slowhand99
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Too much dinner
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Interesting MPG observation with the convertible
- Thread starter captjeff19
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- convertible
tsunami
Well-Known Member
Aerodynamics of convertible top down and up...
As I mentioned in this Forum in the Fall...I ran some aerodynamic simulations on the 2015 convertible and hardtop.
With the top down, the air flow was remarkably smooth until about 45-50 mph. As soon as I took delivery of my convertible I tried to check on the reality versus digital simulation. The air flow was really smooth at moderate speeds, even the reverse flow from the back seats was negligible. The wide top frame of the windshield plays an important role in keeping the flow smooth.
The simulations showed a rapid transition to moderate turbulence over and into the passenger compartment at speeds exceeding 50-55 mph. Pulsing back flow from the back seats to the front started. In my convertible, the pulsing was not as bad as the simulations, but there was significant back flow from the rear. By raising the side windows a lot of the back flow was canceled out.
I purchased a wind screen (no kids or pets) which really blocked the back wind up to about 65-70. Above that, the side windows and wind screen did little to block the turbulence.
My simulations showed turbulent 'rollers' spinning out the interior and off the trunk at speeds above 60 mph.
Computer runs with the top up showed air flows which were almost as smooth as those moving over the hardtop, which surprised me...Ford designers did a beautiful job with the shape of the soft top. Turbulent rollers didn't get very violent until top road speeds.
Turbulent pulsations can create a lot of drag. The 2015 engines are strong enough to pull their way smoothly but at the cost of fuel expended.
So...yes, having the top down should express itself with decreased mpg.
But that will depend on apparent wind moving over the vehicle and the angle of approach. Keep the top up and windows closed when travelling at Interstate speeds to maximize mpgs.
You will lose less mpg using the air conditioner than having the windows open at highway speeds. But I still like to drive with the top down, I pay for that in lower mpgs.
As I mentioned in this Forum in the Fall...I ran some aerodynamic simulations on the 2015 convertible and hardtop.
With the top down, the air flow was remarkably smooth until about 45-50 mph. As soon as I took delivery of my convertible I tried to check on the reality versus digital simulation. The air flow was really smooth at moderate speeds, even the reverse flow from the back seats was negligible. The wide top frame of the windshield plays an important role in keeping the flow smooth.
The simulations showed a rapid transition to moderate turbulence over and into the passenger compartment at speeds exceeding 50-55 mph. Pulsing back flow from the back seats to the front started. In my convertible, the pulsing was not as bad as the simulations, but there was significant back flow from the rear. By raising the side windows a lot of the back flow was canceled out.
I purchased a wind screen (no kids or pets) which really blocked the back wind up to about 65-70. Above that, the side windows and wind screen did little to block the turbulence.
My simulations showed turbulent 'rollers' spinning out the interior and off the trunk at speeds above 60 mph.
Computer runs with the top up showed air flows which were almost as smooth as those moving over the hardtop, which surprised me...Ford designers did a beautiful job with the shape of the soft top. Turbulent rollers didn't get very violent until top road speeds.
Turbulent pulsations can create a lot of drag. The 2015 engines are strong enough to pull their way smoothly but at the cost of fuel expended.
So...yes, having the top down should express itself with decreased mpg.
But that will depend on apparent wind moving over the vehicle and the angle of approach. Keep the top up and windows closed when travelling at Interstate speeds to maximize mpgs.
You will lose less mpg using the air conditioner than having the windows open at highway speeds. But I still like to drive with the top down, I pay for that in lower mpgs.
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