Lotus Elan

Tall Diff 3.0 ratio

PostPost by: EdHolly » Fri Jul 10, 2015 9:44 am

These days to get from A to B we mostly use highways and freeways that simply didn't exist all those years ago when Elans were new. Modern cars have very high gearing, my Ford Falcon cruises at 110kph at 1700rpm, well over 1.6 tonnes and under these conditions returns around 7.5 litres per 100km, or 36mpg.

My Elan gives exactly the same consumption at this speed, yet improves to over 42mpg when cruising about 10-15kph less. The Elan is doing 3900rpm (3.9 diff) at 110- a bit different to the 1700 of the modern car.

I used to have a MGA Coupe 1600 and I had a 3.9 diff in it which gave almost 20 mph per thousand revs (15inch wheels) rather than the 4.3 diff as normal. It also had a close ratio gearbox with a very tall 1st gear - YET - getting off the line from say a set of lights was no more difficult with the 3.9 as it was with the 4.3. Oh and the MGA had a 3/4 race engine so it didn't have a lot of torque down low.

Guess what I am saying is that in a light car like the Elan, when used for the road, the diff ratios we run say 3.9, 3.7 etc ... then we are paying a penalty in making the engine rev a lot higher than it needs to. Sure we can go the 5 speed box route, but the standard Elan box is a delightful gearbox and the gearshift is just in the right place.

Now what if we were to drop the 3900 rpm at 110kph down to 3000 - sure would make legal cruising a lot less busy and a lot less noisey.

So I am contemplating have a 3.0 crownwheel and pinion made to investigate what this does to the driveablity of the car.

Would appreciate any comments ...

:oops: Please don't comment here - comment on main Elan forum please - posted here in error

Ed
EdHolly
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