The standing ¼-mile acceleration time is a staple of the car magazine. If I am looking to buy a sports car, why should I care about this? What exactly is it telling me about the car’s performance?
Example from a recent magazine that pits the 2005 Corvette against the 2005 Porsche Carrera S:
Corvette: 12.9 sec @ 112.3mph
Porsche: 12.8 sec @ 110.2mph
This seems to tell me that the Porsche gets to the ¼-mile marker .1 second sooner but at a slightly slower end speed. Right?
Yes, but those numbers are so close that you’d have to really conclude that the performance of the two cars was the same.
Let’s try an example with the numbers a bit further apart.
Car A: 12.9 s @ 100 mph
Car B: 12.9 s @ 120 mph
In this example, cars A and B can both cover 1/4 mile in 12.9 s from a standing start. However, can B finishes with a much higher speed.
We can infer from these numbers that car A was much quicker off the mark initially. That should also show up in the 0-60 mph figures.
Car B however, has sufficient top-end power to catch up eventually.
Remember in drag racing it’s time not speed.
You can spend half a second burning your tires off and waste time at the line, and get a faster speed. While your opponent gets gets a great hole shot and beats you bon time.
It happens all the time.
As to why they use it in sales pitchees…they do it because it’s a standard.
FTR:
0-60 times:
Corvette: 4.5 sec
Prosche: 4.4
0-100 times:
Corvette: 10.1 sec
Porsche: 10.7 sec
Essentially, they mean…very little.
The quarter mile is the usual length of a traditional drag race (I say “usual” because there are also occasions whe eighth-mile times are used). However…
“Trap” speeds…the time/mph recorded at the end of the run…are dependent upon a number of factors. How good a launch did you get? What was the drivers reaction time to the starting lights? How much wheelspin occured? What were the traction conditions at the track? What kind of tires were used? What was the elevation, relative to sea level, of the track? What were the weather conditions?
It’s entirely possible for a vehicle to turn in a lower quarter-mile time with a lower trap speed (less wheelspin, better reaction time, different tires, etc.). The opposite is also true…slower time, but higher trap speed (started slow but accelerated better)…
It’s all dependent on the driver and conditions. No two runs will ever be exactly the same…drawing conclusions about which car performs “better” in a straight line is basically useless…unless you have essentially identical cars, on the same track, on the same day, driven by the same professional drag racer.
In essence, it’s a marketing/braggin’ rights tool, and the manufacturers and magazines know this. There are very few “regular” people out there who could EVER get the optimum performance numbers out of ANY vehicle. Case in point…I ride a 20-year-old motorcycle that is, in theory, capable of posting quarter-mile times that are quite impressive even by todays standards (10.54 seconds). Will I ever see that level of performance? Nope. I’m simply not capable of extracting it. Neither is 95 percent of the population.
It’s simply become one of the defacto measures of vehicular performance. IRL, it means very little…at least in terms of tenths of a second; obviously there’s a fairly apparent performance difference between a Porsche Boxter and a Yugo.
(Insert obligatory "Your Quarter-Mileage May Vary…)
Besides, sports cars are meant to go around corners! If you’re looking for handling info, take a look at the numbers for G-Forces generated on a skidpad. That’s where the REAL fun is, anyway!!!
Yep. Those last figures you posted show that the performance of the two is very, very close. The Porsche was marginally quicker off the line.
But what do the numbers mean in the real world?
If you’re going to be a stop-light dragster, you want the lowest possible 0-60 time.
Let’s try another example:
Car A: 0-60 4.5 s, 1/4 mile 14.0 s
Car B: 0-60 5.0 s, 1/4 mile 13.0 s
Car A is the better stop-light dragster. Car B is better at high speed, probably because of greater power (probably combined with greater weight). Car B is going to be better at overtaking at highway speeds.
On preview, what TheInterruptingCow says about corners is very important too.
