As many of you probably know, some GM trucks and cars have a feature that will run a v8 on four cylinders, for better fuel economy. This works because engines are most efficient at WOT, because of the increased manifold pressure. With four cylinders running, you have to run with the throttle wider open, thus making the engine more efficient.
Based off of this principle, I had an idea the other day. I have a 2005 F150 with the 5.4 3v. I tried disconnecting every other injector in the firing order (smoother) the other day, and it started right up, but was a little rough. I didn't actually try driving it, just idling and revving it for a minute or so in my driveway. Is disconnecting half of the injectors a crazy idea? Will it destroy my engine? Do the pumping losses from hauling around the other four cylinders make it not worth it? Any thoughts?

 

Yep you're nuts! Sorry just couldn't help myself. I'm not an expert here but I can't imagine what you're doing will result in anything good. JMHO.

 

Its my opinion that something special needed to be done with those other engines so they could do that without damage. My uncle had a Durango that did that and the mpg improvement was very minimal.
Its also my opinion that if this was a worthwhile technology ford would have already incorporated it into their engines.

 

I definitely would not recommend doing that even at idle.

The cylinder deactivation on GMs is mostly a gimmick in my experience.

 

Yep Crazy man, dont do it man! It could cause damage to you motor. Just have a light foot and easy on the take off and you can get better MPG.

 

The 5.4 is not going to get you decent mileage, period. You can get 1-2mpg better if you change your driving habits and keep your tire pressure up, but that's about it. And it may adversely affect your driving experience.

 

Yeah.. Its just not cutting the injectors off...

 

On the TV show Gearz the other week, they had a product that is supposed to do just that for you. You plug it into the vehicles computer and it will drop cylinders at highway speed. Anyone else hear of it, test it?

 

I drove a Silverado from Indiana to Florida with cylinder deactivation. The only time it cut cylinders on the highway was if the road was completely flat with minimal headwind. The smallest deviation from that would kick all 8 cylinders on. Ended up getting barely 16mpg. (single cab long bed, fully loaded).