Understanding 1/4 mile times
18-04-2012, 06:01 PM
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Understanding 1/4 mile times
I did 3 runs at central day in my estate,my 1st run I manged a 13.2 at 100.38mph and 60ft time was 1.894,my 2nd run was 13.4 at 104.78mph and 60ft time was 1.906 and then my 3rd run was 13.7 at 107.55mph and 60ft time was 2.220,what Im struggleing to work out is how my quickest run time wise was slowest speed wise,sorry if its a thick question
18-04-2012, 06:09 PM
#3
Its all to do with you have longer time to gain those extra speeds.
The better the launch the better the car is gripping and thus getting you to the 1/4mile line in a quicker time but not generating a quicker speed because you get there quicker.
If that makes any sense at all?
The better the launch the better the car is gripping and thus getting you to the 1/4mile line in a quicker time but not generating a quicker speed because you get there quicker.
If that makes any sense at all?
18-04-2012, 06:12 PM
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Its all to do with you have longer time to gain those extra speeds.
The better the launch the better the car is gripping and thus getting you to the 1/4mile line in a quicker time but not generating a quicker speed because you get there quicker.
If that makes any sense at all?
The better the launch the better the car is gripping and thus getting you to the 1/4mile line in a quicker time but not generating a quicker speed because you get there quicker.
If that makes any sense at all?
18-04-2012, 06:22 PM
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My 1st run I changed into 5th gear just before the finish line but the other 2 runs I held it in 4th so didn't know if the terminal speeds were to do with that aswell :-/ I can never really get my head round it properly :-/
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18-04-2012, 07:08 PM
#10
Norris Motorsport
Assuming you don't fluff any gear changes, and the run is otherwise identical your fastest actual time will be the run with the fastest 60ft time.
The faster you are doing at the 60ft mark, again assuming you dont fluff any gears and use the same gears (i.e. not changing into 5th) the faster you will cross the line because you are carrying more speed at the 60ft mark with a fixed amount of distance left to accelerate in. For that given distance if you are starting at a higher speed you will end up with a higher terminal speed.
As a very rough ball park we find that ever 0.1 saved on the 60ft time will save you 0.2 secs overall but obviously that is assuming each run is identical other than the 60ft time.
Changing gear just before the finish line is a complete no no! If you can hang onto 4th gear then do so, even if your power is tailing. It will give a quicker time.
Lastly remember your terminal speed is only the average speed over the last 60 ft of the run, not the actual terminal speed. For most cars that are'nt accelerating much at 100mph that won't differ much, but on hugh bhp cars it's a suprising difference. (up to 5mph more at the finish line compared to the 60ft average).
Hope that helps folk understand the drag strip a little more.
The faster you are doing at the 60ft mark, again assuming you dont fluff any gears and use the same gears (i.e. not changing into 5th) the faster you will cross the line because you are carrying more speed at the 60ft mark with a fixed amount of distance left to accelerate in. For that given distance if you are starting at a higher speed you will end up with a higher terminal speed.
As a very rough ball park we find that ever 0.1 saved on the 60ft time will save you 0.2 secs overall but obviously that is assuming each run is identical other than the 60ft time.
Changing gear just before the finish line is a complete no no! If you can hang onto 4th gear then do so, even if your power is tailing. It will give a quicker time.
Lastly remember your terminal speed is only the average speed over the last 60 ft of the run, not the actual terminal speed. For most cars that are'nt accelerating much at 100mph that won't differ much, but on hugh bhp cars it's a suprising difference. (up to 5mph more at the finish line compared to the 60ft average).
Hope that helps folk understand the drag strip a little more.
18-04-2012, 07:23 PM
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Assuming you don't fluff any gear changes, and the run is otherwise identical your fastest actual time will be the run with the fastest 60ft time.
The faster you are doing at the 60ft mark, again assuming you dont fluff any gears and use the same gears (i.e. not changing into 5th) the faster you will cross the line because you are carrying more speed at the 60ft mark with a fixed amount of distance left to accelerate in. For that given distance if you are starting at a higher speed you will end up with a higher terminal speed.
As a very rough ball park we find that ever 0.1 saved on the 60ft time will save you 0.2 secs overall but obviously that is assuming each run is identical other than the 60ft time.
