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Thread: Injector End Angle Tuning

  1. #1
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    Default Injector End Angle Tuning

    I know this has been talked about many times, but I thought I would let people know what worked for me. Not having access to a dyno, I had to tune by how it felt driving. When I first switched to sequential MPFI I was using V3. It didn't have much options in V3. My IEA was at 0° (BDC on intake stroke) when I started tuning. I had a very pronounce stumble just of idle. I couldn't tune it out no matter how rich or lean I made it. So I switched the IEA to -180° (TDC on intake stroke) and the problem was gone. Then V4 came out and I had an IEA table to work with.
    I all ready knew it didn't like an IEA of 0° at idle, so I decided to move it further ahead and spray the fuel on a closed intake valve to see what it would do. It didn't like that either. The AFR at idle got very erratic. Probably because I had too much valve overlap. Fuel coming in the intake valve and right out the exhaust. So I looked at my cam card and found the exhaust valve closing point. For me it was 21° ATDC. Then I looked at some datalogs I had of it idling, and found my IPW at idle. Then I found a link to a site that Danny provided, that gave me the number of crankshaft degrees the crank would turn at a certain RPM in one msec. Get this number and multiply it by your IPW and you know how many crankshaft degrees your injector is open at idle. Then I positioned my IEA, so the fuel would start to spray just after the exhaust valve closed. This gave me a very stable AFR at idle with no off idle issues.
    Then I looked the my cruise areas. At -180° IEA at about 2200 to 2500 RPM, I would get a slight surging, not much but I could feel it and the AFR would jump lean every so often. Kinda felt like your A/C compressor kicking on & off pulling the engine down a little. So I did the same thing I did in the idle area to the cruise areas. I picked 2000 RPM & 2400 RPM. Then I blended the areas in between together. This fixed the surging problem and now my AFR at cruise is a flat line. It has very little movement from my target of 14.7 AFR.
    For the WOT, I decided to go with S2H's (Scott) method in post #13 of this thread: https://forums.holley.com/showthread...-Phasing-Table. I did this because my Duty Cycle at WOT was at 70% at 6000 RPM. So I wanted to get all the fuel in before BDC on the intake stroke. From what I have read, bigger injectors would reduce my Duty Cycle and then tuning the IEA at WOT may give me some benefits, but for now it feels real good at WOT.

    Danny, I tried to find the link to that calculator, but didn't have any luck. If you find it could you put a link here. Thanks.

  2. #2
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    Quote Originally Posted by 81 TransAm View Post
    Then I found a link to a site that Danny provided, that gave me the number of crankshaft degrees the crank would turn at a certain RPM in one msec.
    Danny, I tried to find the link to that calculator, but didn't have any luck. If you find it could you put a link here. Thanks.
    http://www.kylesconverter.com/freque...er-millisecond (RPM To Degrees Per Millisecond Conversion)
    Yes, in order to optimize Injector End Angle tuning, larger fuel injectors are required to spray short injector pulse-width
    durations (especially at higher RPM). This makes it possible to fit the fuel injection event in the programmed time frame.

    This post explains the Injector End Angle table that works very well for me: LINK.
    http://forums.holley.com/showthread....0207#post80207 (Related IEA Forum Post)
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  3. #3

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    Quote Originally Posted by 81 TransAm View Post
    For me it was 21° ATDC. Then I looked at some datalogs I had of it idling, and found my IPW at idle. Then I found a link to a site that Danny provided, that gave me the number of crankshaft degrees the crank would turn at a certain RPM in one msec. Get this number and multiply it by your IPW and you know how many crankshaft degrees your injector is open at idle. Then I positioned my IEA, so the fuel would start to spray just after the exhaust valve closed. This gave me a very stable AFR at idle with no off idle issues.
    I'm not sure how to ask this? If you know the closing point, what does the IPW number do for you? Is there some math that's missing?

  4. #4
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    If you know that at 800 RPM (by using the link to the calculator) the crank moves 4.8 degrees/msec and your idle IPW is 3.5 msec then you can multiply 3.5 x 4.8 and that will be how long the injector is open in crankshaft degrees. In the above illustration, that would be 16.8°. Then if the exhaust valve closes at 21° ATDC, you would add 21° to 16.8°. That would be 37.8°. So you want the injector to start to spray at 21° ATDC and stop at 37.8° ATDC. So in Holley terms you would want an IEA of -142.2° to make this happen.

  5. #5

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    OK, makes sense now. Thanks.

  6. #6

    Default IEA Radical Cam - Issues

    Attachment 3201 Attachment 3202 Attachment 3203 Attachment 3204 Attachment 3205 Attachment 3206 Attachment 3207 Attachment 3208

    I have a 448 BB Mopar Wedge, and I entered -120° for the IEA without the table, and it made a very positive change. It gained 200 RPM, AFR went from 13.9 to 14.6, and vacuum went up 2 kPa. I built an IEA table, but could use some help with the table, and idle areas. The engine was 680 HP on the engine Dyno at 6400 RPM with a carb, originally. I have a stumble and goes very rich on take off. It's a stick car with a 3:08 first gear and a 4:30 rear gear. I have Holley CNP Smart Coils, 36 tooth crank trigger sensor, and a cam sync sensor. Thank you, Mark.
    Last edited by lockjaw-express; 06-07-2018 at 09:10 PM.

  7. #7
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    Screenshots are not much help. We need datalogs and your Global File.

  8. #8

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    That's a really neat way of doing it Mr. 81 TransAm. No doubt you had great results. It really seems like the larger injectors or cam overlap you have the more important tuning IEA becomes for idle, off idle, and low load/RPM situations.

    Just one thought. I'm assuming you tuned the idle IEA using IPW hot idle in gear. Would this not mean it isn't optimal for cold starts? The injector PW would be larger therefore it would be injecting before the exhaust valve closes. But at what point are you splitting hairs? Thanks for sharing what you did, I really appreciate it.
    Last edited by allan5oh; 06-08-2018 at 11:46 PM.

  9. #9
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    Quote Originally Posted by allan5oh View Post
    Just one thought. I'm assuming you tuned the idle IEA using IPW hot idle in gear. Would this not mean it isn't optimal for cold starts? The injector PW would be larger therefore it would be injecting before the exhaust valve closes. But at what point are you splitting hairs? Thanks for sharing what you did, I really appreciate it.
    Yes, I tuned it when it was hot. When cold I run it a little richer until it warms up, and it seems to be happy this way.

  10. #10

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    It would be nice if you could offset the IEA as it's warming up, to keep the injection event start after the exhaust valve closes due to larger PW.

    Anyone have any idea of the distance between fuel injector and valve on a typical SBF? Super Victor EFI intake.

    Cam closes exhaust at 9° ATDC which is -171°.
    Overlap of 12°.
    INJ PW is 2.11 msec at idle.
    At 850 RPM that is 10.761°.
    So that to me is -160.2°.

    This is ignoring the time it takes for the fuel to travel down the port (SBF Super Victor EFI). <---- The S2H "cancel fuel flow map" method.
    So to me this makes sense as to the optimal setting at idle and low RPM/loads.
    The third consideration is getting all fuel finished by BDC. This is the S2H method offsetting everything so idle area is 0. Of course this is at higher loads.

    You know what would be really neat? Making a math channel for this.
    Last edited by allan5oh; 06-09-2018 at 05:03 PM.

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