Page 2 of 2 FirstFirst 12
Results 11 to 18 of 18

Thread: Stumble off idle with Atomic EFI & timing control.

  1. #11

    Default

    Hi. I haven't done that. I can easily do it though. I'll check it out and let you all know. So what I want to do then, is set my light to 15° and I should see the rotor at the #1 terminal when I have the timing locked?

  2. #12
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    1,366

    Default

    I'd run the engine so you can see the spark occurring as the advance changes, and watch the rotor relationship. The rotor needs to be lined up halfway through the advance curve, so the phasing is shared either side of centred throughout the range of curve. Too much on one side creates too much of a gap to the terminal, then the engine misfires or crossfires. Gary
    Last edited by Gaz64; 05-10-2019 at 11:44 PM.
    Regards, Gary

  3. #13
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    21,582

    Default

    To ensure the distributor's rotor-phasing is correct:
    http://documents.msdperformance.com/8644_tb.pdf (MSD Rotor-Phasing Document)
    MSD has a good video on why it's important:
    http://www.youtube.com/watch?v=aWMlNwGW0tM (MSD Tech Rotor-Phasing Video)

    For naturally aspirated engines, the rotor is usually phased halfway between minimum & maximum amount of timing advance used.
    For forced induction engines, the rotor is usually phased at maximum boost retard, because that's when cylinder pressure is the greatest.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2700 RPM converter, 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.

  4. #14

    Default

    Quote Originally Posted by Danny Cabral View Post
    To ensure the distributor's rotor-phasing is correct:
    http://documents.msdperformance.com/8644_tb.pdf (MSD Rotor-Phasing Document)
    MSD has a good video on why it's important:
    http://www.youtube.com/watch?v=aWMlNwGW0tM (MSD Tech Rotor-Phasing Video)

    For naturally aspirated engines, the rotor is usually phased halfway between minimum & maximum amount of timing advance used.
    For forced induction engines, the rotor is usually phased at maximum boost retard, because that's when cylinder pressure is the greatest.
    Thanks guys. This is a huge help! I have the spare rotor cap installed and I can see the relationship between the rotor tip and the #1 terminal with the timing light fired on the #1 plug. I'll go through the procedure and get back to you guys. At first test with the 15° timing locked on the MSD, I see perfect alignment with the rotor tip and the #1 terminal. I'm not sure this is correct, but I'll go through the documents & see.

  5. #15

    Default

    OK, results are in. I believe the rotor phasing is spot on. I ran the engine to 2700 RPM and my rotor/terminal alignment looks just like the MSD video (see below). My car looks just like "after" in the video. So much so you might think it's the same video. The rotor end is slightly in front of the terminal at idle, and then by the time I get to 2700 RPM it's slightly in back just like the MSD (after) video shows. So that is verified.
    Click image for larger version. 

Name:	rotorphasing.jpg 
Views:	9 
Size:	41.8 KB 
ID:	8154
    I get the best performance with the modified timing and fuel settings listed below, but still random backfires under hard acceleration, but only intermittently now. I did change these a few days ago. Along with the timing settings:
    PUMP SQUIRT 25% (Lowered from 30.)
    POWER VALVE ENRICH 15% (Lowered this from 20.)

    Best so far but not perfect:
    IGN Timing:
    IDLE RPM 1000
    TOTAL RPM 2200 (Do you think lowering these two from 1100 & 2700 RPM is the reason for the major improvement or something else?)
    IDLE ADV 10.0
    TOTAL ADV 32° (Should I increase to 34°?)
    VAC ADV 9.0°
    VAC TYPE UNPORTED
    CAM - STREET
    FUEL PUMP PWN with REG
    PUMP SQUIRT 25% (Lowered from 30.)
    POWER VALVE ENRICH 15% (Lowered this from 20.)
    My fuel pressure is right around 40 psi. I will see if 55 psi makes any difference, as I've seen some threads where stumbling was related to lower fuel pressure. However, the backfire still have me puzzled.
    Last edited by toronadoproject; 05-11-2019 at 08:59 AM.

  6. #16

    Default

    OK, made some adjustments with good success so far. Adjusted fuel pressure to 53 psi. No real impact still a random stumble and backfire. Then I did this below. I was not able to see the stumble, but it's intermittent, so I will need to test several times. The engine has good power, is there any downside to my lowering the total advance RPM to 1900?

