Lotus Elan

Final Drive

PostPost by: TWebb » Thu Mar 26, 2020 5:37 pm

Looking for thoughts as to the final drive ratios for use at tighter tracks like Hallett, Blackhawk, etc. and then again for Road America.

Any thoughts appreciated.
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PostPost by: rgh0 » Fri Mar 27, 2020 1:13 am

Depends on your cars weight and max revs, torque curve and tire diameters you run.

A friend with a S4 Seven runs 4.1 on longer tracks and 4.4 on shorter tracks and he has 190+ hp and uses over 9000 rpm and runs 175/60 x13 tyres

In my Elan I use 3.77 on all tracks and could probably benefit from using a 3.9 or 4.1 on the shorter tracks but I don't have the time to be swapping diffs. Despite my heavier Elan I use a lower numerical diff than my friend as I limit my 180+ HP engine to 8300 rpm but the better Elan Aerodynamics mean I have a similar top speed despite getting there more slowly than a Seven. I top out at 8300 rpm with the 3.77 diff down the main straights at 8300 rpm at long tracks such as Phillip Island with 175/60 x 13 tyres. On short tracks like Winton I am running in 2nd and 3rd gears all the time and not getting into 4th

cheers
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PostPost by: Vaughan » Fri Mar 27, 2020 6:25 am

Also big factor is what tyres size and type ie historic Dunlop , Avon, or modern low profile as they have the most direct effect on gearing.

I ran 26R with Dunlop CR65's 550x13's in period it ran with a 3.77 or 3.9, today I've got a 4.1 fitted and like Rohan at tight tracks (with ultra close 2.25 first gear) I use 2 and 3rd gears only on tight tracks. When its back on the track it will be with a 4.4.

Attached is a spreadsheet I update periodically with a tab for each new tyre that I find could suit my S2 26R. I have modelled using Ultra close 2.25:1 first gears and various final drive ratios.

Elan RATIO ANALYSIS.xls
(96 KiB) Downloaded 60 times


Cheers

V
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PostPost by: Frogelan » Fri Mar 27, 2020 7:59 am

Hello Vaughan,

Useful tables. It looks as if you have uploaded the 2.5 1st gear version, but that is easy to rectify.

Andrew
1965 Lotus Elan S2 26/4022 (originally Dutchess Lotus East, PA and NJ Area, USA)
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PostPost by: Vaughan » Fri Mar 27, 2020 11:31 am

There's a mix from memory, the S1 26R is 2.5 close ratio and the tabs noted S2 26R has 2.25 ratios.

Cheers

V
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PostPost by: TWebb » Fri Mar 27, 2020 4:16 pm

Thanks guys.

I have what I need. Appreciate the help.
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PostPost by: Vaughan » Fri Mar 27, 2020 9:02 pm

My pleasure. I'll find another sheet I have the correlates gear and final drive ratios with engine torque curve and post it

Maybe other could add to the sheet with different tyre, gearbox and final drive ration combinations.
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