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Thread: Injector Timing? Reference Periods? refereencing what?

  1. #581
    Senior Tuner kingtal0n's Avatar
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    Quote Originally Posted by anniversaryss View Post
    So your saying you adjusted your EOIT to right after the intake valve opens trying to still utilize the evaporation technique as it was but still moving injection timing later to aid in helping the cam work more efficiently?
    In theory I tried to time the END of injection to the intake valve crack open point, so the full amount of fuel is being injected to the closed intake valve but it may be just beginning to open as the end of injection completes, yes. I did this in attempt to conserve fuel near the valve and keep the reversion effort of upward moving piston while intake valve is open minimized (from about 330* to 365* there is in theory a potential for strong surge of pressure into the intake runner that tries to push air and fuel out of the runner and back into the manifold at low rpm say, 500-1200rpm with mild cam, and higher with larger the cam is).


    Hows the idle smell? Do you feel the car runs better right after the IVO or after the EVC?
    I use a full 3" exhaust and tune it lean, (14.8-15.2) have had many cars like this and never had any 'smell' from the driver seat to really speak of, with any engine, 2.0, 2.4, 3.0, 5.3, they shouldn't really smell if the exh ends at tail of the car and it's tuned right imo.
    It stinks with the cutout open though, regardless of injector timing or any other variables. The engine is so old and so full of aged particles that I bet the exhaust would smell even if you spun the engine by hand, without putting any fuel in.
    I am more interested in the economy, if any, to be had. I'd sure love to break 25mpg (the stock fuel economy for the stock 4-cylinder 2.4L from this car) at five or six hundred hp in an actually robust, daily drivable config.

    Im not entirely sure if i like how it runs with it right after the EVC but it did get rid of the fuel smell. But if i move it toward the IVO with better results then i can deal with some smell.

    Ill do some calculations later and see what i find out.
    From what I can tell so far, If an injector goes 95% duty cycle for example, it will be open all the time right. So it doesn't matter when you "end" the injection spray (after the exhaust valve closes for example) because the injection event starts WAyyyyyyyyyyy before that when it's near 90% duty cycle. So it's going to just be spraying through/during overlap instead of finished spraying before overlap if you move EOIT to past overlap. It might not be an issue with some injectors, but others have this really sharp pin point spray that seems like it would just wash down the cylinder wall with little effort.
    Last edited by kingtal0n; 10-08-2019 at 08:44 PM.

  2. #582
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    Quote Originally Posted by kingtal0n View Post
    In theory I tried to time the END of injection to the intake valve crack open point, so the full amount of fuel is being injected to the closed intake valve but it may be just beginning to open as the end of injection completes, yes. I did this in attempt to conserve fuel near the valve and keep the reversion effort of upward moving piston while intake valve is open minimized (from about 330* to 365* there is in theory a potential for strong surge of pressure into the intake runner that tries to push air and fuel out of the runner and back into the manifold at low rpm say, 500-1200rpm with mild cam, and higher with larger the cam is).
    I misunderstood you i see now. Its not really the exhaust/fuel smell in the cabin its mostly the smell say in the garage or standing behind the car that burns your eyes.
    Starting and ending before the IVO your still losing fuel out the exhaust. After EVC youll lose the smell as ive found out. Not trying to argue just giving my opinon on things ive noticed while messing with this.

    I guess ill do more experiments and see whats besr for what i want and my car likes.
    1997 30th SS. Torqhead 24x, TFS heads, 223/235 cam, 4l80e, S60 D1SC 14psi

  3. #583
    Quote Originally Posted by kingtal0n View Post
    experiment
    First I tried having all the fuel in just a ways after overlap, 6.5 to 6.7 normal with the usual boundary 6.5.
    Noticed immediate improvement in a/f ratios (richer) in cruise and idle regions when fully warm with the mild cam TFS-30602001 @ 5.3L
    Then I took my cam card and found advertised duration rough intake valve opening point 327* (open to .050" by 2*ATDC) and put my end of injection right near that,
    so (5.9+6.5)*90-786 = 330*
    That way the fuel is injected later than factory, but still has a brief moment to touch and cool the intake valve just before it begins to crack open as the piston is moving up, which I think pushes the fuel away from the intake valve slightly for an instant. Then hopefully it can glide through overlap before any fuel is in the cylinder.

