Stock ECU VE table
#45
Former Vendor
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Am I the only person who is entirely uninterested in what the stock ECU does? I tuned a fairly stock '94 last week and found nearly 20ft.lbs of torque at 3000rpm by switching from the stock ECU to an AEM EMS.
If the stock ECU is that far off the mark, then I prefer to just ignore it entirely and build my own maps.
If the stock ECU is that far off the mark, then I prefer to just ignore it entirely and build my own maps.
#52
Tour de Franzia
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#53
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Well mine is also running pretty advanced compared to stock, about 6 degrees advance on the whole map taking into account the fact that the car is pre-tuned for 91 RON, and we can only get 95 RON over here. But even though the drive is awesome, I'm worried that there could be detonation... Anyway to figure it out without buying some det cans?
#54
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A solution looking for a problem, I guess. It would be some use on a 1.6 where you could fit an RX7 AFM instead, but not much use on a 1.8.
Anyway,the law of the lookup table looks like this:
![](https://www.miataturbo.net/attachments/megasquirt-18/43762-stock-ecu-ve-table-94maf.jpg?dateline=1337345639)
(X-axis is input value, Y-axis is output)
#56
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It's only the shape of the chart that's meaningful; the actual numbers are arbitrary. It's not reading airflow in any particular units. It just takes a voltage reading from a 10 bit A-D input and uses that to interpolate a value from a 7 bit lookup table to produce a 16 bit output.
Whatever it does next with that value (divide it by rpm?) will rescale it again.
Whatever it does next with that value (divide it by rpm?) will rescale it again.
#58
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I reckon the AFR target table on the first page makes no sense at all. While on open loop the ECU won't cycle the fuel mixture according to the narrowband sensor, thus that table makes no sense for open loop. And on closed loop it always fluctuates between 14.5 and 15.3 (that, I tested myself) independent of load or speed. Of course, if you go near WOT, or into high revs, the ECU steps back to open loop, therefore that map does not have any meaning in practice. I reckon, if that map was stimmed, then it serves only as a very rough readout of AFRs on a mix of open loop and closed loop...
#60
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How so? It can either go one of two ways...
Either that map was read out of the original memory, and it only makes sense at a purely theoretical level (such as, the ECU calculating the fuel to match this AFR from the AFM data and the injector capacity), and it will not correspond with the actual value because there are always slight variations
or
this map was read from the ECU by stimming it and/or driving around and logging results, in which case it's a mix of open and closed loop driving. I know someone said some posts before this one, that the ECU can't read anything other than rich or lean from a narrowband (which is true) but it can use these values to modify the turnpoint of the lean/rich wave signal, which would work in theory, but like I said there is no change to the AFR targets in closed loop mode in practice.
So, I have no idea what to make of that. Would be nice to be able to set up a Megasquirt to run just the same as the factory ECU, and tune from there, though!
Either that map was read out of the original memory, and it only makes sense at a purely theoretical level (such as, the ECU calculating the fuel to match this AFR from the AFM data and the injector capacity), and it will not correspond with the actual value because there are always slight variations
or
this map was read from the ECU by stimming it and/or driving around and logging results, in which case it's a mix of open and closed loop driving. I know someone said some posts before this one, that the ECU can't read anything other than rich or lean from a narrowband (which is true) but it can use these values to modify the turnpoint of the lean/rich wave signal, which would work in theory, but like I said there is no change to the AFR targets in closed loop mode in practice.
So, I have no idea what to make of that. Would be nice to be able to set up a Megasquirt to run just the same as the factory ECU, and tune from there, though!