For the first time in several years, the family and I headed up to Big Sur via California's fabled Highway 1. This sinuous stretch of two-lane blacktop hugs steep cliffs just before they plunge beneath the waves of the blue Pacific. Porschephiles and Ducati-warriors alike make pilgrimages to the place, as do legions of summer tourists in rent-a-car convertibles. So how did our present-laden 2007 Chevrolet Tahoe take to it?
Well, let's just say that for the first time, I drove slow enough to really enjoy the view...
We had plenty of time and plenty to look at, so as long as I stopped once in a while the passengers didn't mutiny. These Elephant seals, a mere 100 feet from the roadway, were 15 or 16 feet long and weighed 4 or 5,000 lbs - as much as, or more than the Tahoe! Still, after 90 miles of this, my semi-woozy passengers were glad to see the road straighten and head inland at Carmel.
I spent some time playing around with the instant fuel economy meter, which also shows whether the Tahoe's 5.3-liter V8 with Active Fuel Management is running as a V8 or as a V4. Some message board dwellers have complained that the AFM system only engages V4 during while going downhill or when coasting, but I was able to set the cruise control at 70mph and have it stay in V4 mode for miles at a time. If I didn't use cruise, the involuntary, miniscule, manual throttle tweaks I normally overlook are enough to prevent V4 from ever engaging on the same stretches. I'm going to play around with this a bit more in the coming days.
We finally figured out that the vague vibration my wife heard/felt from time to time is a calling card of said V4 mode. The engine note goes slightly but subtly off-song when half the cylinders take a siesta. As soon as V8 mode re-engages, things smooth out nicely. Its a very subtle thing, and once we figured out what the source was, it ceased to be a concern.
Day 2 tally: 218.5 miles, 13.4 gallons added at a cost of $34.92, 16.3 miles per gallon.
Dan Edmunds, Director of Vehicle Testing @ 4,232 miles
carlisimo says:
03:07 AM, 12/24/06
I bet this increases the number of people who think 4 cylinder cars have V4s.
hondacura4 says:
06:14 AM, 12/24/06
Cant be worse than the guy who had a 330i for sale and he said it had a "iniline V6" and he claimed to be a Bimmer enthusiast.
mrjones944 says:
10:09 AM, 12/24/06
Ducati has a nice v4 available. 1L and nearly 200hp and a sweet tune being belted out.
navigator89 says:
02:04 PM, 12/24/06
Great pictures. I liked the ones from your Commander trip as well.
Those seals are 4000-5000lbs???!!! Sure doesn't look like it from the pictures. Guess they're called elephant for a reason.
billt9 says:
04:32 PM, 12/24/06
My car has an inline boxer V4.
You can't beat it, it's the most hightech thing ever.
7driver says:
10:26 PM, 12/24/06
"...but I was able to set the cruise control at 70mph and have [Active Fuel Management] stay in V4 mode for miles at a time. If I didn't use cruise, the involuntary, miniscule, manual throttle tweaks I normally overlook are enough to prevent V4 from ever engaging on the same stretches."
You think perhaps the programmers on GM's powertrain team used the cruise-control state as an input to the AFM algorithm? If cruise is engaged, the likelihood of a large change in throttle position goes down. Also, maybe cruise is able to see changes in speed faster than a driver can and therefore respond with small inputs from the computer vs. large ones from a human?
Just thinking aloud...
actualsize says:
09:53 AM, 12/25/06
That's exactly what I was thinking, and was the reason why I'm going to keep playing with it throughout the trip.
crashtestdingo says:
12:30 AM, 12/26/06
Aren't the four cylinders that get deactivated all in the same bank, so it would be an I4, not a V4?
jerrywimer says:
09:35 AM, 12/26/06
Nope. It's a V4- 2 in each bank get deactivated.
actualsize says:
09:42 AM, 12/26/06
Not if the owner's manual and dashboard indicator are to be believed. They both use the V4 designation. Which 4, and whether or not the same 4 cylinders are always used, I do not know.
crashtestdingo says:
08:32 PM, 12/26/06
Ah, O.K. Thanks. Maybe I was thinking of Chrysler's system. Or maybe that was something I pulled out of my ass. >_<
bobberino says:
08:36 AM, 12/30/06
Anybody have concerns about long term durability/reliability of these
A.F.M. engines??? When towing, would the vehicle ever use only 4 cylinders?
actualsize says:
06:45 PM, 12/30/06
During our tow test, V4 mode did occur, but only when coasting. With a trailer hanging off the back, there isn't enough power for V4 mode to maintain speed on level ground. And tow / haul mode selection doesn't shut it down.
I'm not sure if the system always uses the same four cylinders. It could alternate so that all eight get equal wear. I'll find out.