How far are you guys letting EOI drop?

[Haans249]

easy solution:

set the whole SOI table to 280 and leave all the other tables stock (EOI, gap windows etc)

280 gives plenty of time for injection in all conditions except highly modified WOT and starts injection late enough to make sure the exhaust valve is closed.

if the stock ecm runs out of pulse width to inject before 180 it will back up SOI by itself up to the max injection angle.

Resurrecting this from the dead.

I did some testing on EOI over the weekend and I have to say, that your statement about 280 working for everything but highly modified WOT is accurate.

I set my EOI to 280 degrees and lost some power according to my data logs. I have a 232/240 cam with a IVO of 31 degrees at .006 ATDC and IVC at 71 degrees ABDC (after bottom dead center). At the exact same RPM/gear/speed between two logs, my original setting of 330 had higher cylinder airmass and higher maf lb/hr compared to the 280. I believe that since my valve is opening sooner than stock, I am getting better mixing by starting injection earlier (piston closer to TDC on intake stroke) compared to starting it later with the 280 setting.

But I do want to make sure I'm thinking about this conceptually correctly when it comes to interpreting the number used in the SOI table in our tunes. The tune description for the SOI table is that it is in "crank degrees BTDC". In order to properly 'reference' TDC; 0 degrees = TDC where 360 degrees BTDC (before top dead center) is actually the start of the intake stroke so it is the same thing as 0 degrees or TDC. So in order to properly interpret the SOI number (in my case 330), you have to subtract 360 degrees to get you your crank angle piston position ATDC (after top dead center) of when injection starts. In my case 330 - 360 = -30; or 30 degrees ATDC on the intake stroke. Since my IVO event starts at 31 degrees, this coincides well with my specific intake valve event. Now for an SOI of 280, that would be a start injection piston position of 80 degree ATDC, or well past my 31 IVO event. Is this the correct interpretation of the crank angle degrees for the SOI table?

How about for EOI? With my 330 SOI, my EOI was 210, so would I subtract 180 degrees for the ABDC or BBDC piston position? So for my EOI of 210 - 180 would be a EOI piston position of 30 degrees into the compression stroke? The EOI for a 280 SOI setting was 163 for me.

The reason I have some confusion on this thinking is when I calculate the total crank degree angle injection time for my 330 SOI setting, I get 180 degrees (30-180 = 150 crank degree sweep to BDC plus the crank degrees to EOI of compression stroke of 30). But, for the 280 SOI setting, I am coming up with only 83 degrees. 180 degrees of injection vs 83 degrees of injection just doesn't seem right to me, so I must have this confused... No change in in fueling was observed (same .87-.88 lambda and basically same pulsewidth 3.7 vs 3.6 ms)

[engineermike]

Your SOI reasoning is correct but EOI is backwards. EOI of 210 is 30 deg BEFORE the compression stroke begins, for a duration of 330-210=120 deg. For comparison, I?m running 330-115=215 deg of injector duration.

For SOI I believe it?s much simpler than EOI. See attached graph from Kasseris showing for optimal torque output SOI should be about 60 deg ATDC, or 300 BTDC. Probably not coincidence that the Gen3 coyote was set to 300 across the board when it came out. However, it also shows you can go up to 330 and still retain benefits over port injection. This could be beneficial depending on fuel, injector capacity, piston shape, etc.

Edit: Apparently I can?t upload the graph from my iPhone, possibly due to file size. Sorry.

[TriPinTaZ]

When referencing the SOI and EOI numbers in HPTuners for GM cars its pretty easy.

SOI 380= 20 degrees before TDC on the exhaust stroke
SOI 360= TDC and about to start the intake stroke
SOI 280= 80 degrees into the intake stroke (ATDC)

EOI 210 = 30 degrees before BDC and still in the intake stroke
EOI 180 = BDC and about to enter the compression stroke
EOI 160 = 20 degrees after BDC and currently in the compression stroke

[engineermike]

Looks like Chevy and late Ford count them the same direction. Early Ford was diffferent.

[lt1z350]

Resurrecting this from the dead.

I did some testing on EOI over the weekend and I have to say, that your statement about 280 working for everything but highly modified WOT is accurate.

