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Thread: Injection Timing Assistance Requested

  1. #21
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    Higg's - I'm thinking that you might be thinking of a DI motor - yes? You can move injection boundary all the way to where the intake valve closes if you like - it won't show benefits there... Also peak piston velocity happens long after the intake has opened and exhaust closed - this is another reason why I like degree wheels - it allows you to see the piston stopped points...

    You'll neve have to worry about injecting during spark - if this is the case your lead is WAY too advanced and / or your cam is worthless as your intake valve is still open around peak compression points...
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

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  2. #22
    Senior Tuner Higgs Boson's Avatar
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    Definitely not thinking of DI as the intake valve is basically irrelevant with DI, you might reread my two posts just to make sure we are on the same page.

    I am talking about SOIT and EOIT.

    Lets say peak piston velocity is 70 degrees. 70 degrees after TDC, which stroke are we talking about, I assume all of them.

    If the intake valve is closed no fuel is entering the chamber, right? Which stroke of peak piston velocity is relevant if the intake valve is closed? Which stroke is the intake valve open during peak piston velocity? It can only be the intake stroke since that is when the intake is open, right?

    From post 11: "SOIT (Start of Injection Target), above 2500 rpms or so, occurs right before peak piston velocity and BDC (Bottom Dead Center) of the pistons stroke and EOIT (End of Injection Target) at these rpm points before the intake valve gets within 20 or 30 degrees of being completely closed."

    Indicating a desire to Start Injection at 70 degrees after TDC. If you Start Injection 70 ATDC on the intake stroke (360+70 = 430) the intake valve will close way before you have enough time to inject the needed fuel so by process of elimination we must assume we are talking about a stroke before that which is 0+70 = 70 where of course the intake is closed.

    So I am just wondering how piston velocity matters at all above 2500 RPMs, I could see it making a difference at low RPMs where SOIT is after IVO.
    Last edited by Higgs Boson; 02-11-2017 at 08:14 PM.

  3. #23
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    It actually matters more at higher rpms because you need the engine revs to atomize the fuel at that point... Boundary as you know is the end of injection and the ecm will move soi to where it needs to for the pulsewidth... This is why you need to target right around before the exhaust valve is fully seated for lower rpms - the port velocity via piston suction via piston velocity is too low to properly atomize the fuel at lower rpms... Higher rpms - better fuel atomization and you can target eoi much later - still has to be right to make power 590 to 640 is about as far as you ever want to push it as far as boundary goes... Even though I've found some sc companies like whipple copying me - incorrectly I might add - and pushing it as high as 670 or so to keep fuel from going out the exhaust valve...
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

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  4. #24
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by GHuggins View Post
    It actually matters more at higher rpms because you need the engine revs to atomize the fuel at that point... Boundary as you know is the end of injection and the ecm will move soi to where it needs to for the pulsewidth... This is why you need to target right around before the exhaust valve is fully seated for lower rpms - the port velocity via piston suction via piston velocity is too low to properly atomize the fuel at lower rpms... Higher rpms - better fuel atomization and you can target eoi much later - still has to be right to make power 590 to 640 is about as far as you ever want to push it as far as boundary goes... Even though I've found some sc companies like whipple copying me - incorrectly I might add - and pushing it as high as 670 or so to keep fuel from going out the exhaust valve...
    I am not saying to delay EOI so much that SOI is after EVC, that can't be done anyways except at idle and very low RPM which is done with stock settings anyways (and a stock cam) and also I disagree that low RPM velocity is to slow, a stock cam has no overlap at .050 and relatively little at .006 and idle injection (SOI and EOI) occurs after EVC (and after IVO for that matter) not to mention stock idle is going to be slower than one with a cam, helping it that much more especially if it is timed with peak piston velocity.

    As you say, SOI is what it needs to be based on set EOI, and over about 3000 RPM the stock EOI occurs before the intake ever opens. All of the fuel is injected onto a closed intake and then the intake opens, intake closes, piston goes up for combustion. Below 3000 EOI is timed a bit after IVO and occurs around overlap (except there is little to none on a stock cam) and at idle SOI and EOI occur after IVO.

