MAJOR MISTAKE!!!!! Went in reverse at 60
Lead Driver
Joined: Nov 2002
Posts: 9,555
Likes: 40
From: Concord, NC
The overrun fuel cut takes about ten seconds to engage on my truck, but it does exist above 1500 rpm. I don't know if the newer trucks have the delay before it kicks in or not, but if it mine didn't have the delay, I would never notice.
Post Fiend
Joined: Apr 2004
Posts: 6,473
Likes: 4
From: Lafayette, IN
Originally Posted by andym
Also, I don't believe that the injectors are shut off over 1500 RPMs. For one, I can still hear the engine running in my truck.
Jason
More Turbo
Joined: Jan 2007
Posts: 678
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Originally Posted by andym
Also, I don't believe that the injectors are shut off over 1500 RPMs. For one, I can still hear the engine running in my truck.
Posting Guru
Joined: Jun 2007
Posts: 1,394
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From: Des Plaines, Illinois
Originally Posted by NeXtras
If there wa no gas being pumped in and the engine was still running wouldnt your CEL come on cause your trucks running too lean? not to mention wouldnt you hear knocking or pinging?
Post Fiend
Joined: Mar 2002
Posts: 19,402
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From: Bonita Springs FL
Originally Posted by jroehl
What you're hearing is a 5-5.8L air pump turning, compressing air from time to time...
Jason
Jason
Post Fiend
Joined: Apr 2004
Posts: 6,473
Likes: 4
From: Lafayette, IN
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Post Fiend
Joined: Apr 2004
Posts: 6,473
Likes: 4
From: Lafayette, IN
It does, but there's a whole heckuva lot else going on under the hood that contributes, and most of the sound from combustion is dissipated in the exhaust system, or directed out it, depending on your setup. Besides, what is the sound from combustion? A pressure wave--into the piston, at least in part. Think about how loud a compressor can be--with no combustion going on...
Jason
Jason
Lead Driver
Joined: Nov 2002
Posts: 9,555
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From: Concord, NC
You would be surprised at how loud the valvetrain is all by itself. We have a spintron at work to test valvetrain setups, which has no pistons, rods or crankshaft, but is still so loud that it necessitates a sound deadening enclosure.
More Turbo
Joined: Jan 2007
Posts: 678
Likes: 1
Ok, explain in detail what you mean.
Cause from what your saying, if the engines over 1500 and your foots off the gas, your saying no fuel is being pumped in?
Im sorry to say but by my understanding there, its impossible, the engine would die. Actually its the same as if you turned the key to shut the truck off, cuts the fuel supply which in turn shuts off the engine.
The ignition of fuel is what forces the pistons back down, so without ignition, how is the piston traveling back down? And you cant say the truck rolling is moving the engine either, cause if your foots off the gas, your not putting power to the engine thus no power to the torque converter THUS the wheels wont actually turn the engine.
Simple logic..
Now if i mis understood, please clarify
Cause from what your saying, if the engines over 1500 and your foots off the gas, your saying no fuel is being pumped in?
Im sorry to say but by my understanding there, its impossible, the engine would die. Actually its the same as if you turned the key to shut the truck off, cuts the fuel supply which in turn shuts off the engine.
The ignition of fuel is what forces the pistons back down, so without ignition, how is the piston traveling back down? And you cant say the truck rolling is moving the engine either, cause if your foots off the gas, your not putting power to the engine thus no power to the torque converter THUS the wheels wont actually turn the engine.
Simple logic..
Now if i mis understood, please clarify
Posting Guru
Joined: Jun 2007
Posts: 1,394
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From: Des Plaines, Illinois
Maybe I'm wrong, knowing less about automatics than standards, but I didn't think the torque converter *ever* stopped receiving power. Say for example you stop at a light, foot on brake. The truck will still take off on it's own at idle even with your foot off the gas...that tells me that regardless of your not pressing the accelerator, there is still transfer of energy.
True, ignition forces the pistons down, but they are still connected to a crankshaft that, when spun, will pull them back down simply because that's how the mechanism works with the offsetting of lobes. Lobe reaches high point, piston goes up, low point, piston comes down.
Since the crankshaft is connected to the torque converter, in theory spinning the driveshaft (by forward movement of the vehicle) would be enough to keep the engine turning regardless of fuel flow, meaning the serpentine system still works, so it's not like you'd see your lights dim or anything like that.
The computer seems to have this programmed in, so regardless of how you or anyone views the scenario, it appears to work.
True, ignition forces the pistons down, but they are still connected to a crankshaft that, when spun, will pull them back down simply because that's how the mechanism works with the offsetting of lobes. Lobe reaches high point, piston goes up, low point, piston comes down.
Since the crankshaft is connected to the torque converter, in theory spinning the driveshaft (by forward movement of the vehicle) would be enough to keep the engine turning regardless of fuel flow, meaning the serpentine system still works, so it's not like you'd see your lights dim or anything like that.
The computer seems to have this programmed in, so regardless of how you or anyone views the scenario, it appears to work.
Post Fiend
Joined: Apr 2004
Posts: 6,473
Likes: 4
From: Lafayette, IN
No, that's a misunderstanding of how a torque converter works. For one, an e-tranny can keep it locked up (by computer command) so that there IS engine braking, which occurs by putting NO fuel in the engine, but turning it anyway, basically turning it into a large air compressor--it's only compressing the air charge, not a fuel-air charge. A gas engine does not turn off by cutting the fuel supply (though power to the pumps is cut), but by cutting the ignition, since that is done by spark, which may or may not continue during coasting (not sure how the computer handles that). Once you reapply the gas, the computer turns the injectors back on, and, in essence, the engine is "push-started". For hydraulic trannies, the torque converter can still turn the engine by the vehicle's motion, the fins on the tranny side become the fluid pump acting on the fins on the engine side of the torque converter. Either way, the tranny/driveline keeps the engine rotating, in effect, being the "starter" while you're in motion.
Check this:
http://auto.howstuffworks.com/torque-converter.htm
Jason
Check this:
http://auto.howstuffworks.com/torque-converter.htm
Jason