I set my EOI to 280 degrees and lost some power according to my data logs. I have a 232/240 cam with a IVO of 31 degrees at .006 ATDC and IVC at 71 degrees ABDC (after bottom dead center). At the exact same RPM/gear/speed between two logs, my original setting of 330 had higher cylinder airmass and higher maf lb/hr compared to the 280. I believe that since my valve is opening sooner than stock, I am getting better mixing by starting injection earlier (piston closer to TDC on intake stroke) compared to starting it later with the 280 setting.

But I do want to make sure I'm thinking about this conceptually correctly when it comes to interpreting the number used in the SOI table in our tunes. The tune description for the SOI table is that it is in "crank degrees BTDC". In order to properly 'reference' TDC; 0 degrees = TDC where 360 degrees BTDC (before top dead center) is actually the start of the intake stroke so it is the same thing as 0 degrees or TDC. So in order to properly interpret the SOI number (in my case 330), you have to subtract 360 degrees to get you your crank angle piston position ATDC (after top dead center) of when injection starts. In my case 330 - 360 = -30; or 30 degrees ATDC on the intake stroke. Since my IVO event starts at 31 degrees, this coincides well with my specific intake valve event. Now for an SOI of 280, that would be a start injection piston position of 80 degree ATDC, or well past my 31 IVO event. Is this the correct interpretation of the crank angle degrees for the SOI table?

How about for EOI? With my 330 SOI, my EOI was 210, so would I subtract 180 degrees for the ABDC or BBDC piston position? So for my EOI of 210 - 180 would be a EOI piston position of 30 degrees into the compression stroke? The EOI for a 280 SOI setting was 163 for me.

The reason I have some confusion on this thinking is when I calculate the total crank degree angle injection time for my 330 SOI setting, I get 180 degrees (30-180 = 150 crank degree sweep to BDC plus the crank degrees to EOI of compression stroke of 30). But, for the 280 SOI setting, I am coming up with only 83 degrees. 180 degrees of injection vs 83 degrees of injection just doesn't seem right to me, so I must have this confused... No change in in fueling was observed (same .87-.88 lambda and basically same pulsewidth 3.7 vs 3.6 ms)

I can tell you that on a stock lt1 or lt4 that is 100 percent wrong if your trying to make peak power and stretch your fueling out. I have dynoed many stock cam lt4s and lt1s and depending on where you run the cam timing at is where you should run the soi. I have found upwards of 30whp on the dyno matching the soi to the cam. pushing that injection timing out into an intake valve that has been hanging open is just giving you a much smaller window to spray in. For instance stock lt1 330 soi on full pump ethanol at that setting on a car thats fbo making 500whp will be consuming up most of the stock lt1 injector ms. Take that closer to the lt4 stock soi will decrease the injector Ms and give range on the fuel system if you have enough support like a zl1 intank pump.
I spent a lot of time figuring this out and a ton of dyno time on cars on stock cams and with cams and some of the cars I have retuned that ran like shit for the mods I started in the soi and got both more range and more power from it as this seems to be a major problem for so many tuners. If you have never built an engine tuned a carb or degreed a cam grab a degree wheel and put the cam info on the wheel now look at where it all falls in terms of degrees and injection timing. Tripntaz pretty much nails it down with out saying exactaly how to do it. But it makes sense if you think about how a carb and vacuum works but with direct injection that window changes up a little but basicaly valve timing events is the most important part of injection timing.
In terms of eoi I see the channels from a lot of big tuners and shops and many dont even bother to log it so tells you what they think about how the eoi is falling. I will say that I have found a point that it starts to give up hp and its very very low compared to the 180 that is in the stock lt4 tune. I have seen the eoi change when changing engine timing alone and no fueling so alot goes into all of this way more then most bother to even look at.
Recently took a 2650 lt4 heads cam the works a nice build that a very reputable shop had tuned for him made just shy of 980whp which I thought was low and it was limited to e45 and has xdi 30s and the lpe pump also has about 40gph of meth being sprayed as we even measured it off the car in painters cup did all the math. This shop/tuner out of texas left the soi at 424 injectors 7.6ms and eoi was 200s well beyond jacked up. e45 car had 22 degrees of timing was seeing Kr so called it quits said thats all it has in it. this car is also making 18 psi and higher gears can creep to 20 psi. took the car did a few dragys on that tune before I started on it and was a miserable 5.20 m6 car and no spinning.