    And I am still rich everywhere. I'm pulling fuel out of the VE map around 2% VE (a fuel savings of roughly 5%) some spots. I think this later spraying is conserving fuel within the intake runner and it's early enough that I keep most of what I spray now AND it still hits the back of the intake valves which I can tell by looking down the runners has a slight cleaning effect as well. I can't wait to test fuel economy difference next.
    Interesting points there too. I might need to play around some more in that in-between area. I was hoping I could hit the far extremes first (spray all on closed valve, or spray all in open valve) to really gauge whether there was significant changes due to injection timing. But now that I think of it, a while back I had been riding around with my normal value in the low 6.xx range just trying the delayed timing thing before I finally came across the actual definition of what a reference period was in crank degrees, the math, etc. and I may have digressed. If I remember right, it ran pretty "smooth" on that 6.x value, so I'll try and duplicate the exact tests I tried on the 5.5 and 7.2 extremes. Maybe I just happened to pick values from each end that were equally less than ideal...
    Guess I forgot the fundamentals; 2 points can't determine the shape of a curve, need at least 3. Its just tough out here to get good consistent data with so much ambient temp and humidity swing so I wanted my DOE to be small. If my shop ever has it in the cards to get an eddy current brake dyno and 5 gas analyzer, and EGT sensors, ... and oscilloscope,...?.. and data acquisition equipment I'll disappear for a week straight haha

    It would be really nice for the theoretical side to know the velocity / inertia of the air... and heck, even knowing for 100% certainty which direction the air is flowing through the intake runner and valve at any given time. …. I am fairly handy at 3D CAD, with mechanisms, and at CFD... but I can't imagine ever trying to model an actual 4 stroke cycle with air, fuel, combustion
    Wonder if there is any feasible and reasonable way to instrument the intake runner(s) for pressure and flow just before the valve? without researching it, seems like identifying flow direction would be a challenge....
    Last edited by CaudleDynamicsLLC; 10-08-2019 at 10:02 PM.

  4. #584
    Senior Tuner kingtal0n's Avatar
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    Quote Originally Posted by CaudleDynamicsLLC View Post
    It would be really nice for the theoretical side to know the velocity / inertia of the air... and heck, even knowing for 100% certainty which direction the air is flowing through the intake runner and valve at any given time. …. I am fairly handy at 3D CAD, with mechanisms, and at CFD... but I can't imagine ever trying to model an actual 4 stroke cycle with air, fuel, combustion
    Wonder if there is any feasible and reasonable way to instrument the intake runner(s) for pressure and flow just before the valve? without researching it, seems like identifying flow direction would be a challenge....
    In the picture posted here
    https://forum.hptuners.com/showthrea...l=1#post577011

    you can see they are measuring pressure in the port. The location of each sensor and resulting (sigh) differential... difference (both rate and total) would give the direction of flow I guess. I'm not sure that's the best way to do it though.
    scaling resolution, suitable logging rate, sensitivity/filtering would need to be carefully selected for.
    You don't really need an oscilloscope you just need really good, qualified for the job sensors and a generic user interface would suffice
    Last edited by kingtal0n; 10-08-2019 at 11:12 PM.

