M6 gear ratio for

[dbaxter_ss]

I just picked up a set of these from ThunderRacing and need to know if anyone knows the gear ratio for them, AND most important if I am looking at the correct place in EFI to update for the new gears. If not then where.

Thanks in advance.

69-G875373 MOTIVE GEARS GM 7.5" 10 BOLT, 3.73 RATIO Nothing drastic but better then the old 3.42.


LABELS Selection
Parameters Value
{D1201} 1st Gear Ratio 3.060058 Ratio
{D1202} 2nd Gear Ratio 1.629883 Ratio
{D1203} 3rd Gear Ratio 1.000000 Ratio
{D1204} 4th Gear Ratio 0.699951 Ratio
{D1205} Rev Gear Ratio 2.290039 Ratio

[joecar]

Goto H0103 "Differential Ratio".

The displayed precision of this is 1 decimal point, so it will show as 3.7 even though you enter 3.73;
but look at the tire calculator above and you'll see what you entered.

(The place you were looking at (D120x) is the ratios for the A4 gears.)

Regards
Joe

[dbaxter_ss]

Think I found it under the speedometer parameters.
Just had to put in the width, profile and rim size: hit the little down arrow to get he current tire mm. then put in the new gear ratio ( current diff ) to 3.73 and hit this recalc : ( little button with two arrows ) then save
Down below you can then see it changed the three bolded below :


LABELS Selection
Parameters Value
{H0101} Vehicle Speed Sensor Pulses per Kilometer 30957.101047 Pulses/Km
{H0102} Vehicle Speed Sensor Pulses per Revolution 17.000000 Pulses/Rev
{H0103} Differential ratio 3.730000 Factor
{H0104} Trans Output Shaft Revs/Kilometer 1821.005944 Revs/Km
{H0105} PCM Primary Pulses per Kilometer Output Rate 2485.483997 Pulses/Km
{H0106} PCM Secondary Pulses per Kilometer Output Rate 79535.487897 Pulses/Km
{H0107} Vehicle Stationary Timer 0.900000 Seconds
{H0108} ETC Speed Govern Threshold 410.382847 KMH
{H0109} Maximum Vehicle Speed (Non ETC) 281.635287 KMH
{H0110} Overspeed Timer (Non ETC) 0.025000 Seconds
{H0111} Maximum Vehicle Speed (With ETC) 0.000000 KMH
{H0112} Overspeed Timer (With ETC) 0.000000 Seconds
{H0113} Speed Limiter Disable 1.609344 KMH
{H0114} Maximum Vehicle Speed with RTD Fault 0.000000 KMH
{H0115} Use External VSS calibration No

[Sid447]

I'm needing to get a refresher,

from someone please!
On how to do a CV8 M6 diff ratio change from 3.46 to 3.73.

Can someone please let me know for confirmation the parameters that need to be changed.
The last time I did this was 2005 I think and used V7.3 which wasn't so sophisticated!

The CV8 M6 stock tune file parameters are pasted here (with 3.46FD & 235/45x17 factory wheels & tyres)....

{H0101} Vehicle Speed Sensor Pulses per Kilometer 29891.343 PPkm
{H0102} Vehicle Speed Sensor Pulses per Revolution 40.00 Pulses/Rev
{H0103} Differential ratio 3.4599 Factor
{H0104} Trans Output Shaft Revs/Kilometer 1521.472 Revs/Km
{H0105} PCM Primary Pulses per Kilometer Output Rate 6225.846 PPkm
{H0106} PCM Secondary Pulses per Kilometer Output Rate 79535.48 PPkm
{H0107} Vehicle Stationary Timer 0.1125 Seconds
{H0108} ETC Speed Govern Threshold 239.792330 KMH
{H0109} Maximum Vehicle Speed (Non ETC) 410.382847 KMH
{H0110} Overspeed Timer (Non ETC) 0.025000 Seconds
{H0111} Maximum Vehicle Speed (With ETC) 243.011019 KMH
{H0112} Overspeed Timer (With ETC) 409.593750 Seconds
{H0113} Speed Limiter Disable 1.6093 KMH
{H0114} Maximum Vehicle Speed with RTD Fault 128.747560 KMH
{H0115} Use External VSS calibration No

TIA, SS.

[joecar]

Hi SS,

Set H0103 to 3.73 or more precisely 3.7273 (calculated from 41/11).

[Sid447]

Hi Joecar,

I had been used to A4 & A6 (auto) cars/trucks and the V7.5 "speedo calculator" makes it all quite easy, especially the shift point changes.
With M6 cars being so rare here in the M-East I'd virtually forgotten how I did mine (1st known LHD conversion from A4 to M6, Oct 2003).

Initially I had used the speedo re-cal option and it wound {H0101} up to about 73k. I didn't notice it had gone so high.
When the guy rang me back saying the speed was about 30% of what he was actually doing, I thought I'd better wake up.

I noticed 1999-2004 cars had 17.0 for {H0102} and '05/'06 cars were 40.0 here. So couldn't use my '02 as a reference.

A hunt around stock tune files turned up another VZ that was 3.73 from the factory.
{H0101} on this car was around 32,300 which worked out to be 7.8% higher than this CV8-Z's {H0101} of 29,891 with the 3.46 FD.

That's the percentage difference (7.8) when going from 3.46 to 3.73 and reckoned that must be the way to go for a speedo re-cal. After working out the gearing/roadspeed for a T56 MM12, it was checked on the road using scantool/GPS and was correct to within 10rpm.

Job done.

[joecar]

You're right, I do remember seeing H0102=17 in an M6 file... that completely slipped my mind.

Good job, you figured it out as a percentage change...