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Do FI bikes shut off the injectors coasting in gear?

ScottRNelson said:
Actually, someone on the internet said that certain late model cars completely stop injecting fuel when the engine is revving within a certain range and the throttle is closed.

Before I'll believe it, I will need reliable references. My only firsthand experience contradicts this statement. And we know that to meet emission requirements, it is necessary to keep the air/fuel ratio as close to optimal as possible, which is not what happens when you pump through air without fuel.

I'm very skeptical about the claim.

Anybody want to come up with some hard evidence to support the claim?
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emissions tests aren't run with the engine coasting in gear. SMOG standards are maximum values for whatever you're measuring. so, if all you're doing is pumping air through the motor you'll be under the max numbers, unless the atmosphere fails smog testing in which case you should move.
 
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auntiebling said:
i suppose one could argue that flowing air without any fuel through the catalytic converter for long periods of time will cool off the cat, thus taking it out of the efficient operating temp range and increasing emissions till it heats up again. i doubt the majority of instances where the fuel is cut off are long enough to matter.
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One could argue. But in this case, I got that information direct from powertrain engineers and factory instructors. They don't want that cat to cool down at all when the engine is running. They want it heated up and working as soon as possible which is why we have such things as AIR injection for quick warm up, pre-cats, and like what I saw at Honda before I left...bolting the
cats directly to the head.
 
TheRobSJ said:
One could argue. But in this case, I got that information direct from powertrain engineers and factory instructors. They don't want that cat to cool down at all when the engine is running. They want it heated up and working as soon as possible which is why we have such things as AIR injection for quick warm up, pre-cats, and like what I saw at Honda before I left...bolting the
cats directly to the head.
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please stop quoting my post while i'm editing cuz i read what you posted above as i was posting, then deleted it cuz you have firsthand knowledge that contradicts my suppositions and it makes sense too. thanks :p
 
Okay, I did some research because my memory was a bit cloudy. The Crankshaft position sensor is used to control ignition timing, period. But, the computer does use the Camshaft position sensor to find #1 cylinder.
The computer knows that it takes two crankshaft rotations to complete a full 4 stroke cycle. Once it fires #1 cylinder it will wait two rotation untill it fires it again.

The reason why is because timing chains and belts stretch The crankshaft is a more consistent and reliable source for the ever important ignition timing. Don't believe me, next time start you start you FI engine, after it is running disconnect the cam sensor, i bet you it will still run. (except for Powerstroke Diesels of course)


brichter said:
You are incorrect.

COP (Coil over plug) systems cannot rely on only a crankshaft sensor to determine when to fire the spark plugs because the crankshaft reaches TDC twice for every firing event. The camshaft is in position on the compression/power stroke only once for every firing event, and so is also needed to trigger COP systems.
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Kawowie said:
Okay, I did some research because my memory was a bit cloudy. The Crankshaft position sensor is used to control ignition timing, period. But, the computer does use the Camshaft position sensor to find #1 cylinder.
The computer knows that it takes two crankshaft rotations to complete a full 4 stroke cycle. Once it fires #1 cylinder it will wait two rotation untill it fires it again.

The reason why is because timing chains and belts stretch The crankshaft is a more consistent and reliable source for the ever important ignition timing. Don't believe me, next time start you start you FI engine, after it is running disconnect the cam sensor, i bet you it will still run. (except for Powerstroke Diesels of course)
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Cost of school today: Zero dollars.

:laughing :twofinger
 
Kawowie said:
Honda Outboard... I'd be interested in more information on how it works and the benefits.
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Better ask your questions fast, because the memory is fading fast. Did the V-Tec kick in at 4800 RPM? Maybe 3500? Shit, can't remember, I think 48 and off at 35.


TheRobSJ said:
The CKP (crank) sensor more or less provides the base timing. A modern SFI engine can run (badly) on just the CKP.
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You can disconnect a lot of sensors and it will keep running :laughing

TheRobSJ said:
EDIT: I just remembered. There's also a new ignition system out that doesn't use a CMP sensor. GM's compression sense ignition. It's a waste spark system like the old DIS, but through some trickery in the coil/cassette they can control fuel timing without the need for a seperate CMP. (which of course saves a few bucks producing the engine, and that's what GM is all about)
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Ion sensing?
 
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Miles per gallon is overrated!