Changing gear just before the finish line is a complete no no! If you can hang onto 4th gear then do so, even if your power is tailing. It will give a quicker time.
Lastly remember your terminal speed is only the average speed over the last 60 ft of the run, not the actual terminal speed. For most cars that are'nt accelerating much at 100mph that won't differ much, but on hugh bhp cars it's a suprising difference. (up to 5mph more at the finish line compared to the 60ft average).
Hope that helps folk understand the drag strip a little more.
The faster you are doing at the 60ft mark, again assuming you dont fluff any gears and use the same gears (i.e. not changing into 5th) the faster you will cross the line because you are carrying more speed at the 60ft mark with a fixed amount of distance left to accelerate in. For that given distance if you are starting at a higher speed you will end up with a higher terminal speed.
As a very rough ball park we find that ever 0.1 saved on the 60ft time will save you 0.2 secs overall but obviously that is assuming each run is identical other than the 60ft time.
Changing gear just before the finish line is a complete no no! If you can hang onto 4th gear then do so, even if your power is tailing. It will give a quicker time.
Lastly remember your terminal speed is only the average speed over the last 60 ft of the run, not the actual terminal speed. For most cars that are'nt accelerating much at 100mph that won't differ much, but on hugh bhp cars it's a suprising difference. (up to 5mph more at the finish line compared to the 60ft average).
Hope that helps folk understand the drag strip a little more.
I will be running the car again at classic ford show hopefully so will try and improve on my times a bit more,central day was only the 2nd time I had taken the car up the strip so still room for some improvement from me with getting it off the line and everything else involved
18-04-2012, 07:36 PM
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I did 3 runs at central day in my estate,my 1st run I manged a 13.2 at 100.38mph and 60ft time was 1.894,my 2nd run was 13.4 at 104.78mph and 60ft time was 1.906 and then my 3rd run was 13.7 at 107.55mph and 60ft time was 2.220,what Im struggleing to work out is how my quickest run time wise was slowest speed wise,sorry if its a thick question
18-04-2012, 09:26 PM
#18
I've found that life I needed.. It's HERE!!
repeat your best 60 ft time and hold it in 4th and you will better your time for sure 
it is all won or lost in the first 60ft as that is where the traction is hardest to find and 0.10 sec gained there really make a difference come the finish
it is all won or lost in the first 60ft as that is where the traction is hardest to find and 0.10 sec gained there really make a difference come the finish
18-04-2012, 09:31 PM
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My estate is 4wd so traction off the line shouldn't be a problem hopefully,my 3rd run I caught the revs wrong and it bogged down so just need to practice a bit more
18-04-2012, 09:46 PM
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19-04-2012, 06:40 AM
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19-04-2012, 09:14 AM
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I was holding the revs at about 4000 and then getting off the clutch as quick as possible and manage just below 1.9 for the 60ft and just over 1.9 on my 2nd run,my 3rd run it bogged down off the line so done a 2.2
19-04-2012, 09:32 AM
#26
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Just think a YB'd van would be fun, 4x4 or rwd is the question ?
Its a winter project if i can get a few quid saved up
19-04-2012, 09:59 AM
#28
Lastly remember your terminal speed is only the average speed over the last 60 ft of the run, not the actual terminal speed. For most cars that are'nt accelerating much at 100mph that won't differ much, but on hugh bhp cars it's a suprising difference. (up to 5mph more at the finish line compared to the 60ft average).
19-04-2012, 12:00 PM
#30
Didn't know this either.
Would be smart if this sort of info and 'drag tips' were printed on banners and attached to the barriers on the fire up lane, wouldn't have to cost anything if they got them branded up and so roundabout way, paid for...
Would be smart if this sort of info and 'drag tips' were printed on banners and attached to the barriers on the fire up lane, wouldn't have to cost anything if they got them branded up and so roundabout way, paid for...
