Deep into SOIT/EOIT, looking for a bit of advice

[Allen Vos]

In general, no one is going to agree on the correct or best way to handle SOI/EOI. The OEMs are going to focus on Emissions, Drivability, and Power (in that order). And as for aftermarket tuners, most won't even touch EOIT at all, even if you give them the cam specs. Count yourself lucky if your tuner adjust the Normal ECT table in order to clean up raw fuel smell at idle.

The other fact of life is that there is nothing you are going to be able to log in the scanner to objectively tell you if your SOI/EOI settings are good or bad...well except for fuel trims/wideband...which is your only objective guide. The other guideposts are idle smell, seat of the pants drivability and a dyno (which most of us peasants do not have at our disposal).

I have found a few spreadsheets floating around for this stuff and was underwhelmed by them. This is why I created my program to help with this and make it as powerful as possible. I created a video to arm everyone with the background knowledge needed to understand the HOW and the WHY to tune SOI and EOI. Of course not every "expert" out there will agree with my thoughts on this, and that is fine. And you know what? I am totally happy if they share what they know with me/all of us and we all get better. I am always willing to put away my ego for something better for the sake of learning.

The previous tune I revised for you on that thread a long time ago is exactly how I would set up the initial EOIT stuff if it were my vehicle. And this is a *starting point* for you to advance and retard SOI for the low/mid RPM stuff to find the best fuel trims, and it sounds like you did for idle. Making any improvements here is going to be a slow and arduous process. You are going to have to make small adjustments and analyze the long term fueling trends. I am not talking about LTFT, I am referring to getting familiar with you fuel trims and being able to identify 1% swings in the right or wrong direction. Part of this is being consistent in the way you drive. These are 2D tables that are setup in RPM increments...they are not setup in a 3D format with RPM and MAP (which I would prefer). So in other words, if you use more throttle you are spraying more fuel at a given RPM...so be consistent in how you drive/log/tune. More throttle = longer pulse width = a later EOI during closed loop.

Additionally, if you are finding the car is getting a little lazy, throw a couple of degrees of timing in that area to see what happens. Optimal fueling is going to reduce the chance for knock anyway. And as you will find as you make changes in one area, it is likely to impact multiple other areas as well. MAF/VVE, O2 voltages, rich/lean PI settings, EOIT, and timing are all related.


Just to clear the technical stuff up, the correct formulas are:


1) For normal low RPM/Closed Loop operations with short IPW
1a) If Make Up Mode is enabled (set to Single or Multiple)
SOI = Boundary Angle - Normal ECT - Normal RPM - M/U ECT - M/U RPM

1b) If Make Up Mode is disabled (set to None)
SOI = Boundary Angle - Normal ECT - Normal RPM


2) For high RPM/PE operations with long IPW
You have to understand that SOI is moveable and floating while EOIT (or the Boundary Angle) is not. SOI will be forced to moved when IPW becomes excessive. The definition of excessive is when the engine RPMs are high enough that the window (in milliseconds, not degrees) to spray all the fuel needed is not long enough. So a new SOI has to be calculated.

2a) SOI = Boundary - IPW (expressed as degrees)

My approach is to spray as early as possible (and disabling Make Up mode goes hand in hand here) for closed loop. So long as:
1) you do not short circuiting the fuel
2) do not cause any drivability issues

Other people like spraying late as possible. This is accomplished by setting the Boundary Angle to whatever number you want (520 - 580 or whatever) and then zeroing out the Normal tables. This then forces the ECM to back calculate the SOI every time using the IPW as degrees. I do not like this method personally. Feel free to experiment and report back. This is the same as formula 2a (however, these people also probably have Make Up Mode enabled, so add the default 30*).

So in conclusion:
1) For low RPMs, think of the spray window in degrees and focus on a specific SOI that will be driven off valve events.

2) For high RPMs, you have to ignore SOI since it is floating and you are going to spray on the back of the intake valve and thus some fuel will be short circuited, and there is nothing you can do about it (unless you get bigger injectors and sacrifice idle quality), so focus on EOI which will be best found on a dyno.

The quick formula to convert MS to Crank Degrees:
[RPM] * [0.006] * [INJECTOR PULSE WIDTH IN MS]

The quick formula to convert Crank Degrees to MS:
[CRANK DEGREES] / (RPM * 0.006)

Note we use crank degrees here and not cam degrees since the Boundary Angle and all the EOIT tables are based on 720? for two rotations of the crank for a 4 cycle engine and the cam shaft's valve events are also listed as in relation the crank (TDC and BDC).

