Blkbrd69

Question on math formula for hand tuning VE table?

I know there has to be a standard math correction formula for hand changing VE table cells using track data logs.

For example. Lets say your track/street data log shows 5400 RPM @ 170KPA. You are currently at a VE of 120 burning 11.3/1 on gasoline and want to change to 11.8/1?

I know there has to be a simple standard math equation to lower VE# fueling that could mathematically nail ratios.

Andy Whittle has some great formulas for data logging but cant seem to find the base formula to hand tune. Should be the same one Megasquirt uses in autotune?

DNMakinson

iTrader: (3)

VE (new) = VE (old) * AFR (logged) / AFR (desired)

OR: 115 = 120 * 11.3 / 11.8 for your example.

That assumes that EGO = 100% at time of log

Blkbrd69

Thank you, simple and looks right.

So take my current VE of 120 X 11.3 divided by 11.8 = 114.9 which is my new VE

Why couldn't I find it?

Ted75zcar

iTrader: (2)

Or turn on incorporate

Edit: what you are calling VE is actually a fuel table.

Blkbrd69

Yes fuel VE 1 table guess I deserved that.

Trying to get it pretty much spot on before incorporating and don't trust autotune for on track session. Kinda just like the hands on with datalogs?

My table to incorporate is actually a bit leaner than Im trying to hit now. Trying to be a bit more detailed with things like spool up, and autotune and incorporate was a bit off?

Or I am just a sucker for trying to do things the old hard way?

DNMakinson

iTrader: (3)

irrelevant. He may or may not have been using Incorporate. Answer is still the same.

Ted75zcar

iTrader: (2)

Well, with incorporate and true VE, all one would need to do is change the AFR target table from 11.3 to 11.8. True VE is not a function of target AFR, and thus does not change.

ManiacLachy

You need to re-tune your whole VE Table if you turn Incorporate on, right? I was under the impression that you need to tune one way or the other, the formula changes and the numbers in the VE Table come out slightly different.

Correct me if I'm wrong here.

DNMakinson

iTrader: (3)

Ted,

But his VE table was rich, or at least his mixture was. If he has Incorporate turned on, and his target is 11.8, already, what is he to do? Adjust the VE table.

I think you are assuming his starting with a good VE table. But that is not the case.

Look at the fueling equations. The difference is a factor of 14.7 / AFR target. If his AFR target is 11.8, and he is running 11.3, simply turning on Incorporate will make him 14.7 / 11.8 Richer. He wants leaner.

Step back and visualize what you are saying here.

Maniac, yes.

Ted75zcar

iTrader: (2)

You could probably get a pretty close baseline by doing the inverse of what DNM posted with stoich as the reference.

But yes, VE table needs to be retuned.

Ted75zcar

iTrader: (2)

If ego is at 100% he is at whatever afr is in the target table, no?

DNMakinson

iTrader: (3)

Now I see where you are coming from. Not necessarily, it may be that Authority is zero. My point in my first answer is that if EGO is active, yet he is still not getting where he wants to be, then he has to take that correction into account that IN ADDITION.

I also was not assuming any AFR table target, only his desired target.

I think that was in keeping with the question.

EDIT: Bedtime in EST Zone. I’m not ignoring you.

Ted75zcar

iTrader: (2)

No worries man, respect.

My approach is and has always been, do it right, fix it if you find out it is wrong, and slower is usually faster. I am frequently asked to solve highly complex technology or regulatory problems for others, they are almost always rooted in deviating from that stated approach.

Blkbrd69

Everyone is correct in one way or another.

DNMakinson got it from the start however. Thank you.

My understanding is you want your actual fuel table as close as possible to perfect so less change is needed?

By hand tuning and not using incorporate or target AFR table, I am able to see subtle effects in the datalog with small changes.

IE mixture change, while changing VVT timing. Mixture change just from different gas station mixtures.

FYI noted .3 AFR difference in two different stations that was repeatable.

At my compression and boost in Florida temperatures, that could be the difference between awesome running and shrapnel bouncing around Sebring.