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Thread: End of Injection Timing Open Discussion

  1. #31
    Fuel Injected!
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    Hi There

    This is the information I have on LT and some other GM Cams.

    Part Number .050 Duration 1.5 rockers lift 1.6 rockers lift Lob sep angle Notes
    GM 14093643 202/207 .404/.415 N/A 114.5 1987 350,305 Manual
    GM 10088155 179/194 .350/.384 N/A 109 1987 305 Auto
    GM 10066049 207/213 .415/.430 N/A 117 1988-89 350,305
    GM 10111773 202/207 .413/.428 N/A 114.5 1990-92 350,305 Camaro
    GM 12551705 202/207 .447/.459 .477/.490 117 1993-97 LT1 Corvette
    GM 12551142 203/210 N/A .476/.479 115 1996 LT4 Grandsport Corvette
    Crane 243931(Holden 92029026) 216/226 N/A 0.491/.491 112 1986 VK Blue Commodore(Group A)
    Holden 92060781 214/214 N/A .486/,486 112 1988 VL and VN Group A(215KW)
    Crane H268 883931 206/206 N/A .448/.448 112 1989-91 Holden VN SV5000
    Crane H276 883941 214/214 N/A .464/.464 110 1989-91 Holden VN Group A
    GM 24502586 218/228 .492/.492 .525/.525 112 LT4 Hotcam
    GM 12370847 234/242 .539/.558 .575/.595 112 GM 847 cam for LT1 and LT4
    GM 12370846(19210723 NEW #) 222/230 .509/.528 .543/.563 112 GM 846 cam for LT1 and LT4

    Cheers
    Kevin

  2. #32
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    Hi Mitch

    A small world indeed!

    We have rather larger hills here than Pendle, I went up it once as a child.

    There is a difference between Batch and sequential injection as to what one can do and when the fuel arrives at the valve face...

    With Sequential, 94-97, we can make an effort to get it right....

    With batch like a L98 90-91 Corvette or the 92-93 LT1 corvette all sort of things are happening....

    L98 has a left and right bank batch fire, it fires each bank twice as often as most normal engines Once each rev, both intake and exhaust and as well as that enrichment fuel gets added anytime....

    So batch fire engines typically have the fuel arriving ALL OVER THE PLACE...

    With the 94 we are lucky because its sequential and the great people on this board are adding all these great features...including EOIT..

    Once we know exactly where the EOIT is on the LT1 we can work back from there.

    I do not have any information on that unfortunately.


    Cheers
    Kevin

  3. #33
    Fuel Injected! Stroked 388's Avatar
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    Thanks Mitch that was some helpful information. By my calculations I need to set eoit at around 168 +/- a few thanks again


    Gary
    Last edited by Stroked 388; 01-13-2019 at 07:01 PM.

  4. #34
    Fuel Injected! Stroked 388's Avatar
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    Thanks for the helpful information very useful

    Gary

  5. #35
    Fuel Injected! Stroked 388's Avatar
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    I hope to be able to test and log different eoit changes as soon as the snow is gone off the streets. Only thing I can do at this point is do idel logs. If that will help any I can post them

  6. #36
    Fuel Injected! spfautsch's Avatar
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    While I've been (not so) patiently waiting to get my block back from the machinist I've little to contribute along the lines of actual test data, but I couldn't sleep this morning so came here to catch up. I noticed a bit of activity on the EOIT topic in this thread also.

    A few days ago it struck me that the relationship the EOIT value in $EE has to the power stroke has already been confirmed. kur4o's post here nails it down. I was initially confused at how he was getting 270 degrees because I was working with some assumptions based on of the mis-information that Y body tunes used the same target as the B bodies. Once that was cleared up (Y body tunes are set to 0x60 at normal operating temps) I must have stopped thinking altogether - for some reason seeing the B body EOIT fall on a 90 degree interval caused me to incorrectly infer that it was irrelevant. But it's not.

    Quote Originally Posted by kur4o View Post
    I know for sure that the graph was taken on stock b-body at normal operating temperature. The stock setting on all b-bodies is $50. So if you count backwards from 720* 5 low res pulses you go exactly where the graph is.