I like to think of it in terms of "FUN per gallon", and the bike wins hands down!
 
Okay...I am really confused now. I thought a FI car (or bike) could not run if there was no fuel. If the injectors are shut off, wouldn't all the fuel in the cylinders be burned and then the engine would die? I mean, no fuel equals no combustion, no combustion equals no power, no power equals no movement...right?? So, are you saying that if you cruise down hill, your bike shuts off?? It just makes no sense to me that the FI's would be shut off and the engine still running...Did I miss something??

I know for a fact Chrysler's HEMI shuts off 4 CYLINDERS while on cruise to save fuel.
 
zyrusp said:
Okay...I am really confused now. I thought a FI car (or bike) could not run if there was no fuel. If the injectors are shut off, wouldn't all the fuel in the cylinders be burned and then the engine would die? I mean, no fuel equals no combustion, no combustion equals no power, no power equals no movement...right?? So, are you saying that if you cruise down hill, your bike shuts off?? It just makes no sense to me that the FI's would be shut off and the engine still running...Did I miss something??

I know for a fact Chrysler's HEMI shuts off 4 CYLINDERS while on cruise to save fuel.
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I think you answered your own question. I assume when the motor stops the fuel to the injector, the spark is shut off as well.
 
zyrusp said:
Okay...I am really confused now. I thought a FI car (or bike) could not run if there was no fuel. If the injectors are shut off, wouldn't all the fuel in the cylinders be burned and then the engine would die? I mean, no fuel equals no combustion, no combustion equals no power, no power equals no movement...right?? So, are you saying that if you cruise down hill, your bike shuts off?? It just makes no sense to me that the FI's would be shut off and the engine still running...Did I miss something??

I know for a fact Chrysler's HEMI shuts off 4 CYLINDERS while on cruise to save fuel.
Click to expand...



It CAN "run" when there is no fuel (for a limited time). The engine isn't generating power, the momentum of the bike is. When you are on the throttle in gear, the engine is turning the wheels. When you are off the throttle in gear, the opposite is happening - the wheels are turning the engine. Engine is turning the water pump, alternator, etc...
 
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ScottRNelson said:
And we know that to meet emission requirements, it is necessary to keep the air/fuel ratio as close to optimal as possible, which is not what happens when you pump through air without fuel.
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Air pumped through an engine driven by inertia should pass an emissions test just fine.

It's not just fuel cut, but also ignition. There's no burn, therefore no emissions except for what the catalyst might still be burning off.

Letting the catalyst cool too much might be a problem for emissions once the engine is fueled again, but I've never seen my MPG indicator go from "infinite" to high on a long downhill coast.

You have to be specific when talking about throttles. Someone mentioned idle air control: some cars have the computer controlling the throttle butterfly so when the pedal is in "idle," the throttle might not be nearly closed. BMW Valvetronic engines don't even have throttles.

I wish cars had something like a (reverse) jake brake so you could open the throttle while keeping the gas off to speed up a bit without having to put in the clutch.
 
auntiebling said:
emissions tests aren't run with the engine coasting in gear. SMOG standards are maximum values for whatever you're measuring. so, if all you're doing is pumping air through the motor you'll be under the max numbers, unless the atmosphere fails smog testing in which case you should move.
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Also, when vehicles are being qualified for emissions levels by the federal government, they measure grams per mile not percentage or parts per million, and the method of measurement is different than a standard smog check.

So, when we're discussing the reasons for not shutting off the injectors during decel due to emissions, it's not necessarily with regard to the smog check program.
 
zyrusp said:
Okay...I am really confused now. I thought a FI car (or bike) could not run if there was no fuel. If the injectors are shut off, wouldn't all the fuel in the cylinders be burned and then the engine would die? I mean, no fuel equals no combustion, no combustion equals no power, no power equals no movement...right?? So, are you saying that if you cruise down hill, your bike shuts off?? It just makes no sense to me that the FI's would be shut off and the engine still running...Did I miss something??

I know for a fact Chrysler's HEMI shuts off 4 CYLINDERS while on cruise to save fuel.
Click to expand...
not sure on the cage, but all FI bikes have a idle/pilot fuel circiut that supplies fuel when you close the throttle & the injectors aren't pumping fuel into the combustion chamber. its meant for idle, but still supplies enough fuel to keep the engine running while decelling in gear or @ idle.
 
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