Why does timing map skip 2,800rpm but fuel map doesnt?

[Harey]

Hi All,

I am a very happy ER34 GTT with Nistune owner.

I am wondering why on the timing map the rpm scale skips 2,800rpm? It goes straight from 2000, 2400, 3200, 3600.

But the fuel map doesnt, it goes 2000, 2400, 2800, 3200, 3600 as you would expect.

Second question what does say 2000rpm mean. Is it from that value up to the next value such as 2000-2399rpm? or is it centred around 2000rpm so 1800-2200rpm?

Cant find that info in any of the nistune documents. Any help much appreciated!

[s200rat]

if you want to change the load scales you will need to edit it in the scalers section.

more than likely it has been adjusted to gain higher resolution further up the map

The way the map reads is through interpolation.
the ECU will read the 4 cells nearest to your target and interpolate between them to output a value.

So take a simple example below on a liner map;

Rpm: 1000 2000
Timing 40 30

if your at 1500rpm then ecu will interpolate between the timing cells to tell the motor 35deg is the ignition timing.

[PL]

I think you'll find that the bottom line here is that we don't really know - without being there when Nissan did their development it can be hard to fathom why they do some things. I've always made the assumption that Nissan do some weird things with the scales to increase resolution in certain areas for stuff like fuel economy and emissions improvements.

Often government tests will be conducted at a certain speed/rpm and so you'll see some unusual things in the maps. Non-linear load scales are just one thing.

PL

[Matt]

With regards to in between the values, these are interpolated by the ECU

For example if the timing is 15 at 2000 and 20 at 2500, and the current RPM is exactly 2250 (ie half) then (15+20) * 0.5 = 17.5 would be the timing value. But if it was say 2175 (ie quarter) then would be 16.5 instead due to the interpolation

[Harey]

Thanks guys, exactly what i was after!