Dynamic Cylinder Deactivation

[Phantom]

Originally Posted by Heihetech

I don't think so. Oxygen will not kill the cat, no harm done. Just think when
you release gas padel during cruise speed on general vehicles, fuel will be cut
out, pure air instead of exhaust will be blowed onto the cat. Such case
happens frequently during normal driving, does it kill the cat? NO！So please
don't worry, oxygen will not harm the cat. Something that does harm to the
cat is un-burned HC from lean burn, which will not be involved within DCD.

"Catalytic converters generally function efficiently only when the incoming mixture is within about 4% of stoichiometry, or a lambda range from .96 to 1.04. Let's return to our last example above. At 1.03, lambda is narrowly within acceptable lean limits. But if this borderline lean condition persists over a long period of time, the catalyst will slowly degrade as a result of the excessive heat it generates while cleaning up the exhaust stream."
From http://www.austincc.edu/wkibbe/lambda.htm

[George Tyler]

I did a googlr search on this, there was omly 1 link that suggested that a cat could be damaged by lean mixtures becuase it runs cold and gets water from combustion on it causing corrosion.

[Bill in Houston]

wouldnt a RICH mixture make the cat run hot? and a lean mixture make it run cooler?

[George Tyler]

Originally Posted by Bill in Houston

wouldnt a RICH mixture make the cat run hot? and a lean mixture make it run cooler?

yes, except that if it is lean enough to misfire there will be plenty of fuel in the exhaust as well as even more oxygen

[Heihetech]

Originally Posted by Phantom

"Catalytic converters generally function efficiently only when the incoming mixture is within about 4% of stoichiometry, or a lambda range from .96 to 1.04. Let's return to our last example above. At 1.03, lambda is narrowly within acceptable lean limits. But if this borderline lean condition persists over a long period of time, the catalyst will slowly degrade as a result of the excessive heat it generates while cleaning up the exhaust stream."
From http://www.austincc.edu/wkibbe/lambda.htm

The hyperlink you quoted is all about lean-burn, or misfire condition cause by
engine troubles. Such case will not apply to DCD, BECAUSE, AS I HAVE
MENTIONED MANY TIMES, DCD CONTAINS NO LEAN-BURN. Therefore, there
will be no un-burned HC to heat the cat.

Lean-burn will cause high lambda, but high lambda of DCD is never caused
by lean-burn, instead, it is caused by air injected into exhaust, by oxygen
diluting, resulting a cooler temperature. Why run hot and burn the cat?
Where's the energy comes from? If oxygen could generate heat, why the
engines need to burn gas? Just burn oxygen according to your thinking.

Hope the above will pull you out from the dead zone of lean-burn. Anything
related to lean-burn is not related to DCD, AND will not apply to DCD.

[texanidiot25]

Originally Posted by t vago

Engine misfiring is never good. You may claim otherwise, but it's never a good thing to have completely unburnt fuel-air mix exit the combustion chamber. At best, you're just wasting fuel, and at worst, you're burning up your catalytic converter AND prematurely wearing out your piston rings due to fuel dilution of the engine oil clinging to the sides of the cylinder walls.

And how again do you propose to eliminate excessive NOx and unburnt hydrocarbon emissions with this DCD gadget?

Unless you pass one of them mobile emissions checking trailers. Or until your cat burns out from excess unburnt fuel. Or until your engine starts burning oil from worn-out piston rings due to fuel-diluted oil.

I think you're missing the point of the system. The "dead" cylinders' fuel injectors won't fire, there won't be unburnt fuel. Spraying fuel into the "dead" cylinders would defeat the purpose of the product. And from what I'm reading, it's tricks the ECU into fueling the working cylinders as normal, keeping afrs straight.

Just my 2 cents with out reading his entire article (Let me know if I've missed something, and fuel injectors still spray into cylinders with no spark), and based on what he's posted here.

[Heihetech]

Originally Posted by George Tyler

yes, that is true, but at idle it is open loop, also at full throttle. I am thinging of making a ECU that controls mixture by spoofing the O2 sensor.... it has a pam of throttle opening, manifold pressure, rpm etc and stores what the engine normally does, then with the cyl deactivation on it generates the O2 signal that makes the correct mixture.
Another way to do it is to have 2 separate exhaust systems, with the O2 sensor in only one that is not going to be deactivated. they can join further down

I think you do need a wideband oxygen sensor to close the fuel loop
whenever cylinder deactivation is in progress. Rugular O2S can't see the
high lambda area, then the engine will loss the control.

If you place the O2 sensor in only one that is not going to be deactivated,
the resullt is you could only run deactivation in a fixed pattern, not DCD
which deactivates and activates every cylinders alternatively, resulting a
balanced thermal state in all the cylinders within the engine. In case of
fixed deactivation, some cylinders may run hotter than others; and some
cylinders may run cooler than others, thermally un-balanced, un-reasonable
and un-pleasant.

[Heihetech]

Originally Posted by texanidiot25

I think you're missing the point of the system. The "dead" cylinders' fuel injectors won't fire, there won't be unburnt fuel. Spraying fuel into the "dead" cylinders would defeat the purpose of the product. And from what I'm reading, it's tricks the ECU into fueling the working cylinders as normal, keeping afrs straight.

Just my 2 cents with out reading his entire article (Let me know if I've missed something, and fuel injectors still spray into cylinders with no spark), and based on what he's posted here.

Thanks! texanidiot25,

I think you have reached the critical point that there's totally no fuel
injection in deactivated cylinders of DCD. So there will be no lean-burn, nor
unburnt fuel.

t vago is so smart that would rather sacrifice fuel comsumption to distroy
DCD concept and DCD controlled engine by injecting fuel into deactivated
cylinders, intentionally making lean-burn and unburnt fuel there so that his
knowledge of TLB CAN BE OVER-USED, and his skill of TLB can be ill-played
there.

So it's important to keep dirty TLB away from CLEAN DCD. They have good
clearance in between.

[deathtrain]

All this talk and we have yet to see a product.

[roflwaffle]

Originally Posted by Phantom

"Catalytic converters generally function efficiently only when the incoming mixture is within about 4% of stoichiometry, or a lambda range from .96 to 1.04. Let's return to our last example above. At 1.03, lambda is narrowly within acceptable lean limits. But if this borderline lean condition persists over a long period of time, the catalyst will slowly degrade as a result of the excessive heat it generates while cleaning up the exhaust stream."
From http://www.austincc.edu/wkibbe/lambda.htm

Saying it will slowly degrade the catalyst in general seems kinda weird since 2-way catalytic converters were around for a decade before 3-way cats were and they functioned well. Catalyst heat is only a function of how much stuff it catalyzes, and I think that all three reactions are exothermic, so if we take one reaction out of the picture there will tend to be less heat, barring of course some sort of condition like a misfire that increases the amount of HCs in the exhaust to be catalyzed.