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What is considered a stable fuel trim?

Mine are under load:

LTFI_I: -16

LTFT_L: -2,34

STFT: 0

Not sure I understood your sentence: "Per column . From 3000rpm maybe even 2580 you must select a column from a load higher than 4 . Do not devide , but substract from your column and you will discover how to scale ."

What do I subtract from what?

My WOT lambda reaches up 0,73 which is to rich imho. Under part load everything is fine.

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What is considered a stable fuel trim?

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What do I subtract from what?

My WOT lambda reaches up 0,73 which is to rich imho. Under part load everything is fine.

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Take the highest load cell for each rpm colum. Calculate your desired value for the afr/ve map.

Calculate the difference. Add or substract this value to each cell in that rmp colum. Starting with loads higher than 4.

Repeat this for each rpm colum.

Higher than 3000 or one lower.

To me, this method has proved as very time saving, to get a good starting point.

Afterwards correct te cells that need it.

Edited by razorx
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Take the highest load cell for each rpm colum. Calculate your desired value for the afr/ve map.

Calculate the difference. Add or substract this value to each cell in that rmp colum. Starting with loads higher than 4.

Repeat this for each rpm colum.

Higher than 3000 or one lower.

To me, this method has proved as very time saving, to get a good starting point.

Afterwards correct te cells that need it.

Could you provide an example? Your still being very vague about what to calculate and subtract and what not.

I dont understand what you mean by calculate the difference, the difference betweeen what?

When you say calculate you desired value for AFR/ve does that mean if i want 11.5 I put in 1.28?

Thanks.

Edited by Simply Volvo
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Curious as we'll... I've always thought you subtract for a richer mixture as in 1=14.7 and .92=13.5 afr and so on...

I feel like if the part load/ VE map was richer through out the map it would allow the car to not be so sensitive to knock when you get on it, as in Better heat dissipation with having a richer VE map...

Clarification would be greatly appreciated.

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From what I've seen, the VE map is sort of an inverted AFR table. Since higher volumetric efficiency means more air, you'd need more fuel. The VE table seems to be an adjustment of the values for the amount of air the MAF reads therefore adding fuel to meet that recalculation. I don't know how they have the fueling programmed but that's how it seems to me. Basically, putting a value of 1.13 into a cell where the MAF is reading, say, 500kg/h tells the ecu to target fueling for an AFR of 14.7 for 565kg/h which would end up lowering the actual AFR to 13:1. 14.7 divided by 1.13 equaling 13. Raising the VE values would actually help with knock a little bit, the extra fuel helping control pre-ignition.

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I was unclear. ;) I skipped a few steps in my explanation.

The VE map part load is in fact an inverted AFR map. And being used with all loads.

Change the calculation/conversion in the XDF to 14.7/(x*0.0078125) as I did a few months ago. Makes the table much easier to read.

Than his map looks like this:

2014060401.jpg

This was the original rev5b.

1. Lets say, you get an AFR of 13 at 3000RPM and 8.02load

You wanted an AFR of 11.8 at this load.

2. Simply multiply the value in that cell by 11.8/13 so 14.2545*11.8/13 = 12.94

To do all these cells will be a hard and time consuming task. What worked for me is this.

3. The original value was 14.2545, subtract 12.94 from it. The difference is 1.31

4. After this I subtracted 1.31 from the cells in the 3000RPM column with a load higher than 4

Repeat all four steps for each higher than 3000RPM column. Only use the highest load cell for the calculation.

This only works for the higher load cells in this map. In fact the cells where the map stops behaving as an AFR map and starts being a VE map..

You might even start at 2580.

For me this method worked fine in getting verry stable AFR values under varying loads. See the graph I uploaded two posts ago:

2014060301.jpg

(Bottom curve is AFR without corrections afterward)

The amount of corrections I had to do afterwards was minimized.

Edited by razorx
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Not completely.

The afr values close to 4ms load will be slightly higher due tu the original values in the bin.

Also due to the fact that starting from somewhere around 3000RPM and 4ms load the behaviour of this map changes.

More VE like. You, TMM9 or rkam mentioned this once I remember. While testing I noticed the same.

It is wise to use a lower value than 11.8 in the calculation for the high and high midrange rpm's.

It is only a good starting point. You need far less cells to be corrected afterwards.

Edited by razorx
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1. Lets say, you get an AFR of 13 at 3000RPM and 8.02load

You wanted an AFR of 11.8 at this load.

2. Simply multiply the value in that cell by 11.8/13 so 14.2545*11.8/13 = 12.94

To do all these cells will be a hard and time consuming task. What worked for me is this.

3. The original value was 14.2545, subtract 12.94 from it. The difference is 1.31

4. After this I subtracted 1.31 from the cells in the 3000RPM column with a load higher than 4

Well... it doesn't need not be that hard and time consuming to do the math (multiplying by desired value/actual value) on all these cells

You can copy and paste the table in a spreadsheet. Do the calculations there in a relatively simple manner and copy the result back into the table

But on a side note: I don't think that adjustments this way in cells lower then a load of 8.02 are that meaningfull or necessary.

Since we are trying to make more power, wich means reaching for higher loads than standard, only the last row needs adjusting.

Even better would be to rescale the load axis to higher loads after which only adjustments are needed in the rows with loads higher then 8.02 ..

Adjustments under 8.02 load are, in my opinion, only meaningfull for optimization,

Preferably on a hubdyno on which a constant RPM can be maintained so that in the lower (sub 8.02) load region of the table cell by cell adjustments of the AFR and ignitionretard can be made while the effects on torque are immediately visible.

But all in all the standard settings for loads under 8.02 are reasonably good already.

Edited by Piet
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I tried razorx`s formula on my ve map, Well either i`m doing something completely wrong or my ve map is all to pot.

My VE map.

ve-map.jpg

And my AFR map. VE map multiplied by 14.7/(x*0.0078125)

afr-map.jpg

Hopefully someone can point out where I`ve gone wrong :)

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You should not do this in the function field but in the parameter xdf info.

So if you revert to your bin before this action.

Right click on the "VE" map under fueling. and select: Edit parameter XDF info.

Than go to the tab conversion and click on: Edit global table equation.

Good luck!

-edit- This action does not change the binary values, only how they are displayed.

Edited by razorx
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You should not do this in the function field but in the parameter xdf info.

So if you revert to your bin before this action.

Right click on the "VE" map under fueling. and select: Edit parameter XDF info.

Than go to the tab conversion and click on: Edit global table equation.

Good luck!

-edit- This action does not change the binary values, only how they are displayed.

Thanks :) all sorted.

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But on a side note: I don't think that adjustments this way in cells lower then a load of 8.02 are that meaningfull or necessary.

Since we are trying to make more power, wich means reaching for higher loads than standard, only the last row needs adjusting.

Even better would be to rescale the load axis to higher loads after which only adjustments are needed in the rows with loads higher then 8.02 ..

Adjustments under 8.02 load are, in my opinion, only meaningfull for optimization,

But all in all the standard settings for loads under 8.02 are reasonably good already.

I would agree. I haven't seen any reason to make significant changes to lower load cells, other to refine AFR's in areas due to shift in peak torque range with larger turbo/higher rpm boost onset.

Revising the Load range makes much more sense - TMM9's suggested values are working well so far.

Rev2dPartLoadAdj-04-29_zps12b6b5c8.png

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I like how you extended your load axis ;). I will probably do the same because load of 8 is reached fairly quickly.

@razorx: thanks for the post. That makes much sense now. I did the same for lambda instead of AFR and funnily enough the values I put in the table as desired lambda are pretty spot-on what my LM-2 measures at the exhaust pipe.

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