal is a digital ON/OFF pulse, output once per revolution of the camshaft. The CMP sensor information is used by the PCM to determine the position of the valve train relative to the crankshaft position.
    Camshaft Reluctor Wheel

    The camshaft reluctor wheel is part of the camshaft sprocket. The reluctor wheel profile is a smooth track, half of which is of a lower profile than the other half. This allows the CMP sensor to supply a signal as soon as the key is turned ON, since the CMP sensor reads the track profile, instead of a notch.
    Crankshaft Position (CKP) Sensor

    The crankshaft position (CKP) sensor is a three wire sensor based on the magneto resistive principle. A magneto resistive sensor uses two magnetic pickups between a permanent magnet. As an element such as a reluctor wheel passes the magnets the resulting change in the magnetic field is used by the sensor electronics to produce a digital output pulse. This system uses two sensors within the same housing for the V6 engine, and two separate sensors for the V8 engine. The PCM supplies each sensor a 12-volt reference, low reference, and a signal circuit. The signal circuit returns a digital ON/OFF pulse 24 times per crankshaft revolution.
    Crankshaft Reluctor Wheel

    The crankshaft reluctor wheel is part of the crankshaft. The notches on the reluctor wheel provide a unique pattern for each pair of cylinders that are at top dead center (TDC) at the same time. This is known as pulse width encoding. This pulse width encoded pattern allows the PCM to quickly recognize which pair of cylinders are at TDC.

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