0 - 60 vs 5 - 60 ?

[AZ_G]

I have noticed in most car mags that the testers test 0-60 acceleration as well as 5-60 acceleration along with other tests. I figured the 5-60 was pretty much idle with no braking. What I don't understand is why are they always slower than 0-60 times? Logically you would think that the car with a rolling start is getting a head start and would therefore be faster. Someone care to explain? Thanks.

[Nissan_Admirer]

Actually 0-60 is idle with foot braking. You can possibly get slower 5-60 times than 0-60 times because of your torque curve. Some cars have tremendous torque on lower revs so they can pull away faster from a rolling start than from idle. Other cars need to wind up first to build any torque to get the car moving. Hope that helps.

[mayhem]

5-60 involves getting the car rolling and then just matting the gas pedal, which in pretty mcuh any car with less torque than a CL65AMG is going to bog the motor. 0-60 you can power brake it or pop/slip the clutch.

[Nissan_Admirer]

Not all car magazines test 0-60 with power brake it or pop/slip the clutch. Eg. MotorWeek tests their 0-60 times with engine at idle and foot braking.

[AZ_G]

So are you guys saying that most car mags like Car and Driver, Motor Trend etc. are actually power braking rather than just idle with foot on break when they do their 0 - 60 tests?

Is power braking when you step on the gas and brake at the same time and then release the brake?

[NISSANSPDR]

Isnt 5-60 a "street start"?

[Nissan_Admirer]

I'm not sure about Motor Trend but with Car & Driver. When I used to subscribe to them they had an explanation in the back where the test results were. On how they obtained their 0-60 times. From what I remember they'd test 0-60 times going in both directions a few times and they'd take the best 2 out of 3 runs in each direction and then average them together. With cars with auto gear boxes they'd use the power/torque braking method (eg. feet on both throttle and brake pedals at the same) when it was beneficial to the test. In other words, they'd use this method when it would give better 0-60 times. Cars with manual gear boxes, they'd dump the clutch when they hit the peak of the power band. I hope that helps.

[Madmaster]

Isnt 5-60 a "street start"?





I'm pretty sure.

[Nismo]

I have noticed in most car mags that the testers test 0-60 acceleration as well as 5-60 acceleration along with other tests. I figured the 5-60 was pretty much idle with no braking. What I don't understand is why are they always slower than 0-60 times? Logically you would think that the car with a rolling start is getting a head start and would therefore be faster. Someone care to explain? Thanks.



Low-speed acceleration is all about traction. A car will accelerate best when you deliver to its wheels the maximum amount of torque the tires can handle without losing traction. The real physics explanation to your question is too long for this post, but basically, it's because

(1) Weight transfer - it's easier to regulate weight transfer (and, thus, traction) when starting from zero

(2) Engine power band - gas pedal + slipping clutch allows you to optimize power to the wheels easier than the gas pedal alone

Now if the car was traveling at 5 mph and at that point you gave it a proper clutch-slipping drag racing launch, then it would be slightly faster than a 0 mph start. But the magazines purposely don't do this because they really are just trying to figure out the car's "streetable" low-end power.

On a side note, an F1 race car does 0-60 mph in around 2.5 seconds and 0-100 mph in around 2.9 seconds (that last 0.4s must be really fun), but it would fail the street start 5-60 mph test because it can't drive that slow with the clutch fully engaged. Even with extra-low gearing, it would still do badly because the engine would bog like crazy at those low revs--my shifter kart won't even run below 4000 RPM and I think F1 engines idle at 6000 RPM.

[RickBullotta]

My Maserati Coupe has F1-style paddle shifters and a computer controlled clutch. The clutch doesn't really engage in first gear until about 1500-1800 RPM, and even then, eases things along until about 2500 when it takes off like a rocket.

The Maser, for example, wasn't designed for rapid launch from the line with the F1 shifters, but rather, for a really sweet "5-100" time (or 150 for that matter http://forums.freshalloy.com/images/graemlins/grin.gif ).

In any case, a rolling start is a better indication of raw acceleration and power, as it takes out any tranny or other "wind up" time.

Personally, I find a fast 60-100 time a heckuva lot more useful and fun than a fast 0-60.

[Nismo]

Personally, I find a fast 60-100 time a heckuva lot more useful and fun than a fast 0-60.


http://forums.freshalloy.com/images/graemlins/grin.gif

[Dave562]

Personally, I find a fast 60-100 time a heckuva lot more useful and fun than a fast 0-60.



I've seen a twin-turbo Diablo that did it in 2.2, up a hill.