Confusion on Normal ECT Adder

[kertisallen1]

So I am trying to get some clarification on the EOIT adder "Normal Ect".

I have tuned it to the most "rich" setting, and it is running great...but I'm just trying to understand the math. For the longest time, it seems that the general understanding (not including makeup mode) was Boundary - Normal ECT = EOIT.

For example, most stock applications 520 - 110 = 410.

However, after using Cringer's most recent tool, and watching his videos, he shows a TON of very compelling evidence that the "Normal Ect" adder is measured in cam degrees and therefore doubled....

The place im getting stuck when it comes to the math portion....is that if this is true, then around 70-75% duty cycle even on some larger stock motors you would be advancing EOIT so far that with a 13-15ms PW your injector would have to start injecting for the next cycle before the intake valve even closed on the current cycle.

For example, 520 - (110x2) = 300.

On a stock 5.3 LMG cam (2012 Silverado), the intake valve closes at around 574....so even as the computer pulls the target back towards the Boundary, there is a 54deg section where it can technically start injecting and not cross said boundary.

Like I said from a tuning aspect, I took Ghuggins method and applied it, and it worked great...but even with my current number,s if I use Cringer's math, I'm getting a ton of IPW Overflow as he calls it.

Thanks again just trying to let my brain rest as I HATE not understanding things haha.

[Zeroema]

Hello mate,

Let?s see if Cringer can take a look of this topic. I?m interested as well.

Regards.

[Cringer]

So what is your actual question?

Ignoring the other modifiers, this is the formula:
[EOIT] = [Boundary] - (2 * [N. ECT])

The ECM is advancing SOI so end of IPW = calc'd EOIT. Keep in mind the OEMs spray early to vaporize the fuel on the hot intake valve. That is fine for small overlap cams and catalytic converters.

The EOIT assistant program graphs this all out.

[Zeroema]

One question Cringer,

What should be the strategy for a cam with a lot of overlap (IVO, 32, IVC70, EVO 83.5, EVC 33.5, Ovelarp 65.5).
Im using the formulas that you have posted in another thread and the fantastic tool you developed but still having some issues with cold-warn smell.
I have tried several configurations but the raw fuel smell is very strong at Idle until the car warns up. Once is at 90?C ECT the smell is almost gone.

*I put cats in the car because the smell was pretty hard but even with cats and the tune and without sucess.
*I remove the N. RPM values at Idle.
*My idle at this moment is set at 1000rpm (I already trried several Idle speed: 800, 850, 900)
My Boundary is set at 530 (Bondary 530 - Normal ECT 45 - Cam Offset 7) = . I did of this way to have a EOI at 433? after the EVC at 395.5.
*IPW at Idle: 2.6-2.9. OEM Injectors(42 lb/h).
*The car only has Texas Speed camshaft, ported heads, TBSS intake, long tube headers).

[Cringer]

One question Cringer,

What should be the strategy for a cam with a lot of overlap (IVO, 32, IVC70, EVO 83.5, EVC 33.5, Ovelarp 65.5).
Im using the formulas that you have posted in another thread and the fantastic tool you developed but still having some issues with cold-warn smell.
I have tried several configurations but the raw fuel smell is very strong at Idle until the car warns up. Once is at 90?C ECT the smell is almost gone.

*I put cats in the car because the smell was pretty hard but even with cats and the tune and without sucess.
*I remove the N. RPM values at Idle.
*My idle at this moment is set at 1000rpm (I already trried several Idle speed: 800, 850, 900)
My Boundary is set at 530 (Bondary 530 - Normal ECT 45 - Cam Offset 7) = . I did of this way to have a EOI at 433? after the EVC at 395.5.
*IPW at Idle: 2.6-2.9. OEM Injectors(42 lb/h).
*The car only has Texas Speed camshaft, ported heads, TBSS intake, long tube headers).

