Rich decel...still...also..etc

[hquick]

Hi all,
can someone take a look at this log and tune and see if you can see where my rich decel issue is coming from?
I've tried using RTACS whilst driving and adjusting injector tables (voltage offset, min pulse width and adders) all of which seemed to make no difference.

[swingtan]

From the log, it looks like every time MAP pressure drops below 40KPA, it starts to go rich, lower than 30 and it's significantly rich. It also seems to be consistent with the MAP pressure dropping below the 40KPA point. So I'd would have initially said that the VE is out in those areas, but I guess that's a bit too obvious. Still it seems that every time MAP drops below 40, it goes rich.

Thinking of what can effect the AFR's and make them divert from the commanded.....


Air flow: Controlled by the VE table which I'm guessing isn't fixing the issue as it would be too easy.
Injector Flow Rate: This may be an issue if the injectors are supplying more than their rated fuel as the MAP vacuum increases. You tune has a flat setting in B4001 so this "may" help correct things.
IAT - VE correction: The richness seems to be constant with varying IAT readings, so I doubt it's this. Another point this has is that this also may mean that air flow is not the cause, as the AFR's don't drift.


I'd be looking at the VE for starters ( which you most probably have ) then I'd probably look at B4001, Injector flow rate.

I may of course be wrong.....

Simon.




The other thing is the dreaded "Vampire Teeth" effect ( cells 17916 to 17964 ). This is usually caused by excessive settings in the dynamics, adding too much fuel at throttle tip in and tip out.

[hquick]

Thanks for the reply Simon.
Yeah...obvious thing is the VE. Tried 'RTACS'ing' it after setting filters for decel only. Ended up with the appropriate cells as low as 2.0 and still dropping...so put it back as it was.
IFR is 'apparently' correct for the Bosch (Ford-SVO) 42lb greentop injectors...although...there's ALOT of conflicting info around about them.
The 'Vampire effect' sounds fairly appropriate. Lol!

[mr.prick]

Having gone through this with the Lucas 42`s
I found that i had to change the small pulse adjust {B4005}.
This was tricky with RTACS because, once you get to zero RTACS stops.
To be able to update negative values, the cal.link will need to be changed.

I found this table did not have an immediate effect on fueling but,
if I set the values manually and drove I did notice a difference.
Go over to tech, someone will give you "info" on your injectors but,
I don`t see how they would accurately transfer to a GM OS.

Next time I buy injectors I will go with re-sized stockers.
Unless you know how GM tunes injectors I don`t see how anyone could get
aftermarket injector perfectly correct.
You can get them to act a certain way but in the end it`s not going to be right.
My 2¢