pcmhacking.net

Hi all,

I have found my speed indicated on TunerPro is not accurate and all of my shift points are all over the place.
I have used the calculator as per the picture attached (I have a 4.87:1 Hilux diff in my car) And I need to input 0.0154 but the parameters in TunerPro for the trans do not allow me to put anything less than 0.0194.
Is there a way I can change the XDF so that I can input the correct driveline ratio and have my tune read correctly?

Cheers,

Barbs

If you change the diff ratio in the tune you will have to tune every single shift table to match

That is no dramas at all. What i am finding at the moment is that the ecu is getting up to 255km/h and speed cutting me way before i want it to.
Can i change the diff ratio anywhere other than the driveline ratio parameters in the screen shot?

Thanks
Mark

I'm surprised there is still a speed limiter in there ...

VL400 might be able to shed some more light on this, but generally if the slider in tunerpro is at the end that's as far as you can change the setting.

the two items have different calculations so there might be different limits for each ....

That speed limiter is a bit annoying, especially if you have a high powered car on the dyno that pulls over 255Km/h on the power run.

I'm sure high speed cut was removed from 12P .... maybe not for 11P .... ??

Have you tried setting the scalar "Run Params - Fuel cutoff time threshold" to 0 or 255? It wont fix the problem and Im not sure what the units are but it may buy enough seconds for a dyno run to complete the run. Mind you, > 255kph is pretty fast and you might be better off doing the dyno pull in a lower gear. EG https://www.dyno.com.au/dyno-dynamics/dyno-dynamics-2wd 250kph max here.

Speed is stored as an unsigned 8 bit value, so hardware limitations are 255kph before overflow. I cant see a flag to turn the cut off, and im not sure what would happen if it overflowed. The internal value would probably go back 0 and that could cause a lot of faults and be rather disastrous. vl400 would know more.

yeah its in 11P only, 12P has no limit.

a regular commodore v6 pulls to 200Km/h in 4th which is the gear to run is as its direct drive and gives little as possible losses for more accurate read. You can do runs in 3rd but you can run into wheels spin issues with high powered engines running in lower gears. Its mostly because Holden/Ford naturally run tall diffs compared to everything else on the road.

I thought the commodore 4l60e had 0.7:1 overdrive in 4th and 1:1 in 3rd?

Also my problem is not so much the speed cut now as i have fudged it with an incorrect driveline ratio but i am finding my speedo indicated by the ecu is incorrect and making my shift points all over the place.
Ill make up a spreadsheet and work out the errors then adjust my tune as required.

The ratio limitation can be fixed with some hacks.

If you PPR is 40, multiply that by 1.5 to 60 (which is the max)
Then if your ratio calc is 0.0153 then multiply that by 1.5 and use 0.02295

Can tweak from there to get it spot on with GPS but will get you close if the rollout is accurate.



12P had the speed cut removed, 11P have left it in. Other than a dyno in 4th gear and near stock diff gears, would need some reasonable grunt and balls to do over 255kph in a commodore.