  5. #585
    Quote Originally Posted by kingtal0n View Post
    In the picture posted here
    https://forum.hptuners.com/showthrea...l=1#post577011

    you can see they are measuring pressure in the port. The location of each sensor and resulting (sigh) differential... difference (both rate and total) would give the direction of flow I guess. I'm not sure that's the best way to do it though.
    scaling resolution, suitable logging rate, sensitivity/filtering would need to be carefully selected for.
    You don't really need an oscilloscope you just need really good, qualified for the job sensors and a generic user interface would suffice
    I had to sit down and study that a bit more, the axis/scale for the green line isn't showing, but with it peaking at TDC compression and staying steady while either valve is open it seems to me to correlate more to cylinder pressure as opposed to intake port pressure? I think all the information in that one picture is extremely valuable. If that is indeed cylinder pressure, it would be awesome to also overlay pressure in the intake port, maybe between the valve and injector. I'd tend to agree that the differential between the two pressure sensors (cylinder and port), especially when also compared to overall intake manifold pressure, should give you a pretty reasonable idea when and if there really is significant reversion into the intake, when air actually starts flowing back the correct direction past the injector, and possibly, how much delay between SOIT and fuel actually getting past the valve. That level of detail seems like it would still probably be very combination dependent though and would have to be tested a stock or negative overlap cam, and also on an aggressive positive overlap cam. With air having inertia and a "springiness" to it, there may be interesting pressure waves and reversions even on small cams that this whole EOIT study would benefit.

    On further thought, it would probably have to be tested on a running engine with combustion and thermal effects though, since hundreds/thousands degree F air surely behaves differently than air pumped through by motoring the engine, and if we are looking at pressure differentials, we'd certainly want cylinder pressures to be relevant.

  6. #586
    Senior Tuner kingtal0n's Avatar
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    Quote Originally Posted by CaudleDynamicsLLC View Post
    I had to sit down and study that a bit more, the axis/scale for the green line isn't showing, but with it peaking at TDC compression and staying steady while either valve is open it seems to me to correlate more to cylinder pressure as opposed to intake port pressure? I think all the information in that one picture is extremely valuable. If that is indeed cylinder pressure, it would be awesome to also overlay pressure in the intake port, maybe between the valve and injector. I'd tend to agree that the differential between the two pressure sensors (cylinder and port), especially when also compared to overall intake manifold pressure, should give you a pretty reasonable idea when and if there really is significant reversion into the intake, when air actually starts flowing back the correct direction past the injector, and possibly, how much delay between SOIT and fuel actually getting past the valve. That level of detail seems like it would still probably be very combination dependent though and would have to be tested a stock or negative overlap cam, and also on an aggressive positive overlap cam. With air having inertia and a "springiness" to it, there may be interesting pressure waves and reversions even on small cams that this whole EOIT study would benefit.

    On further thought, it would probably have to be tested on a running engine with combustion and thermal effects though, since hundreds/thousands degree F air surely behaves differently than air pumped through by motoring the engine, and if we are looking at pressure differentials, we'd certainly want cylinder pressures to be relevant.
    we know there is reversion because that's what causes the uneven tone of a long duration camshaft idle region.
    Absolutely combination dependent, as intake runner diameter and length plays a massive role in the inertial ability of air to ram the valve or starve a valve at the right moment thus increasing or decreasing rate of Volumetric filling. Lets not forget all the other factors involved, even though the intake runner alone is responsible for a fair majority of air starved cylinders at specific RPM on various engines (ex. TPI 1982-1992 5.7L ~5400rpm limit before starvation due to the speed of sound and 21" long runner, doesn't matter how big the runners diameter)
    lol found a post from 2003 about runner length
    https://www.thirdgen.org/forums/tpi/...ml#post1317874

    There are many dynamics to consider that are relevant besides intake valve effects though, must not be neglected when considering the behavior of fuel and air throughout.
    For example the exhaust gas pressure of turbocharged engines should be higher than a finely tuned naturally aspirated configuration of headers, which rely on the velocity and low pressure pulse area of exhaust gas to scavenge the exhaust valve region during overlap for intake charge, pulling fresh air (and fuel, occasionally) into the cylinder and perhaps some into the exhaust. This was considered a necessary evil in the day of carburetors but no longer with EFI and DI in general apparently. Because turbo exhaust pressure is higher than intake manifold pressure by a fair margin in general, when the exhaust valve opens at idle I believe there is a good chance that the exhaust actually floods the cylinder which prevents the fuel from getting past the exhaust valve, or at least it must be much more difficult to do so.

