Lotus Elan and Lotus Elan Plus 2 Forums

certainly at 65-70mph it seems to be noisiest with the early +2 exhaust system I have. This dramatically drops off at about 80 (the noise I mean...). is the transverse box noisier than the later in-line i wonder ? ( what precipitated the change eh?)The steering becomes a little too floaty for my liking around 90.. would more air in the tyres improve I wonder?

Paul,

3,700 rpm at 60 indicates 145X13 tyres and 3.9 differential ratio. And you are right, 120 would require close to 7,400 rpm.

Later Elans with 155X13 tyres and 3.77 differential ratio would require almost 6,900 rpm for 120. With the standard ignition cutout at 6,500 rpm, they were 115 mph cars. It was the SE FHCs with 3.55 differential that could get to 130 by getting 7,000+ rpm.

There is a downloadable spreadsheet that allows you to calculate all of these things. Search for "20040227xGearRatios.xls".

David
1968 36/7988

Hi All

I have driven my +2 at around an indicated 120 mph. It was at Millbrook on the banked bowl, it felt a bit light at the front despite the banking and noisy, the drivers door window frame was being buffetted causing it to come away from the seal occasionally. The revs were at around 6,500 and I didn't keep it there for long.

Nice to see what it could do but not a good way to treat such an old lady.

All the best

Andy

I run a 3.55 diff with new 175/70 X14" tyres. My calcs suggest around 129 at 6500rpm. On my run, the rev counter was just past 6k, and the sat nav showed 122, and slowly increasing. The car was willing to go to the redline, but I was not.. The car was stable and I think the extra weight of the luggage and passenger helped. At this speed, I think the aerodynamics of the car are working well - most noise seemed to be from the wing mirrors..

No ill effects to he car - head gasket went two years later, but I don't think this episode contributed to it. Engine runs 20/60 Millers semi synth, ambient air temp mid 20s (degC) - water temp normal, but oil temp was maxed out (above 140C).

Jeremy

paul2s wrote:Great stories fellas, thing is at a steady indicated 60 mph on a level road on a windless day
the rev counter shows 3,700 rpm If that?s correct doesn?t that mean I would be showing 7,400rpm at 120 !!!?
Or doesn?t it work like that?

Cheers Paul

Yes 120 mph would be 7400 rpm assuming your instruments are accurate. Your engine need to be well modified to actually achieve that speed given then power needed and the revs

cheers
Rohan

paul2s wrote:Great stories fellas, thing is at a steady indicated 60 mph on a level road on a windless day
the rev counter shows 3,700 rpm If that?s correct doesn?t that mean I would be showing 7,400rpm at 120 !!!?
Or doesn?t it work like that?

Cheers Paul

Sounds like your tach needs some adjustment Paul. I had this issue when I first got the car; buses were passing me at high engine speed readings. I used David's most excellent spreadsheet to calculate correct RPM's at various road speeds, and then adjusted the tach to read correctly to GPS real speed in fourth gear (1:1). I then confirmed things in all the other gears. My tach drifts a bit at different temperatures, but close enough.