Northpole
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| posted on 22/4/13 at 03:59 PM |
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Dilemma?
I have a Hayabusa engine in Triumph Spitfire and before I test the car in full, I would like to have a estimate on the max speed.
- When I use the calculators on the web I get appr. 170 to 180 km/hrs as top speed with this setup, i.e. 4.11:1 diff ratio, final gear from gearbox
1.043 and tire size 185/70R13.
- Triumph Spitfire has 153 km/hrs at 6000 rpm and gearbox ratio in 4th 1.0 as standard, if the Hayabusa engine revs up to 11.000 rpm, should not the
car have top speed according to this? Which gives appr 280 km/hrs (which is quite scary  ) using the same setup i.e. 4.11:1 diff ratio, final gear
from gearbox 1:1 and tire size 185/70R13.
Anyone have answer on this?
Sigurjon Johannsson
Triumph Spitfire Mk3 1968 Hayabusa powered
http://www.youtube.com/watch?v=ln2Km9mVXYI
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Minicooper
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| posted on 22/4/13 at 04:11 PM |
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On a bike there is a primary reduction ratio to allow for as well, on the Hayabusa it is 1.596
I get 109mph using the bike ratios spreadsheet, which is 175kph
Cheers
David
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cliftyhanger
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| posted on 22/4/13 at 04:14 PM |
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You have assumed no change to air resistance. It is more about power than rpm, but assuming the hayabusa is 150bhp (guess) then that is double the
original spitfire engine.
That would give a top speed approx 1.4 times the original cars top speed. About 215km/h. As a guess. The online calc may have a better idea than my
simplistic approach, after all I have made some large assumptions.
EDIT, OK, I am looking at theoretical top speeds, nothing to do with RPM.
That 4.11 diff may not last very long, especially if it is the early version with the small quartershafts, see
http://www.canleyclassics.com/?xhtml=xhtml/infodatabase/diff.html&xsl=infodatabase.xsl
[Edited on 22/4/13 by cliftyhanger]
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Northpole
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| posted on 22/4/13 at 04:42 PM |
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quote:
Originally posted by Minicooper
On a bike there is a primary reduction ratio to allow for as well, on the Hayabusa it is 1.596
I get 109mph using the bike ratios spreadsheet, which is 175kph
Cheers
David
Thanks David, I forgot the primary reduction ratio in the Hayabusa. This is much better  both the tires and the driver will handle this more
moderate speed 
Can you please inform me what bike ratio spreadsheet you found?
Cheers
sigurjon
Sigurjon Johannsson
Triumph Spitfire Mk3 1968 Hayabusa powered
http://www.youtube.com/watch?v=ln2Km9mVXYI
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ReMan
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| posted on 22/4/13 at 05:15 PM |
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This one :-)
http://www.locostbuilders.co.uk/forum/23/viewthread.php?tid=121319
www.plusnine.co.uk
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snapper
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| posted on 22/4/13 at 05:17 PM |
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Most people use a final drive of about 3.4 to 1
If your putting this in a Spitfire for god sake change the rear suspension
I had a MK3 when I was young and it tried to kill me several times when I lifted off the throttle in a corner
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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INDY BIRD
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| posted on 22/4/13 at 05:19 PM |
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Or this thread
http://www.locostbuilders.co.uk/viewthread.php?tid=171831
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Northpole
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| posted on 22/4/13 at 05:33 PM |
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quote:
Originally posted by snapper
Most people use a final drive of about 3.4 to 1
If your putting this in a Spitfire for god sake change the rear suspension
I had a MK3 when I was young and it tried to kill me several times when I lifted off the throttle in a corner
Thank you for your consern I have done what is possible for it, the diff re-cond, new UV heavy duty and I have now Camber compensator, I hope this
will help....
Can you recommend any other diff? I was thinking Subaro or Jaguar?
Sigurjon Johannsson
Triumph Spitfire Mk3 1968 Hayabusa powered
http://www.youtube.com/watch?v=ln2Km9mVXYI
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Andy S
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| posted on 22/4/13 at 07:27 PM |
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Freelander
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Northpole
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| posted on 22/4/13 at 08:05 PM |
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quote:
Originally posted by Andy S
Freelander
Why is Freelander diff good for Spitfire?
Why not Jaguar, Subaro, Mercedes or BMW?
I need to do some modifications anyway...
Sigurjon Johannsson
Triumph Spitfire Mk3 1968 Hayabusa powered
http://www.youtube.com/watch?v=ln2Km9mVXYI
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bi22le
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| posted on 22/4/13 at 08:22 PM |
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quote:
Originally posted by Northpole
quote:
Originally posted by Andy S
Freelander
Why is Freelander diff good for Spitfire?
Why not Jaguar, Subaro, Mercedes or BMW?
I need to do some modifications anyway...
Freelander is not specifically good for your spitfire, its just a commonly used one in the kit car scene. I think its a case of being common, LSD and
sensible ratio.
Track days ARE the best thing since sliced bread, until I get a supercharger that is!
Please read my ring story:
http://www.locostbuilders.co.uk/forum/13/viewthread.php?tid=139152&page=1
Me doing a sub 56sec lap around Brands Indy. I need a geo set up! http://www.youtube.com/watch?v=EHksfvIGB3I
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