More power vs. less wind resistance? need better MPG.

[DBabbitt]

I have a little under $500 to spend before I take 3000 mile trip hauling a 8. 5 x 24 enclosed car hauler with my 04. 5 3500 Quad cab DRW 5. 9 HO & 48RE with 4. 10s. The trailer is a bumper hitch type with a flat front. Feels like I'm hitting a brick wall at 70 mph. So I'm trying to decide between an Edge EZ box or a Trail-Eze wind deflector to mount just behind the truck's roof. while I'll admit I am an HP junkie just like the rest of us, My real issue here is poor MPG's, about 10mpg @ 70 mph with this trailer. Seems to get about the same loaded or empty so I'm thinking the problem is that big box of trailer. Any thoughts????

 

[nutter3]

I dont have a solution, but I'm in the same boat as you. 8. 5x27' enclosed snow machine trailer. At least mine has the V-nose. Maybe someone else has a few tricks.

 

[Byershome]

This is outside your budget but a topper of the appropriate height with airtabs would probably do more than the wind deflector. I don't think the trailer is going to be close enough behind for the wind deflector to get the air over it. In fact the extra drag created by the deflector forcing the air up may actually make things worse. If you do choose that route though I'd be curious to hear how it goes.

 

[klenger]

Slow down. Speed kills.

 

[kah68]

Do 62 - 65 mph set the cruise keep the RPMs in the 2000- 2100 range. There ya go , better milage at no cost. You have to drive all day steady to make a serious gain in distance from 5-8 mph. Try leaving an hour earlier and enjoy the scenery.

 

[RKerner]

Drag is considerable - long winded reply

I'm not sure a topper would streamline the discontinuity between the truck and the trailer enough to achieve the desired affect. A large amount of the drag is also created at the rear of the trailer where there is a huge pressure differential, you know, the 'vacuum' that attracts road grime and such on the backside of the trailer. The topper itself also adds considerable surface area that adds to the total drag on the system.



I'll be removing the topper from my truck as I have recorded better unloaded mileage without it. (anybody want a really nice flame red topper for a shortbox?)



I'm also going to tow with my Juice/Attitude in #1 to test what happens as I have recorded no significant mileage change in #2 (tow mode - great power though). I also have noted that in tow mode that the overhead will be optimistic by 10% to 25% depending on speed. 65mph towing = 10%-11. 5%, 75mph towing = 22%-26% optimistic. I believe this is due to the increased injector pulse duration that the ECM never sees, which can be researched in several threads found here.



Like Klenger says, slowing down does give consistent gains in mpg. For reference, I get 10. 8mpg at 14. 5K gcwr at an average of 68mph and 9. 8mpg at the same weight at 75mph. Both mpgs are averages over two 2500 - 3000mile trips, highs of 12. 6 down to lows of 8. 1. If I slow down to 61mph unloaded, mpg climbs to the magic 20 mark. (yup, I may stop whining about mileage as somehow my truck is starting to meet my expectations. Oo. ) The problem is with us younger folk is that time is sometimes more valuable than diesel, hence, we drive faster to get to our destination. For me, it is the lake to get my boat wet, or the mountains to go sledding.

 

[DBabbitt]

Yes, I have realized the gains in mpg from slowing down. I don't mind getting passed by the passenger vehicle crowd but when the big rig's are blowing past you it just seems like somethings wrong! Not to mention it's just alot easier to drive when you're flowing with traffic, not being lapped by it. My trips are almost always 99% interstate and the strong majority of people are doing 70-75 mph. which I estimate is up about 5 mph avg. over the past 10 yrs. It just seems like the technollogy isn't quite there yet. And when it gets there people will probably be driving faster!!

 

[viper700]

You did not say that you had gauges in your rig. If you don't that's where I would put some money especially for the Pyro. Pushing that hard you would flip if you monitored the egt's and the transmission temp'. I have a 04. 5 DRW 4WD 48re with 3. 73's. I run closer to the 65 mark and let them pass me all day long. With fuel prices as they are today I think it's more important to take care or my truck and get better fuel milage. I really watch the EGT'S and pulling a hill they pop to 1050 real fast then I will hit tow haul and EGT'S will drop instantly to 800 and rpms will run up to 2450 pulling the hill and then I can get back into OD and rpm's drop back. On some day's last winter touring Arizona and climbing real hard I watched transmission temps get up to 200 and I would drop another gear to get EGT and transmission temp back down. I pulled one hill coming out of Laughlin Nevada NV163 I think to get to US95 going to Las Vegas a lot of people and truckers passed me. I was down into seceond gear and about 40mph but the truck did not get hot. I am also pulling a 3 axel 5er weighing 15k loaded. This was my first winter in the south as I live in Alaska and I have a lot to learn about hauling heavy but my first concern is the truck not my speed. I am 65 and way past the speed aspect. You have a 48re transmission with a few gears and those 18 wheelers have a bunch to find the right power band. But have fun what ever you do.

 

[klenger]

No flame intended to any one here, but I find it interesting that the younger crowd, that has most of their life in front of them, are are the ones driving fast, and us older farts, who have precious little time to do all that we would like to do, are the ones taking it slower.