    Since higher RPMs EOI happens before IVO then SOI is progressively sooner even occurring during the combustion stroke (intake valve is closed of course). Of course engine speed is great enough that everything is happening very quickly so honestly injection timing is less relevant as the only time it's NOT injecting is basically during the intake stroke itself.

    So if you wanted to move EOI from before IVO to just before IVC, then ok, not sure why as I mentioned above. I use injection timing to avoid low speed injection during overlap but after that, not sure why I would move it once spraying during overlap is unavoidable.


    I know you said it feels better on the street but shows no results on the dyno, can you please tell me WHY that is and what is the cause? Are you advancing or delaying injection timing as a whole to achieve this effect? At high or low RPMs?
    Last edited by Higgs Boson; 02-11-2017 at 08:34 PM.

  5. #25
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    Quote Originally Posted by Higgs Boson View Post
    I am not saying to delay EOI so much that SOI is after EVC, that can't be done anyways except at idle and very low RPM which is done with stock settings anyways (and a stock cam) and also I disagree that low RPM velocity is to slow, a stock cam has no overlap at .050 and relatively little at .006 and idle injection (SOI and EOI) occurs after EVC (and after IVO for that matter) not to mention stock idle is going to be slower than one with a cam, helping it that much more especially if it is timed with peak piston velocity.
    Your studies may show differently - I don't think they will - but mine always showed turbulence via port velocity via piston velocity was always too low for proper fuel atomization and burn at lower rpms to push the boundary and soi back that far at lower rpms... Only reason to do this with blower setups is for transient fueling and to keep the fuel in the cylinder - you can actually get much better fuel economy and overall burn by putting blower setups soi back towards stock, but you'll regret it with the transient fueling issues... This is why I target after the exhaust valve has closed on them...

    As you say, SOI is what it needs to be based on set EOI, and over about 3000 RPM the stock EOI occurs before the intake ever opens. Depends on engine - Camaro's all have eoi after intake opens All of the fuel is injected onto a closed intake and then the intake opens, intake closes, piston goes up for combustion. Below 3000 EOI is timed a bit after IVO and occurs around overlap (except there is little to none on a stock cam) and at idle SOI and EOI occur after IVO.

    Since higher RPMs EOI happens before IVO then SOI is progressively sooner even occurring during the combustion stroke (intake valve is closed of course). Of course engine speed is great enough that everything is happening very quickly so honestly injection timing is less relevant as the only time it's NOT injecting is basically during the intake stroke itself. Again this depends on the engine whomever originally tuned them at the factory - Camaro's have boundary at 520 with no rpm adder and ect set to 110 resulting in eoi always being after the intake valve is open... I studied a ZL1 compared to a factory ls3 vette heavily when I discovered what I discovered... Important thing is to throw what the factory is doing out the window and play with it... Only sucks that you have to retune your MAF and VE every time, but you might be surprised with what you find...

    So if you wanted to move EOI from before IVO to just before IVC, then ok, not sure why as I mentioned above. I use injection timing to avoid low speed injection during overlap but after that, not sure why I would move it once spraying during overlap is unavoidable.


    I know you said it feels better on the street but shows no results on the dyno, can you please tell me WHY that is and what is the cause? Are you advancing or delaying injection timing as a whole to achieve this effect? At high or low RPMs?
    I said you MAY not see anything on the dyno - I have personally seen up to 45hp gains on cars previously tuned by other shops I've even done injection timing maps for a couple of the joe gibbs racing guys who take their cars to the drag strips - they were seeing better quarter times... I don't know how, but in a way your putting more fuel into the chamber while still maintaining the same afr's - which I know as tuners - we think of this as being inefficient, but this allows you to run more timing at the same time = making more power and torque...