    Consider that DI engines with cam upgrades still lope. And they fire fuel at the last moment. So the behavior of fuel has nothing/no change to do with the lope and varied distribution of airflow into each cylinder. Specifically the valve events, and the shapes/lengths of everything air touches, is in control.

  7. #587
    Senior Tuner LSxpwrdZ's Avatar
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    Wanted to update this thread with some information. I believe the 784 number may come from the cam offset value in the PCM. I was mapping some parameters and ran across a parameter that is described as "Low Resolution Reference Angle" and it's descriptions states: "Identifies the number of degrees from a low resolution pulse to Top Dead Center of the cylinder". Now this is significant because a full engine cycle is 720 crank degrees. The offset in the PCM for a 24x tune that I was mapping out is set to 65 degrees. It is possible his 784 was off by one degree meaning 785 would be a more accurate number based on the offset from TDC being 65 degrees. Since 720=0 degrees or TDC.

    So this explains a bit more why the 784 (may be 785) came about.
    James Short - [email protected]
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    Quote Originally Posted by LSxpwrdZ View Post
    Wanted to update this thread with some information. I believe the 784 number may come from the cam offset value in the PCM. I was mapping some parameters and ran across a parameter that is described as "Low Resolution Reference Angle" and it's descriptions states: "Identifies the number of degrees from a low resolution pulse to Top Dead Center of the cylinder". Now this is significant because a full engine cycle is 720 crank degrees. The offset in the PCM for a 24x tune that I was mapping out is set to 65 degrees. It is possible his 784 was off by one degree meaning 785 would be a more accurate number based on the offset from TDC being 65 degrees. Since 720=0 degrees or TDC.

    So this explains a bit more why the 784 (may be 785) came about.
    I like it James! I think you're on track. Haven't seen that parameter before, is it one you hacked, or is it in HPT somewhere?

    Is low resolution referring to the cam sensor or the crank sensor?

    When I tested this with my Pico, I found that Bluecat's formula was very close to what I was seeing too.

    To others - remember that the size of the injector has a significant impact on whether or not the injection timing is that important at idle. And that an 80% injector duty cycle at WOT means the injector is open for 576 degrees out of 720. As long as the injection at WOT happens within the current cycle, I doubt there's much difference at all at WOT. But at idle, where the injector duty cycle is only maybe 2% (14.4 degrees), where that happens would be a much bigger deal.

    On a big cam, during valve overlap you have a period of time where there is positive pressure in the exhaust, or at the very least neutral pressure, and there is vacuum in the intake. With both valves open, the high pressure goes towards low pressure and into the intake she blows, carrying any pre-evaporated fuel with it.

    I'm not that concerned about bore wash, because racey cars generally don't spend extended time idling. And they get better maintenance.

  9. #589
    Senior Tuner LSxpwrdZ's Avatar
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    Quote Originally Posted by pontisteve View Post
    I like it James! I think you're on track. Haven't seen that parameter before, is it one you hacked, or is it in HPT somewhere?

    Is low resolution referring to the cam sensor or the crank sensor?

    When I tested this with my Pico, I found that Bluecat's formula was very close to what I was seeing too.

    To others - remember that the size of the injector has a significant impact on whether or not the injection timing is that important at idle. And that an 80% injector duty cycle at WOT means the injector is open for 576 degrees out of 720. As long as the injection at WOT happens within the current cycle, I doubt there's much difference at all at WOT. But at idle, where the injector duty cycle is only maybe 2% (14.4 degrees), where that happens would be a much bigger deal.

    On a big cam, during valve overlap you have a period of time where there is positive pressure in the exhaust, or at the very least neutral pressure, and there is vacuum in the intake. With both valves open, the high pressure goes towards low pressure and into the intake she blows, carrying any pre-evaporated fuel with it.

