has anyone tryed to run motors on less cylinders on the highway

[kamesama980]

Originally Posted by VetteOwner

all i know was when my 4 banger truck's coil pack would get morning dew dripped on it it would wipe out 2 of the cilynders (one coil pack controls 2 plugs)

funny it only did it when you were eavy on the throttle (pulling out into a 4 lane highway) it would idle fine but it would not accelerate at all on 2 cyl.

that also brings into account different conditions for spark in the combustion chamber. at idle there isn't much 'stuff' in the cylinder and it has the most dwell time to charge the coil (not that it's needed) wheras hard acceleration brings much more air and fuel into the cylinder (hard to jump the gap) and higher rpm brings much shorter dwell time. that's why marginal ignition parts are usually missing when they're needed most and present when they aren't

[spl_nut]

Our 06 Odyssey does it... The challenge is not as simple as disabling a cylinder, or cylinders.

Any block / head assembly is designed to operate within a fairly uniform temperature parameter - Run two of four cylinders (if it it'll run at all) and experience failure due to uneven expansion. Engines that run on fewer than all cylinders (in econo mode) do so by alternating what cylinders are firing, and what are dormant - Evenly distributing heat (expansion).

Secondly, every combustion engine (regardless of the number of cylinders) fires each cylinder to maximize force (or apply force as efficiently as possible) on the crank shaft.

Take any cylinder out of the loop (without management) and it's very likely the system will be less efficient.

.02

[VetteOwner]

yea didnt think about the cold spots in a cylinder head, brings another good point.

lol i do know back in the early 80's my mom had an old LTD that ran on 7 of 8 cylinders cuz it blew a piston lol

[theclencher]

Originally Posted by spl_nut

Any block / head assembly is designed to operate within a fairly uniform temperature parameter - Run two of four cylinders (if it it'll run at all) and experience failure due to uneven expansion. Engines that run on fewer than all cylinders (in econo mode) do so by alternating what cylinders are firing, and what are dormant - Evenly distributing heat (expansion).

Prove it.

Everything I've ever read about it says you're wrong.

[kamesama980]

Originally Posted by theclencher

Prove it.

Everything I've ever read about it says you're wrong.

I don't know about catastrophic failure but there would be more wear. if one or more cylinders isn't creating heat, you will have a cooler area. granted a liquid cooling system will go a long way to warming it up but take it apart after 10k miles and I bet the cylinder walls of the dead cylinder will show wear more like an engine that never gets to operating temp. I suppose you could also suffer increase bearing wear from unbalanced operation of a consistent dead cylinder. ideally, yes oil will prevent it BUT the world isn't ideal. engines designed for cylinder deactivation will incorperate a means to reduce pumping losses as well as alternate cylinders switched off so that it's imperceptible in it's smoothness.

Or take the inverse situation: the straight 6 (7M in 86-92 supras and 89-92 cressidas) in my cressida is known the world over for blowing the head gasket at cylinder 6. from everything I've read, it results from a combination of problems: hotter, thinner walled 4v head than the previous gen 2v head, a not-drilled through coolant passage at the very back of the engine behind #6, EGR passage wrapping 1/2 way around #6 instead of 1/4 in the previous gen head, switching from an asbestos head gasket to graphite gasket (needs higher torque) and after all that, not increasing the head bolt torque spec. 2 of those relate to increased heat around cyl#6. different heating=different thermal expansion. add low bolt torque with a weaker gasket and you get leaking then blown head gasket.

[theclencher]

GM, Chrysler, and Honda must all be stupid then, for only EQUIPPING CERTAIN CYLINDERS for shut-off.

[theholycow]

Perhaps he's correct and they've designed those engines specifically to handle the problem.

[theclencher]

What problem? All I see is pure speculation.

[kamesama980]

Originally Posted by theclencher

What problem? All I see is pure speculation.

You give me a few million bucks to throw at blowing up engines and I'll give you hard numbers. Till then I'll stick to stating my speculations, right or wrong. If I am wrong, and it certainly happens, it's usually because I lack info about something and I'm just going on logic. I do very much like to fill in those gaps so when pointing out when I'm wrong by all means feel free to explain at length.

[Rayme]

I think the biggest problem arise from the EFI system, I was looking into it at some point ...

Your o2 sensor will get plenty of oxygen from the cylinders pumping air, then it will think your engine is running too lean and dump more fuel in closed loop.

The best way would be to completely deactivate 2 cylinder by shutting the valves permanently ...then the efi might only see "fire"