Cam has 2 degrees of overlap that happens at tdc so 360 degrees it was logging 424. He had 368 in the main table and was adding 40 more in the adder for ethanol. For one I zero out that table. Ethanol content I see no need for adding as cam timing is not changing with higher ethanol and I do not believe that burn time of the fuel affects soi.
So I zeroed out that table first did a log. Injector ms dropped to 6.2 from 7.6 after getting it back on target lambda and that random kr now gone. it was logging around 390 soi now. So I backed it up more and added 2 degrees of timing. Now Im at 5.5ms 378 soi 24 degrees no kr car feels much better he tells me. I alwasy adjust back to my target lambda to get resluts.
So now I have him go add some ethanol up to e65 I back up the soi a little more and now am around that 360 degree mark in which my intake valve is opening the ethanol timng table has added a little timing and I still am around 6ms on the injectors but my eoi is creeping a little low. I lean the car out a little more and get the eoi around 150 in which I think its fine as the car is now logging a spinning 4.40 60-130 I have yet to get this car back on the dyno but sure its up a good 100whp just by getting injection timing better and giving me a bigger window on more ethanol and some more timing.
The reason that you cannot go to say 280 and just let it ride is the eoi will end up being so low that its losing hp maybe even run like shit. While I do not know the exact bottom number on eoi I kinda ignore it at this point and only worry about the soi being closer to the valve events and if on the dyno Ill move it up and down a little and land on what is best. I have been as low as 145 on a car and still ended up making really good power for the combo and more power then a lot of other similar builds.
So for what I have found in street and dyno tuning the Soi needs to be on point to the cam and valve events and cannot just back it way up and hope it comes out for the best. Backing that number down is advancing the spray so making the spray time shorter and end of injection go longer. You do this your giving up hp I can tell you that 100 percent as tested many times on many cars.
I beleive howard said it earlier in the thread if unsure as no dyno the way you know for sure its helping is the car will keep going more rich and I forgot to mention that up top on the 2650 car. So if at 400 soi and its at .84 you back it down to 380 soi and you now see .80 your going in the right direction. That is how your going to gain that range on the injectors. Now you lean it back out to your target and the injector ms drops. it is a big balancing act and as long as you see it going more rich its going in the right direction. Im sure there is an ideal eoi for the valve events or maybe just when enters the next cycle but that is one thing I am not sure of and just try to use 150s as a target as when can make 1000whp on a stock ported blower with a SBE heads cam combo I do believe that what I am doing is working
This frustrated me a long time so hope this is enough to help with out me saying do X to make the best hp but all of your settings will play a part in how that injector timing shakes out. I do wish I could nail down an exact bottom on the eoi so will say that is one thing I would like to figure out and know.

[TriPinTaZ]

On stock cam LT4 stuff I haven't seen any issues with the SOI backing up to 375-380 and the EOI falling to 140-150 as long as the high side stays above 2500PSI. This is ONLY for when they guys want to go out and run E70+ for max timing and power. There is no need to stretch the fuel system like that every day, but I haven't seen an issue. This is past any level I would allow a customer car to be at. The only guys that I let fall this far are those that a running 20 psi on the stock blower with lots of meth and racing. They know the risks and I monitor their datalogs on the regular.


Doug over as ECS says his high side drops to 1900 and run full e85 but is targeting about ~13:1 AFR (~.89-.90 lambda) on the track with his car. It is a 2019 Z06 that has the ZR1 low side, cat delete and pulley upgrade (I think it was 9% overdrive). He wouldn't give me any details on SOI or EOI, but I imagine his SOI is at least 380 and EOI must be 120-130 range if the high side is dropping to 1900. I would never send a customer car out like that but this is Doug and his personal car. He claimed over on Corvette Forum that he has 10,000 hard miles on that setup.

[Haans249]

This is all extremely helpful and I appreciate your detailed and thorough response. I suppose I was a bit too concrete in my statement that the 280 SOI is true; what I meant to say is that 280 certainly does not work for highly modified WOT cars.