    I'm not that concerned about bore wash, because racey cars generally don't spend extended time idling. And they get better maintenance.
    Nope it's not an available parameter in HPT. It's in some other softwares I believe but none of the mainstream available software.
    James Short - [email protected]
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    2002 Camaro | LSX 427 | CID LS7's | Twin GT5088's | Haltech Nexus R5 | RPM TH400

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    Please excuse my lazyness/ignorance but I've read a fair amount on EOIT calculations and this stuff is still over my head. I have a 228/228 cammed ls1 w/112 lsa, can anyone tell me optimum injection target for 4* overlap, guessing not much more than the stock 5.55?
    Last edited by Mysterion; 12-08-2019 at 09:39 PM.
    2000 TA M6 228/228 .600"/.600" 112lsa cam
    2000 Sierra 4.8 RCSB DD

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    Quote Originally Posted by Mysterion View Post
    Please excuse my lazyness/ignorance but I've read a fair amount on EOIT calculations and this stuff is still over my head. I have a 228/228 cammed ls1 w/112 lsa, can anyone tell me optimum injection target for 4* overlap, guessing not much more than the stock 5.55?
    That cam wouldn't benefit much from injection timing.
    1997 30th SS. Torqhead 24x, TFS heads, 223/235 cam, 4l80e, S60 D1SC 14psi

  12. #592
    Senior Tuner kingtal0n's Avatar
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    Quote Originally Posted by Mysterion View Post
    Please excuse my lazyness/ignorance but I've read a fair amount on EOIT calculations and this stuff is still over my head. I have a 228/228 cammed ls1 w/112 lsa, can anyone tell me optimum injection target for 4* overlap, guessing not much more than the stock 5.55?
    1. tune the ve map so that you know what the engine runs at while idle/cruising
    2. adjust 'normal' from 5.55 original value, to say 6.0 to 6.2 and compare results from #1

    compare 1 to 2, the air fuel ratio may get richer if there is any fuel conserving effect
    it depends other factors such as runner length and valve temperature
    The goal is to use the earliest injection possible to maximize fuel atomization (the numerically lowest number i.e. 5.55 is very low) while at the same time conserving as much fuel as possible through the use of later injections. A balance is struck between the need for fuel vaporization (related to environment/engine temps) and fuel savings. The reason we don't want to use a high value i.e. 6.5 for gen3 apparatus is because at low rpms it may lead to cylinder wall washing. Later, newer systems can advance the injector for higher rpms thus taking advantage of the peak port velocity (intake stroke) and so forth to maximize kinetic energy input to the cylinder but a setting like this is maybe harsh on the cylinders at low rpm. I hope that was clear.

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    Quote Originally Posted by anniversaryss View Post
    That cam wouldn't benefit much from injection timing.
    Probably not but I'd still like to see for any difference
    2000 TA M6 228/228 .600"/.600" 112lsa cam
    2000 Sierra 4.8 RCSB DD

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    Quote Originally Posted by kingtal0n View Post
    1. tune the ve map so that you know what the engine runs at while idle/cruising
    2. adjust 'normal' from 5.55 original value, to say 6.0 to 6.2 and compare results from #1

    compare 1 to 2, the air fuel ratio may get richer if there is any fuel conserving effect
    it depends other factors such as runner length and valve temperature
    The goal is to use the earliest injection possible to maximize fuel atomization (the numerically lowest number i.e. 5.55 is very low) while at the same time conserving as much fuel as possible through the use of later injections. A balance is struck between the need for fuel vaporization (related to environment/engine temps) and fuel savings. The reason we don't want to use a high value i.e. 6.5 for gen3 apparatus is because at low rpms it may lead to cylinder wall washing. Later, newer systems can advance the injector for higher rpms thus taking advantage of the peak port velocity (intake stroke) and so forth to maximize kinetic energy input to the cylinder but a setting like this is maybe harsh on the cylinders at low rpm. I hope that was clear.
    Thanks after reading it a couple times it does start making sense, I'll give it a go.
    2000 TA M6 228/228 .600"/.600" 112lsa cam
    2000 Sierra 4.8 RCSB DD

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    Just a reminder guys, that when you set injection timing, it's EOIT that you are setting. The BOIT is back-calculated, and would largely depend on how big your injector is. So if you believe that valve overlap is blowing your nicely evaporated fuel charge back up into the intake, and you want to wait until after the exhaust valve closes to inject the fuel to prevent that, you will have to set BOIT after EVC by setting EOIT a little later than that.

