vt ss tuning questions?

[vnsswithcam]

hi guys ive just got my self a vt ss 5 litre and i wanna ask some questions about the tuning
ive had a look at the tune i dont know how the low octain spark map works for 1 how does the computer change it does it just detect a knock and then puts it in that low octain mode?
also ive been tuning with all this gear for my vn ss but the vt ss is maf not map so when tuning the spark map what are the things i should look out for that are different than the map based tunes of the vn ss? also does the checksum trick work with the vt ss tunes
cheers

[charlay86]

Yes the checksum trick works, set 0x2008 to 0xAA.
The PCM interpolates between the high octane and the low octane maps, so when it detects detonation it retards the timing and then once it stops detonating the timing will creep back up to the high octane map values.

[vnsswithcam]

ok cool thats easy enough cheers
what about like wot spark map is it the 850 mgc same place where 100kpa would be in a vn ss tune? or is it different the graphs look simular

[Holden202T]

you'll find with the WOT at low rpms it will start probably in the middle of the maf and as the revs increase it will make its way over to the 850mg cells and then might even drop back a bit in high rpms .... its not like map in that respect.

[yoda69]

These are a lot more complicated than the MAP based setup.
mgc readings will be a maximum at peak torque, would be suprised if it actually gets to 850mgc on a stock 5.0 litre.
If tuning with an Ostrich data hit tracing works well to see what cells are being accessed, otherwise you'll need to link the adx and xdf together to see the balloon.
Biggest issue with timing is there are changes also for PE, coolant temp, iat temp, etc. so the main table is a start point and then the values are either added or subtracted from it.

I'm still not 100% sure on the knock tables, maybe VL400 can help out here.
There is a knock factor that pulls out spark and slowly puts it back in, but I'm unsure what is the trigger for it to interploate between the 2 tables.

yoda69

[VL400]

The interpolation is done using an adaptive spark multiplier, its got heaps of qualifiers (RPM, temp, time etc etc) but its just like charlay mentioned and moves between the hi and low octane based on how much knock is happening.

All it does is .. high octane spark - ((high octane spark - low octane spark) * multiplier)

Whats surprising is this is not in the data stream, can request it manually but its not in there nativly.

[vnsswithcam]

ive played around with it a little bit and it goes better around low rpm but once i hit around 3000rpm it seems to be the same ....am i able to use my usb comms board i got off vl400 to connect to diagnostic link and hook it up to tp5 to data log so i can see what cells are being used? is there support for the vt ss

[VL400]

Yep USB will work on it - hook up the data line and ground wire and your good to go. There is an ADX for TP5 in here .. https://pcmhacking.net/forums/viewtopic.php?f=10&t=29

[vnsswithcam]

wierd thing happening with my tune when i select cruise control and activate it my auto drops down a gear and maintains the speed selected just using that gear revs at like 3000rpm ?? as soon as i turn it off it selects the next gear i have used the vt clubsport manual tune as my base tune and ive unticked all the manual options? i might try another tune with the standard base tune and see how that goes........ wierd!!!!

[yoda69]

Most of the manual tunes I've looked at have incorrect auto info as far as shift points and TCC lockup etc., probably a very early base or starting point tune.
Need to start with an Auto Tune.
Manual and Auto tune would have started at a baseline and then diverged and tuning progressed for each tune. Info would never have been recombined.

yoda69