    I studied some old timers who experimented with slow revving (4500 redline if you will) wood mill generators - they found moving injection timing back greatly increased the torque, but made it lazy at really low rpms - this combined with studying stock blower motors setups vs stock na setups lead me to what I discovered...

    I need to go back and rewrite a lot of my earlier postings including the ones on injection timing to better explain things, but I'm always too lazy - just being honest
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
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  6. #26
    Senior Tuner Higgs Boson's Avatar
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    When you say moved injection timing back do you mean they advanced or retarded injection timing? "Back" and "retard" have sort of the same connotation but I can also see how back means advance since it is "further back in the strokes." Are you saying more torque is better or worse than a lazy motor?

    Again are you advocating EARLIER injection timing as a whole or LATER? What gets you more fuel in the chamber? How does more fuel get in the chamber if fuel can only enter when the intake valve is open? I can see more being in the chamber, as I mentioned, if we retard (make later) injection so that less is lost to overlap. If you mean getting SOI during the combustion stroke so that EOI is earlier (like before IVO) then thats exactly what stock does and we should just adjust to make our new cam have the same relationship as it did with the stock one.

    Can you please elaborate? Thanks!

    Here is what I have set to try based on what I am seeing for SOI at low RPMs and EOI at higher RPMs. This is with a zero'd RPM table and a stock ECT table. This makes EOI very late, while the intake is open, EOI is about peak lift on the intake cam here.

    IT.JPG
    Last edited by Higgs Boson; 02-11-2017 at 09:27 PM.

  7. #27
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    Now you know what I mean when I say I suck at explaining things

    Back = Retard injection timing

    More fuel in the cylinder - typically when you retard it - things become not so efficient = having to add more fuel to hit the same afr's = more fuel in the cylinder while still maintaining the same afr's... Also allows you to add more timing for some weird reason?

    More power felt but not seen - 2500ish rpms - typically people run into problems with tires breaking loose where they wouldn't before, but may not show gains at all much on the dyno...

    On turbo setups - I've even been able to gain 70 to 100 hp down low by retarding the injection timing over the stock advanced timing - made turbo's spoil quicker and in these instances actually kept the tires from breaking loose because the power curve was so much more linear...

    There are great things to be had from injection timing on the right setups and lots of secrets to go along with it that I don't even know... Not all setups will show gains and if it's off - you might actually see a 30 or 40 hp loss - it takes experimenting...
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
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  8. #28
    Senior Tuner Higgs Boson's Avatar
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    Then we are talking about the same exact thing. Retarded injection vs stock.

    The question that remains is how retarded can you get EOI without losing out to IVC? My table above I estimate to have EOI right at intake valve peak lift so that any "in between" fuel" might have enough time to travel into the chamber before the intake closes completely. I know this is relatively irrelevant at high RPMs but I do think it matters at mid range, where RPMs are fast enough to benefit from it but not so fast that it's all one big motion of fuel and air simultaneously.

    As I mentioned above, I think the feeling of more torque has to do with combustion quality and also why it doesn't always work. Any fuel injected after IVO is not "atomized" against a hot intake valve and is going to be a more raw fuel but also will be in a different location relative to the spark plug (more direct injection style) when it fires vs stock. But, too much of that "unatmomized" fuel can hurt combustion as well so I guess one would have to experiment with their particular combination.

    So really, if we can figure out a general "max late" EOI then we can work backwards (more advanced) from there.
    Last edited by Higgs Boson; 02-11-2017 at 09:48 PM.

  9. #29
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    Yes, although I could very well be crazy - I believe the key is to get the perfect raw fuel to vaporized fuel mixture at higher rpms - lower rpms you need a high majority of vaporized fuel which is why we try to target more on a "still opening" intake valve to where the fuel will still spray a hot metal valve... It may not be seated, but still present in the "doorway" to get sprayed Also going back to this - this is another reason why port velocity isn't the best thing to target here - you want the fuel to spray the hot valve to atomize it at lower rpms - too high of a velocity and it will bypass the valve all together flowing through the opening flooding the chamber with an extremely high amount of raw fuel...