There are still a few new things I want to experiment with for fine tuning and tweaking EOIT, but for now this has been my strategy:

• I do my best to make the IPW straddle peak piston velocity for idle through all mid range RPM/cruising
• For 4000+ RPMs I would target EOIT of 580* for WOT/PE
• I also suggest leaving make up mode ON and set to MULTIPLE

There are some tricks needed in order to get make up mode to cooperate though. And you are always going to need to test and tweak, just don't set it and assume it is OK.

I will also go on record to say that no matter what you do, you will never be able to eliminate all the fuel smell when you eliminate cats. This is part of my next video that I have been trying to make over the last several months...but just don't have time.

[kertisallen1]

Cringer,

So my question is

Do some (a ton) of stock and aftermarket tunes that set Boundary/ECT Normal to the generic 520/110 allow the injector to fire for the next comb cycle during the current cycle before the IVC.

So your data shows (very convincingly, I might add, as you covered almost every different combination of targets) that Boundary is the latest that the injector is allowed to fire BUT also the earliest when you look at it from the other end of things, correct?

My understanding (may be completely wrong hence why I'm here haha) is that the ECM will only start to push EOIT from the intended target (520-220=300) when the PW is long enough to allow it to try to cross the Boundary (in this case 520)? So as long as it can fit between 520 (-200) and 300, it will continue to use 300 as the EOIT. For example, on my truck at about 5500 rpm, a 14.5ms PW is about 500 deg. So does this mean that set at 520/110 with my cams IVC of 598, that at 5500 rpm, my injector starts firing for the next combustion cycle about 78 deg before the intake valve even closes on the current cycle? And even if PW went up, it would push EOIT back towards the Boundary of 520 while still keeping the SOIT at 521 (-199)?

Cringer i'm not trying to argue or reinvent the wheel. I'm just trying to wrap my mind around this all.

So what is your actual question?

Ignoring the other modifiers, this is the formula:
[EOIT] = [Boundary] - (2 * [N. ECT])

The ECM is advancing SOI so end of IPW = calc'd EOIT. Keep in mind the OEMs spray early to vaporize the fuel on the hot intake valve. That is fine for small overlap cams and catalytic converters.

The EOIT assistant program graphs this all out.

[Cringer]

Cringer,

So my question is

Do some (a ton) of stock and aftermarket tunes that set Boundary/ECT Normal to the generic 520/110 allow the injector to fire for the next comb cycle during the current cycle before the IVC.

So your data shows (very convincingly, I might add, as you covered almost every different combination of targets) that Boundary is the latest that the injector is allowed to fire BUT also the earliest when you look at it from the other end of things, correct?

My understanding (may be completely wrong hence why I'm here haha) is that the ECM will only start to push EOIT from the intended target (520-220=300) when the PW is long enough to allow it to try to cross the Boundary (in this case 520)? So as long as it can fit between 520 (-200) and 300, it will continue to use 300 as the EOIT. For example, on my truck at about 5500 rpm, a 14.5ms PW is about 500 deg. So does this mean that set at 520/110 with my cams IVC of 598, that at 5500 rpm, my injector starts firing for the next combustion cycle about 78 deg before the intake valve even closes on the current cycle? And even if PW went up, it would push EOIT back towards the Boundary of 520 while still keeping the SOIT at 521 (-199)?

Cringer i'm not trying to argue or reinvent the wheel. I'm just trying to wrap my mind around this all.

I think you have some incorrect assumptions or understanding of how this works.

First, forget Boundary. This is just an arbitrary starting point used to work backwards from to determine the EOIT for the (a) main pulse and (b) make up pulse.

The main thing is, EOIT is calculated with the simple math I posted above. Once determined the EOIT DOES NOT CHANGE.

The next step is the ECM has to determine the IPW (in millisec).

Then the ECM has to answer the question, at this many RPMs, when do I need to start spraying fuel (SOIT) so that the IPW ends exactly at the calc'd EOIT crank angle.

