Well, you may be interested in knowing that I recently put a Tahoe Two-Mode through it's paces. I used the same route that I use when I take the FEH out with a journalist to show them what hybrids are capable of and my driving techniques on a route that's ~20 miles city and ~20 miles hwy. During the summer with the FEH, I generally average around 40 MPG with my AWD FEH, which suitably impresses them.

Personally, when I tested BAS a few years back, I thought it was a bad joke. It seemed extremely primitive, had the eco-lame which seemed to give you both little feedback and little improvement over a gas chugger, to which I was quite disapointed.

Anway, taking a behemoth like that, with EPA numbers at 20 MPG, I wasn't expecting too much, However I was surprised and impressed with it's Fuel Economy, especially on a drizzling cool day. I spent well over 98% of the drive in V4 mode, and averaged around 30 MPG with it. It was surprisingly smooth and easy to drive, though it did have some hybrid specific drawbacks that I would've liked changed. The big issue was that I was unable to get the ICE to pop off at any speed above 20 miles per hour (compared to the 40 miles per hour that the Prius and FEH have), and there's no SOC display within the battery display on the power screen (To give a rough idea of the SOC of the HV Battery). There was also a weird "You're doing okay" gauge that would've been better off used by a Charge/Assist style meter, but really those are small potatoes. Two mode seems to work, and work well for delivering fuel economy for those who need a large SUV. It was smooth, transitioned well, and didn't feel much like being in a gas guzzler or a tank.

Personally, I look forward to testing out the new Two-mode Saturn Vue.

I'm not going to get into the "Does this car company care about the environment" arguement, because frankly, I think they're all in the business of selling cars, by any means necessary.

First 4WD Hypermiler

Have you read the FEH FAQ?

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Hi,

If you are under an embargo or planning to sell your review as an article, I would fully understand. I've got a lot of questions.

Good enough, considering the marketing plan and limited initial production. At $50k+ and only 10,000 units, it shares more in common with the Lexus 600h as for as being available to ordinary folks in Huntsville AL.

Were you able to compare your route distance to the vehicle reported trip meter? In a perfect world, you'd have a '5th wheel' but that is a little more involved.

Were you able to inspect the tires for 'current inflation', max cold pressure and tread pattern (aka., knobby versus highway touring?) One of the things I've found with my Prius is the tires are very important and especially the toe alignment. Camber can be off a bit but any excessive toe eats the tires and burns fuel.

How did it track down the road? Do you have any sections where there is a definite crown or drain angle that requires steering correction in a normal vehicle? Did you feel and road 'feedback?' My Prius steering feels numb compared to other cars we've had.

You are giving it more credit than I could.

Estimated temperature? Normal environmental control operation and heating?

Excellent.

Is there a tachometer? Does your test route include any hills or grades long enough to get a sense of ascending and descending performance?

As a suggestion, if you have access to a hill with a significant grade, ~6%, and altitude, ~500 ft., descending the hill would provide a gravity gradient to investigate engine-off ranges. Entering the downgrade at a small speed, say 15 miles per hour, you can either let gravity and/or a light foot try to keep the ICE off for the maximum period of time.

One of the things that I find most maddening is the 'built-in drag' of the Prius transmission. Does the Tahoe have the same foot-off the accelerator, vehicle deceleration drag? Worse, a truly useful 'idiot light' that would indicate when you are exceeding the regenerative braking and are now into mechanical braking is probably missing, as it is on every other hybrid.

Car companies seem quite content to keep us ignorant of the engineering units of what the cars we bought are actually achieving . . . even when the data is available.

It says to the customer, 'You are bright enough to buy an advanced, $50k car and in our appreciation, here is your idiot light.' I can imagine how much engineering talent was wasted on that 'gauge' instead of something to indicate, "mechanical" versus "regenerative" braking.

One of the most difficult problems is the transition from regenerative to mechanical brake at speeds of 5->0 miles per hour. Did you feel or hear anything?

I too hope this will show up in a timely fashion and be sold to ordinary folks. For now, the Tahoe hybrid appears to be marketed more like a Lexus hybrid than something being sold to small businesses and ordinary folks. Maybe in six months they'll rethink the plan.

LATE QUESTIONS:
1) If you are on a level surface and let off on the brake, does it creep up to some speed?
2) If you are on a level surface at say 20 miles per hour, can you put it in "N" and achieve a close to zero transmission drag?
3) Will the transmission hold the vehicle stationary on an up-grade at a stop?

GENERAL QUESTION:
1) Is there a government 'standard' or some standard that requires automatic transmissions to act like they all have torque converter 'creep?'

