heard it called both but either way here is a video that shows it working. Didn't see it anywhere so apologies if it is a repost...
http://youtube.com/watch?v=hV7wvmNyQAI

heard it called both but either way here is a video that shows it working. Didn't see it anywhere so apologies if it is a repost...


I had NOT seen that.
Anyone experimented in this mode to see
( on a level highway )
how fast one can drive & still have AFM activate???
Thanks,
- Ray
Very curious . . .

It took me a moment to figure out what it meant by All Active and Half Active...

All of the cylinders are active
Half of the cylinders are active

How do you access Engineering Mode?

Hold down the enter button when starting.

Excellent video man! That engineering mode rules! Looks to be a really advanced tool to have. Nice to also see that we get some indication on when the AFM is working thanks to the "EM".

Dovi: Great video, thanks! It's nice to see that it is possible to be in a mode that tells you your in 8 or 4 cyl. mode. Nice find.....

Sweet.....gotta play around with EM sometime. What kinda stuff does it show?

I did it today and became dissappointed. Basically, once I pass 65mph, AFM goes away :(

How did you guys find this "Engineering Mode" by holding enter when you start the vehicle? Is it something that is called out in the owners manual?

That seems stupid! Why wouldn't they leave it activated for highway cruising??


I did it today and became dissappointed. Basically, once I pass 65mph, AFM goes away :(

I took that video on a side street just to demonstrate the lower speed stuff. I'll take a highway video tomorrow (depending on traffic). I've noticed depending on wind and incline it will go between 4 and 8 at highway speeds. If your real easy on the throttle you can keep it in 4 mode much longer. Cruise control helps too.

I did it today and became dissappointed. Basically, once I pass 65mph, AFM goes away :(

Now I find that rather disappointing as well.
That is basically what I observed
( without such a display )
in the 2005 Grand Prix GXP with 5.3L V8.

I had expected that in the G8 they could have managed 70 MPH at least.
And I had hoped for 75.

Oh, well . . .
- Ray
grumble, grumble, fuss, fuss . . .

Is the speed cutoff something that can be tuned?

thanks for sharing.

Nice, that's all good to know, I was wondering exactly what all that meant in the dash.

I've also never really heard the GT in normal driving situations, nice to hear that the car sounds like it shifts much like a manual does (as in, it doesn't snap into gears when cruising normally.)

I know my GTP likes to shift hard, but that may be due to my DHP PCM. :angel:

So far have only test driven the Base model G8, but what little taste of it I've had I have fallen in love with the car. Suffice to say, I'm no longer thinking about buying a GP GXP to trade in my car on, the G8 GT is going to be my next baby. I think I'm ready to go back to a black Pontiac.

Now I find that rather disappointing as well.
That is basically what I observed
( without such a display )
in the 2005 Grand Prix GXP with 5.3L V8.

I had expected that in the G8 they could have managed 70 MPH at least.
And I had hoped for 75.

Oh, well . . .
- Ray
grumble, grumble, fuss, fuss . . .


I totally agreee with you Ray. That is why I heard some people with Impala SS's with the 5.3 V8s had to "trick" the car into going into 4 cylinder mode.

Someone should put their car in Engineering Mode, and set the cruise at 80mph. Then, you should use the -1mph button a couple of times to bring the car cruise speed to like 76mph and see if the car goes from 8 cyl to 4 cyl. This is what the 5.3 Impala SS and GXP people had to do to get their cars into Active Fuel Management mode at high cruise control speeds.

:popcorn2:

Thanks Mike.

That works for me. Totally weird. Hopefully I can learn more about this on April 11th when I get my dyno tune and HPTuners software.

Video is not working.

YOU ROCK DUDE! I had to open it twice, but it worked. Did you guys try it in lower gears? Maybe the lack of torque/vacuum, does that.

My G8 will go into half active at 30 mph driving through town. I'll have to see what happens on the interstate today.

I totally agreee with you Ray. That is why I heard some people with Impala SS's with the 5.3 V8s had to "trick" the car into going into 4 cylinder mode.

Someone should put their car in Engineering Mode, and set the cruise at 80mph. Then, you should use the -1mph button a couple of times to bring the car cruise speed to like 76mph and see if the car goes from 8 cyl to 4 cyl. This is what the 5.3 Impala SS and GXP people had to do to get their cars into Active Fuel Management mode at high cruise control speeds.

:popcorn2:

The best mileage I ever received in my GP GXP was with cruise set between 80-85 for long distances. I think it's just something that really helps on the EPA cycle. Granted, I let my car idle too much with the remote start but my GP returns 15-16 mpg, mostly city driving.
:gears:

Yes,

it does take some work to get it in 4 mode above 65. Wind, the slightest hill, will kick it back into 8 mode. I noticed above 65 it would go back and forth quite a bit, however I wasn't able to hold it at any one speed very long... got to love Chicago driving. Another thing I noticed, if you leave the tranny in Sport mode it seems to always stay in 8 mode which is nice to know. More testing to come...

DOD is not determined by your speed. When the engine is under very little load it will activate, it is similar to DFCO on older GM vehicles. You can tune it to be more "aggressive" so it runs on 4 cylinders more often but most tuners just turn it off completely.

I spent some time today in Eng. mode. Mostly flat road with very small hills. Indiana for the most part is flat.
It will engage as low as 30 on a flat road. Driving 62 it stayed in half active most of the time. I had my cruise engaged as well. The slightest incline kicked it out, and as soon as I crested it went back into half active. Tractor trailers passing in the opposite direction caused enough wind to kick it out as well.
I tried 70 but wasn't able to maintain that speed long enough for a good test, however, as 69 it did go into half active.
I think that interstate speeds wind will be the deciding factor. Waiting for a tail wind.............

From the sounds of things, the GXP's mileage won't be as bad as some people think by not having AFM.

More horsepower pushing around just about the same weight as the GT should make it either the same mileage or just a little better.

More horsepower pushing around just about the same weight as the GT should make it either the same mileage or just a little better.

I'm basing my opinion on the pattern that owners are saying the AFM activates/deactivates. It's so sensitive to minor changes that it's almost no change from an engine w/o AFM.

I totally agreee with you Ray. That is why I heard some people with Impala SS's with the 5.3 V8s had to "trick" the car into going into 4 cylinder mode.

Someone should put their car in Engineering Mode, and set the cruise at 80mph. Then, you should use the -1mph button a couple of times to bring the car cruise speed to like 76mph and see if the car goes from 8 cyl to 4 cyl. This is what the 5.3 Impala SS and GXP people had to do to get their cars into Active Fuel Management mode at high cruise control speeds.

:popcorn2:

I tried this today. It did not engage even down to 70 mph where I gave up.

From the sounds of things, the GXP's mileage won't be as bad as some people think by not having AFM.

You are most likely right. We will probably see a difference in highway mileage in EPA testing (1 -2 mpg), but little difference in real world driving. The gearing on the GXP may have as much impact as the lack of DOD.

Chip

I tried this today. It did not engage even down to 70 mph where I gave up.

[[ sigh ]]
Thank you for playing...
- Ray
Hopes dashed....