Nistune Forums

Can you tell me what the difference is between the high gear coefficient 7fc8 and the high gear map 7bc8? How do I turn off the aiv function and map switching? I'd like to keep everything as simple as possible.

Bernard

Not sure on those miscellaneous parameters. I havent checked them yet but have made a note to find out and document on my spreadsheet

The 'AIV flags' under Flag settings is available in latest beta for you to change. Turn off BIT 7 (AIV)

Not sure you can turn off map switching. It could be possible there are flags for this but would need further investigating

When doing your fuel / timing maps use the 'map copy' feature for knock and high gear

I'm not so sure if it's as simple as to reset the AIV-flag to disable the AIV.
As far as I know, those flags are only used by the Nissan Consult units to see if a car has certain extra solenoids/options or not.

best is to use a later binary that doesn't use the AIV

for the high gear maps, set the high gear coefficient to 0 to disable the HG-maps.

this is the code

AD0E : B6 14 07 " " ldaa VEHCILE_SPEED
AD11 : F6 FF C8 " " ldab UPGEAR_COEFFICIENT
AD14 : 3D "=" mul
AD15 : 04 " " lsrd
AD16 : 04 " " lsrd
AD17 : 04 " " lsrd
AD18 : 18 " " xgdx
AD19 : BC 14 0A " " cpx RPM_MSB
AD1C : 25 08 "% " bcs LAD26
AD1E : 7B 04 55 "{ U" tim #$04X0055
AD21 : 26 03 "& " bne LAD26
AD23 : 72 80 55 "r U" oim #$80X0055 >> Flag to set gear map

speed * coefficient value / 8 then compared to upper bytes of RPM
This then sets the RPM if higher. Setting to 0 will ensure that it wont trigger to use the gear maps

The other address 0x7BC8 is not referenced in the code. appears to be a typo and has been removed (along with another duplicate line) in Z32 address file

Interesting ...

But what exactly are these different GearMaps for?

It looks like a nice feature and I would like to do something with it if possible.
I heard the switching was dependent on the actual speed??

We have:

Fuel Map
Knock Fuel Map
(High) Gear Fuel Map
(High) Gear Knock Fuel Map

I don't think it is known exactly what the HG maps are/were meant to be used for, but I assume Nissan was planning to use these maps for better fuel economy at motorway speeds/cruising.

In the twinturbo 300ZX models, the maps were either not used or exact copies of the regular maps...
In the NA models there were only small and subtle changes in the HG maps.

Hi Eric,

Thanks for the reply ..

So were these HG maps ever accessed in the TT or were they just dormant?

If you look through the ROM images this will answer your question

The parameter for example in the JDM models is 0 (not used) but some USDM variants like the NAs Eric mentioned have a figure in here which once certain rpm/speed combination was hit would use the upper gear maps in those cases

I ended up pulling the upper gear maps out of the Q45 VH45DE ECU so the Nistune firmware had somewhere to live on the Type 2 boards

Hmmm

So is there any information on when these maps were actually triggered?

It sounds like a neat idea to have another set of maps ...

Btw. I have now equalized all maps in my ECU and will give it a try next week.
And I do hope the VCT logging will work as well.

Ohh what a great journey of discovery this is

speed * coefficient value / 8 then compared to upper bytes of RPM

you would need to plug that into a spreadsheet with SPEED and RPM columns and you will see at what ranges it goes over. Because its based from formula there is no easy answer which is why that figure is not decoded to something more 'readable' inside Nistune

Matt wrote:

speed * coefficient value / 8 then compared to upper bytes of RPM

you would need to plug that into a spreadsheet with SPEED and RPM columns and you will see at what ranges it goes over. Because its based from formula there is no easy answer which is why that figure is not decoded to something more 'readable' inside Nistune

Thank you ... I will check this out once my engine is performing as planned.

As for

Matt wrote:

speed * coefficient value / 8 then compared to upper bytes of RPM

If the result is 'TRUE' will the ECU then switch maps?

The code is in that snippet above does CPX speedrpm - rpmmsb and does not set the flag if carry set or equal (ie rpmmsb is higher)

If the flag is clear then high fuel table is used. So if the speed converted is above certain RPM then the upgear maps are used

I'm now hiding the high gear maps inside Nistune if this value is set to '0' so it means less confusion (because they are not used)

But if you hide them how can you copy the regular maps of them

Sorry dont understand

If the coefficient = 0 then the upper gear maps are not used. Therefore there is no point displaying the maps inside Nistune. If the coefficient gets changed /= 0 then we will redisplay the maps

Why could you want to copy them when they are not accessed by the ECU?