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Thread: Olds 455 Atomic Efi Settings

  1. #11

    Default Olds 455 Atomic Efi Settings

    Yeah, that's why I said CCW 1/8 turn. Try each thing 1 at a time and let us know how it does.

  2. #12

    Default Olds 455 Atomic Efi Settings

    Well good news I believe I got it all sorted out.



    One thing I noticed when looking closely at the throttle blades was that the rear blades were being held slightly open by the sync rod, meaning they could never fully close. From what I have read all 4 blades should fully close when the IAC screws are backed out and this was not happening with the back blades, I suspect this was leading to my high idle problems. I adjusted the rods as per the instructions so the front blades open 5-7 degrees before the rear blades start to move, and all 4 blades also now fully closed. I did buy this MSD Atomic used so possibly the previous owner attempted to adjust the sync rod...



    I then set the IAC screws to 1 turn on both the front and rear. Then I adjusted the idle, ended up moving the Idle RPM Target to 775 and the Idle RPM to 900 to start the advance then. The car was still cold, I turned the key and it instantly fired, just like any regular new efi vehicle. Perfect! The car continued to idle smoothly and once it warmed up I was able to
    further adjust both IAC screws, ended up having them at 7/8 of a turn.



    The in park idle now maintains in the 800-850 range and in gear it idles around 750-800, which is perfect. The IAC upon cold startup was at 130, within 30 seconds it came down to 0, it maintained 0 when in park, once in gear it stabilized around 10-15.



    Next will be to take it for a test drive, but there's some white stuff on the ground today so maybe by the weekend. I suspect the drivability will still be good like before or maybe even a little better.



    Thanks for your help bojo!!

  3. #13

    Default Olds 455 Atomic Efi Settings

    IAC cnt, idle look really good. Let us know how it drives when you get a chance.

  4. #14

    Default Olds 455 Atomic Efi Settings

    Well I finally got a chance to put some miles on the car for the past 2 weeks, overall quite impressed with how the Atomic has turned out. Still have a few bugs to work out but I am not sure where to start so hoping somebody can give me some direction here.



    Current settings are:

    Camshaft Mild & Performance * see below

    Fuel Pump Non PWM with Regulator

    Idle RPM Target 750



    A/F Targets Idle 14.0 Cruise 14.0 WOT 12.8



    Ignition Timing

    Idle RPM 900

    Total RPM 2700

    Idle Advance 8.0

    Total Advance 34.0

    Vacuum Advance 8.0

    Vacuum Type Unported



    Pump Squirt 25%

    Power Valve Enrich 19%





    When Running Mild Cam:

    The car starts hot/warm/cold great, and
    it idles perfectly as well. Taking off from a stop is good I can hammer
    the pedal and spin the tires easily. The problem that I am experiencing
    is there seems to be a lack of power above 3,000 rpm's. The car runs
    well but it feels like it doesn't run as good when above 3,000...



    When Running Performance Cam:

    Idle and startup are still good as with the Mild Cam. I
    think the Performance Cam made a little difference in the upper RPM's, but
    the drawback was the car did not take off from a stop the same as it did
    with the Mild cam setting. It almost seemed to surge/bog down unless I
    hammered the pedal then it would go but that took away some
    drivability. The A/F Ratio seemed to surge up in the 15-17 range during
    these times, not sure if I could change another setting to correct this?



    Overall Timing Settings:

    I have also tried moving the timing around a little, adjusting the Idle RPM, Total RPM, Vac Advance, etc... tried ported vs non, I'm just not too sure where to go from here to get it dialed in. My engine tends to like about 16-18 degrees at idle and total around 34-36. Looking at the handheld when I get up to RPM of 3,000 the timing shows as 41, should it not max out at the 34 I have set or is this the vac adding in? I assume the Vac Advance is adding some in here but this would back out when I go WOT then it would be 34 degrees?





    I'd be willing to try any setting you recommend, thanks for your help.






  5. #15

    Default Olds 455 Atomic Efi Settings

    When changing cam profiles you should always do a full reset of the Atomic. Any learned offsets will be cleared and you will get a true test. If this is not done, you don't really know what settings you are working with. Also note that when changing the profile the required Pump Squirt and Power Valve settings will be different too based on fuel profile.

    I would think that the settings are real close but I would not jump around so much.

    To get an idea of what you need, I would start back with the mild setting. Record your current settings for engine and timing. Do a factory reset. Enter your settings from above back in, then set to Mild profile and leave the pump squirt and power valve at default.

    Take it for a ride. Note throttle response and or hesitation points, note and stumble RPM etc. Now we can adjust with pump squirt to cure low RPM hesitation and PV for adding fuel through the RPM Range. If you end up adding too much PV, you should start over with the performance profile but make sure you reset first. The PS and PV settings from one profile to another will be entirely different.

    Also take note that IAC readings may change if you modify timing so always recheck.

    Let us know what this brings.

  6. #16

    Default Olds 455 Atomic Efi Settings

    Hi fcsallan thanks for the reply.



    In regards to the default settings I did complete a reset before moving over to the performance cam but you make a good point about moving the settings around possibly too quickly, this could be part of the issue.