I am hoping other folks chime in here as I would like to learn their viewpoints as well.

Thanks for the detailed response Cringer. Its great to be able to understand SOIT/EOIT.

It seems like the important thing here is getting the SOIT set correctly at idle and EOIT/Boundary set for high RPM and most people seem to just stop there.

I would like to put the time in and figure out how to set the mid RPM transition from off idle to high RPM and see where that gets me.


So to start my idle boundary angle is 470 degrees with SOIT at 389 degrees which is 5 degrees before EVC.

I have maximized fuel trims and reduced fuel smell at idle so, I don't believe I need to change anything here.

High RPM has a Boundary angle or EOIT set to 580 degrees which is 30 degrees before my IVC's.

I don't plan on or have access to a dyno so I am just going to have to be content with the 580 degree boundary angle for high RPM, unless you could suggest otherwise?

The car pulls extremely hard in the high rpm anyways with no hiccups or drivability issues so I think we will leave high RPM alone.


MID RPM TRANSITION>>>>>>

This is what I need to set up and what I need a bit of guidance with. More so how to set things up to determine my proper mid rpm SOIT/EOIT.

Did you happen to look at the Excel spreadsheet I posted?

I did 10 different configurations/tunes for mid RPM SOIT/EOT. I stepped out the SOIT values so they were even and smooth, then back calculated what I would need on my normal rpm table to have a smooth transition from idle SOIT to high RPM SOIT.

In a nut shell, low RPM SOIT is 389 degrees and at 4000 RPM SOIT is 315 degrees

The first tune I started advancing the SOIT from 389 to 315 at 1400 rpm and tapered it up to 4000 rpm where it was fully advanced to 315

Each consecutive tune was bumped up one rpm cell in the "normal RPM" table, so one tune for 1400 and another for the next cell all the way up to 3000 rpm.

I was unsure how to log or look at things so what I ended up doing was had the car in 3rd gear, rolling at 25 MPH/40 km/hr at 1300 rpm and then just floored the car until it hit 4500 RPM and just did a "Seat of the pants" feel with each tune.

What I noticed, and the difference was so miniscule it might have all been in my head, but as I advanced the SOIT later in the RPM the car felt a bit lazy. When I advanced it earlier the car seemed to feel snappier. There was no hiccups or drivability issues whatso ever.

So where I am looking for help is how exactly should I set this up with regard to logging?

What I believe you are saying is I need to log STFT's in the scanner with RPM and MAP values in my table?

I will need to drive the exact same with each tune to try and notice the richer fuel trims for best SOIT/EOIT settings

On a side note, it crazy to see how much SOIT is advanced in the higher RPM's to respect the BOUNDARY angle / EOIT.

But as you said , spraying on the back of a close IV in the high RPM isn't really to big a deal.

Now when we log for tuning our VE table, we log STFT against RPM and MAP values.

Would this suffice for figuring out SOIT/EOIT? Might need to change the filters?

[Allen Vos]

Must be something in the water with Allens posts, they always involve some sort of shit fight.

You Fuckers leave me out of this and go fight your battles some where else

I'm just trying to tune my car here.

[Allen Vos]

OK, to be clear, you posted 2 dyno graphs with 4 pulls and only 1 out of 4 was a pull from 1000 rpm. The other 3 were from a reasonable 2000ish RPM.

Trying to say someone should check how good their tune is by starting pulls at 1000 rpm at 1:1 is just idiotic. Definitely the dumbest thing I've seen you say on here.

Take the OP for instance. His vehicle is a LS3 C6, manual trans with a stage 2 or 3 cam. The cam kills low end torque. Why would I or anyone else start a pull on this vehicle at 1000 RPM?

Take his vehicle totally stock, strap it down. Put it in 4th gear, start a pull at 1000 RPM. What happens? On a stock calibration it pulls all the timing out of it to keep from detonating the tops of the pistons off. What do we do, try adding timing so can pull itself out of that hole?

That's diesel shit. You don't start gas powered anything at 1000 RPM. You telling me you're going to put a LSA or LT4 or Hellcat in 1:1 and womp it wide open at 1000 RPM? That's just asking for problems.

Show me some really precise dyno graphs that start +/- 50 RPM. Multiple runs overlaid that look exact preferably. Bonus points for .drf or .wp8 files with accompanying data logs.

You have to remove all the variables. As long as there's variables, there's no A vs. B.

I will say this. Starting a pull at a low RPM, is also a good way to make sure you don't have any cam "bucking", jerking or burbling.

Great to be able to tune that stuff out for guys like me that want something smooth on the lower RPM for a nice driving street car