Scan Gauge Rulze!
I'm looking at a 70% drag reduction, so seeing what you've done is a lot of fun.
I'd agree that at least a 10% reduction in drag has happened, probably 12% as one post stated earlier.
Quote:
Originally Posted by aerohead
If you were seeing 2.25 at 55 mph,then you'd be looking at about a 4.5% drag reduction to explain it.Since it's doing it at 50-mph,then the reduction is even greater,so,shooting from the hip,and considering a generic 12% drag cooling system, it looks like you've cut the cooling drag maybe by half.  |
On an "apples for apples" basis where there was no frontal area change, the 79 Mustang Daytona and 80 Mustang IMSA show cars used a full polycarbonate front cover, one smoked, the other a clear and painted item. In the old quad headlamped cars, such a thing would slam the total drag by about what I've estimated to be 15% (from about 0.45 to way under 0.39). Back in pre 1984 dark ages (before the Lincoln LSC got the fed tick for flush lights and the old World War Two sealed beam rules were enforced), it was easy to drop 15% off the nose just with those two light and grille blocker mods.
For emperical info from Audi, On a 40% cd reduction (approx 0.44 to 0.32 or 0.30 depending on trim), for example, in instances where an engines automatic transmission spec and gearing wasn't changed, a same spec 135 hp engine package, such as in European version of the slick 0.32 Audi 5000, it saved 11 % fuel on the highway cycle, 2.1 US mpg at 56 mph, and 2.6 mpg at 75 mph, and it got an extra 5 mph top speed over the 0.44 predecessor.
So 40% reduction was a nominal 11% fuel saving in that 56 to 75 mph instance.
20% would have been 5.5%
10% would be around 2.25%.
In my opinion, the stock aero drag would be going down 0.03 cd numbers, or a 10% drop in cdA to get a 2.25% fuel economy reduction at 56 to 75 mph, based on empirical data.
You can do coast-downs to quantify the effect, but a fuel economy saving like that is at the very least a solid gold 10% reduction in road load at 50 mph.
Well done!