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Author Topic: Rescaling Axis ?  (Read 3640 times)
mcgas001
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« on: June 28, 2012, 12:28:57 PM »

How is this done roughly ? Is it a case of finding set value in the hex dump and increasing it ?

Or anyone got a guide on how to do it ?


I noticed earlier in a map that one of them had a LDRXN that went to 7200Rpm, and another only went to 6800Rpm. Thats when it got me thinking, I wonder how they do it. Tried comparing the 2 hex dumps, at the same addresses and also jumping the right amount of address step. I noticed difference in places, but couldn't convert it over to a meaning full value.


Thanks in advance.
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Nottingham
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« Reply #1 on: June 28, 2012, 11:21:37 PM »

I usually rescale the maps by using inter/extrapolation, however you need to know the hardware very well to be able to tell if the new values are sane / optimal or not. Ultimately the only way to tell is logging.

I use the 1.8T engine with K03-05x (S) turbocharger as an example.
The maximum flow of the turbocharger is around 165g/s.

The original LDRXN map is set to limit the air charge to 114% (~0,44bar) @ 6520rpm.
Since the original rev limiter is set 6800rpm and the last entry in LDRXN map is at 6520rpm, the value used for 6521-6800rpm is the value pointed by the last know sampling point (i.e highest rpm = 114% / ~0,44bar).

At 6520rpm with 0,44bar boost the engine consumes air around 138g/s (1139g/M³ @ 37C = 7,24M³/min).
Since the same limiter is used at 6800rpm you need to know the air consumption @ 6800rpm with 0,44bar to see if the hardware is up to its job: around 143g/s (1139g/M³ @ 37C = 7,55M³/min) of air will be consumed at 6800rpm / 0,44bar.

Since the maximum flow of the turbocharger is around 165g/s and the engine only requires 143g/s @ 6800rpm we can tell the stock LDRXN limits are sane! Wink

You just need to make sure the maximum air charge at the last sampling point (6520rpm or what ever you set it to) can be achieved at the rev limiter too. However if you only change the last sampling point from 6520rpm to e.g 7000rpm the gap between the last and the previous is likely to become too high (you need to calculate if it does).

If the last two sampling points were 6000 & 6520rpm and you only raise the last one to 7000rpm; the air charge indicated by 6000rpm sampling point will be used between 6000rpm and 6999rpm. The original gap was 519rpm now it is 999rpm. Is it still possible or sane? This is why you need to know the hardware you are playing with.

LDRXN is the easiest map to rescale frankly as there is very little data that needs to be worked on.

If you raise the rev limiter you most likely want to rescale the ignition angle maps atleast.
This is because at the higher rpm you need / want more ignition advance.
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mcgas001
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« Reply #2 on: June 29, 2012, 01:01:49 AM »

Nottingham - Thank you so much, that is an amazing post!


I kinda knew that LDRXN would be an easy map, hence I wanted to start there and work my way up. I'm mainly after KFMIOP as that is limited to 160%, and my car sees over 200% faily often. KFMIOP is a much different map, I understand that as the whole map will need changing again to reset the values up correctly. Also, That makes sence on caluclating the values, to the hardware. I take it if you had a massive garrett that could flow boost like no tomorrow, you could make them quite distant, but with K04's that are pretty spiky, they need to be close to keep a close eye on them. Grin

Bit I'm still stuck with is caluclating the values. I'm gonna play with that later, and try patching into the hex and see how it goes.

I'm using the ME1.5.5 btw.

Thanks again for your reply.  Smiley
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