So....perhaps to your point of confusion...as (a) IPW grows and (b) increases, the SOIT IS CHANGED by advancing it sooner and sooner.

But what happens if we keep advancing SOIT sooner and sooner though?

Eventually it will be spraying continuously...this is 100% IDC. It cannot spray more and we cannot move the SOIT. I mean the injector SOIT and previous EOIT cannot overlap...100% is 100%.

So there are two possibilities for 100% IDC.
(a) SOIT = EOIT for the previous injection event
(b) SOIT = EOIT for the previous injection event + Injector Offtime

Here are some pictures, these are not to scale or anything, just a graphical concept. The basic idea is that we can keep advance SOIT until either we hit a barrier, either previous EOIT or forced injector offtime.
1 EOIT.jpg
2 EOIT.jpg
3 EOIT.jpg
4 EOIT.jpg

[kertisallen1]

Perhaps I'm not fully understanding a certain aspect, or I'm explaining my question/example incorrectly...
I thought the definition of Boundary is the absolute Latest or Earliest that an injection event can start or end. In the case of DC not being at 100% but the EOIT being advanced far enough that even at lower than 100% DC it is trying to cross the boundary of the previous event.

An example would be
520-220=300
EOIT = 300
Inj PW = 14.5ms
Inj DC = 72%
RPM = 5500rpm
Inj PW in Crank Deg = 500
So SOIT = -200 or 520 of the previous cycle

Now this is the part that I'm confused about....if it suddenly wants more fuel in this exact scenario

Let's say it is suddenly as follows
520-220=300
EOIT = 300
Inj PW = 15.5 ms
Inj DC = 76%
RPM = 5500rpm
Inj PW in Crank Deg = 540

So...would SOIT stay at the previous -200/520?
Or would it push SOIT back to -240/480? (overlapping boundary of previous cycle)
Or would it keep SOIT at the previous -200/520 and move EOIT back to 340, which allows it to not cross either boundary.

I think you have some incorrect assumptions or understanding of how this works.

First, forget Boundary. This is just an arbitrary starting point used to work backwards from to determine the EOIT for the (a) main pulse and (b) make up pulse.

The main thing is, EOIT is calculated with the simple math I posted above. Once determined the EOIT DOES NOT CHANGE.

The next step is the ECM has to determine the IPW (in millisec).

Then the ECM has to answer the question, at this many RPMs, when do I need to start spraying fuel (SOIT) so that the IPW ends exactly at the calc'd EOIT crank angle.

So....perhaps to your point of confusion...as (a) IPW grows and (b) increases, the SOIT IS CHANGED by advancing it sooner and sooner.

But what happens if we keep advancing SOIT sooner and sooner though?

Eventually it will be spraying continuously...this is 100% IDC. It cannot spray more and we cannot move the SOIT. I mean the injector SOIT and previous EOIT cannot overlap...100% is 100%.

So there are two possibilities for 100% IDC.
(a) SOIT = EOIT for the previous injection event
(b) SOIT = EOIT for the previous injection event + Injector Offtime

Here are some pictures, these are not to scale or anything, just a graphical concept. The basic idea is that we can keep advance SOIT until either we hit a barrier, either previous EOIT or forced injector offtime.
1 EOIT.jpg
2 EOIT.jpg
3 EOIT.jpg
4 EOIT.jpg

[Cringer]

Perhaps I'm not fully understanding a certain aspect, or I'm explaining my question/example incorrectly...
I thought the definition of Boundary is the absolute Latest or Earliest that an injection event can start or end. In the case of DC not being at 100% but the EOIT being advanced far enough that even at lower than 100% DC it is trying to cross the boundary of the previous event.

