Cylinder Deactivation

MstangsBware · Post by **MstangsBware** » Sat Jul 12, 2008 12:07 am

I took the easy way out on DOD and went with the LS4. Slowly being installed and will see how well the DOD works out. Unless it gets me 35 MPG then it will be done away with and cam, springs, ect will be put in.

The Dark Side of Will · Sun Jul 20, 2008 1:10 pm

Dammit... did I delete the text? Fuck. I didn't mean to do that. Pwned by the moderator control panel yet again.

Anyway, let's give this one another shot.

Xanth · Post by **Xanth** » Sun Jul 20, 2008 1:42 pm

What exactly am I looking at?

Is this a mod for something you're making?

The Dark Side of Will · Sun Jul 20, 2008 1:49 pm

It looks like it's a variable displacement gizmo that lets a cylinder be deactivated at the rocker arms.

bigblockfiero · Post by **bigblockfiero** » Sun Jul 20, 2008 11:45 pm

The fulcrum nut on an ordinary engine typically sets valve lash and becomes a stationary reference point. For displacement on demand to work efficiently valves for the non running cylinders must shut off. This is done on this system when the stationary fulcrum point instead becomes non stationary and moves with the pushrod movement so that the rocker lifts up instead of rocking thereby negating any valve movement.

The picture is of a working prototype that is being tested (on a fiero) and transformed to fit the small block chevy. The system is designed to fill a performance market need and from a performance perspective, it's different and better then deactivation methods currently available.

bigblockfiero · Post by **bigblockfiero** » Sun Jul 20, 2008 11:59 pm

There are several pictures and two videos that someone took at a car show in minnesota of this prototype 8.3 liter cadillac deactivation engine in a fiero. The first video shows it running on eight cylinders and in the second video it gets switched and then runs on four cylinders.

http://s194.photobucket.com/albums/z148 ... 206-28-08/

This is the actual number two pace car fiero. Page one has two videos and two pictures and page two has two pictures.

lucky · Post by **lucky** » Mon Jul 21, 2008 2:51 am

My apologies for crying photochopping. In the pic in that other thread, the bottom edge of the pic was so white it looked faked. If you pause the second vid at about 18 seconds or so you get the same effect.
That's crazy stuff man.

Xanth · Post by **Xanth** » Mon Jul 21, 2008 9:00 am

Very cool, but doesn't stopping the valve from opening create a lot of drag on the engine? Wouldn't you want to hold the exhaust valve open during what would be the compression stroke?

Kohburn · Post by **Kohburn** » Mon Jul 21, 2008 9:13 am

Xanth wrote:Very cool, but doesn't stopping the valve from opening create a lot of drag on the engine? Wouldn't you want to hold the exhaust valve open during what would be the compression stroke?

for least resistance yes you would not want the cylinder to generate any sizable amount of vacuum or pressure. easiest way would be for one bank of cylinders to leave the intake closed and the exhaust open the whole time.

but that could do some funky stuff to the exhaust flow if it wasn't a true dual exhaust setup.

The Dark Side of Will · Mon Jul 21, 2008 9:35 am

Xanth wrote:Very cool, but doesn't stopping the valve from opening create a lot of drag on the engine? Wouldn't you want to hold the exhaust valve open during what would be the compression stroke?

The air that's trapped in the cylinder when the valves are deactivated just becomes a spring. You get all the energy out of it that you put into it, so there's no waste. If the valves were left to operate normally, those cylinders without fuel would still incur pumping losses.

The Dark Side of Will · Mon Jul 21, 2008 9:37 am

bigblockfiero wrote:The fulcrum nut on an ordinary engine typically sets valve lash and becomes a stationary reference point. For displacement on demand to work efficiently valves for the non running cylinders must shut off. This is done on this system when the stationary fulcrum point instead becomes non stationary and moves with the pushrod movement so that the rocker lifts up instead of rocking thereby negating any valve movement.

The picture is of a working prototype that is being tested (on a fiero) and transformed to fit the small block chevy. The system is designed to fill a performance market need and from a performance perspective, it's different and better then deactivation methods currently available.

What other methods are currently available?
What ECM are you using? I @$ume that you're controlling this via a switch in the passenger compartment and that it's very much NOT transparent to the driver?