    IGN Timing:
    IDLE RPM 950 (It was 1000.)
    TOTAL RPM 1900 (It was 2200. My feeling is that this is the reason for improvement?)
    IDLE ADV 10.0
    TOTAL ADV 31° (I heard knocking at high loads so I dialed this back from 32.)
    VAC ADV 10.0°
    VAC TYPE UNPORTED
    CAM - STREET
    FUEL PUMP PWN with REG
    PUMP SQUIRT 25% (Lowered from 30.)
    POWER VALVE ENRICH 17%

    P.S. A pic of my engine bay. I'm really happy with the stock look but hidden EFI.
    Click image for larger version. 

Name:	toro engine small.jpg 
Views:	9 
Size:	91.8 KB 
ID:	8155
    Last edited by toronadoproject; 05-11-2019 at 10:04 AM.

  7. #17

    Default

    I have the same problem. Backfiring only on deceleration after strong acceleration. I upgraded my handheld controller and now I see on the Atomic dash Decel Fuel OFF. There is a posibility to turn this on? @toronadoproject I do the same as you, lowering the total RPM, less backfiring I have. Before 2500 RPM and now 2175 RPM. Still waiting the answer for the same question. Thinking to lowering even more.

  8. #18
    Join Date
    Oct 2018
    Posts
    26

    Default

    Quote Originally Posted by toronadoproject View Post
    OK, made some adjustments with good success so far. Adjusted fuel pressure to 53 psi. No real impact still a random stumble and backfire. Then I did this below. I was not able to see the stumble, but it's intermittent, so I will need to test several times. The engine has good power, is there any downside to my lowering the total advance RPM to 1900?

    IGN Timing:
    IDLE RPM 950 (It was 1000.)
    TOTAL RPM 1900 (It was 2200. My feeling is that this is the reason for improvement?)
    IDLE ADV 10.0
    TOTAL ADV 31° (I heard knocking at high loads so I dialed this back from 32.)
    VAC ADV 10.0°
    VAC TYPE UNPORTED
    CAM - STREET
    FUEL PUMP PWN with REG
    PUMP SQUIRT 25% (Lowered from 30.)
    POWER VALVE ENRICH 17%

    P.S. A pic of my engine bay. I'm really happy with the stock look but hidden EFI.
    Click image for larger version. 

Name:	toro engine small.jpg 
Views:	9 
Size:	91.8 KB 
ID:	8155
    How much HP has your engine? And is it stock or mild camshaft?
    Because to me it looks your ignition curve is to short/high or whatever is the correct English word for it. :-) Further your target RPM of 700 in my opinion is too far away from the idle RPM 1100. I mean my '68 Charger 505 cid with 600 HP has following settings:
    Target RPM 700
    Idle RPM 750
    Total 2500
    Idle adv 17°
    total adv 36°
    vacuum adv 10°

    Vac type PORTED
    Cam - Mild

    I'd try to start with:
    target RPM 750
    Idle RPM 800
    Total 2800
    Idle adv 15°
    Total adv 32°
    vacuum adv 10°

    Vac type PORTED
    Cam - Stock

    With this values set start the engine and if the engine starts wait for it to be hot. When engine is hot and idling check the IAC value when in neutral IAC should be 5-20 and when in gear 40-50.

    When you have reached the recommended values shut the engine off and wait 10-20 seconds then fire her up again and check again the IAC value and start again to adjust it to 5-20 in neutral and in gear 40-50, repeat these steps several times and then go for a test ride. I played two days around with my throttle blades as the most important information is not mentioned in the manual.
    Last edited by rollo1504; 05-26-2019 at 01:15 PM.

Page 2 of 2 FirstFirst 12

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
About us
Holley has been the undisputed leader in fuel systems for over 100 years. Holley carburetors have powered every NASCAR® Sprint® Cup team and nearly every NHRA® Pro–Stock champion for four decades. Now, Holley EFI is dominating the performance world as well as our products for GM's LS engine. Holley's products also include performance fuel pumps, intake manifolds & engine dress–up products for street performance, race and marine applications. As a single solution, or partnered with products from other Holley companies - Hooker Headers, Flowtech Headers, NOS Nitrous, Weiand, Earl's Performance Plumbing, or Diablosport - Holley products can give you the edge you need over the competition.
Join us