    Last night I did another full reset and went back to the mild cam with the settings above, I actually pulled those numbers off the handheld at that time. With the current Mild Cam profile the default PS is 25 and PV is 19.



    After it warmed up I went for a cruise, the car started and idled good, take off from a stop was good it has a good amount of power off the line. When warmed up and in drive the IAC hovered in the 0-5 range, this is with the screws both about 1.25 turns open. I noticed the idle timing on the handheld was around 8 degrees, which is as expected, by 2,000 rpm its in the mid 25 range, then by 3,000 its close to 40. I think this is good, but am not sure what WOT was as I did not check it.



    I went down a backroad where I could really lay it down and I was able to easily spin the tires through first and into 2nd, then it hooked up, the engine seemed to stumble a little at this point so I let off. Not sure how good of a test this was but thought I would share it. The car overall runs pretty good but I still feel that it lacks power in the over 3,000 range. Would adding some PV possibly help this?



    Thanks again

  7. #17
    msdtech1955 Guest

    Default Olds 455 Atomic Efi Settings

    thanks allen



    we had internet and phone issues yesterday .



    by the way guys/gals... allen is a big part of the msd/atomic family

    and has a plethora of efi knowledge . You can count on his advice at anytime.











    fcsallan wrote:
    When changing cam profiles you should always do a full reset of the Atomic. Any learned offsets will be cleared and you will get a true test. If this is not done, you don't really know what settings you are working with. Also note that when changing the profile the required Pump Squirt and Power Valve settings will be different too based on fuel profile.

    I would think that the settings are real close but I would not jump around so much.

    To get an idea of what you need, I would start back with the mild setting. Record your current settings for engine and timing. Do a factory reset. Enter your settings from above back in, then set to Mild profile and leave the pump squirt and power valve at default.

    Take it for a ride. Note throttle response and or hesitation points, note and stumble RPM etc. Now we can adjust with pump squirt to cure low RPM hesitation and PV for adding fuel through the RPM Range. If you end up adding too much PV, you should start over with the performance profile but make sure you reset first. The PS and PV settings from one profile to another will be entirely different.

    Also take note that IAC readings may change if you modify timing so always recheck.

    Let us know what this brings.

    msdforms@msdperformance.com







    Latitude: 31.730125
    Longitude: -106.29673








  8. #18

    Default Olds 455 Atomic Efi Settings

    Thanks JD, I'm just trying to help where I can.

    So as far as PV helping the laydown, not sure yet.

    I would get a friend to take a ride with you and preferably have them drive. You watch the handheld and in particular the AFR in the range above 3K. If it is laying over, it may actually be too fat up there. In any case, I don't want to guess. There are two things that can cause it to feel like it ls losing power, either fuel delivery or timing. The 455 is an odd bird. It likes different timing than a typical big block. In my case my 402, like all in around 2300 RPM, but my buddies GS with a 455 wants to hang on to the curve until nearly 3100, also in his case we were limited to 32 degrees all in. We did add 10 degrees of vacuum advance as well for around town driveability but that made no difference up top.

    I'm not saying these should be your settings, I'm just suggesting that you are "almost there". Now you need small changes and some driving time. If the AFR is near your targets above 3K, then start looking to timing. If they are way lean or fat, then we can talk about profile or PV settings.

    In the end you are working to identify the personality of your engine. They all like something a bit different, you just need to sneak up on it until you both are happy. You will know when you are there when you need to take a trip to the tire shop to replace the shreds.

  9. #19

    Default Olds 455 Atomic Efi Settings

    Sounds good Allen, I plan to put some more test miles on it this week and weekend so I will watch out for those pieces and report back.



    I really appreciate your help with this.



    Rob

  10. #20

    Default Olds 455 Atomic Efi Settings

    Well I got to put some more miles on the car over the past few days, running on the mild cam profile with the same timing and idle settings as per above. Starts great, idles great and feels good off the line, just like before. Was able to get to a less populated stretch of road and have some fun with it, easily cooks the tires in 1st and into 2nd, but had an odd stumble/misfire when it got to right around 4,500 rpm in second. Almost felt like it hit a rpm limiter, my tach started to jump up and down as the car surged on and off, so I let off it ran good, so I floored it again and the same thing happened seemed to have trouble once it got to the mid to high 4,000's. I wish I was able to datalog with this to see what all the readings were at that time.



    My engine is pretty fresh built it 2 years ago has maybe a thousand or 2 miles on it. Not sure if this could be ignition related or Atomic fuel related. Plugs are brand new, wires new when I had the engine built. Running a MSD pro billet with a new cap and rotor. Mallory Hyfire 6AL and coil are used but I ran them before with the carb on this setup last year.



    Now that I think of it I had this same stumble/misfire happen before with the carb installed once when I was playing around too. I assumed at that time that it was a fuel/carb issue but I had a GM HEI in it then with the same Hyfire 6AL also. So this almost points to the Hyfire 6AL or possibly some interference with the wiring for it. The way my sunpro tach was jumping was really odd, I even pulled over to a stop, pressed the button on the tach to see what I had the light set at and it was still jumping around even when trying to set it.



    Any suggestions on where to start?

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