    I have setups out there running 620 on the boundary at peak and 80 to 90 on the ect table - with their cams, blowers and exhaust setups - that's where they liked to be...

    Different fuels also like different settings - Alcohol for example likes a more advanced soi...
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
    Remote Tuning Available at gh[email protected]
    Mobile Tuning Available for North Georgia and WNC

  10. #30
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by GHuggins View Post
    Yes, although I could very well be crazy - I believe the key is to get the perfect raw fuel to vaporized fuel mixture at higher rpms - lower rpms you need a high majority of vaporized fuel which is why we try to target more on a "still opening" intake valve to where the fuel will still spray a hot metal valve... It may not be seated, but still present in the "doorway" to get sprayed Also going back to this - this is another reason why port velocity isn't the best thing to target here - you want the fuel to spray the hot valve to atomize it at lower rpms - too high of a velocity and it will bypass the valve all together flowing through the opening flooding the chamber with an extremely high amount of raw fuel...

    I have setups out there running 620 on the boundary at peak and 80 to 90 on the ect table - with their cams, blowers and exhaust setups - that's where they liked to be...

    Different fuels also like different settings - Alcohol for example likes a more advanced soi...
    yes, but alcohol also needs a more advanced injection because you need so much more of it so more time to inject is better. with alcohol a more advanced SOI doesnt necessarily mean a more advanced EOI (vs gasoline).

    the cam in this LS2 I am tuning is pretty small, a Comp Thumper with low-medium duration but a 109/103 LSA/ICL so I could definitely see a much higher boundary with a big cam.

    I just went back to look at my old 01 Z06 I had 10 years ago with a big cam and stroker and I even retarded injection from stock back then, lol, I guess when you are away from it a while you forget.....that car was in reference periods though, so a bit different.

    Anyways, I guess I will play with it soon enough.

  11. #31
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    Quote Originally Posted by GHuggins View Post
    Yes, although I could very well be crazy - I believe the key is to get the perfect raw fuel to vaporized fuel mixture at higher rpms - lower rpms you need a high majority of vaporized fuel which is why we try to target more on a "still opening" intake valve to where the fuel will still spray a hot metal valve... It may not be seated, but still present in the "doorway" to get sprayed Also going back to this - this is another reason why port velocity isn't the best thing to target here - you want the fuel to spray the hot valve to atomize it at lower rpms - too high of a velocity and it will bypass the valve all together flowing through the opening flooding the chamber with an extremely high amount of raw fuel...

    I have setups out there running 620 on the boundary at peak and 80 to 90 on the ect table - with their cams, blowers and exhaust setups - that's where they liked to be...

    Different fuels also like different settings - Alcohol for example likes a more advanced soi...
    "I have setups out there running 620 on the boundary at peak and 80 to 90 on the ect table..." - This is an important point. It seems the value referenced here and captured in the tune file is NOT normal engine coolant temperature. Normal engine coolant temperatures for most high performance engines is usually between 185 and 205 degrees at normal operating temperature.

    I'm suggesting that the Normal ECT value in the tune file is a "window in time' that accounts for the changes in the combustion process and/or engine efficiency as engine coolant temperature increases. We all can probably agree that most engines run smoother when the have a little heat in them. I'm a Yankee from Boston... I remember my mother trying to start the ole AMC Ambassador station wagon (green with fake wood on the sides) during the winter.

    OK... so if this logic is correct...

    The values in our SPREADSHEET can all be the same, but the values in the TUNE FILE can be different to account for the variances in engine performance based on ECT

    Normal ECT from Tune.JPG

    And if that statement is correct, I would expect that values within the circle shown (in the 176, 198, 219 cells) to be similar, if not the same, AND that these values are the ones we would enter into the spreadsheet for injection timing analysis. In other words, we are using the values in the TUNE FILE in the 198 ECT (for example) cell all the way across in the SPREADSHEET file because we're trying to figure out injection timing for maximum engine performance at normal engine operating temperature (which is often around 198 degrees).

