VR/VS/VT speedo ppk changes

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yoda69
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VR/VS/VT speedo ppk changes

Post by yoda69 »

Looking at some xdf's there is a value for correcting the output to the speedo for different gear ratios.
I've tried several different values with a VS V8 with no change in the speedo or ALDL calculations that I can determine.
Is this another one of the cal options not implemented or bypassed?
I know from the factory holden used to put a ppk figure into the instruments to correct speed for different wheel sizes or diff ratios.
The wiring diagrams show a wire running from the ecu to the Instruments, or am I reading this wrong and it is a signal from the speedo to the ECU?

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VL400
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Re: VR/VS/VT speedo ppk changes

Post by VL400 »

Can change the value of what the PCM sees but not what goes to the dash. The PCM just converts the signal (reluctor to square wave circuit) and passes it on to the dash , no smarts involved.

Its now a driveline ratio rather than PPK, can be worked out using - Ratio = (Tire Rev's Km x Diff Gear Ratio)/ 0.0357

Should see the PCM ALDL speed change if the XDF is changing the correct thing.
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Re: VR/VS/VT speedo ppk changes

Post by Holden202T »

dunno if its the same as the ecotec or not but i've changed the one on my ecotec and its updated correctly in the aldl stream.

its defined in my $51E xdf as NO VS RATIO from memory.
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Re: VR/VS/VT speedo ppk changes

Post by yoda69 »

Thanks guys, may start looking into how to change the ppk value in the dash, cheaper than getting an electrical box to do it.

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Re: VR/VS/VT speedo ppk changes

Post by Doctor Bob »

i have found theres no PPK in some vs v8 bins, vr have it & the ecotec ones have it there.
in vt vx the ppk can be set in the dash, this corrects all areas.
changing it in the memcal wont work

Rob
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Re: VR/VS/VT speedo ppk changes

Post by VL400 »

Do you know which bins dont have the ratio or ppk? Interested in the way the calc is done. There is also a 16bit number of pulse per rev in the VR bins which can be tweaked to fudge the output, and being 16bit gives good resolution.
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Re: VR/VS/VT speedo ppk changes

Post by yoda69 »

I've been trying to work with a VS V8 Auto bin based of BWFU, $83 variant.
I'm guessing this falls into the category Dr Bob was talking about.
I thought it was at $6021 as a 16 bit number with an xdf formula of X*3840/65536

I was wondering if there was a flag or soemthing that said to use this or something similar.

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Re: VR/VS/VT speedo ppk changes

Post by VL400 »

Looks like it has a KPH calc and a MPH calc like a normal VR bin, the KPH is for the engine code and MPH for the trans.

So to adjust the KPH calc (which is whats in the ALDL stream) you need to hack the actual code a little. Address 0xC0E3 has a 16bit value 0xD055, this is the driveline ratio using the calc ... Ratio = (the value at 0x6021) * 1.243.

This is an assembler compiled value instead of a lookup to a value in the cal :roll:

The MPH calc for trans lookups is adjusted using the 0x6021 value. To see the change you can mod the ALDL message 0 to include the MPH, at 0x77DA the bytes are 0x5D 0xDA so can be changed to 0x02 0xCA. The ADX just needs to view the byte at offset 51 with the calc X/2.
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Re: VR/VS/VT speedo ppk changes

Post by yoda69 »

VL400,
Will try and give it a go today.
One issue maybe that it's running a 3.91 ratio instead of 3.08.
Converting $A828 at 6021 by ~27% = $D58E.
Times this by 1.243 = $10972, obviously bigger than 16 bit.
Working backwards, it appears that the largest possible percentage change is around 22.4%.

Biggest pain with this will be having to update all shift, TCC lockup, upchange/downchange, etc. tables and scalars.

Thanks,
yoda69
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