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

Well, since I was the co-pilot on Pravus Prime's 2-Mode drive, I'll go ahead and add a few things. I'll answer a couple of Bob's questions, but I'll leave the bulk of them for Pravus Prime, since it is his perspective as a 3rd party that is more important.

First, I provided the vehicle for Pravus Prime's test drive (surprise, surprise). When I picked up the vehicle, I reset the Avg. Fuel Economy display so that it would only give the results of my time with the vehicle from Friday through Monday. When I handed Pravus the keys, I had achieved an 18.9 mpg average.

We went on the route that Pravus described. When we returned to the starting point 40 miles later, he had improved the average up to 19.3 mpg. I would describe his driving style on the route as "actively applied common sense". We did not disrupt the flow of traffic, we did not get any horn honks, scowls, or one-finger salutes.

As Pravus reported, we were only able to get EV up to about 18 miles per hour and engine off on decel occurred religiously at 20 miles per hour. After the test drive I spent a little time trying to figure out why we could not get EV up to 28 miles per hour as advertised . I discovered that we drove the whole time with the transfer case engaged. The AWD was set to AUTO. I turned the switch to 2WD and I was immediately able to drive EV up to EXACTLY 28 miles per hour. Engine off on decel happened at EXACTLY 30 miles per hour every time. Between that, and using some of the driving tips I picked up from Pravus, I was able to achieve 19.8 mpg avg by the time I turned the vehicle in. That's compared to a sticker rating of 20 / 20.


Bob,

There is a tach. There is also a tire pressure monitoring system that reads out in the same display area as the AVG ECONOMY reading. The inflation status of the tires during the drive was: FL: 35 PSI All others: 36 PSI.

The HVAC system was engaged in AUTO mode, with driver temp set at 71F and passenger temp set at 74F. The HVAC is designed to work in engine off mode.

I'll let Pravus answer the remaining questions, since they relate to his driving experience and not the physical content of the vehicle.

Peace,

Martin

I am NOT the official voice of GM with respect to Hybrid issues

I am NOT the official voice of GM with respect to Hybrid issues

I am NOT the official voice of GM with respect to Hybrid issues

It handles very smoothly, and while you could feel the road, I suppose you could say there was a slight sense of numbness compared to my FEH, but really, it wasn't like you were detached either.

LOL, true enough. It was almost a toss up when I drove it over which was more disapointing, BAS itself, or the guy who was presenting it.

Around 40 degrees as I recall, with a slight drizzle the entire time.

Indeed, I was surprised how fast cylinder deactivation took place. It was literally, EV up, Hybrid mode in V8 to speed, then bam, right into V4. Then, after I got a bit more used to it, EV up, Hybrid mode V8 to near speed, into V4, then continue to accelerate up to speed for the last few miles per hour.

Oh yes, there's a nice big tachometer with a seperate off and Autostop area, to which I used my (highly practiced on the FEH) tach control and figured out the V8 to V4 within that and started exploiting it mercilessly.

It does, at higher speeds shift back into V8 mode to help with hills faster than I would've liked for FE purposes, but for everyone else, they'd probably never notice, and it does shift into V4 mode quickly, for me, just before the crest of any hill, I'd be back into V4 mode.



LOL, that's one of the things I love about the Drive Mode of the FEH, no auto drag. Anyway, no, like the FEH, it doesn't try to regen the moment you're not maintaining or accelerating, so you can get some nice coasts out of it. Unfortunately, the Hybrid Power Flow screen is lower then I would've liked, so I wasn't able to pay too much attention to it and the road and my MPG; the caveat of being in a new vehicle that you're not used to.

True enough, I was actually shocked that they'd have such a nice power screen, but not SOC on the battery, it seems like such a standard part of the display.

It really is the stupidist gauge. I always had it in the middle, which after looking in the manual means that you're optimizing the hybrid technology. When it shifts to the left, it means you're going heavy on the electric system, when it moves to the right, it means you're going heavy on the ICE.

The brakes were touchy at low speeds, but after about three stops, I had them figured out, and was just easier on them then I was with the FEH, and after a few miles, it seemed rather natural, no jerkiness or anything after that, and no difficulties in making it "not jerky" either, it was entirely a matter of adjusting to the Tahoe's brakes.

Martinjlm would be the better one to ask, as I didn't really get that much time to play with it.

First 4WD Hypermiler

Have you read the FEH FAQ?

Live in Michigan? Let it be known in Michigan Roll Call

Read My Automotive Blog at Rich Rambles