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Thread: At wits' end with Sniper 4150.

  1. #11
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    The first thing I'd do is change your Target A/F Ratio table type from Simple to 2D table. Then setup a proper Target AFR. Then I'd get a new alternator. Yours in not good. The newer type alternators are much better than the older designs. I'm guessing that you're using a GM alternator. I use a GM AD244, they are made to put out a lot of power at idle. You have a lot of missing data points in your datalogs. Could the alternator be causing this, I don't know. You'd need to test it after you get a new alternator. If it still acts up, I'd then look at fuel delivery and fuel pressure. A fuel pump that's cavitating can look like what you're seeing. Do you have a fuel pressure gauge on it? I would also look at ignition. A misfire will show up as a lean spike, then the ECU will add fuel. And as Dan said, check all your grounds. You can never have enough grounds, especially in these old cars.

  2. #12
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    Dec 2009
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    https://forums.holley.com/showthread...790#post104790 (Additional Alternator For EFI Information)

    Originally Posted by Danny Cabral
    The Target Air/Fuel Ratio Table & Base Fuel/Timing Table (and MAP kPa & RPM axes/scales) should be configured using the Sniper EFI software:
    In the Sniper EFI software (LINK), Target Air/Fuel Ratio Table (Fuel ICF) & Base Timing Table (Spark ICF), select "2D Table" Type (not "Simple").
    The Target Air/Fuel Ratio Table & Base Timing Table can then be properly configured & tuned for any engine.
    https://www.holley.com/support/resou...Fuel_Injection (Sniper EFI Software & Holley 558-443 CAN/USB Dongle)
    https://forums.holley.com/showthread...679#post100679 (Sniper EFI Optional Comm/Data Cable Accessories)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  3. #13

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    All of what you mention has been checked and/or done multiple times. Voltage per the ECU stays in the 12.7 to 13.5 volt range in operation, depending on what accessories are being run. All contacts have been cleaned with conductive grease applied. Lights remain steady when on, all electrical stuff is working properly and the battery stays charged. No hint of EFI in the radio when in operation. I studied the posts on this forum and tried to do everything that was suggested as potential remedies before giving up on my own efforts. Thanks.

  4. #14

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    Alternator is a Powermaster, selected because it's a plug & play fit into the 1959 bracket and engine compartment. Fuel pressure is steady at 60 psi. No misfires, all plugs firing as intended. While I understand all of the points you made, none of them at least appear to fit the on again/off again nature of the problem, particularly when nothing is changing with respect to the fuel table, enrichment tables, etc. This switch from good to bad literally happens in an instant while driving, with no common circumstances to predict when it may occur. Once it went for a couple of days with no problem, then on another day it switched back and forth twice in the space of 50 minutes. Having the few occasions of superb running make it particularly frustrating not to be able to tell why it's changing.

  5. #15
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    Quote Originally Posted by JMcConn View Post
    Alternator is a Powermaster...
    Powermaster is the aftermarket name brand manufacturer. Which make & model alternator is it actually?
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  6. #16
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    If your ECU voltage is dropping to 12.7, your alternator is not doing its job. And a potential cause for the issues you are having. I'm not saying it is the cause, but it could potentially be adding to the problem. The few datalogs I looked at, your voltage didn't get anywhere near 13.5, it didn't get above 13.
    Last edited by 81 TransAm; 09-04-2019 at 12:17 PM.

  7. #17
    Join Date
    Oct 2016
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    Albuquerque, NM
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    I had previously upgraded to a 94 amp 12SI alternator many years ago on my '68 Camaro. I too had RFI issues after installing my Sniper. I did all of the usual checks and about the only thing that did anything was to replace my spark plug wires that didn’t look like they had any issues. But even that didn’t completely solve the RFI problem. I then replaced the 12SI alternator with a 140 amp CS144 alternator and it appears to have fixed everything, though I don’t have very many miles on it yet. The CS144 alternator was used on fuel injected cars and has high amperage at idle RPM speeds. You will have to buy a new connector and reuse your pulley, but it's fairly easy to do.
    1968 Camaro, 383 with Dart Pro 1 aluminum heads and Comp Cams roller cam, Holley Sniper EFI with Dual Sync distributor, Muncie M21 4-speed transmission, 3.73 12-bolt Eaton posi differential.

  8. #18
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    Connecticut
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    The OP probably has a 12SI alternator too: https://forums.holley.com/showthread...644#post217644 (Related Forum Thread)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  9. #19

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    Be careful with the dielectric grease. It PREVENTS conductivity, not enhances it. You apply it to spark plug boots to prevent the fire from escaping the boot. It also keeps moisture out. It does NOT conduct electricity. From a Google search: The grease does not conduct electricity, so it shouldn't be applied directly to the mating surfaces (pins and sockets) of an electrical connection.FWIW to the OP: I'm running a Powermaster 12SI 100 amp alternator with excellent results. Not to say yours is not causing issues, but I'd move replacing the alternator down the to do list. I'd look at replacing spark plugs wires first and checking grounds & wiring.
    69 Camaro
    400 SBC, ProCharger D1SC

  10. #20

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    Last edited by danford1; 09-05-2019 at 07:12 PM.

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