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How does cylinder deactivation get effected by oil change intervals? Does the oil somehow directly get used to control the ignition, like on a power stroke oil pressure is used to inject fuel (HEUI sytem). I figured it's all electronic, but I haven't owned one, only what people say online about them and what friends and family experienced as well as my dad as he was a mechanic.
I've seen some engine's setup on youtube where the exhaust went into another cylinder so the engine was half normal engine and the other half was used to use more of the energy from the initial fuel. I think they might have been adding water or something, it was a long time ago when I saw the video, pretty sure it was on a boxer engine.
My comment about the vibration is just from the idea of a 4 cylinder 3.65L engine would vibrate a lot more than a 1.8L 4cyl. Really the engine vibration would be the same as the v8, just spaced apart per fire, so it would be a lower frequency and in my mind would be felt more. Kind of like the punch of a sub woofer vs a normal woofer speaker,say 20hz vs 120hz. Actually that's kind of an interesting thing to do the math on, 1500rpm *4 (2 rev per fire per cylinder) is 6000 fires per min/ 60 is 100 fires per sec. That should translate the vibration from the engine would be around 100hz for my diesel at fairly typical speeds (55mph).
No engine is vibration free, but some are balanced much better than others. The fact there's effectively a controlled explosion going on inside is kind of impossible to smooth out to silk smooth. Good engine mounts, transmission mounts, rubber isolated drive shaft (like my LS400 has) can help loads of course but the engine itself still has a vibration while running.
It's not the greatest experiment, but back when I drove my corolla, I disconnected 2 of my injectors to turn the 4cyl into a 2 cyl to see what kind of mpg effect it had. Before I got even a mile down the road I thought of a big issue with that, the ECU is expecting all cylinders to be firing, and the disabled cylinders would be pumping normal air into the exhaust which would trigger the computer to dump more fuel to keep the ratios right. It ran rougher and lacked a lot of power but it did drive like that. If I was able to disable the intake valves as well then it would have worked fine I would think.
It's interesting about the deactivated cylinders having less wear, of my understanding a piston isn't the correct shape until it's heated up, and the majority of the wear is caused when the engine is cold, so if the cylinder is only used to pump air, I figured there would be more wear since it would be cold for longer.
Turning a v6 into a 3cyl or a v8 into a 4cyl is a neat concept in my mind. I might have to toy around with that idea some day with a junker yard vehicle some day. I have a ford ranger in the yard that's just a junker. Would be neat to disable half the engine, put a turbo on the other half, and try to get about the same hp out of it as stock, but using less cylinders. I'd assume it would get better mpg overall but kind of hard to say. The cylinder pressures and pistons, rods, and, valves would see more stress, but the crank and beyond should be fine.
Actually, that corolla of mine could be a prime candidate for the half engine size test. It has a valve cover that's really easy to remove and I have a spare engine that's blown up so I have an extra head and such. Could grind off the intake valve lobes for two of the cylinders (DOHC engine), and see how it does MPG wise. It's a high torque 4cyl, peak around 2800rpm so it shouldn't do too bad as a 2 cyl. The smaller version of the engine is peak torque at 5200rpm and I've drove one of them and it seems to be horrible for mpg but it also has a different transmission (3 speed no lock up vs 4 speed + lockup).
Btw, the corolla has nothing special about the oil system, so I changed it every 15k miles with quality synthetic oil. Not sure if 80k miles would be enough to see issues from it, but I haven't noticed anything yet besides the slight power drop. It had a sweet spot where the timing would pull back and mpg was great, a tiny bit more throttle and it would hit 39 advancement and mpg would tank 10% or so. The last 6 months or so I had a very hard time getting it into the sweet spot, that's the only way I knew it had less power (more throttle to go the same speed).
Also it's worth noting that rpm isn't everything when talking about MPG, generally speaking highest gear and going as slow as possible in said gear gives the best MPG, but different vehicles respond differently. My dad's Mazda 1989 (pre ford era) 2.6L 4x4 truck with 4.30 gearing would at best get 20mpg. He always shifted early and drove the truck easy. He hauled a ton of stuff with it and the mpg would drop a little but normally not bad if he wasn't trying to go fast (like over 50mph). When he bought his T100, he car dollyed it through Ohio and half of Michigan in 4th gear doing 3000 rpm and was getting 20mpg with the load. The T100 is physically bigger than his truck and sat much higher plus the dolly pushed it higher, so the frontal area was massive compared to empty. About the only thing we can think of is that engine likes higher rpm and we were driving it wrong for it's engine's wants. It was a DOHC engine and peak torque high up like the 1.6L corolla engine so it seems to relate to peak torque rpms a bit. I've seen other people mention it's related to piston speed (flame travel speed or something like that).
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