Dynamic Cylinder Deactivation

[t vago]

Originally Posted by Heihetech

There are many posts talking about "misfire" caused by DCD. As I have said
before, this is not true misfire due to missed or abnormal burning.

It doesn't matter. OBD II systems detect misfiring cylinders due to a lack of either fuel (which your device intentionally causes to happen) or spark. You can whine about how unfair this is to your invention all you want, but the fact of the matter is that you still have to work around a federally mandated computer control.

Originally Posted by Heihetech

So, OBD-II should
better use other way to detect misfire, such as combustion pressure, or gas
expansion by knock sensor. Therefore, OBD-II software must be modified
accordingly, give the way to DCD operation.

Oh, sure. Manufacturers should add thousands of dollars to the per unit production costs of their vehicles to add costly and unreliable methods of detecting misfiring cylinders, just so that your precious device can then be made to work without throwing codes and possibly putting said vehicles into limp-in mode.

Originally Posted by Heihetech

We all know OBD-II is the law,
but the law is man-made, and could be revised as required. Detecting misfire
by mechanical irregularity has been out-dated, at least not so perfect.

Do you even know exactly how misfires are detected? Or are you just talking out your rear end again?

And while we're at it again, explain how a completely deactivated cylinder (that's no passage of anything, let alone air at room temperature) will somehow suffer more of a temperature difference than a cylinder that is pumping room-temperature air without firing it? Oh, and please explain how the cylinder that is completely deactivated (remember, not pumping a thing) somehow wastes more energy than a cylinder that is pumping air from a low pressure source (the intake manifold) to a high pressure source (the exhaust manifold)?

[bandit86]

Disconnect the oxygen sensors. Limp home does not automatically entail that it will run like crap. Mine ran semi decent but was obviously gutles with 4 of 8 cylinders deactivated. With only 2 I am happy, barely noticable loss in power

http://ecomodder.com/forum/showthrea...now-21117.html

[deathtrain]

Ok your product makes it put a misfire code and that in turns makes it turn on the CEL. You say ignore it okay I get that.

But what happens when you truly have a CEL that needs attention that can actually harm your engine? Since the CEL is already on and the driver is used to it being on. New codes show up but the driver never knows..... until he is picking up his internal parts off the road.

[Frank Lee]

Everybody's so worried about the dang CEL... hell, half of my cars don't even have CELs.

I'm interested in does it save fuel or not? Nothing said here in the past... year?... tells me it would.

[mwebb]

071 is not a misfire DTc in OBD2
when you do set a misfire DTC in an OBD 2 system
in most systems
first you get a
P0300 which is random misfire , the system has detetcted misfire but is not sure which cylinder set the DTC
then
you get
P030X where X = the #of the misfiring cylinder

then
Mode6 testing is Disabled for Cat converter and 02 sensors

so your actual self induced DTCs number a minimum of 2
assuming not a speed density system

with those 2 DTCs testing is suspended for additional components

fuel trim will be affected by the 02 now present in the exhaust stream , system will appear lean , Mr Computer will attempt to get the 02 sensor s cycling again by adding fuel , LTFT will peg at it's upper limit and

you will set a DTC for
lean condition on the bank you have tampered with and the cat will have to deal with the extra UNneeded fuel present in the exhaust stream

which when added to the extra 02 will combust IN THE CAT. rendering it useless .

or the system may go to open loop , ign timing is retarded power reduced
Fuel economy does not and can not be "improving" as this unfolds
and it goes on ...

your understanding of how OBD2 system s function is
lacking

but
have no fear -
i will be happy to educate your self

your scenario of your own system's function and condition is
not plausible

try again - stop fibbing
i eagerly await your reply ....

thank me very much

Originally Posted by Heihetech

mwebb, to tell you the truth, nothing you mentioned has happened on my
DCD test vehicle over 3 years. I try to clear the OBD-II code once a month,
every time it shows "071"="misfire", no other real trouble generated. It all
depend on how the ECU is programmed to process the troubles. Many DCD
installed vehicles in China even never report "misfire". So it all depend on the
regulation and the related ECU software ----- a man-made issue.

By the way, how do you know the cat converter have already killed??? By
un-burnt fuel??? NO! This does not belong to DCD. DCD will stop injection
for some time, how does un-brunt fuel go into cat converter??? Or killed by
cool bypass air??? YES! DCD does have lot of bypassing air, but every vehicle
has such action when driver releases gas pedal during deceleration.

[ex-x-fire]

On the tv show Gearz lastnite they showed a product called Fuel Smart, they said it turns off the injectors when you are under deceleration.

[mwebb]

most current systems have "decel fuel cutoff"
do not buy something
that
your
system
already has

Originally Posted by ex-x-fire

On the tv show Gearz lastnite they showed a product called Fuel Smart, they said it turns off the injectors when you are under deceleration.

[toc]

On the tv show Gearz lastnite they showed a product called Fuel Smart, they said it turns off the injectors when you are under deceleration.

Only benefit would be more fuel cut.

i.e. I know my Nissan ECU has fuel cut on 2500RPM, and then deceleration mode from 2500 RPM to Idle.

From the rough description posted, Fuel Smart sounds useless, pretty much all ECUs would cut fuel when RPM high and Throttle 0.

What if throttle is > 0 - air only though?

[gone-ot]

...here's what the EPA didn't 'like' about D.I.Y. cylinder deactivation:

http://www.epa.gov/otaq/consumer/devices/511817.pdf

...quoted from paragraph F. on page 7: "...a violation of section 203(a)(3), the Federal prohibition against tampering with emission control systems."

[Frank Lee]

Most interesting report, tele. I think it is "didn't" like, though. They did it 32 years ago on old-school carb'd cars... oddly enough, they complained about the kit's lack of a means of deactivating individual injectors on injected cars which to me would be about 100x easier to do than fooling with the carb on the carb'd ones, and of course the injected cars have so much more mixture self-correcting ability as well.

They mentioned other deactivation systems too dating back to at least 1974; one from Michigan State University, and the Eaton/Cadillac showed different emissions reactions to deactivation. I wouldn't worry about any of it, since I wouldn't try it on carb'd equipment.

They identified many operational shortcomings: somewhat harder starting, stalling, poor acceleration, really not much better fe under any but steady-state cruise conditions, dieseling on shut-down, etc. that the new-gen DoD addresses by basically only deactivating under low-load steady-state cruise. Both old and new DoD seem to have settled on about a 15-20% potential fe improvement at cruise.

I thought it was interesting that they went through so much work to couple the lifter to the pushrod and hold it away from the cam when deactivated. I wonder if harm would come from just letting the lifter and pushrod float i.e. more or less ding around at "top of the lobe" height with only gravity wanting to lower them into contact with the lobe? Or even go the other direction and keep the pushrod and lifter in constant contact with the lobe, deactivated or not.

P.S. There was a lot of cylinder deactivating work going on after 1973; I recall an article in The Mother Earth News detailing how to shut 4 off on an 8 (which I now doubt worked at all since IIRC it didn't alter the valves at all- it was a "barrel valve" in the intake- so the pumping losses remained) and also I recall seeing Mankato State University's "50/50 VW Bug" (named for achieving 50 mpg at 50 mph) via 2 cylinder VW engine mod.