Deceleration and RPM holding in an A4

[Jphdg]

I am trying to research into this but not sure I found what would relate directly to my current issue apart from maybe the possibly obvious.

When I am driving along and release the throttle, I find that the car does not want to naturally decelerate very much when slowing without brakes.

My guess: Could this have something to do with the throttle follower and cracker tables? I am leaning towards it probably is receiving a little too much airflow after the TB closed while coasting?

This is where i plan to do a little logging on and see what I am getting here.

What typical approx MAP pressures should I be seeing in an A4 with a cam in the 228 range with LSA of 112 deg. 0% TPS decel at a VSS of 60-0kph?

Is it possible it is related to the desired idle which is currently set at 1000rpm which is a tad too high for my liking.

I plan to set the 'desired idle' to about 870rpm - 900rpm and see if this makes any difference while decelerating then look further into the issue if that fails.

If anyone can clarify where I should start out and what tables i may need to investigate, this would be greatly appreciated as I am 'very' new to it all so not quite sure if I am on the money or not with this one yet. ;)

If there is anything I have missed, please let me know.

Thanks

[jfpilla]

I've noticed that GM cars do not slow down quickly. I think that's for gas mileage. It could be a result of B4307 also being too high. In any case B4317 using Z06 numbers will slow down the car more quickly. I've tried it and it's noticeable.

[Tordne]

Get your Desired Airflow (B4307) table dialled in. If the values here are too high it will add extra air and give you a bit of a cruise control effect. It will also hold the idle high when coasting out of gear (well it does in an M6 anyway).

Check the Throttle Cracker (B4309) table and see how much air is being added various RPM vs. Speed points and perhaps play with those.

You may also want to look at the Throttle Follower (B4315) table and see how much additional air is being added through there. You will also probably want to look at the decay rate as well.

If you want a sort of engine breaking turn DFCO back on ;)

Have fun,

[Jphdg]

Thanks guys,

Just checking these tables now and seeing what values are in here.

Table {B4313} has values of 0.1 GS decay rates right through from 26kph and up. Perhaps the decay rate is too slow?

Checking table {B4321} TF TPS change = 1.0%
Between 1000 - 1600rpm I am seeing GS values as shown in the jpg attached.

oops.. sorry i just realized I have got it all highlighted but values can be seen.

TFA {B4312} is set below 1.0 GS for anything below 3.55 TPS %
TFA is set between 2.1 and 2.5 GS above 13.55 TPS%
{B4316} = 1.0GS
{B4317} = 0.1GS in 4th between 10-68kph only. Everything else is 0.
{B4318} = 1.0 sec only for VSS of 0-3kph.

The other tables here for P/N are no problem so I don't belive I need to check these.

Also DFCO is on with reasonable values so should be ok.

Anyway thanks for the comments, I will read up more about these tables and then create a new tune file to try some changes in after I log data related to them first.

:cheers:

[Jphdg]

Good news!

Idle is set now from 1000 to 850 and it sound awesome. Even got a comment on how good it sounded at the lights on the first test drive. It does not rock its head off and feels as smooth as it was when it ran at 1000rpm but now with a very nice V8 cammed lope.

Also everything else now seems to be in par and it is not driving itself along anymore :D

It did stall once in R so checked the GS table for lower rpm values around 700 - 900rpm which all seemed reasonable. I enabled and set up the stall saver and it works perfectly.
Idle is solid right from cold start to hot. Punch the throttle quick in R and back off, it does not want to die no matter what you do so all seems good. :)

Problem solved all round and very happy with the above.

now just need to teak my 2-3 upshift on light throttle as it feels a tad funny and resolve my TCC issue and it is then perfect.

May be a good time to try some BIDI functions and do some more logging on the transmission as we have Easter Monday today and I feel like going for a spin.

:cheers: