Drag Limited and Redline Limited.....the difference??

[humaid]

Ok...I thought I knew what drag limited speeds were, but every time I keep reading Red line limited I keep getting confused.

Ok this is what I think drag limit means. The drag limit occurs when the car is using ALL of its power to overcome air resistance, so there is no power left for acceleration (i.e. speed stops increasing and remains constant.)

So what is Red line limited? Is it saying the same thing in a different way? Or have i described red line limit and not drag limit?

help....................

[mindgam3]

Haven't heard of these particular terms but im assuming your refering to top speed...

When a car is red line limited, it's the engine power that's restricting its top speed, not its aerodynamic properties.

Eg a 1.2 clio will go 110mph, not any more because the engine hasnt enough power...

A 1.8 clio will have a higher top speed and be limited by its engine but it still hasnt reached its "aerodynamic peak".

An F1 for example could go much faster than 220mph but because it has so much downforce (and therefore drag) it cannot go much faster than this....

[humaid]

Originally Posted by mindgam3 Haven't heard of these particular terms but im assuming your refering to top speed... When a car is red line limited, it's the engine power that's restricting its top speed, not its aerodynamic properties. Eg a 1.2 clio will go 110mph, not any more because the engine hasnt enough power... A 1.8 clio will have a higher top speed and be limited by its engine but it still hasnt reached its "aerodynamic peak". An F1 for example could go much faster than 220mph but because it has so much downforce (and therefore drag) it cannot go much faster than this....

but doesn't that mean the same? At least to some extent...I mean in my mind, a car with the same body but a smaller and weaker engine has a lower top speed, simply because the lower power can overcome the air resistance to a lesser degree.

I understand what you are saying, but is there a speed limit beyond which a car with a certain drag coeff. can NOT go REGARDLESS of power?

That's the bit that confuses me...

[mindgam3]

Originally Posted by humaid Originally Posted by mindgam3 Haven't heard of these particular terms but im assuming your refering to top speed... When a car is red line limited, it's the engine power that's restricting its top speed, not its aerodynamic properties. Eg a 1.2 clio will go 110mph, not any more because the engine hasnt enough power... A 1.8 clio will have a higher top speed and be limited by its engine but it still hasnt reached its "aerodynamic peak". An F1 for example could go much faster than 220mph but because it has so much downforce (and therefore drag) it cannot go much faster than this.... but doesn't that mean the same? At least to some extent...I mean in my mind, a car with the same body but a smaller and weaker engine has a lower top speed, simply because the lower power can overcome the air resistance to a lesser degree. I understand what you are saying, but is there a speed limit beyond which a car with a certain drag coeff. can NOT go REGARDLESS of power? That's the bit that confuses me...

Yes... as i said, F1 cars to a certain extent....

F1 cars have been going over 200mph for donkeys years, but the aerodynamics have been getting better as well as the engines.... which means greater accelration, better road holding but about the same top speed..

[gottacatchup]

Okay this is how it works,

Drag Limited: car's engine can no longer overpower the resistant force of the air.

Redline limited: The car redlines in the last gear, no longer allowing the engine to rev further and creat higher speeds.

Drag is a problem of power while redline is a problem of gearing.

[TransAm]

If you can get a ride in a CRX VTEC - that is one of the few cars I've driven that is redline limited - it will hit redline in 5th gear (145-148ish) with a sports exhaust and intake.

[humaid]

ok so here's what i understand:

If the drag coeff. the weight of the car and the power the engine produces tell us the car should do more than 200 mph and it DOESN'T, then it is probably an issue of gearing and is hence red-line limited in terms of top speed (ignoring friction and temp. etc)?

So do I understand now or am I still just spewing out a load of...

[jakaracman]

I'll tra to be clear:

Redline limited top speed means that the car basicaly bounces of the limiter (or reaches redline, whichever comes first) in top gear. Aerodinamicaly it could go faster, but engine can't rev higher and there's no more gears.

If the engine has not reached redline in top gear then the car's top speed is drag limited. It can be that with different gearing it could go faster but since it's the drag that's directly responsible for limiting the speed, it's drag limited.

You can make drag limited car go faster simply by driving downhill - gravity will help engine and since it is not on the rev limiter it will go faster. If you go downhill in redline limited car it'll just bounce of limiter and will not go faster.

I hope I have been clear enough ...

[humaid]

You can make drag limited car go faster simply by driving downhill - gravity will help engine and since it is not on the rev limiter it will go faster. If you go downhill in redline limited car it'll just bounce of limiter and will not go faster. I hope I have been clear enough ...

Perfectly clear thanks.

So to enable a car to reach maximum speed (for simplicity's sake let's assume there's just one gear) the car engine should be producing it's maximum power when it's speed get's limited by drag?

[homemade wrx]

just to let you know in future reading redline limtied is also commony reffered to as gearing limited...being they have no gear left due to the redline...

[deth]

Originally Posted by humaid ok so here's what i understand: If the drag coeff. the weight of the car and the power the engine produces tell us the car should do more than 200 mph and it DOESN'T, then it is probably an issue of gearing and is hence red-line limited in terms of top speed (ignoring friction and temp. etc)? So do I understand now or am I still just spewing out a load of...

weight does not effect top speed. just acceleration..............well, it does a little, in the from of rolling resistance, but its negligible as compared to drag.

[jakaracman]

Originally Posted by humaid You can make drag limited car go faster simply by driving downhill - gravity will help engine and since it is not on the rev limiter it will go faster. If you go downhill in redline limited car it'll just bounce of limiter and will not go faster. I hope I have been clear enough ... Perfectly clear thanks. So to enable a car to reach maximum speed (for simplicity's sake let's assume there's just one gear) the car engine should be producing it's maximum power when it's speed get's limited by drag?

Exactly ...