Guide How to set High Gear maps on Z32 ECU :-)

[Adrian]

Hi

I've spent a bit time to the hole story with the High Gear Maps last night. I played a bit and after a few superiors, it was clear how the High gear (Upper Gear) maps works. So i deceid to write a small guide.

What is it?
It is a super nice additional function, that allows to enrich the car in high gears. You can tell the ECU on which gear on it should use the Upper Gear fuel map for injection (from 3th or 4th on , or only in 5th)

High Gear Coeff:
The High Gear Coefficient is used to set the point where the ECU change from the usual Fuel map to the Upper Gear Fuel map.

How to set High Gear Coeff:
-At the beginning of your mapping job, you should set the High gear Coeff to 0 (zero). On this way the ECU acces never to the Upper fuel map and you can set the Fuel Map, without worries that the ECU jumps to the Upper gear map.

-When you think you are finish with the fuel map, you should copy the Fuel Map to the Upper Gear Fuel Map and Upper Gear Knock Fuel map (you can do this with the "copy all" buton, attention Knock fuel map are also affected)

-Now set the Upper Gear map extremly rich

-Drive the car in this gear that you want use the Upper Gear map from around 3000rpm (for example in 4th, if you want use Upper Gear fuel mapp in 4th and 5th) open the High Gear Coeff and advance the number until the car run few richer (because ECU change to the Upper gear map) on this point, advance the number further 2 points (safety factor) Check that the car runs over the hole rpm range on the Upper gear map, and one gear smaller not.
The proceed of adjustmen High gear coeff is basically the same as on the Apexi AVC-R to learn gears.

My values for a RB25 GTS-T with standart transmission ratio are:
Use High gear map only in 5th gear set High Gear Coeff to 36
Use High gear map in 4th and 5th gear set High Gear Coeff to 48



- Go Back to the Upper Gear map and Upper Gear Knock Fuel map and adjust it as you want to run the car from the gear that you adjusted before


Final word:
Usually you set the Upper Gear similary to the Fuel map, but under high load, and high rpm a bit richer to bring exhaust temperatures down on long WOT runs.
Advantage: You can run more ignition, without the problem that the engine starts to knock on long WOT runs in High gears. I see that every time on German Highways. One gear pull, no knock, but as soon as you push the car through several gears, the exhaust temp goes higher and the car starts to knock in the higher gears. Add some extra fuel on this gears solves the problem.

[Matt]

Good write up

[Adrian]

Good write up

I hope that my write up is coherent. If not, please ask and i will try to explain it with other words. My english isn't the best. But i'm learning

Thanks!

[Torque]

Thanks for that ... this would be the empirical way finding out when the ECU switches.

But wasn't there actually a formula based on:
Speed / RPM / Gear Ratio to calculate ?

[Adrian]

Thanks for that ... this would be the empirical way finding out when the ECU switches.

But wasn't there actually a formula based on:
Speed / RPM / Gear Ratio to calculate ?

I don't know how to read this heximal stuff. As soon as i have a bit more time i want learn how to interpret them. But i'm very busy at the moment to learn ecuflash.
I found out alot wirh the emperical methode. It needs time, but it works for me.

If you have done gear coeff adjustments once. It's a 5min job on the next car.

[Torque]

Yes,

I did a lot of empirical analyses myself.

As far as I know the HG-Maps were not used by Nissan on the Z32.
It seems the CPU compares speed to RPM over 3000 and then switches based on the coefficient.

I would like to use the HG-Maps for highway cruising.

Thanks for that ... this would be the empirical way finding out when the ECU switches.

But wasn't there actually a formula based on:
Speed / RPM / Gear Ratio to calculate ?

I don't know how to read this heximal stuff. As soon as i have a bit more time i want learn how to interpret them. But i'm very busy at the moment to learn ecuflash.
I found out alot wirh the emperical methode. It needs time, but it works for me.

If you have done gear coeff adjustments once. It's a 5min job on the next car.

[Adrian]

Think must work internally this way. Rpm vs speed x coeff. However the important thing is that we know how we can use that for tuning. The proceed in my write up works well and its not a big job.

What i know, high gear maps is only used for european 300zx, cause the german autobahn.
Romchip has mention that somewhere in the forum. He knows very much over the z32 ECU's.

[my1path]

I found the High Gear Coefficient in the bottom scroll bar under "Variable Cam Timing" (Which I do not have VCT) and setting it to "0" certainly leaned out my 5th gear.
But I cannot find the "Upper Gear Maps"

I'm running an 1990 Infiniti M30 ECU. Am I correct in assuming that can only edit the Coefficient and not the actual map this ECU?
If that's the case I'll just leave the Coefficient turned off. "0"

[RomChip200]

Code: Select all

CODE:ADE5 cf_26:                                            ; ...
CODE:ADE5                     ldaa    speed
CODE:ADE8                     ldab    speed_coef_4
CODE:ADEB                     mul                           ; D=speed*speed_coef
CODE:ADEC                     lsrd
CODE:ADED                     lsrd
CODE:ADEE                     lsrd                          ; D=speed*speed_coef/8
CODE:ADEF                     xgdx                          ; X=speed*speed_coef/8
CODE:ADF0                     cpx     rpm                   ; Engine speed / 12.5 (rpm)
CODE:ADF3                     bcs     cf_27                 ; if rpm>speed*speed_coef/8 then branch
CODE:ADF3
CODE:ADF5                     tim     #%100, flags6         ; Neutral flag ?
CODE:ADF8                     bne     cf_27                 ; If neutral then branch
CODE:ADF8
CODE:ADFA                     oim     #%10000000, flags6    ; Set gear engaged and high gear flag
CODE:ADFA
CODE:ADFD
CODE:ADFD ; Compute starter flag ---------------------------------------------------------
CODE:ADFD
CODE:ADFD cf_27:                                            ; ...

speed is your kph speed divided by 2
rpm is your real rpm divided by 12.5
OEM speed_coef_4 can be 0, 46, 47 or 53.

So, for Use High gear map only in 5th gear set High Gear Coeff to 36:
when cruising @ 90kph, it switches to high gear when rpm becomes below : (90/2 * 36 / 8 )*12.5 = 2531 rpm

For Use High gear map in 4th and 5th gear set High Gear Coeff to 48:
when cruising @ 90kph, it switches to high gear when rpm becomes below : (90/2 * 48 / 8 )*12.5 = 3375 rpm