Cylinder Deactivation

[bigblockfiero]

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

I could do that and still use my stepped base circle cam but it would still be allot of work and even harder to sell as a kit. Also that lifter type is prone to internal clearance variance under load which alters the dynamic bleed down rate. Also consider that after the sbc retrofit we could move on to the sbf, bbc, etc so the layout I have now is more compatible for that.

[teamlseep13]

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...

Ya my wording was odd. I was just saying that besides pumping losses, OE's leave them closed because of the O2 that would be pumped into the exhaust.

[Kohburn]

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...

Ya my wording was odd. I was just saying that besides pumping losses, OE's leave them closed because of the O2 that would be pumped into the exhaust.

which still wouldn't be an issue if the whole bank was turned off and it was a true dual exhaust. the computer wouldn't even be looking at the O2 when the bank is off.

but yeah pumping losses kills the simplest method anyways.

[Kohburn]

i am curious what the pumping loses really would account for though. if any of you have ever clocked dual cams incorrectly so that they overlapped too much and tried to start the engine, it cranks like the engine pistons aren't even there it just spins it up really fast. (yes i clocked my subaru cams wrong once when i was tired)

[The Dark Side of Will]

which still wouldn't be an issue if the whole bank was turned off and it was a true dual exhaust. the computer wouldn't even be looking at the O2 when the bank is off.

Then you have firing order issues. A square crank V8 is two V4's end-to-end, NOT two inline 4's on a common crank.

With the cylinders pictured deactivated, it becomes one V4 with some extra junk rotating with it.

With a Chevy, for instance, set up as pictured, every OTHER cylinder in the firing order is deactivated and the engine remains even fire. 18436572 becomes 1_4_6_7_. If one bank were deactivated, the engine would be odd fire. 18436572 would become 1__3_57_.

The Cadillac firing order is 15634278. It looks funny because the 3-4 and 5-6 pairs are in opposite order and it has the opposite bank forward, compared to a Chevy.

[Kohburn]

Then you have firing order issues. A square crank V8 is two V4's end-to-end, NOT two inline 4's on a common crank.

true, using an existing v8 would do that. but if designing from scratch it would seem to me to make more sense to build it as two engines with a common crank, one a full time engine, and one turning on and off.

[The Dark Side of Will]

That's the way it's done, BUT it's done as two interleaved V4's, rather than two inline 4's. Flat crank V8's vibrate too much for normal cars (Ferraris of course are not normal cars).

[teamlseep13]

Ya vibrating V8's in peoples SUV's isn't exactly what the common public wants.
If you shut off an entire bank with a true dual exhaust then the cat gets cooled off, and has to re light off once you re activate the cylinders on that bank.

[The Dark Side of Will]

Mercedes (and BMW?) do cylinder deactivation in their V12's by dropping a whole bank. The remaining cylinders, however, form an inline 6 and are still a smooth engine.

[teamlseep13]

I wonder how they keep the cats from cooling off....interesting.

[CincinnatiFiero]

Mercedes used* (not sure about today) use common cats, so its a dual in dual out single cat. One bank will keep it hot still.

[whipped]

I was wondering if it would be simpler to inject an inert gas (NOT exhaust) into the intake. Co2?

It would make it a variable displacement without the throttling losses.

[lucky]

3/4 of the ambient air being drawn into the intake is already inert gases anyway....

[The Dark Side of Will]

I was wondering if it would be simpler to inject an inert gas (NOT exhaust) into the intake. Co2?

It would make it a variable displacement without the throttling losses.

Where/how are you going to carry it and where/how/how often will you refill it?

[whipped]

sodium bicarbonate is cheap?

a kilo of bicarb will make 26 moles co2, or 582 liters. Not going to do any more math than that, but it seems like it could be done with a reasonable quantity. Idle VE is almost nil anyways. :la:

[whipped]

and you thought it was going to take a co2 cylinder.... admit it! :bootyshake:

[The Dark Side of Will]

I didn't feel like going through the math to figure out how much mass you'd have to fill up every week. :scratch:

[bigblockfiero]

I was wondering if it would be simpler to inject an inert gas (NOT exhaust) into the intake. Co2?

It would make it a variable displacement without the throttling losses.

Variable dynamic displacement maybe a little, but the inert gas must be included as mass.

I think it is understood that displacement refers to anything that is within a cylinder rather then what is not in a cylinder, either statically (volume) or dynamically (mass).

I see what your saying and how an inert gas could be incorporated with cylinder deactivation somehow (under a carb I suppose to divert mixture away from a runner) but you cant say that substituting displacement air and whatever, with something else makes it a variable static displacement and also, altho inert, the substituted mass would displace heat from the dead cylinder and surrounding water in the block thus making the whole engine very inefficient which is why it is so important for an engine to be truly "mechanically" variable displacement.

It is of course true that displacement air mass changes technically makes an engine variable dynamic displacement and so actually all engines are variable displacement such as when the throttle is half closed or when you drive up into the mountains, and on that point I say this reduced power should convince even a fiero tech troll that displacement matters (see the argument in the thread "displacement matters").

The throttling losses deal you speak of isn't clear to me.

[whipped]

Think of it this way. Say you have a 2 liter, 2 cycle engine. If I inject 1 liter of CO2 into each intake stroke, the engine contains half as much oxygen as it normally would. So if you're running 14.7:1 stoichiometric mix, you can use 1/2 the fuel. Which also means half the power, and is the equivalent of 1/2 the displacement. Because it will be making less power, the throttle will necessarily be opened more for a given power level. Which means less intake restriction, and less losses from the engine having to pull air past a throttle.

I'm not talking about shutting off cylinders by killing them with CO2. And this wouldn't work with a carb.

It would be difficult to implement, but I think it could be done with excess bicarb and a carefully regulated pump spraying concentrated acid on the bicarb.

[bigblockfiero]

Think of it this way. Say you have a 2 liter, 2 cycle engine. If I inject 1 liter of CO2 into each intake stroke, the engine contains half as much oxygen as it normally would. So if you're running 14.7:1 stoichiometric mix, you can use 1/2 the fuel. Which also means half the power, and is the equivalent of 1/2 the displacement. Because it will be making less power, the throttle will necessarily be opened more for a given power level. Which means less intake restriction, and less losses from the engine having to pull air past a throttle.

I'm not talking about shutting off cylinders by killing them with CO2. And this wouldn't work with a carb.

It would be difficult to implement, but I think it could be done with excess bicarb and a carefully regulated pump spraying concentrated acid on the bicarb.

This makes sense now, like one of the advantages that a diesle engine has on overlap and in terms of exhaust flow at part throttle.

The overlap period is always a compromise on a gas engine. At full throttle and at drastically different vacuum conditions. These issues where the motivation behind a project I was involved with in the early 90's called V.I.C. (variable intake closing). This system used a constant velocity carborator calibrated to always run at 2 inches of mercury at idle and such but diaphram/venturi assisted to run at .5 in the upper rpm ranges. The throttle peddal did nothing more then change the intake closing period. I never made a dime on that effort and in fact really wasted allot of cash, kind of like most of my projects today.