    Correct?
    Last edited by scottt28; 02-12-2017 at 07:42 AM.

  12. #32
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    Quote Originally Posted by Higgs Boson View Post
    yes, but alcohol also needs a more advanced injection because you need so much more of it so more time to inject is better. with alcohol a more advanced SOI doesnt necessarily mean a more advanced EOI (vs gasoline).

    the cam in this LS2 I am tuning is pretty small, a Comp Thumper with low-medium duration but a 109/103 LSA/ICL so I could definitely see a much higher boundary with a big cam.

    I just went back to look at my old 01 Z06 I had 10 years ago with a big cam and stroker and I even retarded injection from stock back then, lol, I guess when you are away from it a while you forget.....that car was in reference periods though, so a bit different.

    Anyways, I guess I will play with it soon enough.
    Once again, I didn't explain things that well... Alcohol requires more advanced timing at idle and cruise... Since the ect table above all other tables defines soi - with alcohol you have to raise or advance the timing for alcohol... You'll most likely find that even with blowers - alcohol likes being advanced... It's also weird that you won't have the transient issues with alcohol like you will gas... Advancing alcohol gets the bank to bank differences closer together and cleans up the burn better...

    "I have setups out there running 620 on the boundary at peak and 80 to 90 on the ect table..." - This is an important point. It seems the value referenced here and captured in the tune file is NOT normal engine coolant temperature. Normal engine coolant temperatures for most high performance engines is usually between 185 and 205 degrees at normal operating temperature.

    I'm suggesting that the Normal ECT value in the tune file is a "window in time' that accounts for the changes in the combustion process and/or engine efficiency as engine coolant temperature increases. We all can probably agree that most engines run smoother when the have a little heat in them. I'm a Yankee from Boston... I remember my mother trying to start the ole AMC Ambassador station wagon (green with fake wood on the sides) during the winter.

    OK... so if this logic is correct...

    The values in our SPREADSHEET can all be the same, but the values in the TUNE FILE can be different to account for the variances in engine performance based on ECT



    And if that statement is correct, I would expect that values within the circle shown (in the 176, 198, 219 cells) to be similar, if not the same, AND that these values are the ones we would enter into the spreadsheet for injection timing analysis. In other words, we are using the values in the TUNE FILE in the 198 ECT (for example) cell all the way across in the SPREADSHEET file because we're trying to figure out injection timing for maximum engine performance at normal engine operating temperature (which is often around 198 degrees).

    Correct?
    Yes, in essence your correct - but for the spreadsheets purpose - it just needs to be one number...

    The higher numbers in the ECT table represent advancing the injection timing to keep the fuel on a "warming up" intake valve longer - to better atomize it... As we've been discussing at lower rpms - engines do not like to ignite rawish fuel...

    However - what you may find in the future is that once again this varies setup to setup... Some cams and setups actually do better with one number all the way throughout the ect range, because advancing causes the fuel to go straight out the exhaust... This is especially true with lower LSA cam profiles with PD blowers... Centri's like keeping to OE number transitions, but far less advanced in the colder temp ranges...

    I like visual representations, but for these reasons and every setup being different - I don't think you can have a spreadsheet that says "this is what you need to put into your tables" - at least not without a whole whole lot of R&D time spent with many different setups... This is also why I like spreadsheets like what your making Scott28 - it doesn't give you numbers saying to put this in - it just gives you the visual along with the soi and eoi that you wind up with... The end result is left up to the user...
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
    Remote Tuning Available at gh[email protected]
    Mobile Tuning Available for North Georgia and WNC

  13. #33
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by GHuggins View Post
    Once again, I didn't explain things that well... Alcohol requires more advanced timing at idle and cruise... Since the ect table above all other tables defines soi - with alcohol you have to raise or advance the timing for alcohol... You'll most likely find that even with blowers - alcohol likes being advanced... It's also weird that you won't have the transient issues with alcohol like you will gas... Advancing alcohol gets the bank to bank differences closer together and cleans up the burn better...
    I think the issue we are having is you are reading my posts and boxing them into an "exclusive quote" as if everything I don't type out is something I don't know or agree with. Again, we are on the same page, just because I typed something doesn't mean it's the only thing, in this case the ONLY reason alcohol needs an advanced SOI but it is definitely a reason.

