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Thread: Lean AFR after shifts, ECU still removing fuel - Scout II 345 V8 Holley C950

  1. #1
    Carb and Points! jeepmb's Avatar
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    Lean AFR after shifts, ECU still removing fuel - Scout II 345 V8 Holley C950

    Hey guys,

    So I'm running a Holley Commander 950 on a 1976 IH Scout II SV 345 V8 engine, and after two years with this system I just yesterday upgraded from narrow band to wide band and am really loving life .

    But now that I am digging into the datalogs I have a few system events that I was never able to see before. Right now I am seeing that after shifting gears (manual trans) the AFR is temporarily lean at around 16.6:1 pretty much every time. It stays this way for a few seconds before returing to my target AFR of about 14 to 15 when closed loop compensation responds to the lean situation. I realize this is a short period of time, and that in some ways it is probably good that the ECU doesn't panic and try to rapidly add fuel, but it still makes me wonder if it should be responding more quickly to the lean condition or why it is occuring in the first place.

    Here are a couple screenshots of my datalogs for reference. The upper orange line is the AFR, the lower orange line is Closed Loop Compensation, the blue line is RPM, and the red line is MAP:

    Attachment 9782

    Attachment 9783

    So should I be modifying ECU compensation response times to more quickly and appropratly respond to these events, or am I just being overzealous and should let this go? Honestly the engine seems to run fantastic, but there is always room for improvement!

  2. #2
    Fuel Injected!
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    I will take a stab at this... I know Holley's new software not the old 950 ecm.
    First, when you say it is going lean, at what time when you shift? My knee jerk reaction would be to say it would go rich when you let off the throttle and shift the gear. Unless it is going lean when you let off the clutch and push down on the throttle.
    I would compare the lean spike to your throttle % and figure out the correlation.
    If it is going lean when you let off the clutch and apply throttle I would try and fine and acceleration enrichment vs throttle % and try bumping it up in small increments.
    Also when you let off the throttle there could be excess fuel so the ecm tries to pull to much when you are getting back on the throttle. See if there is a blanking value that would slow down the ecm's reaction to the rich condition.
    Last edited by riche; 11-24-2015 at 01:08 PM.
    Richard
    1969 C-10 SWB Step
    355 Small Block
    Stock Vortec heads
    Howard's Cam (110951-08)
    Stealth Ram, Holley HP EFI
    700R4 Trans, 2200 stall & 3.73 gears

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    Carb and Points! jeepmb's Avatar
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    Thanks riche, I agree on the idea for modifying acceleration enrichment, as it is going lean right after I roll on the throttle after shifts. Before I make any changes though I wanted to see if it's a normal occurrence, but it doesnt sound like it.
    1976 IH Scout II | SV345 V8 | T19 4spd | Commander 950 TBI Wide Band | Small Cap HEI | Ramsey PTO | York On Board Air | CAI

  4. #4
    Load goes up as you upshift. Where was the tune built load wise? By that I mean in what gear. If the VE table is correct then AE would be the next place.

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    Carb and Points! jeepmb's Avatar
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    Sorry, Ive only worked with the C950 system not the new stuff, not sure what VE is. Vacuum Enhancement?

    As far as tune, this system has no self-tuning, and there was never an IH base map, so its been tuned by driving up a hill in every gear and taking datalogs while changing values by hand.

    My real challenge here is trying to modify my AE tables without making the throttle jumpy. I have no way to datalog AE so its kinda just guess and check.
    1976 IH Scout II | SV345 V8 | T19 4spd | Commander 950 TBI Wide Band | Small Cap HEI | Ramsey PTO | York On Board Air | CAI

  6. #6
    Fuel Injected!
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    Yeah he means volumetric efficiency table. Holley calls it a base fuel table. The new one is in injector pound hour not sure about your software. I think he is trying to tell you to check your table in the load are and see if you can tweek it.
    Holley is funny tho. Don't try to tune your table for AE stuff make sure it is good cruising and under loads. Then modify the AE stuff to help with any shortcomings.
    Doesnt the commander have a closed loop mode with an air fuel ratio table?
    Richard
    1969 C-10 SWB Step
    355 Small Block
    Stock Vortec heads
    Howard's Cam (110951-08)
    Stealth Ram, Holley HP EFI
    700R4 Trans, 2200 stall & 3.73 gears

  7. #7
    Carb and Points! jeepmb's Avatar
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    So after looking at my base fuel map, and re-examining modifiers I think I found part of the issue. When I looked at my Acceleration Enrichment vs Coolant Temperature instead of being numbers like 100, 102, 107 (%'s), it was numbers like 17, 19, 25 where it didnt before . Also, I have recently found other modifier tables showing COMPLETELY different values than I had left them. Like a lot. It's really infuriating and I have no idea why it is happening or what to do about it.

    Otherwise, after correcting those values some points in my AE table could use enrichment after shifts, but I still havent figured out how to calculate where to change the values, as it only list SLOW or FAST. Below is what I'm working with:

    Attachment 9884
    1976 IH Scout II | SV345 V8 | T19 4spd | Commander 950 TBI Wide Band | Small Cap HEI | Ramsey PTO | York On Board Air | CAI

  8. #8
    Fuel Injected!
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    I would always keep some dummy base tune files to go back and check settings when things get all out of wack. Holley usually has decent base tunes for AUTOMATIC transmissions. Most guys with standards usually end up hating the system until the get all the bugs worked out.
    I get what you are saying about being frustrated, nothing is more aggravating than things not being the way you left them.
    With that being said get some numbers that halfway make sense with the AE vs temp back in the table. Then I would switch gears to AE vs TPS and the AE vs MAP.
    There may be some info in the manual about haw those numbers work. Im with you, they really don't make sense to me.
    For instance in the AE correction vs TPS %. the bottom number is 15,31,47,63... is this TPS % if so then wouldn't the 100's in the top column have to change. they can't be the same amount. In my mind that would mean there is no change.
    In the pic I attached you can see the TPS % and then the fuel pound hr. change as the TPS rate increases.
    You also could got to holleys forum. Danny over there knows this stuff... He can help, but you have to be patient b/c he is very detailed oriented. He will also probably tell you that you need to buy the new system. lol

    This might sound crazy but you could turn off closed loop and see if things go way out of wack... If they do then you know that you still have issues with your base fuel table.
    Richard
    1969 C-10 SWB Step
    355 Small Block
    Stock Vortec heads
    Howard's Cam (110951-08)
    Stealth Ram, Holley HP EFI
    700R4 Trans, 2200 stall & 3.73 gears

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