Cylinder deactivation systems

SanteeRuss · #1 (**permalink**) 01-24-2008, 05:29 PM

Any reason why Toyota doesn't use this system?? According to a website I just read, only one Japanese manufacturer uses it (Honda). I rode in a 2007 Sierra last week & we cruised along at 70. 4 of the 8 cylinders were shut down and the cpu said the current mpg was 21.1 This was on a flat freeway. Just wondering..

Thanks!

Badfish · #2 (**permalink**) 01-24-2008, 05:40 PM

I had an 07 Tahoe with the Flexfuel 5.3L, put 16,xxx on it and averaged just over 18 mpg. I now have 10,xxx on my 5.7L and am averaging 14.4. Sure would be nice if the 5.7L could do the same as the 5.3L.

LeeinAZ · #3 (**permalink**) 01-24-2008, 05:50 PM

That's the main reason I didn't buy another Silverado...I didn't want their Active Fuel Management system. It might work on lighter weight vehicles, but in a truck with any kind of load it's always hitting on 8 anyway. Do some research on Google and Yahoo and read the reviews about that system in trucks.

I have a 2wd DC, 5.7, with 18k miles and I always get between 17.8 and 18.5 mpg calculated...freeway driving and using 87 octane. Luv my Tundra!

Brent87LT1 · #4 (**permalink**) 01-24-2008, 05:57 PM

My '07 Avalanche w/ AFM avg 15.7 city/hwy. This thing wouldn't pull squat (over 7,000 lbs)

My Tundra avg 14.7 city/hwy & towing. It pulls great.

brow · #5 (**permalink**) 01-24-2008, 06:18 PM

I have the cylinder cutout system in my '07 Odyssey. If I am cruising on a flat hwy at about 60MPH, system works great. Any hills, forget it, back to 6cyl. If I am going faster, ie up to 70MPH the system goes back and forth between 3 & 6 cyl. Anything over 70MPH, the eco mode does not stay on much. For mileage, I am around 21MPG. Apparently the normal 3.5L gets around 19-20MPG in real life driving. So is it worth it...??

FWIW, I have a buddy with a Hemi equipped with this and it does not get very good mileage

DanielAcosta · #6 (**permalink**) 01-24-2008, 06:40 PM

From a thermodynamics standpoint, it takes the same amount of energy to propel the vehicle, regardless of how many cylinders are being used to generate the thrust. There comes a point where you do gain efficiency using a certain number of cyclinders for a given load, so there could be some merit to cylinder deactivation.

When I test drove 07 Silverados and Tundras, the instantaneous and average mileage readouts were comparable. The Chevy was higher in V4 mode, but lower in V8 mode. The window to operate in V4 mode was small. Thus I could achieve higher average economy in the Tundra by cruising with light throttle on 8 cylinders than the Silverado cycling between 4 and 8 cylinders.

Industry tests bear this out. Every report I have read on full size trucks gives the highest mileage to the Tundra, even though it has the most power. The 5.7 even has better ratings than Toyota's own 4.7.

Similarly, every test I have read gives lower mileage to the 08 Accord with cylinder deactivation than the Camry, even though they both are rated at 268hp and the Camry is quicker in acceleration.

I personally increased my 5.7 4x4 city mileage from 14 to 17 by doing the battery disconnect reset trick. I still can hardly believe the results, and wish I had tried this 20K miles ago. Cruising at 90 still only returns 13mpg, but if I keep it below 70 or at most 75, I get high teens on the highway too. The battery disconnect reset seems to have had more benefit around town than on the highway.

DanielAcosta · #7 (**permalink**) 01-24-2008, 06:44 PM

Quote:

Originally Posted by brow

I have the cylinder cutout system in my '07 Odyssey. If I am cruising on a flat hwy at about 60MPH, system works great. Any hills, forget it, back to 6cyl. If I am going faster, ie up to 70MPH the system goes back and forth between 3 & 6 cyl. Anything over 70MPH, the eco mode does not stay on much. For mileage, I am around 21MPG. Apparently the normal 3.5L gets around 19-20MPG in real life driving. So is it worth it...??

FWIW, I have a buddy with a Hemi equipped with this and it does not get very good mileage

My 05 Odyssey gets the same mileage (21) cruising at 85 with 6 cylinders as it does at 80 on 3 cyclinders. Still, it's fun trying to keep the ECO light on, but the actual benefit seems slight on the highway. Around town, though, I get 20, whereas my older 02 Odyssey without deactivation only got 18 in town. Odd thing is the old Odyssey actually did better (23) on the highway cruising at the same speeds.

brow · #8 (**permalink**) 01-24-2008, 08:02 PM

Since I've had this van I wished they had made the system only cut out 2 cylinders vs 3. I bet in 4 banger mode the van could probably perform better and get better mileage.

