Re: What differential ratio is needed?
Posted: Fri Nov 10, 2006 9:33 pm
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
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