What differential ratio is needed?

[msd1107]

Eric,

As to being somewhat apprehensive about going 150 in an Elan, a couple of things need to be addressed.

The first is needing VR rated tires, which is not too much of a problem.

The second is attending to front-end lift problems. The Elan was designed before the need to carefully manage airflow under and through the car was considered important. Thus the air intake is above the bottom of the body, forcing air down under the car. When the Elan was designed, theory indicated that this airflow would just go under the car. It was not appreciated how aerodynamically inefficient this is, and modern day cars attempt to minimize the air that goes under the car. The other part is that air that goes through the air intake is not well managed in the car, probably leading to high-pressure spots under the hood and high drag figures in getting the air out, since there is no clear exit.

The Lotus Elan Workshop Manual recommends the use of 036B 1525 to close off an air gap by the steering unit and cutting 2 2.5in holes in the LH wheel arch.

Other methods could be considered. I have seen a Europa that had an air exit cut in the top of the hood, and large air ducts leading from beside the radiator to the cockpit.

To minimize the amount of air pushed under the car, an additional hole should be cut in the underside of the front, behind the radiator intake and before the end of the body section. Something like 24X3 or 24X4 would get most of the benefits, and fill the hole with body colored wire mesh. This would minimize the visual intrusion, and you would have to be on hands and knees to see it anyway.

Exhausting the under hood air would require some experimentation. Some adventuresome person needs to measure the under hood pressure to identify the high pressure spots, and then cut in an exhaust grill to minimize the visual impact.

Adding large air duct tubes from the side of the radiator to the passenger area and/or foot well would allow that air to flow through the passenger cockpit and be exhausted from the rear vents, as well as providing more ventilation into the cockpit.

I am sure there are other ideas that some one can propose. But the result would be a more stable Elan for those top speed jaunts down the Autobahn.

David
1968 36/7988

[christoph]

Christoph,
Fabulous seven installation, looks superbly engineered.
Just for the sake of discussion, if a bike engine were to be fitted in an Elan, how would you overcome the excessive propshaft length required? As the engine would have to fit in the same position as the twink or further forward the propshaft would have to be it's existing length plus gearbox length, ie around 6 foot in length. I suspect it would be too long to operate correctly/safely. Fitting even a 200 BHP bike engine sounds superb how do you think it would go for day to day driving?
Regards
Dave

Hi dave, thanks, as you probably know the devil is in the detail I was probably as please to make it to Le Mans and back this year in a sub 50second Brands Hatch car, stopping only for fuel and speed traps ops, than some of the performence stats .

Prop length should not be a problem as we would need to install a reversing box, (from someone like Quaife) + benefit is a mid bearing point. Engine wise the best of the crop is the Hayabusa, it makes about 170bhp, all from a smog friendly 1300cc. On paper a 170 bhp 6 speed sequential box, with a weight saving of probably 70 or so kg , over the Twink/box sounds to good to be . The main trade off's are torque and drive line backlash from the sequential dog box, (if only I hadn?t dumped those rotaflex's ). Torque is best addressed by forced induction, a Rotrex supercharger has less of a problem with radiant heat, than a turbo and may be easier to package. A light puff of around .5 bar, would see about 235bhp, reliable all day long. Final drive, I don?t have any hi torque experience with the Lotus diff carrier, so not shure what it'll take, I bet someone here dose . The TTR drive shafts and Quaife ATB are more than up to it, in fact the TTR's proberly need 50bhp just to turn them
Hope it's of some intrest, Chris,

[1964 S1]

David, after reading your latest post and with all due respect, it's still yeah, I wouldn't want to go 150mph in a stock bodied Elan, period. Eric

[garyeanderson]

Christoph

It may be a little better balanced if you were to loose the Passenger seat on a RhD Elan and put the Hayabusa engine in its place. With a .5 bar of boost Busa in a 1000 to 1100 lb car, who would ride with you anyway?

Gary

[christoph]

Christoph

It may be a little better balanced if you were to loose the Passenger seat on a RhD Elan and put the Hayabusa engine in its place. With a .5 bar of boost Busa in a 1000 to 1100 lb car, who would ride with you anyway?
Gary

Gary, balance would improve, but not sure I could take the heat, not to mention a wayward rod at 11000rpm Squeezing one in transversely behind the seats would just go, Quaife make a bit of kit for this, http://www.quaife.co.uk/catalogue/page83.htm the use of a Spyder chassis necessitates, or better still start with a Europa must have been done Now that has got me thinking
I run may dax Rush (7 esque) at about 650 - 700 bhp per ton on the road, and surprisingly there are always takers for little thrill jornts around the block, however they seam to lose speech and the use of there legs on return
Chris.