19-04-2012, 12:08 PM
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Personally I did mine 4wd as there is hardly any weight at the back so would always be eating rear tyres,I will be going with a skyline box sometime soon for the extra peace of mind for the strength
19-04-2012, 12:17 PM
#33
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Its your bloody estates fault
Too many projects not enough cashflow hahaha+
19-04-2012, 12:24 PM
#34
While I totally understand what Karl is saying there, and my own stab at the theory would say exactly the same, my experience suggests that a worse 60ft on a turbo car (especially a big turbo) often leads to a higher terminal speed, as per the thread starters results.
A friend of mine has an 11 seconds viva that he has a massive amount of data with and there is a massively strong correlation for him between higher 60fts and higher terminals.
Can only assume its due to spool time on the turbo, as I can think of no other reason for the effect that would make any sense.
Ie Karls assumption that a worse 60ft time means you are going slowing at the 60ft isnt always correct, if you go very slowly for the first 30ft and during that time the turbo spools well it will accelerate better for the next 30ft so although you have taken longer to get to 60ft you have done so at either the same or a higher speed and with the turbo spinning faster at the time.
A friend of mine has an 11 seconds viva that he has a massive amount of data with and there is a massively strong correlation for him between higher 60fts and higher terminals.
Can only assume its due to spool time on the turbo, as I can think of no other reason for the effect that would make any sense.
Ie Karls assumption that a worse 60ft time means you are going slowing at the 60ft isnt always correct, if you go very slowly for the first 30ft and during that time the turbo spools well it will accelerate better for the next 30ft so although you have taken longer to get to 60ft you have done so at either the same or a higher speed and with the turbo spinning faster at the time.
19-04-2012, 04:12 PM
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I had to do the headgasket on mine last week and had a nightmare all day Saturday and finally got it all sorted and home at 22:30 ready for Sunday so I could take it up the strip lol hopefully I will be able to start saving for the skyline box in the next few months,so it might be a winter project to do the box unless mine gives up the ghost before lol will you be at classic ford show looking around atall
19-04-2012, 04:25 PM
#38
Quite true
Often a faster ET will yield a lower trap speed.
But even a shitty run with a slow ET on the same car can yield a good trap speed.
It almost makes sense when you think about it, then it doesnt.
But trap speeds usually vary less unless the run is a total fuck up, and trap speeds are a good indicator of power.
ET's are largely down to traction first and then power.
Often a faster ET will yield a lower trap speed.
But even a shitty run with a slow ET on the same car can yield a good trap speed.
It almost makes sense when you think about it, then it doesnt.
But trap speeds usually vary less unless the run is a total fuck up, and trap speeds are a good indicator of power.
ET's are largely down to traction first and then power.
19-04-2012, 04:30 PM
#39
While I totally understand what Karl is saying there, and my own stab at the theory would say exactly the same, my experience suggests that a worse 60ft on a turbo car (especially a big turbo) often leads to a higher terminal speed, as per the thread starters results.
A friend of mine has an 11 seconds viva that he has a massive amount of data with and there is a massively strong correlation for him between higher 60fts and higher terminals.
Can only assume its due to spool time on the turbo, as I can think of no other reason for the effect that would make any sense.
Ie Karls assumption that a worse 60ft time means you are going slowing at the 60ft isnt always correct, if you go very slowly for the first 30ft and during that time the turbo spools well it will accelerate better for the next 30ft so although you have taken longer to get to 60ft you have done so at either the same or a higher speed and with the turbo spinning faster at the time.
A friend of mine has an 11 seconds viva that he has a massive amount of data with and there is a massively strong correlation for him between higher 60fts and higher terminals.
Can only assume its due to spool time on the turbo, as I can think of no other reason for the effect that would make any sense.
Ie Karls assumption that a worse 60ft time means you are going slowing at the 60ft isnt always correct, if you go very slowly for the first 30ft and during that time the turbo spools well it will accelerate better for the next 30ft so although you have taken longer to get to 60ft you have done so at either the same or a higher speed and with the turbo spinning faster at the time.
I think a lot of it is simply that the more traction you have, you cover that ground so much faster in terms of time. So you also cross the line in less time so have had less chance to attain speed. It's certainly not that you've went slower.
As Luca said, you're speed vs time will remain similar, but distance vs time is greatly affected by getting good traction at the start.
Most times Ive run, the 0.1s 60ft gains you 0.2s at the top end is usually pretty damn close ( again assuming a similarly good run )
