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General Information => General => Topic started by: mystery3 on May 15, 2011, 11:12:39 pm
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Do shells have much impact on fuel mileage? I'm no engineer but I'd think the aerodynamics should be improved enough over the open truck bed to offset the +/-80lbs. The shell I have is an old gemtop, the roof is basically flush with the cab.
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You tell us. Put that bad boy on there and run it for a month (or two) and compare. I've been thinking about making a tonneau for mine. Did you see the mythbusters episode about tailgates?
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i think i would go with a tonneau for mpgs..
80 pounds on a caddy is alot when they only weigh 1800, and only have 60 hp. lol..
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I dunno. I've never met anyone who got over 45 MPG out of a caddy. Yet, I've met many people who get 50+ out of a sedan.
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my grandpa gets 52 out of his caddy. so he says. 1.6 n/a with a GC 4 speed. he definitely drives it like a grandpa too.
he had the can-of-pee on there for a little while, then took it off, im thinking he left it off because of better fuel economy..
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I owned two 1981 VW pickups:
1) gas with NO topper and 4 speed trans (not any version of 3+E)
2) n/a diesel with Glasstite topper (about 4 inches above cab) with the FF or FO (whichever one had the 0.71 fifth) trans.
#1 never seemed to get above 24 mpg the whole time I owned it....but, who really cared on 76 cent gasoline!
#2 was driven in SD, all over Nebr., WY.,Kansas, Missouri, Oklahoma and north Texas. I don't really think I ever got above 42 mpg. Going into the wind was annoying torture. The 0.71 was just not that realistic with a topper like that.
I've ALWAYS been really skeptical of all these guys who report these super high mileage figures. ::) I think there is a lot of resistence in the pickup body. Sure, I suppose there were a few times I putt-putted on a back road with a 6-pack going real slow and got better......but, just how realistic was THAT......ooops. Sa-wee!!! (kids, do not try this at home.....)
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yea, my grandpas truck pretty much lives at loopin speed.. thats prolly the only reason he gets that good of economy.
i know my car only gets around 40 mpg (maybe a lil more now that i fixed my fuel leaks) with mixed driving.. small, narrow tires, and a light foot definitely help with fuel economy. and aluminum wheels.. holy crap.. big upgrade over the stock steelies in acceleration, so im sure they are nicer to your fuel econ too.
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I usually pull 40-43 in the truck in mixed driving. Last I weighed it at the dump after dropping 1180lbs of concrete it was 2160 with a basically full tank and me, 135lbs fully dressed, in it. I filled my tank the same day I put the shell on so I'll do some experimentin' hey at least the shell isn't sitting in my sideyard anymore!
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I actually used to get high 40's in my caddy. Under pretty ideal conditions, flat terrain 90% highway at 55, minimal traffic, no A/C. Sometimes 48-49.
Funny, I went to the dump last weekend too, and the scales read something like 2400 lbs with a full tank, an extra tire ( I was dumping) , a heavy toolbox (just came from upullit) and me @200 lbs.
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I dunno. I've never met anyone who got over 45 MPG out of a caddy. Yet, I've met many people who get 50+ out of a sedan.
Nice to meet you! my name is nathan and my 81 caddy with a franken motor, aaz-k14 running 18psi, 2.5 straight exhaust, fmic, pump tuning on a stock pump HAS gotten 50mpg at 55-60mph, if I go 75mph, though I can still get 45. I actually got 45mpg out of a tank with a set of 15in corrado steel wheels (pretty heavy). All recorded with a gps.
But I drive it hard, I have never done an easy tank on it.
Oh, and myke_w believes I am over 100-110hp, so it scoots.
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My first VW diesel was a 1980 N/A pickup with a cap. Put 48k on it in 8 months of 7 roundtrips a month between Long Island and Wash. DC. Always did 70-75 on the interstate and my best was 48 mpg. Many times getting this I stayed a little close to the back of an 18 wheeler.
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When I get the AAZ installed in the Caddy, I'll do some mileage checks. My brother gets 45-48 consistently with his 1.6 turbo Caddy and zero aerodynamic mods. I've been exploring a website called 'Ecomodder' that's all about the use of aerodynamics for getting high mileage. My plan was to get it installed, check mileage, and do some mods to see what's possible. I'm aiming for 80-90mpg with the tall gears & reserved highway speeds.
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My best was 51-52, and I don't think I had the shell on. I think tailgate down might be best.
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My caddy did ~50mpg when unloaded. It had a cap on the bed.
The better tail shapes taper to reduce eddys, but obviously that reduces cargo capacity.
As stated, Ecomodder has some members with custom caps that taper. http://news.cnet.com/2300-13833_3-6230378-8.html
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I haven't spent nearly as much time on Ecomodder as I have here. It's obvious that aerodynamics plays a much bigger role in economy than what can be done with a motor. It's also obvious that in order to accomplish high mileage it's going to look real 'different'. Function is way more important than looks, to me.
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I shell will add more drag than just the standard bed. Adding the large drop and flat surface on the back causes more air disturbance and drag, it makes more "dirty air".
Mythbusters (everyones favorite, I know) did a show about this very thing and found that the open bed will actually trap air inside creating a bubble of high pressure forcing all new air to flow from the top of the cab out over the tail gate and not into the tailgate. You still get the swirling effect from the cab itself but not all the way to the bed floor. Thats why stuff doesnt just fly out of your bed as you drive around, but if you open your rear slider you will get some stuff flying into the cabin.