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Old 09-14-2010, 10:27 AM   #27 (permalink)
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Originally Posted by saand View Post
Thanks edkiefer, good link explains balancing well. If others dont know if a 2 or 3 cylinder engine is "balanced" as described in the link in the last post by edkiefer it doesn't mean the engine will be free of vibration as other modes of vibration occur.

Well i tried out removing the injector signal to 1 and 2 injectors and it was an interesting ride. The car lugged a lot when accelerating up but if i was sitting at 70 kph it was drivable. I believe the lugging is because there is a dead spot in acceleration during a quarter of the cylinder cycle so less power therefore require higher revs to go to the next gear. My automatic car obviously didn't know this so every time it went up to the next gear it would lug. So i don't think i can go any further until i see if i can make a manumatic out of my auto.

In general besides the lugging it wasn't too bad i think when actually moving at speed i would barely notice the missing cylinder.

Not sure about vibration though which could compromise the life of engine parts.

So at this stage im going to look into changing my car to a manumatic and ill have to think about if i can deactivate a cylinder on the fly from the cabin. This would let me get up to highway speeds, deactivate a cylinder and reduce some fuel usage. The issue i have to think about is how to stop the pumping losses of the cylinder on the fly
If you want to disable half your engine, find out your firing order. On many 4 cylinders, it is 1-3-4-2. The outside cylinders are both at top dead center at the same time that the inside cylinders are at bottom dead center. Since you are going for economy, disable cylinders 1 and 4 and you should have a non stumbling engine.

I apologize I haven't read the whole thread, but one thing to watch for is if you are doing this to a fuel injected car, you need to consider what the o2 sensor is going to do when it detects 2x the o2 it should be seeing; ie it will detect a highly lean condition and the ECU will dump fuel in an attempt to correct it. There will be so much excess fuel in the 2 running cylinders it will wash past the piston rings into the crankcase and dilute the oil. I had a Explorer I did just that to; I disabled half the cylinders remotely from the drivers seat. But I noticed the oil level going up (it had a slow leak, so it was something I checked on regularly.) A little bit too late I realized the problem and the engine quit on me.

Don't think I believe it to be impossible, but either through electronically halving the signal from the o2 sensor or rerouting the exhaust, it will need to be dealt with if you value your engine.

Something else to consider, a 100 hp 4 cyl running on 2 cylinders will produce less than 50 hp at the crank due to the pumping losses from the 2 dead cylinders. My best guess would be about 35 hp but that's a shot in the dark sort of guess.
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Originally Posted by jamesqf View Post
I think you missed the point I was trying to make, which is that it's not rational to do either speed or fuel economy mods for economic reasons. You do it as a form of recreation, for the fun and for the challenge.
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