Question about the limp-home feature.
6/11/04, 02:56 AM
#1
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Will it be possible for you to decide if you drive on "limp-home mode" at your own control, meaning even if there's nothing wrong with the engine. You know, freakin' Europe high gas prices are killers. I read the new Chrysler 300c had a Multiple Displacement System, which allows you to turn off cylinders for maximal fuel-efficiency on the 5.7 Hemi V8.
I was wondering if the limp-home feature could be used in the same kinda way to create this effect? A simple push on a button?
I was wondering if the limp-home feature could be used in the same kinda way to create this effect? A simple push on a button?
6/11/04, 03:49 AM
#2
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It would be good if the computer could control which cylinders were used under which circumstances, i.e. when you are cruising at 75mph, shut down two or four of the cylinders, lift the valves and cut off the fuel. If you hit the throttle for any reason, the cylinders fire up again (might be a little lag though). That way, if you are driving in a style of a 4 pot 2.3, you could get 4 pot efficiency.
On efficiency though, My father-in-law has a 5.0 1990 Thunderbird and can get 32 imperial mpg out of it on a run (I'm averaging 28 in my V6!)
On efficiency though, My father-in-law has a 5.0 1990 Thunderbird and can get 32 imperial mpg out of it on a run (I'm averaging 28 in my V6!)
6/11/04, 07:04 AM
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the system on the 300c is designed to improve fuel economy...i have not seen any literature describing it as a limp-home feature, but since the feature is designed into the software of the ecu and controlled by same, there's no reason why it couldn't be utilized as a failsafe in the event of a loss of coolant...that's how the original system on the cadillac northstar was designed...it will pump air into half the cylinders if the ecu senses a loss of coolant. if there is a loss of OIL...whether it's the oil pressure or the oil it self....the only system you want is one that SHUTS the motor down.
another point about the md on the chrysler: since it's controlled by the ecu and a bunch of parameters must be met before the ecu will go into the md mode, it's not something controlled by the driver. jackg 90seville 94k
another point about the md on the chrysler: since it's controlled by the ecu and a bunch of parameters must be met before the ecu will go into the md mode, it's not something controlled by the driver. jackg 90seville 94k
6/11/04, 09:14 AM
#4
I Have No Life
Limp home sounds like...
If something goes wrong between the throttle pedal and throttle body...that it opens enough that you can cruise without using the accelerator...
And it may come on in other instances as well.
Its a safety feature, and not used for anything else.
If something goes wrong between the throttle pedal and throttle body...that it opens enough that you can cruise without using the accelerator...
And it may come on in other instances as well.
Its a safety feature, and not used for anything else.
6/11/04, 10:22 AM
#5
Shelby GT500 Member
Fail-Safe Cooling
A fail-safe cooling system lets Mustang be driven under limited power for short distances if engine coolant is lost, eliminating the cost and inconvenience of towing. If the coolant level sensor reads below a critical level, the engine computer module switches the engine to an emergency limp-home mode, in which only half the cylinders get fuel. With only half the cylinders firing, the engine operates at lower power and generates much less heat. The cylinders alternate between even- and odd-firing pistons in this mode. The engine can move the vehicle at moderate speeds (up to about 50mph)
6/11/04, 10:28 AM
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yeah, thought i got it right...the use of variable displacement engines to improve fuel economy is something that needs to be pursued more aggressively than it has been. that technology could offer a real improvement in fuel economy on large displacement (relatively speaking) motors. there is some question about incorporating variable displacement on ohc motors. i have heard from engineers that it's rather tricky and expensive to manufacture. the 300c is a cam in block v8, so it's much easier and cheaper to produce. jackg 90seville 94k
6/11/04, 11:09 AM
#7
Originally posted by GhostTX@June 11, 2004, 11:25 AM
Fail-Safe Cooling
A fail-safe cooling system lets Mustang be driven under limited power for short distances if engine coolant is lost, eliminating the cost and inconvenience of towing. If the coolant level sensor reads below a critical level, the engine computer module switches the engine to an emergency limp-home mode, in which only half the cylinders get fuel. With only half the cylinders firing, the engine operates at lower power and generates much less heat. The cylinders alternate between even- and odd-firing pistons in this mode. The engine can move the vehicle at moderate speeds (up to about 50mph)
Fail-Safe Cooling
A fail-safe cooling system lets Mustang be driven under limited power for short distances if engine coolant is lost, eliminating the cost and inconvenience of towing. If the coolant level sensor reads below a critical level, the engine computer module switches the engine to an emergency limp-home mode, in which only half the cylinders get fuel. With only half the cylinders firing, the engine operates at lower power and generates much less heat. The cylinders alternate between even- and odd-firing pistons in this mode. The engine can move the vehicle at moderate speeds (up to about 50mph)
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