Shrike6

I was present at the 2007 LeMans 24 hrs, and saw the #64 retire due to the vibration from the cylinder deactivation breaking a carbon fibre driveshaft. Now we find out that the C7 will have cylinder deactivation, and they had to use a steel torque tube to help with the vibration issue. Also, an extra flap was added to the exhaust system to improve the exhaust note when running on 4 cylinders. When you add all the extra weight and complexity needed to achieve a satisfactory NVH result, is this system really that necessary?
The engineers created an absolutely fantastic aluminum frame and saved 99 lbs there. They engineered lighter weight suspension components, and took weight out wherever they could. But, they increased the size of the car, and added weight back in ( some of which is due to the AFM ). To me, this represents a bad compromise.
We still wait for independent tests to show the results, but I can't help thinking Tadge could have done a bit better by not increasing the size, and by leaving out the cylinder deactivation and it's required weight penalty. What would have been the final curb weight without the increase in size and without all the AFM stuff?

Mike Mercury

I have two GM vehicles with DoD (displacement on demand; or cylinder deactivation).

With those; it's rarely in the deactivation mode. Around town driving - even when taking it easy - it never deactivates cylinders. The only time deactivation happens is on the interstate - driving a constant speed.

And certainly not at idle. If you get up to - say - 50mph, and let off the accelerator & coast down to zero; the deactivated clyinders are re-activated around 1800 rpm; long before your car would fully stop.

Unless the DoD on the C7 is a radical departure from all other GM products... it's not going to be an issue. Current GM vehicles with DoD have not added weight to accomidate the vibration - simply because the deactivated cylinders are re-activated just before the point the added vibration would occur.

Shrike6

For such a minimal use of the system, why have it at all?
We know that the system increases weight and complexity and also, the steel rather than aluminum torque tube, and whatever sound deadening, and the extra exhaust flap.
Is it really worth it?

mike100

Is it going to be available with both transmission types, or just the automatic?

Mike Mercury

ask this numb-nuts... and those that support his party:

Mike Mercury

we were told by the GM "person" that it will be on the manual as well as the auto. I remember him saying that because he said this was the first time it's ever been included on a manual shift GM car.

LawrenceFromTorrance

Why not let the buyer be able to deactivate the deactivate, how hard would that be? Then the driver would have the best of both worlds (except for added weight).

C6NRED

GM is quoting 18 city and 30 HWY for the C7......those are impressive numbers, and if the C6 is any example, 34+ may be possible in the right conditions....we'll have to see how much hay GM wants to make of that, but there is not another 190 mph+ car that can corner at 1+G and get that kind of MPG!

Mike Mercury

it's now "corporate" fuel economy. So it's now a different formulation - based on all products combined.

I can't imagine anyone associated with Corvette - sitting down and saying "lets force cylinder deactivation on everyone, even though we don't need to".

I dunno; doesn't make sense.

Thrill6

The formula has ALWAYS been "corporate". That's why it's called CAFE or Corporate Average Fuel Economy which has been around since 1975. The reason cylindar deactivation is being used on the Corvette is because it's now a pretty mature technology and it will ensure that the Corvette is not subject to the Gas Guzzler tax.

LawrenceFromTorrance

Actually your statement is just conjecture, with direct injection, less weight and extra gears I don't think the Corvette would be subject to gas guzzler penalties anymore than the C6 was. I don't know why they did it but I sure won't assume what I might think was actually the truth.

Sorry, that was a bit harsh but the point was it may not have been neccessary and they could have given the driver the option to turn it off.

VETTEMANN

Great question. And, common sense would suggest that 'minimal' is not true - or how else would there be such a large gain in fuel efficiency? If you're saving gas, then the system is shutting down cylinders (it's surely not due to weight savings )...

3rdchildhood

Had it on my 2010 camaro bad gas mileage my 2011 coupe is better with out it.....

fastyellowss

My wifes 2011 Camaro has cylinder deactivation, and as stated before, its rarely in this mode. I bought a Diablo tuner and shut off the cylinder deactivation.

Mike Mercury

we all know who is the most responsible for this type of craap today (well, those of us not caught-up in a cult truly know).

Unless GM has completely changed the way DoD has been implemented in the past; you won't even notice it's there.

LawrenceFromTorrance

Mike, I had a Chrysler 300 where the driver was not supposed to notice the deactivation and I certainly did, in fact it bugged the hell out of me.

BAREFOOT JOE

I'm pretty sure the reason AFM was put in the C7 was an engineering work around current and projected Government regs. Thank God what happened in 1969 is not happing now. Back then after 1969 to 1972 the cars just got slower - really slow. I think many are missing the point, the car has had to pork up to meet newer safety regs, get better milage, and meet stricker emissions. Dispite all this, she is projected to be faster. This is the world we live in. Thank God there is technology to keep us in our dream world.

Shrike6

What bugs me is the added complexity and weight associated with it.
Everything I have heard suggests that the system will not be operating very much, so not a significant savings for the average user.
Sounds very much like they decided to use it to juice the EPA numbers.

z06inVB

I only experienced it with my 2009 Challenger R/T auto. I hated the sound of it and it was just too invasive for me. ( Others say it isnt in all fairness ). I then bought a 2011 R/T Manula which diod not come with it. Exhaust note far better, drivability better and fuel MPG was 2 mpg combined driving better than the auto with the MDS.

I admit to being a little leary of the LT 1 until i can drive it myself.

Mike Mercury

Sorry to hear that. I've haven't owned a Chrysler product in the past 15 years; the last bein g way before they started doing DoD.

Lets hope this is a non-issue on the C7.