pcmhacking.net

Hey guys!

I've finally decided to take the dive into some good ol' tuning for my VXII V6 N/A Commodore.

I've done alot of reading around, and i just want to make sure that I'm understanding things correctly and heading in the correct direction!

Firstly, it is the PCM that gets flash tuned, not the ECU? Or is the ECU in the PCM? If somebody could clarify this for me. I know the VTs had a memcal that could be swapped out easily enough, but now we are on flash roms.

I'm guessing that I'm going to need:

An ALDL USB cable (to connect laptop to car)
Spare PCM (to clone my original to in case i screw up)
The FlashTool 1.35 (to save changes to the PCM)
Tuner Pro V5 (to make changes to the BIN files?)
Memcal ID Tool (for the bin and xdf files)

All that I really aim to achieve from this to begin with is adjust my Auto. Reason being, I've just bought a 3.46 LSD to replace my 3.08 single spinner, and I'm going to have to adjust my shift points to suit, and also would like to firm up my gear changes (increase line pressure?)

I've already had a look through Tuner Pro v5 using the VX bin and xdf files, and I've found that i can modify the normal and performance shift points from 1-2 2-3 3-4 (and reverse). As i understand it, im going to have to do some maths to find out how fast i will be going when my engine is at max revs (5,500ish if i recall correctly?) using the 3.46 gears or just scale back the 3.08 values proportionally to the 3.46 values so hopefully it should behave the same.

I couldn't actually see anything through searching, but has anybody already done this work and is it available for download? and has anybody uploaded their tunes for others to use? (Equiv of a greenfoam tune for vn's etc)

Also, what other things can i easily modify to get better performance / economy? Not much in the way of performance mods, 2.5" redback with hotdog in the rear, K&N Filter.

Any tips or corrections would be greatly appreciated!

effectively ecu/ecm and pcm are the same thing .... newer cars from about VR commodore onwards have been referred to as pcm which is powertrain control module, and powertrain is engine and gearbox, everything before it had gearboxes that were controlled by hydraulics, vr was the first to have electronically controlled tranny (in the autos this is)

weather they use a flash chip or a removable eprom etc depends on model really.

your pretty well on the money for what you need i believe, but i'll leave that up to the guys that have experience with flash pcm's

Rather than change all shift points change the ratio scalar. Use this

Stock Tyres
205/65R15

(205 x .65)/25.4 = 5.25 inch Tyre Diameter

20168 / ((5.25 x 2) + 15) Works out Overall Tyre Diameter & Results Rev/Mile

(791 x 3.08)/60 = 40.60 Approx RPM/VSS Ratio

i changed the same thing when i put the ecotec in the torana, but i still had issues of it hitting the rev limiter before it changed gears, i ended up having to remove a few kms off the upshift points at WOT, and the only thing i can work out is that with the change in diff ratio it accelerates quicker and then the box can't change the gear in time ... i also had a less than perfect gearbox so it might have just been that causing it.

ive put a 3.9:1 diff in a VR before and didnt change a thing.... you have to remember, the VSS is actually on the gearbox, so even though the final speed is different, the rpm at which it shifts doesnt change as the vss is taking all its info from before the diff anyway. it worked perfect. just leave the VSS at its factory value and save having to needlessly stuff around with the shift tables. if you want the dash speedo correct, put a jaycar corrector box behind the dash.

Jayme wrote:ive put a 3.9:1 diff in a VR before and didnt change a thing.... you have to remember, the VSS is actually on the gearbox, so even though the final speed is different, the rpm at which it shifts doesnt change as the vss is taking all its info from before the diff anyway. it worked perfect. just leave the VSS at its factory value and save having to needlessly stuff around with the shift tables. if you want the dash speedo correct, put a jaycar corrector box behind the dash.

yeh but the speed the pcm see's would still be incorrect, that's the whole idea of changing the vss to correct for the wheel speed change. Leaving it as is and fixing the dash with the jaycar the shifts would still be out and speed out? or have i missed the boat.

Holden202 wrote: i ended up having to remove a few kms off the upshift points at WOT

then that would suggest the vss number used wasn't right, would be reading to fast as the gain was to high?

The1 wrote:

Jayme wrote:ive put a 3.9:1 diff in a VR before and didnt change a thing.... you have to remember, the VSS is actually on the gearbox, so even though the final speed is different, the rpm at which it shifts doesnt change as the vss is taking all its info from before the diff anyway. it worked perfect. just leave the VSS at its factory value and save having to needlessly stuff around with the shift tables. if you want the dash speedo correct, put a jaycar corrector box behind the dash.

yeh but the speed the pcm see's would still be incorrect, that's the whole idea of changing the vss to correct for the wheel speed change. Leaving it as is and fixing the dash with the jaycar the shifts would still be out and speed out? or have i missed the boat.

you are still thinking of wheel speed. dont even think of it as speed... pretend the ecu sees a bunch of pulses reading tailshaft speed. it decides when to shift based on this tailshaft speed. you then change the ratio of the diff gears. at any given rpm, the tailshaft is still going the exact same speed. nothing has changed because the final drive all happens after the tailshaft, the ecu and its calculations. the shift will happen at the same rpm as it always has. the ecu wont be using the real kmh speed in its calculaitons anymore, but who cares, its just a reference point.

yeh call me picky but id like the real speed in the pcm and dash lol

I never look at the pcm speed in tunerpro anyway, im just happy correcting the speedo in the car dash with a jaycar corrector box, and leave the pcm to its own devices.