Rescaling TP

[Torque]

Hi,

After a new Turbo was fitted I need to rescale the load scale ..
Before the scale ended at 100, not I would need about 130 (or even much more)

What's the best approach for that?

Obviously I don't want to loose too much resolution down low.

Also, I want to retain most of my old mapping.

So if I designate a cell to be 130 (JUST AN EXAMPLE) and before it was 100 (the cell)
do I have to shift the content of the cell further 'left' so it matches the 'new' 100-cell?


I guess that does not make sense will have to post a picture....

[Matt]

Look at your TP when boosting and see what it is reaching on the scaling to work out what your maximum is going to be

Then readjust with a smooth curve and keep your resolution for the top end rather than bottom end of the map (you want more fine tuning when on boost)

Depending on your existing mapping with the new scalers you probably will end up moving the existing fuel mapping to the left (ie. up to where it used to reach) and then have to expand for the new area created on the fuel map

Timing is all going to have to be rechecked once your AFRs are looking correct again

[Fusion Ed]

Pull timing out first before you start too much work on AFRs as rescaling will advance all your timing map (as the ecu is no longer interpolating from the last cell value)

[Torque]

Look at your TP when boosting and see what it is reaching on the scaling to work out what your maximum is going to be
(you want more fine tuning when on boost)

Hmmm ..

I would have thought that you rather have more resolution down low where the car goes through a lot of transitions.

In my case I have a raster of

81 90 100

and my last log showed a TP value of 110, so all I want to do is retard timing from 105 onwards.

I therefore changed only the ignition scaling to

81 90 105

and merged the ignition values from the former 90<->100 to the new 90->105 cell (they were quite similar).
The new 105+ cell was populated with reduced timing compared to the old 100+ cell.

Since the A/F ratios will stay pegged I saw no need to change these.

[PL]

You can adjust the load scales to achieve whatever you want. I tend to set the last value (130 in your case) and then work backwards keeping it roughly linear.

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Another way is to leave the low load portion as it is and kick up the last (on boost) half. This leaves all your low load tuning untouched and stops it from hitting the last column prematurely. But you have poor resolution in the boosted area. This works but what you'll find is that it's difficult to optimise your timing for all boost levels. For example, if you run 18psi to hit your last column then you'll find that at 16psi it might drop back one column but then it'll stay in that same column at 16, 14 and 12 psi. But you really wanna be running more timing at 12psi than you are at 16psi. I used to tune this way until I realised the error of my ways.

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So now I do the opposite. I steepen the ramp in the low load area and then flatten it out in the second half. This gives better resolution at different boost levels. Do I care about the difference in timing between low load cruise and slight throttle tip-in? No, not really. Do I care about the difference in timing between 12 psi and 16psi? You bet I do!!!

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Pete L

[Torque]

Hi Pete,

That's very interesting, I have not thought about the timings at 16PSI/18PSI++.
Wasn't there some rule of thumb to reduce timing by X amount for every PSI?
(very crude .. but to get you started)

I think what one has to establish, is what boostlevel represents which load cell and then decide on the resolution.

The VQ-Map is not linear, is it? Then I suspect that load cells are not representing a linear increase in 'load' (airflow) either.

I was meaning to do a log on the open road to find out

[bachig24u]

yes there is a rough guide, for every pound of boost you generally remove somewhere between 1 and 3 degrees.

naturally the rule changes the higher you are boosting.. maybe 1deg /psi below 9 and 2deg between 9 and 15psi, and 3deg 15 -24psi. thats very rougly what happens, anything over 24psi you will most likely run a different fuel and the rules change again.

it is relative to what you start with, how cold the air charge is, compression ratios, environment, etc..