What you state below makes perfect sense and what I had originally thought was the way to do this; that the SOI should be more closely correlated to the cam valve events. And any changes to the valve timing will need some tweaking on SOI for max power. After some more conceptualizing, I created a spreadsheet ,

I believe there is a general "happy" medium to this on NA applications, where you get optimal air/fuel mixing when the incoming air is at peak acceleration into the cylinder - which I believe would align (with some delay in the pressure wave) to the piston being at its peak acceleration on the intake stroke. Where is this at exactly? Well, its hard to say, but maybe you guys can provide some input on this based on your testing results. But I calculated this as being halfway between .006 intake valve opening and whatever your ICL is on your specific application. Before doing this exercise, I suspected that my optimal SOI was likely in the 320-330 range just based on my own logs. Using the concept of SOI starting at halfway between .006 and ICL, my spreadsheet spit out 320.

I also added a couple "sanity checks" into the mix as well that I think are prudent to keep in mind. 1) I don't think it is optimal to inject before the exhaust valve is closed, so I put a check there. 2) You probably don't want to inject at TDC - and certainly do not want to inject at anything BTDC on the exhaust stroke - that is just a complete waste of fuel and injector. 3) While I think it is generally ok to inject part way into the compression stroke, I just don't know at what point it will cost power, but think optimally, injection should stop before it, unless your fuel system is maxed and you need to stretch the injectors to get the fuel in there.

Please take a look and let me know if this makes sense, or if it even lines up with what you've seen on your NA setups.

SOI Calculator - GM DI.xlsx

I can tell you that on a stock lt1 or lt4 that is 100 percent wrong if your trying to make peak power and stretch your fueling out. I have dynoed many stock cam lt4s and lt1s and depending on where you run the cam timing at is where you should run the soi. I have found upwards of 30whp on the dyno matching the soi to the cam. pushing that injection timing out into an intake valve that has been hanging open is just giving you a much smaller window to spray in. For instance stock lt1 330 soi on full pump ethanol at that setting on a car thats fbo making 500whp will be consuming up most of the stock lt1 injector ms. Take that closer to the lt4 stock soi will decrease the injector Ms and give range on the fuel system if you have enough support like a zl1 intank pump.
I spent a lot of time figuring this out and a ton of dyno time on cars on stock cams and with cams and some of the cars I have retuned that ran like shit for the mods I started in the soi and got both more range and more power from it as this seems to be a major problem for so many tuners. If you have never built an engine tuned a carb or degreed a cam grab a degree wheel and put the cam info on the wheel now look at where it all falls in terms of degrees and injection timing. Tripntaz pretty much nails it down with out saying exactaly how to do it. But it makes sense if you think about how a carb and vacuum works but with direct injection that window changes up a little but basicaly valve timing events is the most important part of injection timing.
In terms of eoi I see the channels from a lot of big tuners and shops and many dont even bother to log it so tells you what they think about how the eoi is falling. I will say that I have found a point that it starts to give up hp and its very very low compared to the 180 that is in the stock lt4 tune. I have seen the eoi change when changing engine timing alone and no fueling so alot goes into all of this way more then most bother to even look at.
Recently took a 2650 lt4 heads cam the works a nice build that a very reputable shop had tuned for him made just shy of 980whp which I thought was low and it was limited to e45 and has xdi 30s and the lpe pump also has about 40gph of meth being sprayed as we even measured it off the car in painters cup did all the math. This shop/tuner out of texas left the soi at 424 injectors 7.6ms and eoi was 200s well beyond jacked up. e45 car had 22 degrees of timing was seeing Kr so called it quits said thats all it has in it. this car is also making 18 psi and higher gears can creep to 20 psi. took the car did a few dragys on that tune before I started on it and was a miserable 5.20 m6 car and no spinning.