An example would be
520-220=300
EOIT = 300
Inj PW = 14.5ms
Inj DC = 72%
RPM = 5500rpm
Inj PW in Crank Deg = 500
So SOIT = -200 or 520 of the previous cycle

Now this is the part that I'm confused about....if it suddenly wants more fuel in this exact scenario

Let's say it is suddenly as follows
520-220=300
EOIT = 300
Inj PW = 15.5 ms
Inj DC = 76%
RPM = 5500rpm
Inj PW in Crank Deg = 540

So...would SOIT stay at the previous -200/520?
Or would it push SOIT back to -240/480? (overlapping boundary of previous cycle)
Or would it keep SOIT at the previous -200/520 and move EOIT back to 340, which allows it to not cross either boundary.

You are interpreting "Boundary" incorrectly.

This is the "Boundary Angle" as it refers to the Otto cycle combustion process (there is an imaginary 'boundary' between each cycle). It has nothing to do with when the injector can or cannot fire. I will refer again to my previous comment:

First, forget Boundary. This is just an arbitrary starting point used to work backwards from to determine the EOIT for the (a) main pulse and (b) make up pulse.

[kertisallen1]

I have been going off Chris's definition of it.

"More on the boundary angle of 520 degrees, courtesy of Chris HPT.

Boundary is the latest point in time that fuel can make it into the cylinder for the current injection period. It is measured in degrees AFTER TDC compression. It is also the earliest the injector can fire again after the completion of the last injection event. ie. the boundary defines the start/end of a complete injection cycle."

So in this case, you're saying it would move SOIT farther back. So -240/480

You are interpreting "Boundary" incorrectly.

This is the "Boundary Angle" as it refers to the Otto cycle combustion process (there is an imaginary 'boundary' between each cycle). It has nothing to do with when the injector can or cannot fire. I will refer again to my previous comment:

[Cringer]

Don't trust me or Chris. Get an oscilloscope and test.

At least keep in mind the N. ECT table is not correct in HPT. I believe this is really a scaling factor when converting from a 16 bit float to an integer (in other words, a defect in HPT). So even mistakes are made on Chris's part.

[Cringer]

Boundary is the latest point in time that fuel can make it into the cylinder for the current injection period. It is measured in degrees AFTER TDC compression. It is also the earliest the injector can fire again after the completion of the last injection event. ie. the boundary defines the start/end of a complete injection cycle."

I think this is tricky wording but is the same thing I have been saying.

If Boundary is 520 and N. ECT is 0...EOIT is 520...no fuel is sprayed after this.

If Boundary is 520 and you have a super long IPW (100% or greater), it cannot be sprayed before 520 from the previous cycle.

[kertisallen1]

So, is it possible to advance EOIT far enough to actually limit yourself and lean out?

I really don't understand the factory tune for my truck. It was factory tuned to 520 at idle and slopped to 360 at the top end. So, 360 boundary with 110 ECT means that EOIT was 140 deg for anything after 4096 rpm. That is why I have been trying to figure out if the ecu is able to push the EOIT back towards Boundary in situations like this.

I think this is tricky wording but is the same thing I have been saying.

If Boundary is 520 and N. ECT is 0...EOIT is 520...no fuel is sprayed after this.

If Boundary is 520 and you have a super long IPW (100% or greater), it cannot be sprayed before 520 from the previous cycle.

[Cringer]

So, is it possible to advance EOIT far enough to actually limit yourself and lean out?

No. You can influence the fuel trims rich or lean, but that is not due to some imaginary (Boundary) line in the sand.

I really don't understand the factory tune for my truck. It was factory tuned to 520 at idle and slopped to 360 at the top end. So, 360 boundary with 110 ECT means that EOIT was 140 deg for anything after 4096 rpm. That is why I have been trying to figure out if the ecu is able to push the EOIT back towards Boundary in situations like this.

Injector timing has everything to do with manipulating fuel vaporization. The 520 to 360 taper makes sense. At low RPMs we can spray fuel later as it will sit and vaporize in X millisec. When engine RPMs increase now we need to spray sooner to give the same number of millisec to vaporize.