GM deactivates the same 4 cylinders every time.

 

E85 vehicles are a joke. I see Flex Fuel vehicles all over Atlanta, and there is not an E85 station in the state.

 

That must do wonders for engine wear.

And you would be wrong. I count 4 that are not private facilities. See here:
http://www.e85refueling.com/location...43339338fa6fb7

Aside from that oversight, FFV's are hardly a joke. It allows the driver more options when it comes to refueling their vehicle, at no added vehicle cost. Good deal if you ask me.

 

I guess they have finally added a few. last time I checked there were none. My opinion on E85 from what I have seen is maybe it gives you the option on where to fill up, but at what savings? All reports I have read say you get worse mileage with E85 than gasoline, and there is not much if any difference in price. To me it is pointless. The only person this would be a good deal for is farmers who get government subsidy's for growing crops that can be used for E85.

 

My '04 Sport Trac is flex fuel and I love it. It gets 19 mpg on gas and 15 mpg on E-85. The saving for ethanol will come in when gas is over $5.00 /gal. The only other thing that must be calculated along with the mileage is the fact that oil change intervals are every 3,000 miles instead of 5,000 and plugs need to be changed every 30,000. Right now it seams like the oil company's are raising the price of e-85 to get us used to paying it so there is less complaining later on. Back in 2002 E-85 by my house was still under a dollar even when gas was over $2.00. The BP refinery by my house bought up quit a bit of acreage around them to build an Ethanol plant. It is coming weather you like it or not. All I can say is my Torino will be fueled by E-85 and my Maverick is about as flex fuel as I can get it by using two different carbs. I also found out that the reason it is not pure ethanol is because then the "G" would not get the taxes out of it if it were consumed as drinking alcohol ,so they make it toxic by putting gas into it.When I move out of this crappy city I will be cooking up my own high octane fuel.

 

Please explain;

What exactly gets worn out faster (or slower???)

 

dodges mds does squat... we live in Louisana, dead flat sealevel, everything you could want for mileage and the new dodges are getting the same to worse... my dad has a hemi w/o the mds, and i've gotten up to 16.1 on the lieometer... i also drive the identical truck just a year newer w. the mds and get 12 at best. wait... one trucks red, and the others white. thats got to be the difference =)

 

Good Point. I'm no automotive engineer but I would think that as long as the crank turns so do the rods and pistons. The only thing I can think of wearing faster would be the valve train components that stay - on ,for the lack of a better word.

 

Well, that's my thought........and someone a while back explained that the Dodge MDS actually closes the valves on the cylinder being de-activated.

(which kinda fried my mind because I'm thinking that there's a lot of compression to overcome doing it that way... but the explanation was that during the down stroke there would be stored energy BECAUSE of that compression)

So again; what would wear out any faster????

If ANYTHING, the cylinders that are de-activated may have LONGER valve wear if they aren't working during de-activation.

 

Link to good description of GM's AFM
Definitely more moving parts to wear out than a fixed displacement design. But, with a 5 year/100,000 mile warranty, I guess GM is pretty confident in the durability.

 

First off, yes, I know GM refers to their MDS type system as DOD. I'll just use MDS to keep it simple.

The four cylinders that do the work when MDS is active are running at a higher load (twice the load) than they normally would have, while the other four are running under no load. The four that MDS uses will therefore wear out faster than the other four, and will wear out faster than they would have in 8 cylinder mode. Also, the other four will see extended service life.

What would get worn out? Crank, bearings, wrist pins, rings, pistons, and valvetrain parts of the four cylinders that MDS uses. Instead of evenly distributing the load over all 8 cylinders, MDS concentrates that load on 4.

I thought it would be pretty obvious.

 

Always afraid to debate with you..........negative rep points are sure to follow.

Still not obvious to me. The other 4 cylinders are still pumping, rings are still sealing, bearing surfaces are still seeing rotation.

Add into the equation the DOD is used only during extremely low power needs and I doubt you'll see any negligble increased wear.

 

I think uneven wear is just another one of those misconceptions/rumors that got started by someone.. sort of like ford owning cummins or diesels being able to idle forever.. etc.

I don't see how or why it would wear unevenly when the cylinder still sees compression with both valves closed. Even if it does, its not going to make any major difference in the life of the engine.

 

Whats all this talk about MDS? My truck wont even pull OD on flat ground at 70mph on all 8 cylinders

 

This could be true. But at those low loads, the 4 cylinders still active are doing the work that would have normally been done by all 8. Basically the 4 cylinders used for DOD do more work over the life of the engine than they would have in an engine without DOD and they therefore will wear out faster. Going along with this the other 4 cylinders that are not used in DOD will most likely see extended life over what they would have in a non-DOD engine.

How much this affects engine life is still up for debate.

The rep points were given because you refuse to understand and insist on arguing for the sake of arguing.