    On the DI stuff we have modifier tables for SOI and alcohol content. Here is what it does with it:

    DI SOI ALK.jpg

    Typical stock table with random values in some places but at idle they clearly retard SOI for alcohol and advance it at WOT. Part throttle is a crapshoot.


    Also, I am not sure saying that the ECT table is what primarily defines SOI is accurate. The ECT table, like RPM table, is a modifier to the Boundary table, which directly affects EOI and then SOI is a result of desired EOI unlike the DI setups where SOI is commanded/desired and EOI is what it is until it gets to a limit before spark then the ECM will start advancing SOI and increasing pulse width and fuel pressure.

    I say that especially because the ECT table is temporary from cell to cell as the engine warms until you get to operating temp where all the values are the same. Your engine isn't going to be at 40 degrees, for example, very long, it will keep moving up pretty fast. The ECT table is a cold start/emissions modifier table.
    Last edited by Higgs Boson; 02-12-2017 at 10:17 AM.

  14. #34
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    Quote Originally Posted by GHuggins View Post
    Once again, I didn't explain things that well... Alcohol requires more advanced timing at idle and cruise... Since the ect table above all other tables defines soi - with alcohol you have to raise or advance the timing for alcohol... You'll most likely find that even with blowers - alcohol likes being advanced... It's also weird that you won't have the transient issues with alcohol like you will gas... Advancing alcohol gets the bank to bank differences closer together and cleans up the burn better...



    Yes, in essence your correct - but for the spreadsheets purpose - it just needs to be one number...

    The higher numbers in the ECT table represent advancing the injection timing to keep the fuel on a "warming up" intake valve longer - to better atomize it... As we've been discussing at lower rpms - engines do not like to ignite rawish fuel...

    However - what you may find in the future is that once again this varies setup to setup... Some cams and setups actually do better with one number all the way throughout the ect range, because advancing causes the fuel to go straight out the exhaust... This is especially true with lower LSA cam profiles with PD blowers... Centri's like keeping to OE number transitions, but far less advanced in the colder temp ranges...

    I like visual representations, but for these reasons and every setup being different - I don't think you can have a spreadsheet that says "this is what you need to put into your tables" - at least not without a whole whole lot of R&D time spent with many different setups... This is also why I like spreadsheets like what your making Scott28 - it doesn't give you numbers saying to put this in - it just gives you the visual along with the soi and eoi that you wind up with... The end result is left up to the user...
    I've updated the spreadsheet a little bit. Here's a screenshot. Full files using my cam specs and tune/log information attached. GHuggins/Schpenxel/Mowton... I would appreciate it if you found time to comment.

    Injection Timing Screen Shot.JPG

    Agreed. There is no such thing as "one size fits all" when it comes to tunes. The spreadsheet is just a tool to try to show what's happening. I'm not going to include a lengthy disclaimer here. Anybody reading this has to use his/her own judgment on the tools and/or the suggestions.

    Here's a what my Injection Boundary curve looks like:

    Injection Boundary.JPG

    Excel spreadsheet attached
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  15. #35
    Senior Tuner Higgs Boson's Avatar
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    Your idle injection is right at 358-360, which is also during overlap and the piston is still moving up....IMO, I would retard it a bit more, put SOI closer to 400-430 (especially if you are thinking .006 rather than .050) so the piston is on the way down and the exhaust is closed. Not to mention this is peak piston velocity to assist in pulling that fuel down. If you are concerned about it hitting the intake to atomize, use your ECT table to advance it when the engine is cold. I don't think you will notice a difference at operating temp anyways, at least not any positives putting it around an open exhaust valve.