You've heard of Hot Rockers, right? http://www.hotrocker.com/

Indy · Post by **Indy** » Mon Jul 21, 2008 9:46 am

Kohburn wrote: for least resistance yes you would not want the cylinder to generate any sizable amount of vacuum or pressure. easiest way would be for one bank of cylinders to leave the intake closed and the exhaust open the whole time.

but that could do some funky stuff to the exhaust flow if it wasn't a true dual exhaust setup.

If you leave the valves open, you'll end up with pumping losses, big time. The efficiency of a closed-valve setup like this is determined instead by cylinder leakage. With no leakage, the effective work done by the deactivated cylinder would be zero no matter what the pressure inside when the valves are closed.

Edit
N/M Will already stole my glory.

Xanth · Post by **Xanth** » Mon Jul 21, 2008 11:07 am

Okay, that makes sense to me. I was thinking only of the resistance during compression stroke, not considering the resulting spring action.

Xanth · Post by **Xanth** » Mon Jul 21, 2008 11:11 am

One other question now, what keeps that from being noisy as shit?

Wouldn't the rockers smacking up and down create a huge amount of noise?

What is done to reduce the impact of the deactivated rockers falling back onto the pushrods? Even when deactivated, is there a spring keeping some tension so the rocker stays firmly seated on the pushrod?

teamlseep13 · Post by **teamlseep13** » Mon Jul 21, 2008 1:10 pm

Pumping losses aside, in the OE spectrum of things leaving valves open of deactivated cylinder does one big no no; pump unburned air into the exhaust.

Your O2 sensor sees this as a huge huge lean condition, jacks up the injector pulse widths and now the whole point of turning off half of your cylinders becomes pointless since you are running way too much fuel into the active cylinders.

Rockers were engineered to be just that, rocking. If you have them moving up and down during deactivation, i would be worried about wear on that fulcrum point, that is unless you have already looked into that.
Also, when reactivating, is there anything keeping the pushrod from really smacking hard into the rocker?

I think grabbing a set of the lifters and the oil manifold and solenoids for the DOD LS motors would be a lot easier to adapt to an old small block. You already have most of the engineering and R&D done for you as well.
Just my 2 cents, hope it all works out.

Hunter

The Dark Side of Will · Mon Jul 21, 2008 1:14 pm

teamlseep13 wrote:Pumping losses aside, in the OE spectrum of things leaving valves open of deactivated cylinder does one big no no; pump unburned air into the exhaust.

:scratch:

All the OE systems leave the valves closed...

lucky · Post by **lucky** » Mon Jul 21, 2008 3:03 pm

BBF, I'm assuming from the ziggurat shaped valve covers that you only have these installed on the center 2 cylinders on each bank. Don't most OE systems vary which cylinders are deactivated to prevent uneven cylinder wear or something?

bigblockfiero · Post by **bigblockfiero** » Mon Jul 21, 2008 8:28 pm

The Dark Side of Will wrote:
bigblockfiero wrote:
What other methods are currently available?
What ECM are you using? I @$ume that you're controlling this via a switch in the passenger compartment and that it's very much NOT transparent to the driver?

Other methods don't properly remove all the valve lash that is a design necessity for the system to engage and disengage smoothly. Up to .050 is lost and the cam profiles have to be compromised so as not to smack the lifters after .050. My setup uses a stepped base circle cam that allows the switching to happen then and then takes out the overabundance of lash before the opening ramp arrives, This then makes possible aggressive cam profiles wile having a smooth operation.

My switch is the stock window defogger switch, I never used the defogger anyway.

bigblockfiero · Post by **bigblockfiero** » Mon Jul 21, 2008 8:39 pm

lucky80 wrote:BBF, I'm assuming from the ziggurat shaped valve covers that you only have these installed on the center 2 cylinders on each bank. Don't most OE systems vary which cylinders are deactivated to prevent uneven cylinder wear or something?

The center two on one bank, and the outer two on the other. I could have reversed this but you'll notice this coincides with the upper and lower manifold plenum layout, one plenum becomes dead.

For thermal efficiency reasons to the running cylinders its better to not switch around which cylinders are running. These system types you are referring to are designed for horrible thermal efficiency so as to cool off an overheated motor.