8.1 8 cylinder to 4.0 4 cylinder

[luscombe8]

with some of the older engine technologies offering variable cylinder firing, i.e. 8-6-4 in a Cadillac, i have an idea.
by turning off the misfire codes with my Diablo Predator, would it be possible to pull a fuse for the fuel injector bank on either side and run the 8.1/8 engine as a 4.0-4 cylinder? are there any ideas on how to successfully run the big block in a 4 cylinder mode? i think the firing order will allow it to run. preliminary experiments let me drive only a 1/4 mile before the check engine light came on and it was rough running at low speeds, would not idle on it's own, i had to tickle the gas pedal to keep it running. at 340 hp in 8 mode, it seems logical that the truck would run on 170hp. it may shift more, but economy wise, it would do a lot better.
all intelligent replies are welcomed.

[Tdragone]

My engine experience is limited to shop class in high school.
I;d think the answer on killing one bank would be a no because of the order in which the cylinders fire.
Kiling an entirre bank would be the equivalent of making your truck fire in a non sequential order; killing the timing order of the clyinders and screwing up the way the cam is turning/weighted. Just my thoughts.

[luscombe8]

ok, the firing order is 1-8-7-2-6-5-4-3. If I short wire a switch to the injector ground for 1-7-6-4, it should fire in sequence. an additional switch for the remaining cylinders could be wired for alternate running, thus balancing the wear over time.

the Oxygen sensor will still read the same O2 because the cylinders are still burning the same mix, quantity is not affected only the percentage would cause a code, so if the percentage in the exhaust is the same, the diminished quantity will still read the same. i.e. 87 Octane is the same if you have 2 gallons or 30 gallons. so, O2 is the same if you have 15 units or 30 units. the truck should run cooler, but the thermostat would take up the slack.

i think I'll go ahead and wire it up.

i was hoping for someone who knew about the variable firing geometry to speak up.

thanks for your reply.

[silicon212]

There's a reason those V8-6-4 engines never made it in the marketplace. The idea was novel but was way ahead of its time.

To make it work, you'd also have to run variable valve timing and turn off the injectors to those cylinders you want to deactivate.

'Tis the only way to make it work.

[CD Smalley]

Also, GM and I think Chrysler use a switch to control oil flow to the lifters. They shut oil of to the lifters for the cylinders not in use and use those as... what do I want to say.... cushions. They also use fly by wire thorttles so they can open them up to compensate for a pulsing effect which happens...

[silicon212]

Originally Posted by CD Smalley

Also, GM and I think Chrysler use a switch to control oil flow to the lifters. They shut oil of to the lifters for the cylinders not in use and use those as... what do I want to say.... cushions. They also use fly by wire thorttles so they can open them up to compensate for a pulsing effect which happens...

Yes, that's the variable valve timing I speak of. GM calls this 'Displacement on Demand', and while it is available for 4.8/5.3 and perhaps 6.0 engines, I am not sure if it's available for the 8.1.

[Sonny01]

There's a reason those V8-6-4 engines never made it in the marketplace. The idea was novel but was way ahead of its time.
It seems to me that Cadillac had an engine like this...my dad worked at a Cadillac dealership and told me to stay away from them. They were a maintenance nightmare and never worked as advertised.

[silicon212]

Originally Posted by Sonny01

There's a reason those V8-6-4 engines never made it in the marketplace. The idea was novel but was way ahead of its time.
It seems to me that Cadillac had an engine like this...my dad worked at a Cadillac dealership and told me to stay away from them. They were a maintenance nightmare and never worked as advertised.

Yes, the engine was actually an Oldsmobile 350 engine that was modified to cut out 2 to 4 cylinders, in a first ditch attempt at cruising fuel economy. This was back in the days of fuel rationing and block-long lines at the pump, 1978-1979. The engine was frought with problems.

The current Displacement on Demand has the same idea behind it, but they can effectively take the cylinder out by opening the valves (to cut compression), and cutting off fuel and spark. These ones work much better.