    I was thinking to add a 2d table end of injection vs rpm target , but at max rpm you need to be below 50-60% Injector duty cycle to make it useful.
    I am at almost 85-95%DC so it is almost full time open.
    Anything above 70% inj dc, the injector starts spraying while the intake valve is still open, and that spray should be for next ignition event.
    This all makes perfect sense now. Sorry for being so dense!

    Mitch I believe contrary to my earlier supposition, your table here is correct. The F and Y body / aluminum head tunes have the EOIT target at 180 or BDC of the power stroke, on a closed intake valve. As long as I'm not once again horribly mistaken the value you came up with through testing (0x63 if memory serves) was actually giving the fuel slightly more time to evaporate, not keeping it from being injested into your exhaust system. To move your low pulsewidth injection window so there can be no fuel in the port while the exhaust valve is open, assuming it closes at 388 degrees as in your chart you'd need some value less than 0x3b. Not to mention subtracting some margin for nominal idle pulsewidth, which would need to be converted to degrees at your target idle speed.

  7. #37
    Fuel Injected! Terminal_Crazy's Avatar
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    Quote Originally Posted by spfautsch View Post

    This all makes perfect sense now. Sorry for being so dense!

    Mitch I believe contrary to my earlier supposition, your table here is correct. The F and Y body / aluminum head tunes have the EOIT target at 180 or BDC of the power stroke, on a closed intake valve. As long as I'm not once again horribly mistaken the value you came up with through testing (0x63 if memory serves) was actually giving the fuel slightly more time to evaporate, not keeping it from being injested into your exhaust system. To move your low pulsewidth injection window so there can be no fuel in the port while the exhaust valve is open, assuming it closes at 388 degrees as in your chart you'd need some value less than 0x3b. Not to mention subtracting some margin for nominal idle pulsewidth, which would need to be converted to degrees at your target idle speed.
    I had hoped we'd have some people testing this & collecting data.
    I'm not 100% sure mine is accurate. The LHS seemed to respond whilst the RHS went the other way.
    I've just swapped out my O2's and seem to be getting slightly differing data than previously.
    The rhs looked whiter than the left.
    The VE table now looks a little healthier than before.
    I've also rewired by wideband and am getting more stable results than before.

    Car ran well but still rich untill i get the VE table to settle down.
    Eoit is something i will retest when i'm happy the car is better.

    Eoit:
    Moving past the exhaust closing point didn't seem to improve anything but I wouldn't trust my data 100% here.
    Yes adding the extra 15 degrees seemed to lower the BLM's slightly before the inlet opens.

    Mitch
    '95 Z28 M6 -Just the odd mod.
    '80 350 A3 C3 Corvette - recent addition.

  8. #38
    Fuel Injected! spfautsch's Avatar
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    Bear in mind that when you change EOIT to inject directly into the cylinder you'll be throwing at the very least the lower MAP areas of your VE table out the window. Unevaporated fuel doesn't burn the same as raw.

  9. #39
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    Hi Folks

    Just to put some perspective of how long it may take for the Fuel to get from the end of the injector to the valve face, here are some calculations:

    It is about 2.6 Millisecs at 2000 RPM and 0.8 Millisecs at 6500 RPM, it varies depending on revs, the airflows are from STD EA files that come with the software, I have averaged them.

    This time needs to be taken into account in the overall timing for EOIT.

    Who knows what speed the Injector is actually spraying at? But we can only assume its mixes with the air and assumes that velocity and that will have to do.

    I now finished some other calculations that show the EOIT really is only relevant at low revs because the rest of the time it will never be right anyway, as per what the Lucas Racing reference I posted earlier says.

    Still useful for the Low rev scenarios though.

    I have updated the original table I had in this post to show transit time of the fuel from the Injector tip to Valve face in Milliseconds.

    I have added a second table that shows that for the STD LT1 cam the Intake duration where flow is meaningful(@.050 onwards) is exceeded by the actual Pulsewidth from 2000 RPM on even for small throttle openings.

