Cutting fuel to cylinders

[Shinjitsu]

I've read about people putting kill switches on to cut the signal to the injectors momentarily to kill the engine for coasting. I got to thinking, what if you cut one or two of the cylinders (more for larger engines like a v8 or v6) and run the car at highway speeds - just a steady pace. My car uses about 20hp at 70 mph. I'm sure 3 cylinders would carry it easily and I would hardly notice that 1 cylinder is missing - and 2 cylinders would probably still carry the car just fine.

Has anyone tried anything like this? It would be more convenient than pulse & glide and could have comparable results. I've gotten the wiring figured out I believe so my only question is this: Is there going to be any damage caused from cutting the signal to the fuel injectors for extended periods of time? I would assume that if one cylinder never had combustion take place, it would be in better shape than the other cylinders which had the extra stress of the combustion heat and pressure. So I would think there would NOT be any long term damage caused by doing this but please, correct me if I could be wrong - I cannot afford to blow my engine right now.

[Piwoslaw]

Cylinder deactivation discussion
Cylinder deactivation attempt
Killing individual cylinder ignition
idea, 4 cylinder to 2 cylinder engine conversion

[phunky.buddha]

Without clicking through to the links- just from an engineer's perspective- it would be a VERY bad idea to just cut fuel to one or two cylinders. You don't want to upset the balance of your engine like that. Cutting 1 cylinder out of 4 if you're talking about the Prelude in your profile would mean something like this:

1 - 3 - 4 - 2 <-- normal firing order

1 - 3 - x - 2 <-- really lumpy

It would feel like your laundry machine with a huge weight stuck on one side during the spin cycle... which in an engine means lots of vibration -> dead bearings -> oops I need a crankshaft. Or something along those lines.

[Shinjitsu]

See, I knew someone would think about something that I wasn't. Thanks a lot - glad I didn't try that! I guess I'll just install the kill switch to cut fuel to all cylinders for pulse & glide.

[SlideWRX]

The bigger issue to me would be the emissions equipment and fuel control. Without shutting off the non-firing cylinder completely, it is pumping air into the exhaust. That will throw the O2 sensor for a loop and the computer will dump fuel in to try to burn the extra Oxygen it is detecting.

[Shinjitsu]

I had thought about that and I figured it would be a pretty big issue - burning rich and throwing check engine codes. The fresh air would definitely mess with the computer.

[vskid3]

What about using two separate computers? Have a V8 that is treated like two 4cyl, have an intake and exhaust dedicated for each side. Then you can just kill the fuel to one side (and open that side's throttle to reduce pumping loses), and the other computer doesn't have a clue. Kind of a roundabout way of doing it, but probably the easiest DIY solution.

[SVOboy]

Originally Posted by vskid3

What about using two separate computers? Have a V8 that is treated like two 4cyl, have an intake and exhaust dedicated for each side. Then you can just kill the fuel to one side (and open that side's throttle to reduce pumping loses), and the other computer doesn't have a clue. Kind of a roundabout way of doing it, but probably the easiest DIY solution.

This doesn't sound like a very good solution, as not only would you have to somehow decode and reprogram your car's fuel injection programming, but you'd also have to design and build a set of dual intakes to accomodate these sorts of things.

Either way, I wouldn't bother with trying to shut off fuel to certain cylinders. Unless the engine is designed for it from the git go, it won't work out too well.

[vskid3]

I was thinking 2 Megasquirts for ease of modification. By no means would it be easy, it might not even work, but its the way I would go if I were to try it.

[abently]

Why not relocate the 02 Sensor to the header runner that won't be connected to a deactivating cylinder?

You may still have an Engine balance issue, but Oil pressure would remain normal so I doubt bearings would die prematurely...