1/4 Mile Question

[pizza boy]

Quick question as to how/why some cars clock the 1/4 mile at...lets say 110mph but still only get 13.8 and others clock it at 103 and get 13.5

Whats the crack here?

[Bibbs]

cause they accelerate quicker .. but then tail out ..

Or take a while too spool up and then start raging .. it's different shaped acceleration curves ..

[Unity Jon]

its beacause their reaction times are different thats all....

[Fizz]

its beacause their reaction times are different thats all....

[Bibbs]

No ..

Cause the reaction time doesn't add to your 1/4 mile time ..

Your reactions could be 30seconds and you still run a 14 sec 1/4 mile @ 100 mph ..

[Bibbs]

okay guys .. I've got a car that'll do a 1/4 in about 14 seconds

I do a 1/4 mile run where I slowly pull away and then gradually put my foot down harder .. at the end I'm 100 throttle .. I'll have a good end speed, but a 1/4 mile time of 30 seconds ..

Now if I accelerate like a daemon .. and then ease off the throttle at the end .. I'll have a lower end speed, even though I can cross the line at the same time as the first run.

Reaction time has nothing to do with it ..

[ZeroBlade]

aye like bibbs said in his first reply its due to the acceleration.

Thats why int the case of ur example pizza boy the cars prolly been modified for greater acceleration (low end), which usually has the knockon effect of reducing top end.

-Z

[Unity Jon]

I raced in VWDRC for 5 years i still say its down to reaction time......

[Fizz]

okay guys .. I've got a car that'll do a 1/4 in about 14 seconds

I do a 1/4 mile run where I slowly pull away and then gradually put my foot down harder .. at the end I'm 100 throttle .. I'll have a good end speed, but a 1/4 mile time of 30 seconds ..

Now if I accelerate like a daemon .. and then ease off the throttle at the end .. I'll have a lower end speed, even though I can cross the line at the same time as the first run.

Reaction time has nothing to do with it ..

now that also makes sense... shows what i know...

[Bibbs]

So on a 1/4 mile strip the first car does 10 mph all the way down .. the other does 5 mph till half way, and then does 15 mph for the rest ..

A noddy maths way ..

Both have covered the same distance at the end, in the same time .. so both have the same average speed .. the 2nd car is going 5mph quicker and the 1st car out accelerated him ..

[pizza boy]

Aahh tar for explaining that Sir Bibbs.

Unity Jon.. Bibbs is correct about the reaction time. Because I was at crail raceway and its very normal to see one car shoot off due to better reaction BUT the other slower reacting car still can get the better time.

Theres basically two timers...the moment you trip the start line thats when the 1/4 timer begins and the reaction timer ends.

[dawesy]

terminal speed has more to do with HP time has more to to with acceleration (traction, launch etc) i have been beaten a couple of times by an impreza we both had very similar reaction times they only beat be by a couple of tenths but i was doing about 5-10mph more.

this can be explained by the fact that i had more HP but couldnt ut it all down until i hit third gear, by this point the scooby has a good lead, however when i give my car full stick in third i catch up very quickly.

as a bench mark you can tell a cars HP by T/Speed

[Master_Simon]

Can I be devils advocate here, the reaction time is only strictly relevant when racing, and then obviously a fast reaction time is going to be better than a grandad start, but for outright 1/4 mile time serious 'orsepower is required as is the ability to control the power, nice smooth correctly placed gear changes etc all mean quick times.