SMG with 4.44 diff or higher

[silaciM3]

Has anyone tried this combo? I'm particularly interested in the coding side since K_SMG_I_HA only goes up to 4.25 (FF).

Also, would anyone happen to remember how these are used? There are scalars for every gear.
K_GANG_GRENZE1_2
K_S_GANG1_NV_MIN
K_S_GANG1_NV_MAX

I remember Terra posting an explanation on the old forum, but that's gone now.

[R3Z3N]

Shortest differential gearing may only be 4.25 due to BYTE limitation in ECU IE FF=255. DME Calc is X/60. 255/60=4.25

I figured out Grenze/Gange curve well enough to work for my E30 swap/cruise control and uploaded the spreadsheet to the E30 Swap items on github....

[silaciM3]

Thanks for the spreadsheet! That helps

Any idea or best guess on what would happen if one where to use a diff shorter than 4.25? Would that only affect auto mode or manual as well?

[silaciM3]

Alternatively, do you happen do you know the address of the conversion factor in the program? A program mod should theoretically allow us to use much shorter diff ratios.
As conversion factor of 45-46 would open the ratios up to 5.44

[eacmen]

Subscribed. Shorter gearing on the smg would be epic.

[silaciM3]

Bumping this up. Pretty sure lots will be interested in running shorter diffs on the track, and I'm willing to test that out once we get some more details.

[silaciM3]

No one?

[R3Z3N]

^ I would not count on any programming/OS changes, outside of flashing a modified bootsector/OS to run CSL tunes on a non CSL HP DME which is already finished.

Anyway, I think the stock trans gearing is pretty poor for racing anyway. If it were me I would put in a Winters quick change diff and sequential and another brand Ecu....

[George Hill]

I'm putting a 4.44's in behind my S54, but am running a ZF8 trans. My 8th gear ratio with 4.44s is nearly identical to a 420g with 3.62s in 6th. Curious to hear feedback on this setup from stick cars especially if you are going wild with a ZF5, lol.

[terra]

I'm putting a 4.44's in behind my S54, but am running a ZF8 trans. My 8th gear ratio with 4.44s is nearly identical to a 420g with 3.62s in 6th. Curious to hear feedback on this setup from stick cars especially if you are going wild with a ZF5, lol.

I imagine you're using a separate controller for the ZF8. What are you specifically trying to accomplish DME wise? Getting cruise and that sort of thing to work?

The gear ratio parameters above only really apply to SMG cars. The parameters seem to mostly impact how well auto mode works, but there might be other subtle effects I'm not aware of. I'd have to see how the data flow works, but I suspect there isn't much room for change there without also modifying the SMG computer program since the data is communicated over the smg can-bus.

The various _NV value are used for the DME to detect what gear it's in for manual cars. That can be corrected fairly easily for different diff ratios (though naturally for a ZF8, the car's program is not designed to be aware of 8 gears)

[George Hill]

I imagine you're using a separate controller for the ZF8. What are you specifically trying to accomplish DME wise? Getting cruise and that sort of thing to work?

Yes, I am using a TurboLamik TCU for the transmission.

I'm not trying to accomplish anything as far as this conversation goes it just peaked my interest because I am also installing that gear ratio and this would be good info for a future project if I had a client want to put this ratio in their car (which would likely be a ZF5/420g based transmission). Most of what I am around are daily drivers or "street cars" so a 4.44 ratio in one of those cars is pretty rowdy. I would imagine most people are not installing them in a car they drive (much) on the highway, but most of the people I'm around do. The feedback of that ratio in real world applications is not something that is widely known or at least that I have come across.

With that said, I had written of being able to make cruise work for the reasons you stated, but if it would be possible with the 8spd that would be assume, not holding my breath though lol.

[terra]

Yes, I am using a TurboLamik TCU for the transmission.

I'm not trying to accomplish anything as far as this conversation goes it just peaked my interest because I am also installing that gear ratio and this would be good info for a future project if I had a client want to put this ratio in their car (which would likely be a ZF5/420g based transmission). Most of what I am around are daily drivers or "street cars" so a 4.44 ratio in one of those cars is pretty rowdy. I would imagine most people are not installing them in a car they drive (much) on the highway, but most of the people I'm around do. The feedback of that ratio in real world applications is not something that is widely known or at least that I have come across.

With that said, I had written of being able to make cruise work for the reasons you stated, but if it would be possible with the 8spd that would be assume, not holding my breath though lol.

These are the values you're interested in. Attached an excel sheet to help calculate the correct values

[silaciM3]

Thanks. Now anyone putting a "race" gearset wouldn't be caring about auto mode anyway. In manual mode, first thoughts that come to mind are downshift overrun protection, and possibly rev matching.
I guess we'll have to try and see.