Cam has 2 degrees of overlap that happens at tdc so 360 degrees it was logging 424. He had 368 in the main table and was adding 40 more in the adder for ethanol. For one I zero out that table. Ethanol content I see no need for adding as cam timing is not changing with higher ethanol and I do not believe that burn time of the fuel affects soi.
So I zeroed out that table first did a log. Injector ms dropped to 6.2 from 7.6 after getting it back on target lambda and that random kr now gone. it was logging around 390 soi now. So I backed it up more and added 2 degrees of timing. Now Im at 5.5ms 378 soi 24 degrees no kr car feels much better he tells me. I alwasy adjust back to my target lambda to get resluts.
So now I have him go add some ethanol up to e65 I back up the soi a little more and now am around that 360 degree mark in which my intake valve is opening the ethanol timng table has added a little timing and I still am around 6ms on the injectors but my eoi is creeping a little low. I lean the car out a little more and get the eoi around 150 in which I think its fine as the car is now logging a spinning 4.40 60-130 I have yet to get this car back on the dyno but sure its up a good 100whp just by getting injection timing better and giving me a bigger window on more ethanol and some more timing.
The reason that you cannot go to say 280 and just let it ride is the eoi will end up being so low that its losing hp maybe even run like shit. While I do not know the exact bottom number on eoi I kinda ignore it at this point and only worry about the soi being closer to the valve events and if on the dyno Ill move it up and down a little and land on what is best. I have been as low as 145 on a car and still ended up making really good power for the combo and more power then a lot of other similar builds.
So for what I have found in street and dyno tuning the Soi needs to be on point to the cam and valve events and cannot just back it way up and hope it comes out for the best. Backing that number down is advancing the spray so making the spray time shorter and end of injection go longer. You do this your giving up hp I can tell you that 100 percent as tested many times on many cars.
I beleive howard said it earlier in the thread if unsure as no dyno the way you know for sure its helping is the car will keep going more rich and I forgot to mention that up top on the 2650 car. So if at 400 soi and its at .84 you back it down to 380 soi and you now see .80 your going in the right direction. That is how your going to gain that range on the injectors. Now you lean it back out to your target and the injector ms drops. it is a big balancing act and as long as you see it going more rich its going in the right direction. Im sure there is an ideal eoi for the valve events or maybe just when enters the next cycle but that is one thing I am not sure of and just try to use 150s as a target as when can make 1000whp on a stock ported blower with a SBE heads cam combo I do believe that what I am doing is working
This frustrated me a long time so hope this is enough to help with out me saying do X to make the best hp but all of your settings will play a part in how that injector timing shakes out. I do wish I could nail down an exact bottom on the eoi so will say that is one thing I would like to figure out and know.

[TriPinTaZ]

I don't think Higgs was suggesting you actually want 280 SOI to make power, he was suggesting that setting the SOI table to 280 still result in the ECU backing the SOI up to where it needs to be even all the way back to 360 ish.

I personally don't do this but have seen others have this work. Having recently tuned a 2022 ZL1 I can say the login in the ECU is a little bit different in the following ways:

Flex Fuel: In the 2022 ECU, the flex fuel tables all rely on the "virtual" output from the ECU, meaning the O2's ability to sense stoich changes with fuel volume. You still set the sensor to Enabled and Physical and change the stoich table, but the ECU will wait until the ethanol content PID updates before it makes any adjustments. The alcogol PID from the actual sensor can read 60% after fill up, but until Ethanol Content PID adjusts it wont even move. On top of this it actually uses the gas tables at anything under about 15% ethanol. This means if you're running E55 and then have to fill up with pump 93, and the content falls back close to E10, the ECU will actually switch back to the gasoline fueling PE and spark tables. This was different in prior years where if you set the sensor to physical and enabled flex fuel, it always uses the alcohol tables.

SOI: I have also found the ECU actually uses the SOI base and SOI alcohol offset as a hard limit to backing up SOI. In earlier years you could set the SOI to say 360 and the alcohol table to 0, but SOI would back up to 370-380 if it needed time to inject due to running out of fuel system. On the 2022 I recently tuned, the SOI NEVER backed up at all beyond the value in the SOI tables. Setting the table where you want it actually locked in the SOI tables as a hard limit. EOI still moved as a result of SOI.

[engineermike]

Taz that’s how the Ford works. It pulls Soi right off the commanded soi table regardless of what else is happening. Eoi floats based on fuel demand, fuel pressure, and several limits.

[TriPinTaZ]

Taz that’s how the Ford works. It pulls Soi right off the commanded soi table regardless of what else is happening. Eoi floats based on fuel demand, fuel pressure, and several limits.

In previous years the SOI table was usually followed but the ECU would magically back up injection if it needed to. So it was a little difficult to lock in the SOI. On the 2022's the SOI table was a hard limit from what I could tell. Since I've only tuned one 2022, I can't say for certain if this is 100% correct or just happened to be what I observed at the time. If I tune another 2022 I will pay attention to the SOI behavior.