    EOI at higher RPMs is when the valve is closing so you're pushing it out a little further than me, around 450 when my intake is around peak lift. That's the part I am unsure of is how late you can push it.
    Last edited by Higgs Boson; 02-12-2017 at 10:34 AM.

  16. #36
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    Higg's - that's a DI motor - I always like to think of them oppositely of a normal port injection motor because your targeting the same thing - yes - but their happening entirely differently - I try to leave them out of the 4th gen talks... Their retarding the injection timing for alcohol to get it at a higher cylinder pressure = alcohol likes compression and heat which is why advancing it on a 4th gen does the same thing... AND then like you stated they advance it with rpm because alcohol requires more advance with rpm simply because of the quantity on the DI motors...

    In my studies - boundary won't necessarily change soi - it does - don't get me wrong, but you change the ect the same amount - it definitely changes... You notice this more with cams than anything else... Boundary is a last resort "wall" - seems like the ecm will always try to keep it away from this wall... This may be what the other tables below the main ones define? I haven't played with them and the last time I checked - the injection timing pids were taken out of the scanner... Don't think they ever worked in the first place when I tried them which may be why they disappeared? If they're back - I'll start studying things again...
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
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  17. #37
    Senior Tuner Higgs Boson's Avatar
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    I'm thinking:

    IDLE: set SOI as early as possible without risk of an open exhaust valve to keep all fuel in the chamber.

    MID: retard EOI as late as possible without risk of closed intake valve to reduce loss during overlap and get that late fuel into chamber for responsiveness and street power.

    HIGH: Advance SOI as much as possible to maximize time for injector to do it's thing, engine RPM will handle overlap and mixture for you.

  18. #38
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    Do the cross hairs open and close to represent soi and eoi? That would actually be nice if done that way...

    Also you might want to remove the ppv suggestion - as pointed out - that will never be possible unless your running huge injectors and that will change all of this once again - we can get into that too if you like, but for now this is good Didn't look at your numbers yet, but the general slope looks good...
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
    Remote Tuning Available at gh[email protected]
    Mobile Tuning Available for North Georgia and WNC

  19. #39
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by GHuggins View Post
    Higg's - that's a DI motor - I always like to think of them oppositely of a normal port injection motor because your targeting the same thing - yes - but their happening entirely differently - I try to leave them out of the 4th gen talks... Their retarding the injection timing for alcohol to get it at a higher cylinder pressure = alcohol likes compression and heat which is why advancing it on a 4th gen does the same thing... AND then like you stated they advance it with rpm because alcohol requires more advance with rpm simply because of the quantity on the DI motors...

    In my studies - boundary won't necessarily change soi - it does - don't get me wrong, but you change the ect the same amount - it definitely changes... You notice this more with cams than anything else... Boundary is a last resort "wall" - seems like the ecm will always try to keep it away from this wall... This may be what the other tables below the main ones define? I haven't played with them and the last time I checked - the injection timing pids were taken out of the scanner... Don't think they ever worked in the first place when I tried them which may be why they disappeared? If they're back - I'll start studying things again...

    Alcohol and DI talk aside, boundary 100% changes SOI when pulse width changes. Again ECT is just a modifier for a cold engine otherwise it is not used (as it's value is a constant at operating temp).

  20. #40
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    Quote Originally Posted by Higgs Boson View Post
    I'm thinking:

    IDLE: set SOI as early as possible without risk of an open exhaust valve to keep all fuel in the chamber.

    MID: retard EOI as late as possible without risk of closed intake valve to reduce loss during overlap and get that late fuel into chamber for responsiveness and street power.

    HIGH: Advance SOI as much as possible to maximize time for injector to do it's thing, engine RPM will handle overlap and mixture for you.
    The mid and high are the same thing - you just used different words BUT for mid - you actually want to target the "middle" - this is just for regular rpm free revving sake (lower gears being strung out)
    Last edited by GHuggins; 02-12-2017 at 10:48 AM.
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
    Remote Tuning Available at gh[email protected]
    Mobile Tuning Available for North Georgia and WNC