Silverado aerocap build thread

[Fubeca]

Originally Posted by MetroMPG

I think your relative efficiency increase will remain close to 4% regardless of ambient temperature.

Phil can correct me if I'm wrong, but when he said his cold weather aero enhancements didn't really "show up" at the pump until the return of good weather, I believe he was referring to his "previous best" (warm weather) MPG performance, not strictly a before/after comparison in cold conditions.

All else being equal, your absolute MPG will also be higher when the warmer weather returns, but the relative improvement of aerocap vs. open bed should be about the same (at the same testing speed).

This is intuitively what makes sense. I'm curious to see if it holds to be true. If it is, I'm curious what about my design makes it less effective than those of others who've experienced better gains.

Meanwhile - I'm patiently waiting for spring and enjoying the beautiful snow

[ChazInMT]

Fubeca, what did you use as a heat source to shrink your plastic? I'm guessing heat gun. Just occurred to me this instant, I wonder if an iron covered with a bit of welding cloth would work? If it were at just the right temp, you could shrink, shrink, shrink, without fear of melt, run, drip, smoke.

[aerohead]

Originally Posted by MetroMPG

I think your relative efficiency increase will remain close to 4% regardless of ambient temperature.

Phil can correct me if I'm wrong, but when he said his cold weather aero enhancements didn't really "show up" at the pump until the return of good weather, I believe he was referring to his "previous best" (warm weather) MPG performance, not strictly a before/after comparison in cold conditions.

All else being equal, your absolute MPG will also be higher when the warmer weather returns, but the relative improvement of aerocap vs. open bed should be about the same (at the same testing speed).

Darin,that's it.The cold weather was "suppressing" the overall efficiency of the truck,and influencing the mod I had added in the "cold".
And I did not attempt to do A-B-A tests in the cold,as the bellypan would literally take days to remove and re-install,so all the data got caught within the "creep" of temps.
If Silverado is comparing his aero cap mpg in the winter to a 17+mpg summer baseline I suspect that the numbers will improve with the weather.

[aerohead]

Originally Posted by aerohead

Darin,that's it.The cold weather was "suppressing" the overall efficiency of the truck,and influencing the mod I had added in the "cold".
And I did not attempt to do A-B-A tests in the cold,as the bellypan would literally take days to remove and re-install,so all the data got caught within the "creep" of temps.
If Silverado is comparing his aero cap mpg in the winter to a 17+mpg summer baseline I suspect that the numbers will improve with the weather.

Sorry,wrong name!

[nubbzcummins]

Here is a quick way to figure an angle from top of cab to top of tailgate on a truck.....Distance from top of cab to top of bed in inches = A.....Distance from back of cab to end of bed = B.....A/B = C which is the ratio of height to length.....Multiply C by 45 which will give you the angle from top of cab to top of tailgate. Example for my truck: A = 24".....B = 82".....24/82 = .29268..... .29268 x 45 = 13.2 degrees. These are not exact figures but very close.....Hope this helps.....

[Fubeca]

I did use a heat gun - I'd be curious to see if your idea works. It could make it easier, and the finished product might look nicely pressed

[MetroMPG]

Fubeca: I think it may boil down to speed at which you tested. A 4% gain is respectable at a 55 mph test speed. The faster the test, the larger the percent difference between MPG with aero cap vs. open bed. (Note that Brett & Phil tend to test at higher speeds.)

A rough illustration using the aero + rr formulas embedded in the calculator:

If I change the Cd of my car from 0.34 to 0.23 (which is within the realm of possibility when all the aero mods I've tried are in place), it tells me I'd see a 31.9% MPG improvement at 50 mph... but a 39% improvement at 75 mph. (Owing to the fact that aero load increases with the cube of speed.)

[Frank Lee]

Originally Posted by nubbzcummins

Here is a quick way to figure an angle from top of cab to top of tailgate on a truck.....Distance from top of cab to top of bed in inches = A.....Distance from back of cab to end of bed = B.....A/B = C which is the ratio of height to length.....Multiply C by 45 which will give you the angle from top of cab to top of tailgate. Example for my truck: A = 24".....B = 82".....24/82 = .29268..... .29268 x 45 = 13.2 degrees. These are not exact figures but very close.....Hope this helps.....

It is my observation that very few trucks sit level.

[KamperBob]

Originally Posted by MetroMPG

KB: maybe you've arleady seen this.... but bondo's is the Swiss army knife of truck caps! It opens like a hatchback, can be converted into a conventional square camper cap with the addition of side & rear curtains, and the upper hatch can be removed entirely for transporting tall objects. See this thread for photos: http://ecomodder.com/forum/showthrea...d-cap-583.html

Also, regarding flow effects, you may be interested to view on-road tuft testing of a tapered bed cap: http://ecomodder.com/forum/showthrea...per-11522.html . That thread somewhat addresses the issue of the flow transition from the side to upper surfaces (in that case a sharp transition, more likely to trip flow, yet it still appears to work well - though the upper angle is shallower than most).

MetroMPG, thanks for the links. BTW, we had a 95 Metro from 'til 2000. Bare bones. We just drove the darn thing yet regularly saw ~50 mpg. DW still misses her little kiwi some times but we outgrew it. At 130k it still looked and performed like day 1. Suzuki done good. I'm glad to see there was more up side for the envelope pushers to find.

Rock on
KB

[nubbzcummins]

Originally Posted by Frank Lee

It is my observation that very few trucks sit level.

Frank: This was just to find the angle from top of cab to top of tailgate. I realize that very few trucks sit level, as I hope most are aware of, that which will make the angle greater due to the direction of air flow. This is why I mentioned it will be a close calculation. Hope this makes sense. EX: My truck needed 2.5" lift in the front to level it which means it had about a 1 degree downward angle in stock form. I have a 140.5" wheelbase. This would be even less angle variance with a longer wheelbase truck. Take this info for what it's worth.....