Wheel Circumference

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Famine
What car are you driving that has a 1st gear ratio of 11mph/1000rpm?
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My GT5 garage has a metric butt load of muscle cars running comfort hards that are geared similarly. Not much point in a first gear that does nothing other than burn off your tires.
 
If your car is running and your foot is off the gas pedal your car will return to idle unless it stalls.

That being the truth, if your car is in gear it will move at some type of speed. if it is in neutral, it will not move unless it was previously rolling or on a hill.

my corvette went almost 60 mph in 1st gear at approx 6000rpm.
 
Unless you have clutch slip...


When you say my Corvette, do you mean a real Corvette, or a GT5 Corvette? I wouldn't really want any car engine to go to 6000 continuously unless you want the pistons to go stage left.
 
I didn't realize my post got so many responses. I just logged back in to check.


Someone above figured it out, but this is from a high hp, high torque muscle car. The peak ranges are mid rpm.

I was working on a model that would allow me to calculate the last gear's ratio needed to hit a target speed at a target rpm. I use minimum final possible to max hp to the wheels, and want to hit max expected speed at the peak point in powerband.

So far the model is working for me.
 
yes it was my actual corvette. a 96 lt4 with stock 3.4x gears with the stock trans. ran 12.9 @ 109. in real life.

even if your clutch slips (not a possibilty in gt5) your car will still move if its in gear and your foot is off the clutch.
 
lav01
even if your clutch slips (not a possibilty in gt5) your car will still move if its in gear and your foot is off the clutch.
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Which isn't idle. Idle specifically refers to a state of no work - with the gearbox in neutral or the engine disengaged from the wheels. It's a specific term in physics and in mechanics.

When moving, in gear and with no throttle, the engine speed the car will try to reach is the stall speed - which may be well below or above the idle speed, but is commonly there or thereabouts. If it doesn't have enough torque to keep itself above the stall speed for the engaged gear... it stalls.


Anyway, a nearly 7 foot circumference will give a just over 2 foot diameter and on a 16" wheel that's 4" of tyre sidewall top and bottom - equivalent to a 50 profile, 205mm tyre. So the formula looks about right.
 
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You can think what you want, but if your car runs, you can put it in a gear..... if it doesnt stall it will move. Idle rpm will slow down dramatically on a lesser torque motor. but the car can idle in gear. take an automatic hyundai (for example) put it in drive and take your foot off the brake and the car will move.

thats all i was saying.
 
Yes, it's been covered. It's nothing to do with wishful thinking, it's a specific term. "Idle" specifically means in a state of no work - with the engine either decoupled from the transmission (by clutch) or with the transmission in neutral. In fact those are two different idles, since one is loaded with the input shaft and the other is unloaded, but they're both idles.

Shift it into gear and couple the engine and transmission and you're no longer idling - work is being done to turn the output shaft, driveshafts and hubs. The engine now requires a torque output to prevent it from stalling. If you shift from neutral to first, out of idle, the car will pull itself along providing it has the torque to do so and it'll maintain the rpm required to prevent it from stalling - stall speed. If it doesn't have the torque you're required to open the throttle a little to increase rpm, increase torque and manually keep it above stall speed.

And thus we return to the absolute statement that what engine speed a car idles at - the speed it maintains when in neutral or decoupled from the transmission and no work is being done - is irrelevant to what engine speed it requires in any given gear to travel at any given road speed. What you're talking about - the stall speed - requires gear ratios to be taken into account and is thus not the idle speed which requires neutral or decoupled transmission.

You can't move under power and be idling, because idling requires no movement under power.
 
then we just have a different view of idle. mine is no foot on the pedal. and im thinking yours is if its neutral.

what if your on a hill and in neutral and under idle.... will the car move then?
 
lav01
then we just have a different view of idle. mine is no foot on the pedal. and im thinking yours is if its neutral.
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As I say, it's not a question of view but a specific physical and mechanical term. It requires no work to be done (physics) and this is achieved either through a decoupled transmission through a clutch or a transmission in neutral (mechanical).
lav01
what if your on a hill and in neutral and under idle.... will the car move then?
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Famine
idling requires no movement under power.
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Whether it rolls away due to gravity or not is irrelevant - idling requires it not to move under power.
 
i understand, but the engine to just be running is doing work. the gravity comment was out of bounds, sorry for that.
 
lav01
i understand, but the engine to just be running is doing work.
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Quite - it moves ancillaries like aircon and *spits* power steering - and even, if you're talking about a neutral idle, the gearbox input shaft (though that's considered part of the crankshaft as it forms a single continuous piece).

But it's work done to move the car that constitutes the delineation of an idle state from a non-idle state. If the car is not moving under power with the engine on, it's idling - or badly broken. If it is moving under the engine's power, it isn't idling.

The engine speed required to just pull the car along in 1st without any throttle input is commonly very close to the warm idle speed of the engine, yes. But it's not idling when it's doing it because idle requires no work to be done to move the car.
 
Famine
Quite - it moves ancillaries like aircon and *spits* power steering -
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Don't hate on power steering, little old ladies like to drift too!

*goes back to lurking because this is a really interesting read*
 
lav01
idle needs power. if you have no pwer the car wont turn on.
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Famine
If the car is not moving under power with the engine on, it's idling - or badly broken. If it is moving under the engine's power, it isn't idling.
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Moving under power. Moving. Under power.

Idle requires the engine not to do work to move the car. Idle in physics means in a state of no work being done (work, by the way, means the application of a force to result in displacement in the direction of the force, in physics). Idle in vehicle mechanics means in a state of no work being done by the engine's power to displace the vehicle.
 
jimipitbull
Idle in engine/vehicle mechanics can also be defined as "running with no throttle input"
http://www.driverside.com/car-dictionary/idle-9-129
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Then we're looking at a potential transatlantic confusion of terms.

A car moving under engine power is experiencing a displacement proportional to the (geared) force of the engine. When force (engine) is being used to displace an object (the car), work is being done - and that's very specifically not what idle means.

Of course the throttle (which isn't your right foot) is always used to provide the engine with air or it won't work (save for coasting, when the wheels drive the output shaft, keeping the crank above stall speed), so that definition falls on mechanical terms too.

But if that's the norm for US usage of the term "idle", I can't really expect someone in the US to use it any other way.
 
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To complicate things further the term "Idle" has different meanings in different countries/languages, I think this is where the problem stems from, so both or all of the descriptions for the engine/car being in a state of idle are correct.

Edit... Famine beat me to it by 2 mins...
 
Let's just hope it's not an aluminium engine, or we'll be here forever.
 
all is good. if my car is turned on and it is in a gear it will move. gt5 is different as its a video game and not real.

idle to me means you started your engine and not stepping on the gas pedal. maybe in gear or not.
 
A ZC VTEC or D16z6? :dopey: Well... There are a few technicalities between both, but, ehh... And they're both aluminum. :sly:

I wouldn't really want any car engine to go to 6000 continuously unless you want the pistons to go stage left.
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And mine has the ability to go above 7500rpm reliably. It doesn't make power up there, but, it can go up there if I commanded it to.
 

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