    Cheers
    Kevin
    Last edited by kevinodb1; 01-22-2019 at 12:30 PM.

  10. #40
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    I Also found this EOIT Spreadsheet, which I think was from an LS1 Forum.

    Which may or may not be useful.

    Cheers
    Kevin
    Attached Files Attached Files

  11. #41
    Fuel Injected! Terminal_Crazy's Avatar
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    Something i don't understand, if my table is correct.

    When we are at temp 90C, we finish around 0x60, well before the intake opens to allow fuel to vapourise a little.

    When cold the tables are set to 0x20 which would finish us somewhere around the intake closing.

    Why would we be spraying into the open cylinder when cold ?

    Mitch
    '95 Z28 M6 -Just the odd mod.
    '80 350 A3 C3 Corvette - recent addition.

  12. #42
    Fuel Injected! spfautsch's Avatar
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    Quote Originally Posted by Terminal_Crazy View Post
    When cold the tables are set to 0x20 which would finish us somewhere around the intake closing. Why would we be spraying into the open cylinder when cold ?
    If I had to guess I'd say because at lower temps the fuel isn't going to evaporate much if at all. Better to have the raw fuel get where it's needed immediately then to spray it in the intake port and rely on the air charge to have to draw it off the walls of the port. kur4o touched on this back in post #19.

    Quote Originally Posted by kevinodb1 View Post
    I now finished some other calculations that show the EOIT really is only relevant at low revs because the rest of the time it will never be right anyway, as per what the Lucas Racing reference I posted earlier says.
    Furthering this thought, assuming the intake valve closes exactly at BDC of the intake stroke (I don't think this is the case even with stock B body cams) with the stock EOIT set at 0x60 and injector duty cycles greater than 37.5% there will still be fuel being sprayed directly into the open cylinder.

    And if that doesn't blow your mind, research the topic of what an oxygen sensor really tells us. I just digested this subject far enough to come to a remedial understanding and realized why tuning to AFR is a misnomer when oxygen sensors tell us how far from lambda / stoich the combustion process is, regardless of the composition of the fuel being burned. Almost all fuel readily available in the US is minimally 10% ethanol with a stoichiometry of about 14.15:1.

  13. #43
    Electronic Ignition! JimCT_9C1's Avatar
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    B-Body Cam Specs

    Quote Originally Posted by Stroked 388 View Post
    Does anyone know at what Degrees the intake valve opens on a stock 94 LT1. I can't find any type of cam card for a stock cam. The cam I have now opens at 15.5* BTDC. But the eoit tabe is still stock
    Been following along... this is from the impala forum:
    B-Body LT1: INT - 191 .418" EXH - 196 .430" LSA - 111 P/N 10243779

    Not sure about the factory installed intake centerline, but assuming its 111 straight up I get the following at 050, with roughly +/- 25 degrees for lash points:

    IVO @050: 111-191/2 = 15.5 ATDC (-25=9.5 BTDC@lash)
    IVC @050: 111+191/2-180 = 26.5 ABDC (+25=51.5 ABDC@lash)

    EVO @050: 111+196/2-180 = 29.0 BBDC (+25=54.0 BBDC@lash)
    EVC @050: 111-196/2 = 13.0 BTDC (+25=12.0 ATDC@lash)

    Hope this helps -

    Jim

  14. #44
    Fuel Injected! vilefly's Avatar
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    Sorry I was extremely late to the table, guys. Do you need a scope of injector on time vs tdc vs crank signal? I only have my stock B-body to play with. I might have time today to grab some scope shots. I also have a thermograph camera at my disposal, but not much use unless someone shows up in an F-body with headers.

  15. #45
    Fuel Injected! spfautsch's Avatar
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    As I mentioned in the PM - I don't think there's anything more to learn. I completely shifted my brain into neutral after getting hung up on the misinformation and completely overlooked the elephant in the room.

    You sure have some cool toys available to you. The idea of using a FLIR to identify header temps / cylinder balance never crossed my mind but it seems there are some relatively affordable pieces available now that are made to attach to a smartphone.

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