Rear spoiler source for Mk1 Mini?
Discussion
For my mid-engine Mini project, it'll be limited to about 130mph, where I'm concerned about handling. Brick-shaped isn't the best way to go, and having large wheel flares doesn't help. Even though the car is still in construction I'd like to find a source for a rear wing/spoiler/lip thingy. Aero testing will be done but it would be nice to know a spoiler is avaiable should it be required.
BTW, has anyone seen anything in the British press about someone instrumenting a Mk1 Mini and doing aero tests? I'm keen to know what the airflow's doing over the car. Being here in the States makes finding such info tough. Thanks.
>>> Edited by kb58 on Thursday 11th March 15:50
BTW, has anyone seen anything in the British press about someone instrumenting a Mk1 Mini and doing aero tests? I'm keen to know what the airflow's doing over the car. Being here in the States makes finding such info tough. Thanks.
>>> Edited by kb58 on Thursday 11th March 15:50
I don't know what bhp you'll need to get 130mph out of a Mk.1 Mini.
Remember, the aerodynamic drag increases as the square of the airspeed. Thus to double the speed gives 4 times the drag and, in theory, requires 4 times the power.
It's probably over-simplyfing things a little, but if you had a car which was flat out at 100 mph to go to 125 mph would require a power increase of 50% over the power to do 100. To do 100 in a Mini probably needs about 90 bhp, so for 125 you would need 135 bhp. It's not absolutely correct as the final drive ratio, peak power revs, transmission drag, etc, will all have an effect, but it indicates why 25% more power doesn't give 25% more top speed.
The suggestion that de-seaming removes 45 sq. ins. of drag-inducing frontal area is an excellent way to reduce aerodynamic drag on such a box-shaped little car.
Taking very simple figures, an 850 requires 35 bhp to do 70. Thus to do 140 would require 4 times that power i.e. 140 bhp, but that would be at 5200 rpm, as the 850, and with the 3.76 final drive. Thinking about it, that figure is probably not far out although I don't know how you'ld get 140 bhp at 5200, more likely 7000. Then the power would be very 'peaky', so you'ld have a gearing problem.
Fascinating, ain't it? I hope it's not too complicated and helps a bit.
Peter
Remember, the aerodynamic drag increases as the square of the airspeed. Thus to double the speed gives 4 times the drag and, in theory, requires 4 times the power.
It's probably over-simplyfing things a little, but if you had a car which was flat out at 100 mph to go to 125 mph would require a power increase of 50% over the power to do 100. To do 100 in a Mini probably needs about 90 bhp, so for 125 you would need 135 bhp. It's not absolutely correct as the final drive ratio, peak power revs, transmission drag, etc, will all have an effect, but it indicates why 25% more power doesn't give 25% more top speed.
The suggestion that de-seaming removes 45 sq. ins. of drag-inducing frontal area is an excellent way to reduce aerodynamic drag on such a box-shaped little car.
Taking very simple figures, an 850 requires 35 bhp to do 70. Thus to do 140 would require 4 times that power i.e. 140 bhp, but that would be at 5200 rpm, as the 850, and with the 3.76 final drive. Thinking about it, that figure is probably not far out although I don't know how you'ld get 140 bhp at 5200, more likely 7000. Then the power would be very 'peaky', so you'ld have a gearing problem.
Fascinating, ain't it? I hope it's not too complicated and helps a bit.
Peter
I agree with everything you've said... which is why I'm using a 200hp Honda Prelude engine
The carbon body is "deseamed" of course, but my main concern is rear lift at high speeds. That's why I asked if someone had some aero data on a Mk1 Mini.
>> Edited by kb58 on Saturday 13th March 23:01
The carbon body is "deseamed" of course, but my main concern is rear lift at high speeds. That's why I asked if someone had some aero data on a Mk1 Mini. >> Edited by kb58 on Saturday 13th March 23:01
Hey, kb58, that sounds great.
I don't think anyone has ever done any proper aero-d testing at those speeds and rear lift could be a big problem. You obviously are very aware of the possible problem and i would guess that the silly looking rear spoilers on the market are just for show (can't think why anyone would want one), but for your sort of performance you do need real data.
Good luck with it all.
Peter
I don't think anyone has ever done any proper aero-d testing at those speeds and rear lift could be a big problem. You obviously are very aware of the possible problem and i would guess that the silly looking rear spoilers on the market are just for show (can't think why anyone would want one), but for your sort of performance you do need real data.
Good luck with it all.
Peter
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