Whitson Metalworks Full Length Rack MPG Test!

Whitson Metalworks

Whitson Metalworks

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Well this may not be the most official test but it should help out for those who are worried about what a full length rack does to gas mileage. First of all, I drive like a grandpa on the interstate, usually 65 tops, which REALLY helps. Aerodynamics of our bricks being what they are, 75-80mph is an mpg killer in stock form. I took advantage of an interstate errand and snapped some pictures of my scanguage at different speeds on flat ground. I've found my SG to be pretty much accurate over the past year or so.

50 MPH, just enough throttle to maintain speed (SGII helps you SEE how much throttle you actually need BTW)

60 MPH, again, only enough throttle to maintain speed

68 MPH, i never drive this fast on the interstate and wanted to check 70 mph but i ran out of flat ground before hitting it.



oh yeah, I forgot to mention I was carrying my 16' WS Tarpon Kayak:biggrin2::biggrin2:
 
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Wow that truck is a monster. I love it more every time I see it.
My average MPG is less than half that, but I suppose that's because I drive like an 18 year old.
 
TheeMikeB said:
I love those racks, Do you think you can attach a RTT to it?
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Actually I was emailing him about gather same thing. His racks will work perfectly with a RTT. He is also able to modify the rack to be a flat top or basket. Honestly, Josh, is one of the easiest guys to work with. He ha several different options.

Btw from what other have reported of running an RTT is that the average loss is about 1-2 mpg for a RTT.
 
smkd13 said:
Actually I was emailing him about gather same thing. His racks will work perfectly with a RTT. He is also able to modify the rack to be a flat top or basket. Honestly, Josh, is one of the easiest guys to work with. He ha several different options.

Btw from what other have reported of running an RTT is that the average loss is about 1-2 mpg for a RTT.
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I gave up being concerned about fuel mileage the day I bought this truck.
 
Oops, missed this question. I've had a few folks ask me about RTT mounting and while I've never seen a single one in person I don't see any reason why you couldn't do it. Even if it takes a spacer here or a shim there, and depending on what the RTT manufacture gives you to work with, if you can change your own oil it should be an easy thing to do. And I dont mind working with folks with custom needs.
 
Whitson Metalworks said:
Well this may not be the most official test but it should help out for those who are worried about what a full length rack does to gas mileage. First of all, I drive like a grandpa on the interstate, usually 65 tops, which REALLY helps. Aerodynamics of our bricks being what they are, 75-80mph is an mpg killer in stock form. I took advantage of an interstate errand and snapped some pictures of my scanguage at different speeds on flat ground. I've found my SG to be pretty much accurate over the past year or so.

50 MPH, just enough throttle to maintain speed (SGII helps you SEE how much throttle you actually need BTW)

60 MPH, again, only enough throttle to maintain speed

68 MPH, i never drive this fast on the interstate and wanted to check 70 mph but i ran out of flat ground before hitting it.



oh yeah, I forgot to mention I was carrying my 16' WS Tarpon Kayak:biggrin2::biggrin2:
Click to expand...

No offense my friend, but I feel as though something isn't adding up. Whose motor spins at 641 RPMs while going 50MPH? Or 970 RPMs at 70 MPH? You've got a Limited, so a manual transmission isn't an available option.

I do a lot of traveling, and to kill boredom I like to watch the different sensor values on my Actron scanner (yeah I'm a bit of a geek). I've watched the MAF values enough to know how easy it is to go from 2.0lbs/min of air to 4.0lbs/min by even a slight depression of the throttle. It would be better if you had your cruise set to a certain speed when you take your measurements.

Even still, I seriously doubt you would ever see 27.7mpg when going 50MPH over the long term, even on the flattest of roads. Even with you being 2wd, I don't think the MPGs you display are that realistic. Aren't those instantaneous mpg calculators notoriously inaccurate anyways?

Again, I'm not trying to start a pissing match with you, but I feel that your numbers are a bit deceptive.
 
This is in my 99sr5, 3.4 auto 4x4. The "1" is about burned out on the gauge but looking closely, its there. I've got no desire to tout erroneous data, as stated, this is not the most official test but I promise on flat land anyone with a good tune-up and a steady foot would see numbers like these. My SGII is accurate as verified by number crunching at the pump for comparison. The tps values help me with economy a great deal. BTW, at idle the tps value reads "9", not sure if that's a percentage or what but at 50mph its reading 5 points higher, that's not a lot of throttle. I've done this kind of driving over and over and over and this time of year, my kayak is on the roof a good bit. I'm 100% confident that if I somehow had a tank full of driving on flat ground at 50mph my average mpg would be somewhere between 26-28. You know as well as I do that all the low speed/high load driving is what tanks your average, I regularly see instant mpgs of 6,8,9 etc when accelerating or going up steep grades. Overall, for the past year or more, my tank average is 19-20. At any rate, the info was to help show that a full length rack does not guarantee a drop in MPG.
 
