MLL

I have a 2007 Suburban.
Does anyone know if the AFM is operational during "towing mode?"

Thanks,
Mary Lou
http://www.home-matters.com/

73shark

It is on my 2007 Tahoe. In fact in city driving, it will go into V4 on slight grades in "Tow mode". Tow mode at lower speeds kicks it out of OD and raises rpm. Even with the higher rpm, I found the mpg is higher than when not in tow mode and in V8 mode. Have run the same stretch multiple times both ways.

MLL

Thanks Shark. I'm sure that the powertrain in my Suburban is like the one in your vehicle. I haven't towed my camper trailer with my new Suburban yet but its good to know that the AFM will still work in tow mode. It appears that the tow mode reduces the amount of transmission Overdrive and torque converter lock-up. The resulting higher RPM should work to increase the intake manifold vacuum and therefore allow more Active Fuel Managment (cylinder deactivation) action. I'm expecting relatively good fuel consumption while towing.

Thanks again,
Mary Lou
http://www.home-matters.com/

tahoe07

It'll consume real good while towing.

Love to hear your regular MPG and your towing MPG results. Let us know how you make out.

engine2

I have always been told that you can ruin your tranny if you tow in overdrive. So I am guessing its best to get a few miles less per gallon than to damge the tranny. maybe someone can shed some light.

MLL

engine2,
I have heard that too. When I towed with my 2004 TrailblazerI left it drive as the owners manual stated. I was unsure but I did what the book said. I think that this caused too much slip at the torque converter clutch. I think that the control system monitors the difference between the engine speed and the converter turbine speed to calculate slip. Its strange but I think that this slip may have caused my cruise control to stop working temporarily while towing.The last time that this happened I had to take it to the dealer to get the codes reset. The Trailblazer had a line 6.

Now as far as fuel consumption, it seems that with the 2007 Suburban there are two ways to reduce the engine pumping work (decrease intake manifold vacuum) at a given vehicle speed: slow down the engine speed with overdriveand torque converter clutch or choose a lowergear (higher engine speed) and let the AFM do its job on the intake vacuum. In the sameway, someone told me thatyou can getalmost the same fuel economy with a higher numerical final drive ratio if you have AFM. Same story, the engine thinks that its more lightly loaded andit goes into four-cylinder mode more often. It may be an urban myth but it makes a good story. Anyway, I just love love LOVE my new Suburban.

Thanks for listening to my rambling.
Mary Lou
www.Home-Matters.com