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Thread: Camshaft and Injector Timing

  1. #1
    Senior Tuner Higgs Boson's Avatar
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    Camshaft and Injector Timing

    Anybody making changes to injection timing when changing valve events? Care to describe?

  2. #2
    Advanced Tuner yonson's Avatar
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    If you want the optimum power you definitely want to calibrate both of these. With the stock and smaller cams you might only need to change the SOI a few percent, however with bigger cams I've increased the SOI by up to 25% in the upper load/RPM ranges with positive results...

  3. #3
    Senior Tuner Higgs Boson's Avatar
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    These are changes on DI motors, right? Just checking because the injection timing is already different from port versions.

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    i wonder if the timing can be changed proportionally to the valve events.

  5. #5
    Advanced Tuner yonson's Avatar
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    Yes, I'm talking about DI vehicles (cars and trucks) Under Engine, Fuel, General, Injector Timing, SOI Base.

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    Senior Tuner Ben Charles's Avatar
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    If you advance your Ignition and cam timing tables, you need to modify the injections timing tables. I think for the most part raising these numbers is best practice, I don't see how lowering them will help on a stock/modified motor. I see tuners working on the Gen 5 complain about knock when they advance there Timing, however if you take the injection angle and make it earlier it can get rid of most of the knock. The higher the number the "earlier" the injection, likewise the lower the number the "later" the injection. I have also seen tuners have difficulty with Fuel pressure dropping, this can also be due to ignition timing and injection window being off, take the Start of Injection Base table and put a lower number in those cells as a test, this will cause all types of injection misfires and the engine will run like crap.

    Log Knock retard and or fuel pressure off a table that shows Injection Timing if you get Knock retard/drop in fuel pressure make a change to the injection timing and see if the Knock or drop in fuel pressure goes away. The only other thing it could be would be fuel or spark so if your good on these 2 its injection timing causing the problem.

    I have not had a chance to play with this a ton, mainly just been watching the scanner a lot on my 2015 C7 and building Gen 5 Config Files. Tuning these rigs are going to be full of fun and lots of POWER.

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  7. #7
    Senior Tuner Ben Charles's Avatar
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    I want to add some more to this for anyone reading. Please take a look at this picture


    Few things I want to point out is you see Crank degrees on the outer edge and you see TDC at 0 degrees at the top of the picture. Also note where the intake valve opens BTDC in crank degrees (roughly 300-348 degrees) and where ignition timing advance correlates with Crank degrees. If anyone looks at the injector SOI Base table you will notice its in Crank degrees and these values will make sense. In fact at 6500 rpms you will notice on cylinder load .80 to 1.36 crank degrees is at 332.0, correlating this to the picture above would be roughly 30 degrees of timing, so essentially "increasing" injection window to 340 crank degrees should make more power due to injecting fuel at the correct timing level of around 20 degrees for a WOT LT1 engine.

    If anyone brings up the SOI Base table and examine it you will notice on other areas that need some work,look at the decel/heavy decel regions makes sense with crank degrees of 260-290. Also, look at the high load/low rpm cells (heavy acceleration from a low speed), they need some work which in factory form just kills power.
    Last edited by Ben Charles; 11-20-2014 at 09:40 PM. Reason: additinal input

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  8. #8
    Senior Tuner Higgs Boson's Avatar
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    great info, ben, thanks for the input. where did you produce that wheel? I would love to plug in different cam specs to see how injection timing could be changed. i guess i will just fire the injectors early according to the change in intake valve opening, just like previous ls motors....

  9. #9
    Senior Tuner Ben Charles's Avatar
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    Higgs for the last few nights I have been researching and doing math. I think I have another way to figure this out with some math dealing with injector MS and RPM, going to test it some and see if it computes.

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  10. #10
    That wheel is a fantastic visual for the events and makes complete sense with these DI motors and how picky they are with the injection window. Looking forward to digging into these more.

  11. #11
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    I too am struggling with low rpm/high load knock retard. I've played with the soi base after reading this can't seem to find a pattern of improvement upon making changes. Any pointers?

  12. #12
    Senior Tuner SultanHassanMasTuning's Avatar
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    ^return to the stock timing tables correct your SOI and fuel targets then rework your timing
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  13. #13
    Senior Tuner Ben Charles's Avatar
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    If you get a fuel pressure drop or high ms of fuel..... You need to adjust

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    So, stock tables, log fuel pressure against a histogram with axies same as the soi base table and make changes until the histogram is fairly uniform across the board? Logging fuel rail pressure right? Not the low pressure side?

  15. #15
    Senior Tuner Ben Charles's Avatar
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    Thought I may add something interesting I've seen......
    My stock 15 A8 C7 ran 121.90 mph Bone Stock at the track and cylinder airmass was .88-1.04 at WOT which would call for an SOI of 332.0 to 338.0 crank degrees based on the RPM and Load. At 6400 rpms it showed a 4.3-4.4 injector MS.
    So a little math of 6400rpms X 720 crank rotation = 4,608,000/60,000=76.8
    76.8 X 4.3 = 330.24 MS or 76.8 x 4.4 = 337.92
    Which these numbers fall VERY CLOSE TO THE 332.0 o 338.0 in the factory calibration.

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    This is a great topic. Just goes to show how much different these Gen V cars/trucks are.

    Ben, was that wheel something that you made? Or is it available somewhere where we can put our own valve events in? It's a great visual to have.

    In the equation that you posted above, where did you get the 60,000 figure from? Maybe I just need to pay more attention, its getting late...

  17. #17
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    So I'm logging fuel rail pressure against the soi base table and I'm not really seeing a drop anywhere. Also don't have any kr today. gonna make a few more logs before I change timing

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    Made a few more test logging kr and frp against the soi base table. The fuel pressure seems steady, incerases with load and rpm, but no dips. I started multiplying the soi base table by perent from my kr table. Slowly, the kick became less and less. I'm about 3* advanced from the stock timing table at wot with no retard, but no more increase in power. Still have a degree or two kr to play with at cruise. Overall it seems to run better and I'm hitting a throttle limit that I wasn't before. Delivered torque numbers are up alot from stock. All engine torque management has been maxed except for peak torque table. Guess I'll raise it some more
    Last edited by SilverBullet6.0; 12-18-2014 at 05:01 PM.

  19. #19
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    I've messed with these tables it works got a single cab 5.3 to run a 13.6 on just tune
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  20. #20
    Senior Tuner Ben Charles's Avatar
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    Great results guys, yes modding this table is a MUST!!! Most tuners won't change this table or know how too,,

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