DanielAcosta · #9 (**permalink**) 01-24-2008, 08:06 PM

Quote:

Originally Posted by brow

Since I've had this van I wished they had made the system only cut out 2 cylinders vs 3. I bet in 4 banger mode the van could probably perform better and get better mileage.

That's exactly what the 08 Honda does: 6, 4, or 3 cylinders. They claim a 10% mpg increase over the old system, but the 08 Accord still gets less mileage than the Camry.

tundrahq · #10 (**permalink**) 09-10-2008, 03:30 PM

I was just doing a little research on this and I found a post on Toyota's Open Road blog that answers this question fairly definitively:

"Use of VVT-i basically trumps cylinder deactivation. Cylinder deactivation, of course, is a way to burn less fuel by allowing a V8 engine, for instance, to run on as few as four cylinders. But cylinder deactivation works best on unladen vehicle driven at small throttle openings. If you add a load or if you accelerate, the engine has to work harder, so it picks up cylinders again and becomes a full V8. The benefits of the technology disappear. Indeed, testing has shown that it’s hard to keep these engines in cylinder-deactivation mode. If you accelerate or add a load, they go to full V8 mode, and you lose the benefits of the system."

Read the full post at: TOYOTA OPEN ROAD BLOG: VVT-i: It's All a Matter of Timing

I'm glad to hear that this is off the table - it never made much sense to me in a truck. Maybe in a highway cruiser (like a big Caddy or the Avalon or something)...

shawn_speed · #11 (**permalink**) 09-10-2008, 04:45 PM

What nobody has mentioned or I missed: 6 speed transmission. It is a lot easier to get the same effect by the 6th gear being an overdrive of .6 or so ratio.

6 speed was the main reason I switched to Toyota from Ford. The monster V8's growl and hi tech didn't hurt either.

Shawn

Burger Steak & Eggs · #12 (**permalink**) 09-10-2008, 06:25 PM

Quote:

Originally Posted by tundrahq

I'm glad to hear that this is off the table - it never made much sense to me in a truck.

Totally agree. In both magazine tests and EPA numbers, there is nothing earth shattering about cylinder deactivation. This can be rationalized by physics etc, but the bottom line is in the results. I simply don't see revolutionary fuel efficiencies in vehicles like 300C or Grand Prix GTP with MDS compared to, say, a Corvette. It sounds to me like OEMs would be better off concentrating on minimizing weight, optimal aerodynamics, general engine technology to get these numbers up instead.

jarheadfor4 · #13 (**permalink**) 09-10-2008, 06:55 PM

Have you felt the delay in the Chevy trucks? When I push the throttle down, I want the truck to move.

I have an 07 DC 4x4 and I get 16.5 mpg. I don't drive like my grandmother either. I push 80 on the interstate and enjoy the truck around town too.

Chevy trucks and Dodge trucks just don't impress me with the deactivation mode. I think they are wasting their time.

stevencrosbie · #14 (**permalink**) 09-10-2008, 08:14 PM

The 08 3.5L Accords are not getting the mileage of the old 3.0 even with the new VCM system of the 6, 4, 3 cylinder choices.

I average between 18-20 in the Tundra in the commute. I probably attest that to the 2wd choice I made.

The cylinder deactivation is a lot of hype in my opinion. The guys on the Honda forum are not averaging numbers close to the 7th generation, but I attest that more the extra weight Honda added to the 8th generation.

As stated above, almost all long term tests show the Tundra toping the charts for mileage over all of the "better" choices.

OTR · #15 (**permalink**) 09-10-2008, 09:27 PM

I can avg 20-21mpg at a boring speed of 65-70mph on a level hwy all day long (without a heavy headwind). I've spoken to several new GM owners and they can only dream of those figures in the real world. All of them have stated an avg. 18mpg at the same speed. I think the Tundra has a lot going for it with the combination of the vvt-i and 6-spd and with the added HP of the 5.7L. I used to have a Dodge Dakota with a 318-V8 and I could avg. 23mpg on the hwy with a CAI, exaust, and Mopar chip. The motor would just lug around 1700 rpm at around 65mph and never kicked out of overdrive. Too bad the engine was the only good thing about that truck, you needed a runway to come to a stop.