I don’t think the quarter mile time is important in and of itself–that is, in absolute terms. However, it’s a fairly quick and easy way to compare two cars; if car A has a quarter mile time of 12 seconds, then it’s a pretty damn fast car. If car B has a quarter mile time of 16 seconds, then I can tell that it’s quite a bit slower than car A. When researching what car to buy, if one has a second shorter quarter mile time, I might infer that its acceleration is better, and thus I should test drive it over the other.
More interesting to my mind is the rolling start 5-60 mph test. After all, the time acceleration is most important is on highway ramps (or passing), where you’re not completely stopped.
[quote]
Yep. Those last figures you posted show that the performance of the two is very, very close. The Porsche was marginally quicker off the line.
[quote]
You do realize that, that is more likely because of the driver and not the car.
[QUOTE=Reeder]
[quote]
Yep. Those last figures you posted show that the performance of the two is very, very close. The Porsche was marginally quicker off the line.
Those numbers aren’t arrived at in a one-off. It’s usually the best number achieved after doing it over, and over, and over again.
True, a real sports car is made for the twisties but I wouldn’t use stock skidpad numbers to determine handling.
Skidpad numbers (of a stock car) will depend highly on the stock tires which are the easiest to change. The only way to compare 2 skidpad numbers is to use the exact same tire on both cars.
FTR my $33K (CAN) Matrix XRS stock out handles a $41K (CAN) WRX skidpad wise (0.83 vs 0.78g). I love pointing this out to my buddy who has one and who I’ve defeated on a track every 2 out of 3 races (legal race track, not a street).
Seems covered. I’ll add a few things to consider when you look at those times.
All these things will affect the elapsed 1/4 times;
Driver
Tires
Staging technique
weather
track surface
Automatic vs manual trans.
Now if the two cars are at the same track and have the same driver then the only variables will be tires and drivetrain. And luck. When you’re looking at any car that tops 100 at the trap and is faster than 13 secs in the 1/4 then you’re looking at a car that has lots of potential. I would not go by the 1/4 mile times at that point, the overall feel of the car and the way it handles would be more of a decider. Since a car with that kind of power can be modified to be even faster than factory stock, I would look into some aftermarket mods and those costs for each car. Straight line power is impressive but can be improved after you posses the right car.
Those number speak to the power of the car. Higher MPH = higher power/weight ratio. The Vette is slightly more powerful than the Porsche but because the Porsche has all that weight (rear engine) over the drive tires, it launches better and thus makes it to the finish first. AWD cars often show impressive ET’s (elapsed time) but only because the car covers about the first 100 feet fast, but not too much power shows up in the MPH.
60’ times, 0 - 60, 1/4 mile and MPH offers lots of information about how the car will pull when the right leg gets straightened out. An example of how the numbers help is where the small high revving engine that gets the good looking horse power rating but does not run so good in the 1/4 mile - No Torque.
1/8th mile tracks are only around because there was not enough room for the full 1320. Lots of people also only run for the 1/8th because the car does not meet all the safety specs for running a full 1/4 mile
All true except for the reaction time part - the clock does not start until the car breaks out of the second staging light so one may wait for a long time after the green light to go. Of course the other car will probably be headed down the track and it is the first to finish without running out that wins.
Different track conditions will affect cars on all types of tracks. To say straight line performance is useless is just false. Typically even novice drivers can get close to a pro with regard to MPH (in the same car), it does however, take lots of skill to get the car off the line as good as possible which is where the good ET’s come from
Marketing/braggin’ just as much as all the other specs - why is it any different from any other spec on the car? It is a very useful spec for one with more interest than simple transportation.
Bikes are way harder to drive than cars on the strip.
OK, then how do we rate real world power? Should we change it to zero to 1,500 feet or 0 to 1,300 feet? We should be glad there is a universal standard for comparison.
Baahhhh, road racing is just a drag race to the next turn 
The brake and skid pad specs are there for a reason too.