: Does Northstar turn off cylinders like 4-6-8?



LuborK
01-08-04, 07:20 AM
This is what I read on ebay:
Yes, the car has 8 cylinder motor, but that doesn't mean that it is a gas guzzler! When the car shifts into overdrive it shuts down 2 cylinders - this is why this car is so reliable and gets 28MPG on the highway! GM introduced this when they came out with the North Star engines, real sweet!

I never heard about it and I don't belive it is true. You can find it at http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=6151&item=2451726760

What do you say about that? Is it lie or not?

maydog
01-08-04, 08:27 AM
That guy has been pulling that crap for a while. I think the same car was for sale a few months ago. I've the northstar does not have DOD and does not have 330 horses. You have to be very careful when buying from Ebay - there are just too many people giving misinformation, sometimes mistakenly but in this case intentionally.

LuborK
01-08-04, 10:54 AM
Thanks for info, I do not plan to buy Caddy in the U.S. because it is almost unable to get license and plate for used U.S. vehicle here. I was just curious what you could buy right now :-)

El Dobro
01-08-04, 07:53 PM
In a way, the Northstar does shut down cylinders, but not like the 8-6-4. If the Northstar engine starts overheating,it'll shut down combustion in 4 cylinders at a time to pump air to cool the motor when it goes into the limp home mode. It's not for fuel savings by any stretch of the imagination.

cadillac6
01-08-04, 11:38 PM
I only get about 20 on my N*. I dont know where this 28 MPG came from. Especially on the highway, lol. They are good motors. Some people love them and some people hate them.

LuborK
01-09-04, 02:53 AM
In a way, the Northstar does shut down cylinders, but not like the 8-6-4. If the Northstar engine starts overheating,it'll shut down combustion in 4 cylinders at a time to pump air to cool the motor when it goes into the limp home mode. It's not for fuel savings by any stretch of the imagination.
Yes, I know about this feature. My friend with STS once experienced "limp me home".

elwesso
01-09-04, 05:11 PM
I wonder if there would be any way to put the car into 4cy mode (It just turns off those injecotrs) during cruising.... That woudl be golden....

airbalancer
01-09-04, 05:33 PM
GMC is suppose have this feature in a year on their trucks

JimD
01-09-04, 06:25 PM
The Displacement on Demand (DOD) system is coming to all GM V8 powerplants. Mercedes has a similar system on the road now in some V12 vehicles. Car makers live in a CAFE driven world; small gains in fuel economy times large numbers of vehicles is the target for GM.

GM's DOD application will manipulate fuel and spark control to provide 8 cylinders when appropriate and 4 cylinders when that is appropriate. But not 6 cylinders this time (balance problems).

Way off topic from the original V8-6-4 question; just a little peek into the near future.

Playdrv4me
01-09-04, 08:20 PM
The Displacement on Demand (DOD) system is coming to all GM V8 powerplants. Mercedes has a similar system on the road now in some V12 vehicles. Car makers live in a CAFE driven world; small gains in fuel economy times large numbers of vehicles is the target for GM.

GM's DOD application will manipulate fuel and spark control to provide 8 cylinders when appropriate and 4 cylinders when that is appropriate. But not 6 cylinders this time (balance problems).

Way off topic from the original V8-6-4 question; just a little peek into the near future.

Hopefully the damn car-makers get it right for once. Almost every attempt before proved to end in failure or not make it off the drawing board. The 2005 Grand Cherokee will receive the 5.7 Liter Hemi WITH Cylinder Deactivation, Displace on Demand, whatever you want to call it, Detroit is re-visiting this one heavily with the increased emmisions standards. Think about it, this will allow them to once again build monstrous engines, and maintain compliance by providing that power only when necessary.

Heres a cool article from Popular Science describing the methodology of the V-8-6-4. http://www.sfu.ca/~ajgee/mags/864.html

Thanks to member RALPH for posting these.

El Dobro
01-09-04, 09:08 PM
Cadillac even has DOD on the Cien and the Sixteen, two cars I must have.

Ed_B
01-11-04, 02:01 PM
I only get about 20 on my N*. I dont know where this 28 MPG came from. Especially on the highway, lol. They are good motors. Some people love them and some people hate them.

I get 24 MPG from my '99 Eldorado with N* engine and that is a mix of maybe 70% freeway and 30% town driving. Can't say what my freeway-only mileage is but it would have to be 26-28 MPG to get the 24 MPG average. Same thing for the in-town driving. I am guessing that I am getting around 18-20 MPG there. In any case, this is about 8-10 MPG better than I thought I would get from this car, so I am very pleased with its fuel efficiency. Add to this that this car is no slouch in the accel department and that I am not shy about using it when entering the freeway or passing other cars. :)

BeelzeBob
01-12-04, 09:41 PM
The Displacement on Demand (DOD) system is coming to all GM V8 powerplants. Mercedes has a similar system on the road now in some V12 vehicles. Car makers live in a CAFE driven world; small gains in fuel economy times large numbers of vehicles is the target for GM.

GM's DOD application will manipulate fuel and spark control to provide 8 cylinders when appropriate and 4 cylinders when that is appropriate. But not 6 cylinders this time (balance problems).

Way off topic from the original V8-6-4 question; just a little peek into the near future.

Actually the V-8-6-4 and the upcoming DOD operate exactly the same....

In order for the sytem to provide efficiency gains by reducing the pumping losses of the engine the intake and exhaust valves must be stopped in the closed position. That way the cylinder becomes a sort of gas spring. All the energy that goes into compressing the residual in the cyilnder is returned to the piston by pushing it back down. Cylinders are deactivated by closing the valves and leaving them closed. The difference between V-8-6-4 and DOD is the means for closing the valves and leaving them closed. In the older Cadillac V-8-6-4 sytem the rocker arm pivots were disconnected and the rocker arm pivoted against a soft spring ...not moving the valve in the process. The DOD deactivates the lifter at the camshft. The lifter still moves up and down on the lobe but is disconnected internally via a pin driven by oil pressure controlled by a solenoid commmanded by the PCM.

When the cylinder is deactivate the spark still happens like normal. The fuel is deactivated by simply turning off the injector.

Just turning off the fuel or spark will not effect DOD or V-8-6-4. If the valves are still left to open and closed there will be tremendous pumping losses and efficiency will suffer accordingly.

The limp home mode that the Northstar uses to protect itself when overheated operates by simply turning off the fuel at the injector. The cylinder still pumps air as the valve actuation is inaffected. That is how it provides supplemental cooling when overheating...by pumping air thru the cylinder and internally cooling.