Its been real hard staying in EV Mode when leaving a light.
I have to barely touch the pedal for it to accelerate. But then the cars behind get impatient.

If no one is behind me, its takes forever to get to 25 mph

Is anyone having this issue?

 

I've always had that problem. It does seem to vary every once in a while but no good indication why (sometimes I can accelerate at a decent clip on level road). I've always gotten 15-16 mpg doing just city driving, thought it was because I always have the AC going and our roads in Honolulu are rarely flat. If I do some freeway driving I can get it up to 19 mpg or so. My mpg's aren't what I was hoping for but I'm still very satisfied with the truck.

 

I have the same problem too. When leaving a light my Yukon goes to about 10 MPH in AutoStop and the engine starts.

What I have been doing lately is accelerating to about 30MPH and the letting go of the gas. After a few seconds and a couple couple of MPH less (25 to 27 MPH) it goes into AutoStop. Then I can keep going for a half mile to mile before the engine will start again, but have to keep it under 30MPH.

One thing I noticed with the engine is that it always revs up to about 1,500 RPM right before it goes to EV mode.

APM

 

Good I thought I was having an issue.

If the roads were flat, I know I can get great gas mileage. Because cruising anywhere up to 65 mph, Instant MPG show 25-35 MPG.

I have been wondering which that would be better. Accelerating to cruising speed quickly. Then get into V4 mode. Or Accelerating slowly.

 

My guess would be to get to 65 quicker (within reason of course). If you watch the instantaneous mpg, even mild acceleration takes you down to less than 10 mpg. The longer you're in that range the worse your overall mpg will be. I think the main reason for the horrible ICE mpg at low speeds is the 6.0L engine, versus say the 5.3 that's in regular gas Tahoes.

 

So the revving up to 1500rpm before going into autostop is the transmission downshifting. Yes, it seems that at about 10mph, you have to back off of the throttle slightly to keep from ICE start, but what is weird is that about 12mph, the thing starts accelerating harder without pressing harder on the gas, so I try to not let it pull too hard.
Yes, I agree, you can't have people behind you. I test drove a Ford hybrid the other day at the Ford Design Center in Irvine. The West Coast Sales Manager was in the back seat and he was very impressed with my ability to get good mileage out of it, so he egged me on to see how fast I could go from a stoplight without switching to ICE mode (the gauges in there help to do this). Well, there were some really irritated drivers behind me as I was passed by a school bus...
Our Tahoes are much, much faster in pure EV mode.

 

Curious you all regard this as a "problem". Clearly the vehicle is working as designed. Hybrids were such as the Tahoe and Yukon were never designed to be electric vehicles. EV mode is actually horribly inefficient beyond a certain point.

Think about these 2 power paths:

non-EV: engine-wheels done! Very efficient!

EV mode: engine-generator-charge battery-drain battery-motor-wheels... Very inefficient!

Sure you get a small amount of EV mode for "free" from regeneration but any extra EV mode beyond that is very inefficient, mostly due to the inefficiencies of charging and discharging the battery.

 

I do since they state the vehicle is capable of doing EV mode up to 30 mph.

 

As an experiment, I tried to stay in EV mode while pulling away from lights -- it is definitely not something that can be done without making the drivers behind you very impatient.

 

I thought about this while I was driving back from Ikea over the weekend. I tried to see what is happening around 12mph that causes it to start the ICE. It seems there is an upshift type event in the transmission that you can feel if you don't let it start the ICE (easy on the throttle) and maybe this pushes it over the edge. Like I said, if you feather around 10mph, you can make it through this shift and it will accelerate with more gusto just after. Now, since I still have not done my homework to understand where it shifts through its four gears and where it works as a continuously variable trans, I cannot state that there is actually a shift going on, but there is some kind of "event" happening in the driveline.
I am starting to get habitual about the feathering, but I think they should fix this (add this feature) in software.

We need a GM hybrid drivetrain engineer on this forum!