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Old 19-11-2009, 07:46 PM   #1
toyotaxr8
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Default How to workout top speed
I am wondering how you work out top speed that a car can theoretical get up to not including factors like wind, drivetrain losses and stuff like that. My combo is going to spin to 9000rpm through an AOD with a final gear ratio of 0.67:1 then to 3.9:1 diff gears and out to the 26x11x15 inch tyres any help would be greatly appreciated.

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Old 19-11-2009, 07:59 PM   #2
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This site will tell you but you will need to know the convensional tyre size, ie: 265/60 15.
http://www.boosttown.com/gearbox_dif...calculator.php
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Old 19-11-2009, 08:03 PM   #3
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Jack it up and rev it's bits off in top gear.
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Old 19-11-2009, 08:08 PM   #4
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Quote:
Originally Posted by Falc'man
Jack it up and rev it's bits off in top gear.
Just had memories flood back of Ferris Bueller's Day Off.
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Old 19-11-2009, 08:12 PM   #5
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9000 input shaft RPM
/0.67 = 13432.85 RPM output shaft
/3.9 = 3444.32 RPM at the ring gear/halfshafts
Assuming your tyre dimensions are 260mm/11%/15" (260/11/15), diameter = 43.82cm
=1.38m circumference = 4741.60 m/min.

4.74k/min
=284.49 km/h.
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Old 19-11-2009, 08:12 PM   #6
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thanks for that, 428.93km/h top speed in perfect conditions
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Old 19-11-2009, 08:22 PM   #7
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If your engine does 13536.16 RPM?
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E Series Owner Syndrome
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Old 19-11-2009, 08:37 PM   #8
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Quote:
Originally Posted by Deech
9000 input shaft RPM
/0.67 = 13432.85 RPM output shaft
/3.9 = 3444.32 RPM at the ring gear/halfshafts
Assuming your tyre dimensions are 260mm/11%/15" (260/11/15), diameter = 43.82cm
=1.38m circumference = 4741.60 m/min.

4.74k/min
=284.49 km/h.
Deech, the size is the imperial measurement. ie the tyre is 26" tall = the diameter is 26" which is 660mm tall.
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Old 19-11-2009, 08:38 PM   #9
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Ahhh. I stand corrected. Yep, 428.5 km/h.

Quote:
9000 input shaft RPM
/0.67 = 13432.85 RPM output shaft
/3.9 = 3444.32 RPM at the ring gear/halfshafts
Assuming I learn to read dimensions properly diameter = 0.66m. pi*diameter =2.073 m circumference
=7141.62 m/min.

7.14 k/min
=428.498 km/h.
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E Series Owner Syndrome
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Last edited by Deech; 19-11-2009 at 08:52 PM.
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Old 19-11-2009, 08:54 PM   #10
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Thanks Phillyc.
OP, sorry about the initial misinformation.
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Old 19-11-2009, 09:19 PM   #11
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All you need now is a 428.5 km/h tail wind and you will be set!
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Old 19-11-2009, 09:26 PM   #12
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this is a pretty good program and its free

http://locost7.info/gearcalc.phphttp...o/gearcalc.php

gives speeds in each gear, rev drops, speeds at max power and max revs etc
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Last edited by yetchh; 19-11-2009 at 09:31 PM.
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Old 19-11-2009, 09:54 PM   #13
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Quote:
Originally Posted by yetchh
this is a pretty good program and its free

http://locost7.info/gearcalc.phphttp...o/gearcalc.php

gives speeds in each gear, rev drops, speeds at max power and max revs etc
The link doesn't seem to work.
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Old 20-11-2009, 03:31 PM   #14
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http://www.locost7.info/gearcalc.php
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Old 22-11-2009, 08:37 PM   #15
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Quote:
Originally Posted by 4VCLEVO
The link doesn't seem to work.

sorry i doubled up by mistake... outback_ute's got it right
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Old 22-11-2009, 10:00 PM   #16
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Yeah and by those figures my stock as a rock auto AU six cyl has a top speed of a bit over 300!

YEAH RIGHT
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Old 23-11-2009, 12:23 AM   #17
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Quote:
Originally Posted by Mr Hardware
Yeah and by those figures my stock as a rock auto AU six cyl has a top speed of a bit over 300!

YEAH RIGHT
the theoretical top speed mey be that high, but power + drag mean limited speed figures
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Old 23-11-2009, 01:25 AM   #18
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Quote:
Originally Posted by Deech
If your engine does 13536.16 RPM?
His daily is the McLaren MP4-23
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Old 23-11-2009, 06:46 PM   #19
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Quote:
Originally Posted by imugli
His daily is the McLaren MP4-23

that would be tail shaft rpm, so it is not that much.

13536.16x0.67(overdrive ratio)= 9069.2272
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