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Old 29th October 2011, 12:00   #1
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Question Steps in calculating the acceleration timings [0-100 & in-gear]?

Mods: Please move the thread to the correct section if this is not the one. Please merge if there is a similar topic already in discussion - did a search, but could not find one dedicated to this discussion.

There would be NO true car lover who would not have bothered about the 0-100 timings at-least once during their ownership period! There could be another LOT who even have this as one of their MAJOR criterion in choosing their ride! Even among those who don't choose a ride based on this, there will be a handful who will go to any extent to improve their 0-100 timings!

Leave 0-100 timings, which is touted as a non-realistic every day driving style, there are other parameters called the "in-gear acceleration" times which are better related to everyday driving style.

Now this leaves me with a doubt - How are these timings captured?! I know, there are certain "equipments" [V-box?] used to get this & some car magazines use a "test track" to arrive at these figures. Naah, I am NOT talking about the equipment; rather the way these speeds are tested & how!

Questions:

1. 0-100 timings: So how do we test this timing? Is the objective of the driver to some-how reach 100 kmph limit or does he have to follow some steps like, he has to reach some speed in each gear before he upshifts to the higher one? Or is it "shift early & reach the 100 kmph mark"?

2. In-gear acceleration time: What are the different in-gear accelaration types? Like 0-60 or 20-80 or 40-100 ??

3. Again what are the steps involved in doing the in-gear acceleration tests? For example, if you take 20-80 kmph test, in what gear should the driver start testing when he is on 20 kmph? Similarly for other in-gear acceleration times as well?

So the guys who are familiar with this testing, please provide the details.
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Old 29th October 2011, 13:03   #2
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Default Re: Steps in calculating the accelaration timings [0-100 & in-gear]?

Try launching the cars at different RPM to manage the best times. Most cars have different power and torque characteristics, so finding the perfect upshift point especially with Diesels requires repeated runs.

Acceleration figures are good reference to a car's actual on road performance, but testing conditions are not always same for fair comparison. Lot of factors like Altitude, Humidity, Road etc do matter.

The only correct way to capture the timing accurately is using professional gear like VBox etc. I have observed the iphone/Andriod apps to be very inaccurate, i got timing lower than the manufacturer claimed time in my Laura while testing with a Android app with satellites locked. Testing with speedometer and stop watch is not even close to accurate.
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Old 30th October 2011, 01:23   #3
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Default Re: Steps in calculating the acceleration timings [0-100 & in-gear]?

Quote:
Originally Posted by swiftnfurious View Post
1. 0-100 timings: So how do we test this timing? Is the objective of the driver to some-how reach 100 kmph limit or does he have to follow some steps like, he has to reach some speed in each gear before he upshifts to the higher one? Or is it "shift early & reach the 100 kmph mark"?
Plainly speaking, the objective of the driver is to reach 0 to 100 the fastest way. He can choose the best driving pattern, in which the car accelerates the most. It varies for different cars. AFAIK, the best timings are achieved in several tries, and not just one. Also, cars with a slightly taller 2nd gear (though impractical in daily drives) have much better in 0 - 100 timings. Say about 3/4 sec quicker than the a car with same specs. (You save shifting time - in manual 'box)
Quote:
Originally Posted by swiftnfurious View Post
2. In-gear acceleration time: What are the different in-gear accelaration types? Like 0-60 or 20-80 or 40-100 ??
These figures are mainly to show off the cars highway capability. 3rd , 4th , 5th are the gears with matter much, and the speed range is 40-120.
Quote:
Originally Posted by swiftnfurious View Post
3. Again what are the steps involved in doing the in-gear acceleration tests? For example, if you take 20-80 kmph test, in what gear should the driver start testing when he is on 20 kmph? Similarly for other in-gear acceleration times as well?
In this specific example of yours, 20-80 roll tests on can be done in 2nd 3rd and 4th gears in modern cars.

So, if its the 2nd gear test, then, AFAIK, you have to be in 2nd gear and moving (not accelerating) @20kmph steady. After which, @20 you floor the pedal, and you note down the time taken by the vehicle to reach 80, in the same gear.

Same procedure for all gears/speeds.

P.S - Please correct if I'm wrong.

Last edited by dhanushs : 30th October 2011 at 01:25.
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Old 31st October 2011, 00:51   #4
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Default Re: Steps in calculating the acceleration timings [0-100 & in-gear]?

I think what dhanushs has explained is spot on.

But the question remains whether a common man can actually measure these on his daily ride!

The only practical way i can think of is:
- Two people: one in the car, one outside wid a stopwatch communicating via wireless or mobile phone
- An empty stretch of road, preferably a track
- Driver indicated when he starts accelerating, flashes the lights when he reaches the desired speed!
- The guy outside does the timing

Crude, but cant think of anything better.
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Old 31st October 2011, 05:44   #5
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Default Re: Steps in calculating the acceleration timings [0-100 & in-gear]?

Quote:
Originally Posted by swiftnfurious View Post
1. 0-100 timings: So how do we test this timing? Is the objective of the driver to some-how reach 100 kmph limit or does he have to follow some steps like
The aim is to get to 100 as fast as possible.

From the driver's point of view, going as quick as possible means :
  • Getting the best launch
  • Choosing the best shift points (typically at redline for petrol cars, but depends on gearing and power curve of the engine)
  • Getting the fastest shifts


Things that can alter the consistency of this timing :
  • Typically (as noted in drag racing too), getting a good launch is key to getting the best timed run from a standstill. This is also the area where any driver is typically the least consistent (as compared to his shifts, or keeping his foot on the gas!).
  • Passengers and additional weight in the car can affect timed runs negatively.
  • Environmental factors such as high ambient temperatures or high altitudes can have a negative effect too. Search the forums for detailed discussion on these. Colder air = more horsepower, a place where Indian timings usually lose out.
  • Track/Road conditions play a part too - dust or dampness = less traction at launch, concrete vs asphalt behave differently too. If you want to get really picky, then track temperature can affect traction too.
  • Choice of tyres (stock vs broader widths on higher variants vs aftermarket) can significantly affect traction and rolling resistance.
  • Tyre pressure (once again traction and rolling resistance)
  • Wind and slope of the road can typically be countered by doing 2 runs in opposite directions and then averaging them out.
  • Electronic aids are often overlooked! Sometimes traction control and other aids can sometimes slow the car's 0-100 down.
  • Auto-tranny settings are sometimes forgotten about too. Always best to have it in the highest level of sport mode. Accelerator + Brake just before launch can also get best results in the case of ATs.
  • Launch control (if available) can take the largest doubt of the launch out of the equation, though in rare cases a manual launch could give better results.
  • Errors in calibration or quality of the timing equipment.

^ As you can see, thats a long list! So keep in mind that theres always a +/- factor around these figures, regardless of how super-accurate the timing gear is.


Quote:
Originally Posted by swiftnfurious View Post
3. Again what are the steps involved in doing the in-gear acceleration tests? what gear should the driver start testing when he is on 20 kmph?
The window (eg. 20-80km/h) and gear are always mentioned. Usually the choice of both is to pick a long enough pull to exercise the engine through a wide enough range, as well as pick a gear that isn't too high or low a ratio.

From the drivers point of view this is easy - no clutch to be used - pedal to the metal on "go".


cya
R

Last edited by Rehaan : 31st October 2011 at 05:45.
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