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Thread: Interesting info on B3702 Injection timing

  1. #1
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    Default Interesting info on B3702 Injection timing

    I messed with this value on my 454 and it seemed to make it run a little better at idle so I figured I would mess with it on my wife's dragster.

    The dragster has a 2001 LS1 with PRC 2.5 Heads and MS3 cam, all else is stock and has 80K miles on it.

    First run at the track was with no changes from prior runs for the past year, corrected altitude was 7123 and the times were typical for the D/A:

    60 -> 1.338
    1/8 -> 5.899
    MPH -> 116.65
    1/4 -> 9.270
    MPH -> 145.02

    Did nothing but add 20% to B3702 across the board. The next run the D/A was 7380 which is little worse then the first run:

    60 ->1.305
    1/8 ->5.822
    MPH ->117.73
    1/4 -> 9.164
    MPH ->146.38

    It was a pleasant surprise to see such a huge reduction in ET. At this point the WB02 was reading rich so I leaned it 2% and it ran:

    60 -> 1.311
    1/8 ->5.801
    MPH -> 119.01
    1/4 -> 9.103
    MPH -> 148.44

    We're talking .17 reduction because I changed the injector timing which in turn show it running too rich. Keep in mind that the program I have has been running since last year and being a dragster what extremely consistent, so this is a true reduction.

    Next time out I will get the WB02 correct then add some more to B3702 and see if there is even more to be gained. It's amazing how the air/fuel mixture changed so much....

    Food for thought.

    Lee

    230" Dragster - 2000 LS1, 02020003 Speed Density, PRC 2.5 Heads,
    MS3 Cam 237/242 .603/.609, Vic Jr. intake, Holley 1000CFM TB,
    PowerGlide, 5000 stall converter. 8.70@154 MPH

    My Projects Homepage: http://www.horsepowerracing.com

  2. #2
    Lifetime Member 5.7ute's Avatar
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    Thanks for posting that info Lee.
    Just to complicate things a bit, what injectors are being used in this combo? & what duty cycle are they maxxing at?
    I have lost a couple of mph since upping the injectors for a dry nitrous shot, all other things being equal & was going to be looking at this table. I believe the smaller pulsewidth for the larger injectors is not getting a decent mix in the cylinder. Hopefully I should be getting back on the dyno before the 1320x meet here & will post any thing I can add to your findings.
    Cheers Mick
    The Tremor at AIR

  3. #3
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    The injectors are accel 36#, fuel pressure is 50# max duty cycle is 71% and max 13ms.

    I can only assume that since the cam is larger then stock it's going to be opening way sooner so by adding to the table it sprays closer to when the valve is closed so it gets better atomization.

    It also makes sense why it shows running richer afterwords. If the fuel wasnt atomizing and some raw fuel was was leaving the head it would tend to cool the O2 and give a false lean condition. I estimate that it's probably around 5% too rich after this change.

    Cant wait to make more changes next time out!

    Lee

    230" Dragster - 2000 LS1, 02020003 Speed Density, PRC 2.5 Heads,
    MS3 Cam 237/242 .603/.609, Vic Jr. intake, Holley 1000CFM TB,
    PowerGlide, 5000 stall converter. 8.70@154 MPH

    My Projects Homepage: http://www.horsepowerracing.com

  4. #4
    Joe (Moderator) joecar's Avatar
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    Very interesting, thanks for posting.

  5. #5
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    Just an update:

    Took the dragster out last night and played with injector timing on one run. I increased the value 15% more and reduced the et by .070.

    I wanted to experiment more but it was only the last two runs for that setting to verify the next run wasnt a fluke. Both runs picked up .07 with the identical DA.

    Here's the data for B3702:

    LABELS Injection Timing (mS)
    ECT °F {link: SAE.ECT} Value
    -40 3.523438
    -18 3.523438
    3 3.523438
    25 3.523438
    46 3.523438
    68 3.523438
    90 4.902344
    111 6.281250
    133 6.281250
    154 7.660156
    176 7.660156
    198 7.660156
    219 7.660156
    241 7.660156
    262 7.660156
    284 7.660156

    And B3703:

    LABELS Injection Timing Trim (mS)
    ECT °F {link: SAE.ECT} Value
    -40 7.660156
    -18 7.660156
    3 7.660156
    25 7.660156
    46 7.660156
    68 7.660156
    90 7.660156
    111 7.660156
    133 7.660156
    154 7.660156
    176 7.660156
    198 7.660156
    219 7.660156
    241 7.660156
    262 7.660156
    284 7.660156


    Next time out I will increase it more and see what happens.....

    Lee

    230" Dragster - 2000 LS1, 02020003 Speed Density, PRC 2.5 Heads,
    MS3 Cam 237/242 .603/.609, Vic Jr. intake, Holley 1000CFM TB,
    PowerGlide, 5000 stall converter. 8.70@154 MPH

    My Projects Homepage: http://www.horsepowerracing.com

  6. #6
    Joe (Moderator) joecar's Avatar
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    Some of us are trying to figure out what crank/cam/valve event the injector timing tables are relative to (e.g. time BBDC...?)...

    We appreciate your efforts in experimenting with this...

    5.7ute (Mick) is very interested in this.

  7. #7
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    Another interesting fact:

    The WBO2 showed 1.3% richer then the previous run. The first time I changed the tables a few weeks ago it showed more like 5% richer afterwards. Since it showed a smaller percentage maybe it's closer to optimal now. When I get a chance again in the future I will up it again. If I remember right it max's out at 8.0ms.

    It would be interesting if someone else could back up this data at the strip....

    Lee

    230" Dragster - 2000 LS1, 02020003 Speed Density, PRC 2.5 Heads,
    MS3 Cam 237/242 .603/.609, Vic Jr. intake, Holley 1000CFM TB,
    PowerGlide, 5000 stall converter. 8.70@154 MPH

    My Projects Homepage: http://www.horsepowerracing.com

  8. #8
    EFILive Distributor dfe1's Avatar
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    The reduction in ET is impressive, but I've found that it is often difficult to correlate some modifications to improvements in elapsed times. On the other hand, mile per hour is typically a very reliable indicator of horsepower. What I find particularly impressive about Lee's results is the improvement in mile per hour-- a 1.3 mph improvement from changing injector timing is HUGE, as is 3 miles per hour resulting from injector timing and mixture changes. That kind of mile per hour improvement indicates that definite horsepower increases should show up in dyno testing
    DigitalEFI- EFILive US Distributor
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  9. #9
    Lifetime Member GAMEOVER's Avatar
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    This thread is very interesting!!!
    2008 2WD Ext.Cab Silverado 1500 6.0 V-MAX E38(L76) & T42(4L70E) MAF Only CL Corvette Servo AFE CAI INNOVATIVE LM-2 WBO2

    FLASHSCAN V2 & AUTOCAL

  10. #10
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    wouldn't injection timing be very dependent on valve events? i know that most OEM calibrations do injection against a closed valve, but if the timing wasnt important, they wouldnt have the table for it, would they?

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