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Thread: Interesting info on B3702 Injection timing

  1. #101
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    I corrected my previous post, IVO not IVC.


    EOI happens just before the inlet valve opens at normal operating temps, fuel is vaporised before IVO. When cold EOI is advanced earlier to allow more time for vapouristion. As RPM and IPW increases, SOI approaches the boundary, when it reaches the boundary, EOI has to happen later after IVO and during overlap.

  2. #102
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    It makes sense now. I had to pull up some diagrams of valve events in a 360* circle and study those to get it all straight in my head. I added 24* across the board to my B1205 table to account for the difference in IVO between the stock cam and my cam and imported the stock tables to B1206 from every other car that I have with an E40 or E67 ECM like you suggested. It seems that at idle the tables are 0 and from there they taper up to 185* at 4,094 rpm to compensate for crank or piston speed. Still haven't figured out why my B1206 table is populated with 0. The only part of the equation I am missing now is where the 490*-220* calculations are derived from in B1205. They don't match up to the at .050" cam degrees. My thought is that maybe it is calculated off of the .002" or .006" cam degrees. I still think the extra fumes at idle are from EOIT happening after the IVC point and that fuel sitting there waiting for overlap to occur somewhere near TCD. Once the piston begins to travel down word after TDC the vacuum from that begins to pull in the new fresh atomized charge. Thanks for the help. I won't be home for another month to test any of this but I will let you know how it turns out when I get it all done.
    02 Z06, 573/530rw N/A 416, 10.21@136.12.

  3. #103
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    B1205 & 1206 advance EOI back from the boundary, the boundary is 585 degrees after top dead centre on the power stoke.

    The calculation for stock

    585-490=95 when cold, which is 95ATDC during the power stroke, an extra 270 degrees of duration required for cold vaporisation

    585-220=365 when hot, which 5ATDC induction stroke, 13 degrees before IVO at 18ATDC

  4. #104
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    Thanks, that sheds a lot of light on it. So since I added 24* to the whole table to account for the new IVO point there will still be the same amount of vaporization time but it will be geared to my cam now. I guess next will be adjusting IPW to get it to stop the EOIT just as IVC happens so there isn't any wasted fuel in the runner. I also need to plan my B1205/6 adjustments off of the EVC event to find the happy medium of when the exhaust valve is open during overlap and where the piston stalls at TDC to not waste any fuel there either. I know IPW has minimum adjustment tables but its actual duration is calculated by data from the VVE and MAF table settings correct?
    02 Z06, 573/530rw N/A 416, 10.21@136.12.

  5. #105
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    Now that I am looking closely at all of this. If the tables are defined by EOIT then shouldn't we be doing our calculations off of the IVC event? What controls SOIT? That seems more important to me in my particular situation. My IVC event is almost identical to the stock cam but the IVO event is quite different. I guess moving the EOIT forward will help this situation and extending IPW by adding more fuel will take care of the back end. Assuming you don't run into boundary. I am also assuming that boundary is where the injector will not extend past or open before no matter what.
    02 Z06, 573/530rw N/A 416, 10.21@136.12.

  6. #106
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    Default Interesting info on B3702 Injection timing

    The boundary coincides with IVC event, it's the last point at which fuel can enter the cylinder for the current cycle, and the earliest point for SOI on the next cycle. EFILive doesn't provide the calibration to adjust the boundary, it doesn't really matter as long as you know where it is, your IVC is 580ATDC, 5 degrees earlier than the PCM boundary value. If you adjusted to your cam, it would give you 5 more degrees before EOI would start retarding finishing later after IVO.


    The PCM calculates the IPW for airflow from MAF or VE table, it calculates the number of crank degrees required for that IPW, and calculates SOI back from EOI, B1205 and B1206.


    The complete SOI to EOI happens before IVO, as IPW and RPM increase, SOI eventually meets the boundary where IVC from the last cycle. EOI has to start extending past IVO still injecting at the beginning of induction into the air stream, at these high loads I imagine cylinder temps are high enough to maintain vaporisation but may not be mixed with the air as efficiently.

    Another way to look at it, there are 720 from IVC to next IVC, at above 85% duty cycle, SOI to EOI takes over 612 crank degrees, there is a minimum off time for the injector in between. It's flat on all the time. The purpose to maintain less than 80~85% Duty cycle may well be to ensure EOI before IVO..?

    I see where you going injecting after the EVC, IVO, but If you look at your inlet duration 227 minus the overlap 11 degrees, minus the minimum injector off time, you could be down to say 190, it could be OK at idle and low rpm, but how efficient is mixing and vaporisation of homogenous charge?

    Injection happens on a closed inlet valve long enough before it opens to allow vaporisation and cooling of the IV. During overlap some vaporised fuel may be lost to the EV, but not raw fuel, if it still smells raw fuel I would experiment and try increase B1205 values to allow more time for vaporisation.
    Last edited by Gelf VXR; March 23rd, 2014 at 11:30 PM.

  7. #107
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    Thanks a lot for all of your time and explanations. They have been a huge help in understanding this whole process. After my last post I looked up more valve events images and found a great explanation that made perfect since to me. Now I understand where the 585* boundary comes from. http://www.carcraft.com/techarticles...amshaft_power/ This helped me visualize it much better and understand what was happening and when. I have been making a cheat sheet with everything we have been talking about and researching. This is going to be a great help in future tuning and is fantastic information I should have already known. I guess what you don't know can hurt you. Now I just need to figure out Dynamics and I should be set. Thanks again for all the help.
    Last edited by PRAY; March 24th, 2014 at 02:57 AM.
    02 Z06, 573/530rw N/A 416, 10.21@136.12.

  8. #108
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    Glad to share

  9. #109
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    I'm re-reading the above and wrapping my head around it...

    some 720* diagrams may help.

  10. #110
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    Joe, click on the carcraft link in my last post. That is the graphic that explained it the best to me. It really helped me understand where my valve events are happening and why they are labeled the way they are.
    02 Z06, 573/530rw N/A 416, 10.21@136.12.

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