topper vs no topper

so i thought toppers would give better mileage due to increased aerodynamics? i bought my truck with a topper on it, not a heavy one by any means, me and my dad lifted it off NO problems, and both of us have wrecked shoulders -- usually we feel the slightest weight -- but not this time.

anyways, after taking off the toper, i'm getting WAY better mileage. i usually hit a 1/2 tank at about 130-150 kms, 320-350 on a full tank. since taking it off, i'm at a 1/2 tank in 202 kms.... does this make sense to anyone? i really dont understand it, i figured i'd get about the same, maybe 5-10 kms less without the topper per tank -- but no, its increased by like 50-75 kms ATLEAST so far this tank (first tank since taking it off).

anyone have any ideas?!

I have an idea, if its flush with the roof of your cab, you can sell it to me. Post pics of what it looks like.

Other than for what Sierra is looking for,toppers are NASTY and must be removed immediately.

I just have a soft tonneau cover on my truck,and I'm usually at a half tank around 200-250km,and I can stretch my tank as far as 400km before the needle is on empty. I find it takes about 100km to go through a quarter tank,because I'm 100km to 3/4 of a tank,200 to a half,and 300ish to a 1/4 tank.

only reason i have it is to protect my stuff through the Praries when i move to Ednomton on May 11. its coming off again when i get there... i still dont understand the gas mileage though...

the areodynamics of a topper is way worse then without one. Without one, a vortex is created in the bed which keeps the air flowing over the truck smoothly, with the topper, as soon as the air flows over the back of the topper it crates a pocket of air that drags on the back of the truck.
I'll try and draw up a diagram of what happens, but a topper cuts down on the areodynamics of a truck.

the only way I can explain the voretx made in the bed without a topper is when you have loose leaves in the bed toward the front near the cab, when you are driving you will see them float in the air and back into the bed, those leaves will still be in the bed when you get somewhere, that is becuase the vortex kept it in your bed.

bed covers actually have worse areodynamics then without one also, the only way to improve the areodynamics of a truck without investing lots of money into desgning, is to get replacement tailgate, a fabric one, with slits cut in it, and remove the metal tailgate all together.

-Mike

I think Mythbusters would beg to differ that! They had a show about a tonneau cover vs exposed bed vs no tailgate. Guess what won? The tonneau cover!

The vortex developed inside the bed ALSO creates a drag on the truck, which is bad. Without the tailgate the vortex only moved to the back of the bed. With the cover, the vortex probably may have moved to behind the truck.

All in all, they got better gas mileage with the cover than anything else! Anyways, I would'nt know about the canopy though...

yeh, being HUGE into racing and knowing alot about aerodynamics, i'm gonna argue that too. the only thing i see being a negative to the aerodynamic flow of the vehicle with the topper, is the inch or so gap between the cab and the topper. thats the ONLY thing i see restricting it -- and thats minimal as most if the airflow is diverted from one side or the other, with minimal air being stuck between in the middle causing drag; without the topper the air has all that room to get "stuck" in the box, with minimal air getting OVER the tailgate top -- a worse sinereo (sp??)....

i still dont get it

actually, you need to go back and watch it cuase their wasnt much difference between tonneau cover and without one, the one that won was the replacement tailgate, the fabric one that said it would improve gas miliage and actually did, that was part of the second tests they did during the revisit of that myth.
having a cover actually pushes the vortex up creating more drag on the truck.

I am not claiming to be an expert on this sort of thing, but I do know their is no advantages to have a canopy when dealing with aerodynamics, its like driving a van, some toppers are slanted in the back which do help with the flow but not much.

I remember watching that episode cuase I wanted a bed cover to help with gas on my 4x4, then after watching that, I decided to get replacement fabric tailgate, but havnt purchased one yet becuase my 4x4 hasnt gotten on the road yet.

I dont want to argue with anyone and if others know more please correct me, I just know what I have researched and based on the old muscle cars during the aero wars. all I know is having a slant for the air to move on it better then have a big drop off, that the vortex in the bed makes up for that slant and the replacement fabric tailgate removes the drag on the tailgate.

I'm more of a muscle car guy so all this new stuff with making your car faster by changing the bumpers and scoops and stuff is kind of silly to me, so just dissregard what I had said, didnt mean to offend anyone with more experience.
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edit:
I could be very wrong on a bed cover, I forgot that the nascar trucks have sheetmetal over their beds with a spoiler to help the air flow over thier trucks, but even if I am wrong, I will still stand with my statement that a canopy has worse aerodynamics then no canopy. my dream car is a plymouth superbird, which is a car I will prolly never get to sit in and prolly have less of a chance to drive one, but if I am wrong with a canopy, please prove me wrong, cuase I am very interested in these kinds of things, I am not being a dick or anything, I would love to see the stuff on a truck with a canopy.

i like my topper i just put it on.....