Running On 1 Less Cylinder.

[Corey]

I just want some light shed on my theory.

Now…a lot of people say running on one less cylinder is bad, because it’ll flood the cat with fuel.
However, if you disconnect the fuel injector and the coil connectors, won’t everything be okay? Shouldn’t it run just like the newer cars do with cylinder deactivation? The cylinder should just pump air.

My next question is…what happens to the fuel that is still in the fuel rail going to that disconnected injector?
In theory, if the injector isn’t connecting (meaning it can’t let fuel spray out), won’t that cause back pressure in the fuel rail, or no?

Topic

[college man]

In theory what you say about stopping fuel and spark will
shut that cylinder off per say. But you engine will be down
on power and the other injectors will need to compensate for
lost fuel (Lean) which will tell the computer to add more fuel.
Let alone set a misfire code,Lean code and make the engine possibly
knock. Also not good to try and compress air. I’m not for the idea. :blink:

[Daniel]

For your first question: when an automobile deactivates cylinders it also leaves the exhaust valves open. The reasons for this are: a.so the cylinder does not pull air charge from the intake which would throw off sensors like the maf. b. If the deactivated cylinders were still compressing air it would create a huge drag on the motor. c. If the deactivated cylinders are pushing huge amounts of (un regulated) oxygen rich air into the exhaust it could shorten the life of your cat (possibly even detonate it.) Your engine has an air pump that injects air into the cat to burn off unused fuel but, the volume of air it injects is closely regulated by the computer.
As for your second question: The fuel rail feeds multiple injectors. The pressure through the rail is regulated by a vacuum or electronically operated fuel pressure regulator. Any fuel that that one cylinder does not use will eventually be used by other injectors. The regulator would keep the fuel pressure at a constant pressure even if no injectors were operating.
If you want to disable a cylinder, in theory, you could unplug the injector, and remove the spark plug. The open spark plug port should releive any compression drag. You would also want to cap off the power supplies for the plug and injector, with some kind of insulated cap. Otherwise they would arc to the closest ground, which would create a short and blow a fuse.

[Bill]

Engines with cylinder deactivation disables the injector but it also deactivates the valves. These engines have a lot of problem with oil burning especially GM trucks. It tears up the rings for some reason. (I have my theory but that’s for another time).

The fuel pressure regulator takes care for any excess fuel pressure.

[Corey]

Wouldn’t deactivating the valves cause the engine to stall? The sealed cylinder would try to go downwards, but would be closed off. I assume it’d be similar to trying to get the engine to run with the throttle body 100% sealed (closed)?

[Bill]

Because it’s only one or paired cylinders it has no effect.

[Daniel]

When the valves are disabled the exhaust valve stays open, and you only disable the valves for the cylinders that you want deactivated.

[Author]

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