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I really like your racks, actually believe they are the best looking out there.

But I don't think you are adding up your mileage correctly. You need to drive a full tank to calculate true mpg. Preferably at least half a tank. Just driving down the freeway the SG can say anything. My old BMW used to say I was get 45 when driving certain roads; it all evens out after a full tank.
 
BrianSD_42 said:
I really like your racks, actually believe they are the best looking out there.

But I don't think you are adding up your mileage correctly. You need to drive a full tank to calculate true mpg. Preferably at least half a tank. Just driving down the freeway the SG can say anything. My old BMW used to say I was get 45 when driving certain roads; it all evens out after a full tank.
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yes i realize instant mpg is different than average. These numbers are instant, i stated that my average is 19-20, like always, rack or not. i showed the instant readings since most people seem to think aerodynamic drag, at speed, will kill efficiency; im simply showing that i see no evidence of such.
 
Hmmm I drive 68 pretty much very where I go on the freeway and have seen about 19 - 19.5 mpg. When I go 75 it kills my mileage. So your average makes sense. When going into the whole aerodynamic drag thing, your rack sits low enough that it joint disrupt the natural flow of air too much. Especially combining it with a fairing.

At 68 mph my tach sits at around 1900-2000 rpms. Like josh said the biggest thing that will kill mileage is the low speed/ high load. It is physics. It take more force to get a vehicle moving than it does to keep it moving.

Glad to hear that your rack is not effecting mileage that much. All the more reason to buy on personally :)
 
Whitson Metalworks said:
yes i realize instant mpg is different than average. These numbers are instant, i stated that my average is 19-20, like always, rack or not. i showed the instant readings since most people seem to think aerodynamic drag, at speed, will kill efficiency; im simply showing that i see no evidence of such.
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The problem is, you haven't shown any evidence that says the rack doesn't negatively impact MPGs. You just discredited your own numbers by stating that your averages are much lower than the pictures you posted. Furthermore, you also haven't established any baseline with pictures of your readings without the rack and kayak installed on top, with the same speeds on the same roads. But since it's so easy to manipulate the instantaneous readout, a truer test would be to drive a tank of gas on the freeway with the rack, and then do the same without the rack, and compare numbers.

I got to do this when I drove back and forth between Columbia, SC and Chattanooga, TN for six months. I got to do a lot of testing with rack on vs. rack off. I found that my Yakima rack, which appears to have a similar aerodynamic profile as your rack, degraded my MPGs by a fair amount, and obviously exaggerated the problem the higher the speed.

Anyways, I'm not bashing your roof rack by any means. I think it looks pretty awesome. I'm just not convinced that the mpg hit with a rack and kayak is as minimal as you make it appear.
 
Robb235 said:
The problem is... you also haven't established any baseline with pictures of your readings without the rack and kayak installed on top, with the same speeds on the same roads.
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exactly ^^ We jut need numbers to compare to, so take pictures of your SCII at the same speeds and same roads with just the rack (no kayak) and then with the stock roof rack, so we can compare! but your racks are already aerodynamic and as long as its not a dramatic decrease in mpg I'm sold. :gun6:
 
dooods, all i was pointing out was that the rack doesn't, or hasn't affected my mileage at all. I stated right off the bat that this was no official test, just a little something to help dispel the notion that a full length rack is like a sail on the roof. the scII numbers i pictured are completely typical for how I drive yak or no yak. with that said, the kayak is easy to drive around with, its obviously the most aerodynamic thing on the truck. i threw a tire up there on a recent 300 mile trip and lost a consistent .5mpg. the roof is not an ideal place for a spare.
 
Whitson Metalworks said:
dooods, all i was pointing out was that the rack doesn't, or hasn't affected my mileage at all. I stated right off the bat that this was no official test, just a little something to help dispel the notion that a full length rack is like a sail on the roof. the scII numbers i pictured are completely typical for how I drive yak or no yak. with that said, the kayak is easy to drive around with, its obviously the most aerodynamic thing on the truck. i threw a tire up there on a recent 300 mile trip and lost a consistent .5mpg. the roof is not an ideal place for a spare.
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Ha ha ha tire on the roof is like having a sail attached and going a giants the wind. A rack with a faring should not create a substantial amount of drag.
 
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