    You can figure out how much by calculating how many degrees of crank rotation your injector would be open for at a particular duty cycle. Add that to your BOIT to come up with EOIT.

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    There are some very good calculators out there that can help you calculate your EVC events and normal settings. The better ones include EOIT based on injector size and PW.
    1997 30th SS. Torqhead 24x, TFS heads, 223/235 cam, 4l80e, S60 D1SC 14psi

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    This thread just keeps going; i like that.
    not like i'm some grand tuning master with opinions that matter, but in my new found laziness this is what i do when the case comes up:
    since i only tune my personal garbage i just make multiple passes on the dyno adjusting the normal in stages to find where the mid range picks up the most. i make changes in .1 increments. 5.55, 5.6, 5.7, 5.8 etc.. if the cam is of good size i don't even start my testing until about 5.9 because i know it will be in the 6's typically. i plot average torque from 2500-4000 and peak torque in two separate graphs. this way i can isolate runs to look for irregularities. typically test about 5-6 runs maybe a few more if fueling gets out of my preferred range. i gave up on the math because i realized i was calculating a guess and if i was already guessing then i can just perform that guess on the dyno and get physical results. i keep the calc around just in case i have some monster cam and/or injectors and want to know where that EVC point would land just for numerical reference.


    i also find i can get decently close by watching the wideband lambda value drop. i leave it stock and tune in to 1 lambda outside of pe. then i only make changes to the normal table. as the lambda drops and goes richer i know im heading the right way. once i find a nice range of inactivity i pick the lowest normal value and re-tune to lambda 1 again. i perform one more quick sweep close to the new normal value to see if i was off a little bit and then just call it good. most of the time im running 48 lb/hr injectors on a mild cam so this works great as im not chasing the EVC point to satisfy large cam/injector properties.
    2000 Ford Mustang - Top Sportsman

  18. #598
    Quote Originally Posted by LSxpwrdZ View Post
    Wanted to update this thread with some information. I believe the 784 number may come from the cam offset value in the PCM. I was mapping some parameters and ran across a parameter that is described as "Low Resolution Reference Angle" and it's descriptions states: "Identifies the number of degrees from a low resolution pulse to Top Dead Center of the cylinder". Now this is significant because a full engine cycle is 720 crank degrees. The offset in the PCM for a 24x tune that I was mapping out is set to 65 degrees. It is possible his 784 was off by one degree meaning 785 would be a more accurate number based on the offset from TDC being 65 degrees. Since 720=0 degrees or TDC.

    So this explains a bit more why the 784 (may be 785) came about.
    Under cranking spark, the max is 64 degrees. This means that the maximum amount of spark during any cycle under any event available in the hard code is 64. 720 + 64 happens to be 784. That's what I'm going with. Makes sense to me.

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    On gen 3 pcm what do you do with the makeup value?
    Also what issues come along if your injectors aren't big enough and spray into the cycle before at WOT?
    1997 30th SS. Torqhead 24x, TFS heads, 223/235 cam, 4l80e, S60 D1SC 14psi

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    Ok so i went back and read about 17 pages.
    Looks likes we are changing our makeup table the same amount as we increase the normal.

    Also ive come to gather we are moving our injection timing to end as the exhaust valve close and not start?

    Assume it takes a little playing around but this is what ive come to understand.
    1997 30th SS. Torqhead 24x, TFS heads, 223/235 cam, 4l80e, S60 D1SC 14psi