RB26 Stock to Nismo MAFs

[Junkie]

Hi, I'm changing stock AFMs on an R32 GTR for Nismos (z32 internals). The current settings are;
Current VQ map: BNR32 RB26DETT (290 HP)
Halve (GTR ECU): On
Double (GTR MAF): Off

There's two options for the New VQ map:
Z32 VQ VG30DETT (500 HP)
Z32 VQ VG30DETT (GTR ECU) (500 HP)

I assume that i should select "Z32 VQ VG30DETT (GTR ECU) (500 HP)" and leave "Halve (GTR ECU)" and "Double (GTR MAF)" unchanged - is that right?

Tune will be checked/corrected afterwards since viewtopic.php?f=8&t=3262 shows that the Nismos are not an exact match for the Z32.

[Junkie]

VG not VQ...

[Matt]

From what I recall Z32 MAF were quite a bit different to Nismo MAFs (cant remember which curve the customer ended up using)

However use the 'Halve (GTR ECU)' tickbox and normal Z32 MAF selection

"Z32 VG30DETT (GTR ECU) (500 HP)" is just for display purposes (so it displays correct MAF after using Z32 MAFs with R32)

[Junkie]

Thanks Matt. FYI the link in my post has the Nismo vs Z32 graph, and it looks pretty close. AFAIK the Nismos are just Z32 guts in a GTR AFM shell.

[Junkie]

Ok, i've installed the MAFs, changed the MAF setting in Nistune and reset the fuel trims.

The car starts but runs too lean to hold an idle. Pumping the accelerator works, but holding the pedal down doesnt.

I assume i now need to tweak K by using the injector resize option, is that right? And to adjust K in the right way I will make the new injector size smaller than the current injector size, as that will increase pulsewidth to the injectors, right?

[Junkie]

Had a play with K using the injector resize, 550 -> 250 gives an idle of around 17:1 and 200 gives around 14:1. Since that's a massive difference I'm worried that I did something wrong with the Halve / Double settings...

[Matt]

Post an image of your VQ map

If you can get AFRs good at cruise, but its wrong everywhere else then the VQ map is off (incorrect calibration)

[Junkie]

Its 10:1 at cruise... I'll get the VQ map - is that the one called VQ translation in Nistune?

[Junkie]

Here's the VQ map.

vq-graph.jpg

(29.23 KiB) Downloaded 5613 times

[Junkie]

Re the comment ""Z32 VG30DETT (GTR ECU) (500 HP)" is just for display purposes (so it displays correct MAF after using Z32 MAFs with R32)"

I just tried loading the original tune, then changed the MAF to;
Z32 VG30DETT (500 HP) -> causes slight tweak of MAF VQ curve (a bit lower in the middle), and if I go back into Change MAF it shows "Current VQ map detected" as "Z32 VG30DETT (GTR ECU) (500 HP)"

However, If i reload the original tune and change the MAF to;
Z32 VG30DETT (GTR ECU) (500 HP) -> MAF VQ gets halved, and if it go back into Change MAF its says "Current VQ map detected "NONE FOUND".

Version is 1.2.62. Since the MAFs are changing from 290HP to 500HP, should the MAF VQ graph look very different? If so, i'm guessing that using the "Z32 VG30DETT (GTR ECU) (500 HP)" may give me the right result. FWIW, K changes from 233 to 401 with both options.

[Junkie]

Hi Matt - any ideas on this? Or will I just have to get it fully retuned?

[Matt]

I just tried loading the original tune, then changed the MAF to;
Z32 VG30DETT (500 HP) -> causes slight tweak of MAF VQ curve (a bit lower in the middle), and if I go back into Change MAF it shows "Current VQ map detected" as "Z32 VG30DETT (GTR ECU) (500 HP)"

This is what is meant to happen - the second 'GTR ECU' VQ map is basically a copy/paste of what happens after doing MAF resize

However, If i reload the original tune and change the MAF to;
Z32 VG30DETT (GTR ECU) (500 HP) -> MAF VQ gets halved, and if it go back into Change MAF its says "Current VQ map detected "NONE FOUND".

I'm not sure why that happened, since when I did it here, still shows the 'GTR ECU' selection from the drop lost. This second option will not adjust K constant however

Version is 1.2.62. Since the MAFs are changing from 290HP to 500HP, should the MAF VQ graph look very different? If so, i'm guessing that using the "Z32 VG30DETT (GTR ECU) (500 HP)" may give me the right result. FWIW, K changes from 233 to 401 with both options.

The VQ map is only an airflow/voltage conversion table. The actual HP adjustments actually are taken into account by K constant. The HP number shown is used to modify the K constant from current to new value (new hp/old hp x K)

If you have trouble running after the resize, then K may require further adjustment until you reach the end of the maps within the factory load scales