Copied this from what I sent to the LT1_Edit list:

With all this talk of gas prices it got me thinking. Why not turn my V8
into a V4? Now, I've been very happy with my car's performance, both on the
track and highway, but it did spark my curiosity.

I quickly altered my flash to shut off the injectors (every other in the
firing order), raised the idle a bit, and put the car into open loop (this
would never work with closed loop). Uploaded the new flash, and started the
car.

I'll be damned. It worked! I laughed at my idle for just a little bit,
backed the car out and pulled it back in. It seems like this would work
just fine. I didn't want to actually road test because I still run cats,
and this would destroy them in a hurry, especially with my cam. I'm almost
tempted to swap in the offroad pipes just to see how it drives.

Supposedly the injector balance tables don't affect WOT. If this is true
all 8 cylinders would come online when in PE. VTEC aint got nothing on
this, . I would imagine this could also be helpful for getting
"healthy" cars through emissions. Run cats, shut off 4 cylinders, and run
the car ever so slightly rich (too rich and you'll cook the cats, a wideband
would be helpful here).

I'm not sure what to think of any added wear this might add from lack of
fuel and different thermal distortion. DOD essentially does the same thing
(without actuating valves too) and this is coming standard on some cars.
Would be interesting to see how much this would help fuel economy.

Just thought I'd share my goofy experiment

 

seems kinda cool but dont u think u would get just about teh same gas mileage, i mean ur trying to push all that weight with half teh power?

 

unless it was constant stop and go it would probably work, once u get going it wouldnt be pushing that much.

 

You still have some frictional losses through the other cylinders but it should be more efficient.

The remaining four cylinders will operate under a higher load, making them more efficient. I wouldn't be surprised at all to see a 10% improvement. That would change my 30 mpg figure to 33 mpg. Not all that insignificant. Since it's also running in open loop I could lean it out more than stoich. at cruise as well

If I was really bored I would prove it, I'd rather get to tuning WOT though

 

Once, we pulled the inj bank 2 fuse on my friends LT1 Vette just for fun. We thought it would make a bit less than half the power it put down before. WRONG! It made 80 rwhp...
The cylinder wall fricitional loss is one thing, the major loss is coming from the other half of cylinders making compression.

 

I thought of this a long time ago for a bit but figured it wouldn't work very well, if the valves are still opening then you would have compression on the remaining cyclinders making the engine very inefficient, when the valves are closed they suck little to no air so there is nothing to compress, so that works okay but not here. The thing with air care I will try one day for my big cammed setup run in open loop with all 8 cylinders and get the o2's to read a constant 400mv no more (big cam extra air) then disconnect 2 cylinders and hope she doesn't stall LOL.

Also, if you pull bank 2 then obviously you'll make no power, you have to do every cylinder in the firing order, pulling one side I'm suprised it even fired and ran for long

The other thing I wanted to add, I guess on my car I can just mark the rocker nut set screw for easy no adjustment needed install, this is so that can after turning off say 2 cylinders remove the rocker set for it as well I can do this safely because I have an AFR hydra rev kit so the lifters will still ride the cam no problem, no hydra rev and you'll destroy things.

 

I am very interested in knowing how your car would drive on the street and if you get better gas milage. Are you planning on giving this a try?

 

very interesting. kool. Dont the newer style engines do this?

IMO. They should make modern 8 cyl cars with a performance button. press the button you get all 8 if you dont you use 4 . and to take care of the compression issues just use solonoids and oil pressure to make nessasary valve train adjustments. kinda like the oposite of a vtec.

 

New stuff cuts oil pressure to the lifters, but they remain pumped enough to not build cyl pressure.

If you just cut fuel, you still have compression without the power stroke. Not a great idea.

 

yeah what he said,....this is a neat idea, but the consequences are not. You have cylinders compressing nothing and getting nothing in return of the work they're doing. i would actually be willing to bet your fuel mileage would go down from doing this or maybe remain the same. Not to mention now you're just slinging these pistons around that are doing nothing, but im sure thats gotta change the balance of the engine while its running.

 

The trickiest thing would be to get the cylinder pressure to drop so it didnt compress. If there was a such thing as like a racheting pushrod kit or somthing that clicks a certain amount of times then releases on compression stroke every other cycle dono but i bet they could think of somthing. I dont think balance would be an issue because your not changeing the amount of reciprocating mass your just re-organizing when its used. And as far as gas milage i dont think it would even stress the motor not using them as long as they dont compress. you can turn your crank by hand with very little resistance with the engine off so i dont think with it running its gonna make much difference. All very good points to ponder. It would make some ricers hella mad if someone could get it to work. lol

Anyone know how the 300m does it?

 

how does DOD (displacement on demand) work ? isnt this the same scenario?

 

Read what I wote above....

DOD cuts oil pressure to lifters.

 

my bad

 

this is interesting.. how did cadillac do it on the 472s back in the late 70s? they ran a 4/6/8 scheme as a function of speed and transmission gear but i don't remember exactly what they were doing.

must prove that i'm an old fart