When towing, I find myself driving slower on the open highway where there is plenty of room for others to pass me. If I'm in town, I keep up with traffic so as not to be a hazard.

 

[sewman]

hen I'm driving I try to stay around the speed limit(to many tickets in my younger days) but it's fun to watch how many people esp woman drivers doing 80+ passing me time & time again. Since they must be stopping to unload all the spring water.

So what I'm getting at is drive slower stop less & still get there w/better mpg's.

Bob

 

[TFucili]

aero help

Dbabbit, I pull an enclosed m/c trailer and am amazed at how hard it pulls given the fact that the weight is so low. I sent for literature from Nose Cone. They make "bubble fronts" that will fit our trailers. I have not called for pricing yet. FYI 1-800-227-3266.

 

[TX Gooseneck]

You could line the bottom of the truck with formed sheet metal. It'd take a fair amount of time, pre-fitting, rebending etc, but it should yield some results.

 

[DBabbitt]

Does anyone know if there are any real benefits to the V-nose trailers that have come out in the last few years? Seems like there could be some gains there but not sure. I've been thinking of fabing a frontal shroud to my flat nose box which would mimic the v-nose design.

 

[RustyJC]

Just a hint (that was mentioned earlier) - the key in determining coefficent of drag (Cd) isn't as much in the shape of the front of the object as you would think, but rather the shape of the back, not that there's a whole lot that has been done back there.



The turbulent area between the back (there we are again) of the cab and the front of the trailer is certainly another problem since it means the trailer is running in dirty (turbulent) air.



Rusty

 

[LesStallings]

Slowing down is one way to improve fuel consumption but...



When I'm pulling 14K, I find the motor really likes 2,200 RPM. With a gooseneck, I don't seem to have the brick wall you are talking about and putting the rig in the "sweet spot" makes the grades much easier with very little downshifting.



I drive 4,000 miles round trip and almost always go 3-4 MPH over the speed limit. The rig is extremely stable and I obviously slow down for less than perfect conditions.



I'm an old fart too, but 3 MPH over 60 hours of towing gets me to my daily stops 30 minutes quicker and shortens the total round trip considerably. I've also learned that the last 30 minutes of a long day is the worst.



Also, I'm much more in the flow of the traffic, not passing too many people and only getting passed about ½ as much.



Out west where speed limits are 75 MPH, plus my 3 MPH results in 78 MPH and a really nice 2,200+ RPM. With the EZ, downshifts are only on the steepest grades around Flagstaff on I-40. Only when I need to downshift do I have to watch the EGT like a hawk. All the other times the needle will just touch 1,200° while on cruise control.



Having a trailer with 3 axles and 6 brakes helps some, but at the higher speeds, I am VERY careful to be looking ahead and I will quickly click off the cruise control at the slightest indication of a need to slow down.



Just because I grow old does not mean I have to grow up! Screw the fuel cost...

 

[Sarge]

Well, i'm not an old fart, or a young guy, but I gotta agree with slowing down a bit. The scenery is better, the stress level is lower, and I enjoy the trip more. With that being said, I do admit to thumping the go pedal on hills sometimes just to embarass some powerstroke... ... No really, the smartest thing is to reduce drag if possible, which is exactly what you are doing by slowing down. The other smart thing is make sure the tires are aired up (drag) and avoid running with extra weight. It's been said on here often that life is too short to worry about gas mileage, but saving a buck in the process is nice too... ... ..... Sarge

 

[testraub]

I've been beat testing a "Mileage Program" for SP Diesel. I just ran up to Buffalo, NY from Arlington, VA. With the box in "stock" mode on the way up, hand calc and driving it careful (2K Tach 65-70MPH) got 15. 2 MPG. On the way back with the box in "Economy" with a bit heavier foot (2200 Tach 75-80 MPH) got 16. 3 MPG. They can be reached at http://www.spdiesel.com. Give them a call and tell 'em "Tom sent me"!

 

[rluft]

The Edge EZ will be with you every time you turn the key, and many say they get better fuel economy than stock if they keep their foot out of it. The wind deflector will only be useful when towing the trialer, even then I have read that besides deflecting bugs they aren't that useful.



Your mileage doesn't seem right. I get between 9 and 11 mpg pulling a 12. 5 ft tall, 37 ft long fifth wheel that weighs 12,000 lbs and that is running 70 mph. BTW, I have installed AIRTABS at the back of my fifth-wheel which may be making a difference.

 

[Sixpac2]

Airtabs

What are Airtabs and how do they work. Do lots of people use them? Thanks

 

[NVR FNSH]

I'll be removing the topper from my truck as I have recorded better unloaded mileage without it. (anybody want a really nice flame red topper for a shortbox?)

Interesting. I found the exact opposite to be true on my '85 Toyota 4wd. I lose MPG if I take the shell off.



In the original poster's situation I would recommend a shell that tapers front/back with AirTabs on the shell and rear of trailer.



Heard/saw an interesting presentation many years ago at Cal Poly, SLO from an engineer with Peterbuilt (I think - might have been KW) regarding the aerodynamic testing they were doing on big rigs. They were able to increase MPG from 4 to 8 by adding wheel skirts/ground effects, a ball/socket type joint between the tractor & trailer and a 'teardrop' at the rear of the trailer.



Brian