"A few people have seen improved mileage when upping the AFM deactivation point from the 6% throttle positon it is set at to something like 11%."
- posted on another Forum

Is this actually something that a 'Tune' can change adjust?

Has anyone here done this?

Result?

Thanks,
- Ray
Just very curious....

That will cause the engine to knock at part throttle since it should be out of DoD by then, we do alot more than that for fuel economy; it's not that simple ;)

I learned the hard way about tuning with my 2004 2500HD. I was hoping a change "over here" would follow through with a change made "over there". Like Vector said, its not that easy. I dunno if I can explain it, but in this example if you cruising around HPTuners you may find something like DoD Deactivation point set to 6%. So you wold think leme see what happens at 11%. One of three things will happen:

1. It actually worked with no ill effects (good luck)
2. Something else is worse about the car
3. Nothing happens at all

There are so many other variables, when it tries to stay in AFM passed 6% , other varibles may say O2 readings are off leaving the exhaust too hot, so the computer will increase fuel comsumption to keep the catalytic converters cool in order to maintain stoich (14.7:1). At this point you will have to review many other tables in an attempt to allow DoD to operate at 11% that have absolutely nothing to do with DoD.

This exact example may not be the truth about what happens when raising AFM deactiviation, but it does give you an idea about how tuning works and why its a pain in the arse!

On another note, A dyno tune from the local tuner typically will not do anything beyond maximum HP when you are wide open throttle. All other settings are left stock. It KILLS me not to have a VMS Tune because they do "both" dyno and driveability tunes at a cheaper price. I just like to tinker around since I like to learn this stuff and since they lock the ECM I can't.

[QUOTE=vhato;50417]
On another note, A dyno tune from the local tuner typically will not do anything beyond maximum HP when you are wide open throttle. All other settings are left stock. It KILLS me not to have a VMS Tune because they do "both" dyno and driveability tunes at a cheaper price. QUOTE]

That is the reason on my last 2 cars (my 06 mustang and my G8) I've went to the best (VMS for the G8) for mail order tunes, I consider driverablity and part throttle response to be the most important. I figure I spend less than 1% of my time at full thottle and really don't give a damn about bragging rights on the most RWH. For me it's the total package that really counts.

This can't be accurate. If I am cruising on the hwy @ 60 and I completely let off the throttle, my Dashhawk reads 7%tps, If it only came on at 6% and below, it would never come on on the HWY?
But my engineering mode shows it kicking in. Maybe they are referring to engine load %??

[QUOTE=vhato;50417]
I figure I spend less than 1% of my time at full thottle and really don't give a damn about bragging rights on the most RWH. For me it's the total package that really counts.

Totally agree.

Real world, seat of the pants. Thats what matters most.

Answer this question, (anybody who wants to play along)

Which engine would you want in your G8, one that produces 600 HP or 400 HP?

Answer to follow.

This can't be accurate. If I am cruising on the hwy @ 60 and I completely let off the throttle, my Dashhawk reads 7%tps, If it only came on at 6% and below, it would never come on on the HWY?
But my engineering mode shows it kicking in. Maybe they are referring to engine load %??


They are referring to calculated enging load. It is calculated as (current airflow / peak airflow @ sealevel) x (barometer @ sealevel / current barometer) x 100%

Your dashhawk shows your throttle position sensor. As these cars have an electronic throttle body and not a drilled mechanical one, you will never see a TPS reading of 0%. Your throttly body will stay slightly open (the 7% you are seeing) to allow the engine to idle.

Totally agree.

Real world, seat of the pants. Thats what matters most.

Answer this question, (anybody who wants to play along)

Which engine would you want in your G8, one that produces 600 HP or 400 HP?

Answer to follow.

Trick question. trickier answer.

To dust off a ZO6 I'll take the 600hp, and blow $100 of gas in teh process.

To claim bragging rights and still get crap from eth w. that the mileage sucks I'll take the 400

For today's real world drivability plus returning close to a blown 3800, then it'll have to be 361.

For the best of both, I would have the 5.3 303 hp V8 from the last GP GXP, but with a s/c giving me oh, around 360-375 when I need it, yet better fuel economy than AFM. ANd if I really want to save I would install a a/c type clutch (and air flow divertor) so taht I could choose to run around on just 303 hp when I want. Oh and I'd chuck about 500 lbs off this porker.