Most M6 logs i've reviewed suffer from a timing issue due to LT1 stall saver code only active in manual calibrations. Please read on to enable a much smoother transition into low RPM when decellerating, and ensure a stricter adhesion to your chosen spark table values at lower RPM....

( from http://fbodytech.com/tuning.html#stallsaver )

The $EE code contains a very odd type of 'stall saver' routine that uses timing advance only.

This tends to work alright on a stock engine, but on modified vehicles, it can cause major timing fluctuations. It is only enabled by default in manual transmission cals (automatics don't have to worry about it).

Symptoms include up to 10 degrees of randomly flucuating timing advance during gentle coasting or decelleration below 1600rpm on f-bodies and 1400rpm on y-bodies, which can show up as a surge or a general lack of drivability. Some people mistake the issue as simply being too far outside of their cam's operating range, when in fact their car would decellerate smoothly if it wasn't hitting the stall saver bug.

Simply pushing the clutch in and coasting in neutral will reveal the error in logs. The stock configuration makes the surge less obvious on y-bodies, as they use roughly half as much stall saver...

Note the following log as I approach a stop light when TPS drops to zero, and RPM tips below 1600, which is the stock MAX RPM threshold, and note that the timing surge doesn't stop until CL idle control (at a dead stop) is reached:



During that surge, the car is bucking and stuttering.

This is also often mistaken for problems with alignment with the closed tps spark advance tables, or an issue with transition into the idle underspeed/overspeed spark correction routines.

To alleviate this problem, disabling or reducing the effect of the stall saver is necessary. I reccomend disabling it entirely.

Download my latest XDF file: http://resfilter.net/files/carstuff/...DF_CURRENT.zip

... and alter the following parameters:

 

Great info and work again Steveo!

 

Very cool, I have never even heard of this.

Do you have a log of the same deceleration with the fix enabled to compare visually?

 

see attached

 

Wow that is a HUGE difference!

This is something I would definitely do if I had a t56 car.

 

seriously a must-have.. i can cruise at 1500rpm now, before i thought i had too much cam to be cruising that low since it acted so crazy, so i just kept it above 2 grand.

 

I can cruise at 1200 with my cam. If I did this I may have to change my spark tables?

 

Awesome! Thanks for all the hard work you have put in to this so far and the fact that you bother to explain it goes a long way.

 

you'd have to log and see if you're affected by the problem.....

 

Just implemented this earlier today, made a huge difference in my cammed car, so much easier to drive around town. Thanks steveo, you da man!