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A question for Joe!



  Trophy


Joe,

Just want to ask you a few questions but they will be one at a time and will depend on your response to the previous one!

Basically i want to confirm that you believe that the power of a car and its weight are directly linked to the 1/4 mile time said car can achieve?



Mat.
 


Just to jump on the thread.

1/4 mile time is directly related to torque at the wheels, weight and traction. Air resistance and friction comes in to it too, but that can be compensated for in equations.

Its easy enough to model a cars acceleration. A guy on MIG created a visual basic spreadsheet model of a 1/4 mile that can produce some damn accurate times.
 


Just to add Mat.

Force = mass * acceleration .. that is not mine lol.. but Newtons second law.

Its not simply a matter of if I believe it.. it is fact with physics as we know it.

Predicting the DIFFERENCE in 1/4 mile times is easy, due to this law of physics. eg, if you add bhp or reduce weight, the calcs will hold up.

the above also predicts the MIN time achievable. Factors such as gearing, traction and gear change time / quantity obviously come into play.

Joe.
 
  Trophy


Ok Joe,

Following on with this.

Two cars, same model so approx same weight have almost identical 1/4 mile times! so would you predict that they would have roughly the same BHP?

Obviously different drivers will effect it slightly but well come to that later!



Mat.
 


;)

yes... IF the following were true


Same gear ratios and FD
Same power delivery curve
Same driver
Same track
Same Cdrag
Same tyre contact area
Same drive configuration
Joe.... (I remember that show...... 20 questions me thunks lol!)
 
  mk2 172


wonder what id get with more power then?, i only have 120 atw, so no interior and some non supermarket petrol and jons addative, hmmm, 14.8?????, oh yeah, and a working rev counter!(which i never had beforeand still dont)

craggy
 


Jan n Dean.... yessssssssssssssss... hee hee

me thinks we are leading to a rolling road result type question here.. but.. as usual... me could be wrong...

Me thinks Mat is Rolf Harris in disguise.... "Can ya tell what it is yet ?"

:)

J.
 
  Trophy


Right Joe,

You consider RE to be a very accurate RR, yes?

What im getting at is the fact that Jon with the willy #159 got 149bhp @ the wheels at RE and manages a 14.800 1/4 mile! Yet i have 131bhp @ the wheels at PE and i got a 14.738 1/4 mile!

So i just wondered if the figures for one of our sessions from the RR are wrong or im just a better driver than Jon?;)



Mat.
 


Mat.. ya cant compare figures on different rollers..

Weigh each car..

test each one on the same day, same tyre pressures, same rollers, same fuel etc



then let me know..



Physics is Physics..



n Ben... sri dood.. its good black...

Joe :devilish:
 
  mk2 172


mat, jon is no slouch on the 1/4, i was on the recieving end of the 14.8. was my first time though and 15.0 is good for an untouched engine.



craggy
 
  Trophy


Joe,



Thats what im getting at. you think that RE are accurate so im thinking that i might be able to get more power just by putting my car on a different RR;)

Ill let you know how we get on at york on the 6th when we will be going head to head!



Craggy,



Thats the thing mate, it was my first day when i got my 14.738 and if Jons engine is untouched howd he get 149 ATW?



Mat.
 


assuming a willy weight (DOWN Jilly lol !) of 2347 lbs..

then 137.44 bhp @ wheels would give a 15.00 secs



and....... 143.9 would give 14.80 secs..



are ya happy now craggs.. ???... you got more than ya thought....

Joe.
 
  Trophy


Weight,

My other idea might be to keep this car and get a willy 1 too!

Wouldnt drive the willy much though.

This bloody edit is confusing!!!!!



Mat.
 


EDIT*oh, i see, sorry i deleted it!*

EDIT*didnt want to start a 172 vs valver debate!*

EDIT*why the 2 thou mate?*

edit confusing??!! what you mean??*EDIT

EDITTED BY weight @ 23:21,23:22,23:24,23:25
 


Now if you really want one that puzzles you here it is ;)

Said car weighs about 1380kg, its AWD, 1/4 mile time is 9.86 secs so how much power?

Should keep you going for a while ;)



Tony:D
 


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