roof top wind deflectors

[GlennWest]

Anyone every tried one? I'm only getting 7.5 mpg pulling my MS. Wondering if it would help.

[RonS]

I would first try a power programer, and maybe slow down a little. I have a Hypertech and tow on stage II, and try to keep the speed around 65mph. I noramlly get 12mpg when towing. But I tell everyone I get 23 when towing, that 13 hwy and 10 in town = 23mpg.

[wingnut60]

Glenn,
I got 9-10 with my old F350; now I am getting 8-9 with my F450--BUT, I am pulling a trailer that probably weighs 3000lbs more than your trailer. Speed is the biggest factor in mileage--if you run 70+ (easy to do) than mileage will suffer. I have 2 friends with GM trucks, and both do better than you are saying. What I think is going on---you are a pipeliner, going between jobs, and need to get there quick. That may be the problem. Using a wind deflector won't make a 0.1 mpg difference.
Joe

[Huck]

I tried one years ago on a previous 5er.
The manufacturer guaranteed 10% better mileage, but I didn't get squat!

The only good thing it will do for you is keep the middle of the front of your trailer free from bugs.

[GlennWest]

I'm running 60 and getting 7.5.

[wingnut60]

Glenn,
Leaving tomorrow with four couples--3 GMs: '06 dually, '07 3/4T, '08 1 Ton SRW. Dually is pulling 36' Jayco, 3/4 T pulling 30' TT, 1Ton pulling 34' HitchHiker. Will let you know in a few days what their mileage is--yours sound pretty low for 60mph.

[billr]

Glen,

You didn't mention if you have a Duramax or Gasser?

When we towed with an 04 Chevy Duramax and our 38RL3 was 17300lbs we got around 9-10 at 60mph and that was with an Edge programmer on setting 1 and 4" exhaust and cold air intake.

If its a Duramax it sure sounds low for 60mph. Are you towing with Overdrive on or off? Should be on unless its down shifting a lot on grades. If you have it selected off, then that will do it for sure.

If thats not it, you might want to take it in to GM and get it scanned. May have a problem they can see, or an update that hasn't been done.

As far as the wind deflectors go, I have only heard what you have been told so far. They do squat for mileage.

Bill

[GlennWest]

It's a Duramax. Had the injector balance test done. Found nothing. It runs great, pulls great, no check engine lights, Pull in toe/haul mode. I've been leaving od on. Try with od off next pull. WHat about you guys?

[Diesel-Gypsy]

I seem to get good mileage with the stock set-up, but I would like to hear about anybody's luck with a SNOW DEFLECTOR !
http://inlinethumb43.webshots.com/44330/2216273850097642812S200x200Q85.jpg (http://outdoors.webshots.com/photo/2216273850097642812QZbiFD)
:lol:
Pretty soon I'm going to need one...

Rick

[RodeWorthy]

For comparison I get just under 10 MPG towing my 36RS3 with an '08 Chevy 3500 dually with all the exhaust filters --- DPF et al. Always under 60 MPH except on some extreme downhill grades. Unless in an area where I need it I leave tow-haul off. This allows me to run in 6th gear between 1500 and 1600 RPM. I don't think you have the 6th gear.

The tow-haul is useful when negotiating hills and in variable speed traffic. Transmission 'braking' is much improved in tow-haul mode.

Do you check your mileage with the Driver Information Center (DIC) or calculate it yourself based on fuel volume and miles driven?

[billr]

It's a Duramax. Had the injector balance test done. Found nothing. It runs great, pulls great, no check engine lights, Pull in toe/haul mode. I've been leaving od on. Try with od off next pull. WHat about you guys?

Your ok with tow haul on, won't effect mileage too much, just ups the shift pints a bit so not to drop out of the sweet spot too far. Turning off the OD will only use more fuel.

If you want better mileage and a wind deflector on a totally stock truck try this: :lol:

[anijet]

I just pulled CA to MO on I40 running 70 mph where legal and speed limit otherwise. Got a little over 10 mpg and had a head wind all through NM. You should be in the 12+ range with a 32' running 60. I've bumped timing, pulse width and boost with EFIlive but I don't think it made a lot of difference to MPG.

With the 5 speed let it run in 5th with T/H on. With the 6 speed 6th is a little too tall a lot of the time.

[GlennWest]

Thanks everyone. This verifies that I do have a problem with my truck. I do have 235X85 tires and they bring my effective gearing down to 3:42 instead of the factory 3.73. Can't believer they are hurting me that much though. Those of you with the 6 speeds should use 5th when pulling your MS. It will actually hurt mpg. Engine won't have the rpms it needs to make the needed torque required to pull that much weight. It is great for empty though. Again, Thanks and God bless.

[GlennWest]

My mpg is figured by calculation and not DIC. It always is wrong.

[anijet]

Just to let you know, I'm running the same size tires. 235X85 Michelins.

[RodeWorthy]

...... Those of you with the 6 speeds should use 5th when pulling your MS. It will actually hurt mpg. Engine won't have the rpms it needs to make the needed torque required to pull that much weight.......

Duramax LMM develops maximum torque - 660 ft-lb @ 1600 RPM -- my stated cruising RPM. In any case I let the transmission decide. That's why we buy automatics.

[GlennWest]

According to everyone on the Durmax forums, including dealers, Duramax's make peak torque at 2100 rpm. Many on the forum have complained about poor mileage pulling in 6th gear and were advised to use 5th and mileage increased, temps lowered.

[Beaver]

I have used a large Taylor Wing while hauling 3 different 5th wheel units. Current truck is the 08 F350 dually with 2wd with tow haul. I can tell you the following facts after hauling 1000's of miles
1. Mileage runs from 7.5 to 10+ running 60 to 65.
2. Does keep bugs off all but the upper area of the rig
3. My estimate of mileage gain would be no more that .05mpg
4. The one area it makes a huge difference is pulling into a head wind. It slices right through and keeps the mileage up.
5. Would you recover the purchase price. Probably not.
6. Key to the best gains is location on the truck, and the correct angle. If one had access to a wind tunnel I know the mpg gain would be much better.

[RodeWorthy]

According to everyone on the Durmax forums, including dealers, Duramax's make peak torque at 2100 rpm. Many on the forum have complained about poor mileage pulling in 6th gear and were advised to use 5th and mileage increased, temps lowered.

You did not provide direct references but my guess is "everyone" on the forums knows better than the people who make and test the powertrains. Think about it -- who in their right mind would want a diesel making peak torque at 2100 RPM? A few years ago peak torque was around 1800 RPM and that was found to be too high. Ford and Dodge led the way to reduce that to 1600 RPM and Duramax followed suit with their most recent versions.

The Duramax is considered to have a flat torque curve (see chart below). At 2100 RPM there is still significant torque (over 600 ft-lb) but when encountering an uphill grade there is some reserve as the engine slows down the torque will build to its peak at 1600. As RPMs fall below the peak level the transmission will shift to a lower gear to increase the RPM and get back into the optimum torque band. Running in the higher portion of the power band (which is not flat) by running in a lower gear will produce more HP but will burn more fuel - not less. You will get the sense of better performance because the transmission will not shift as often on grades. There are many factors affecting fuel mileage including the objective of the driver. The most signifcant of these is speed if the load is constant.


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On Edit moved following comment outside limited space in uploaded file.
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General Motors horsepower and torque numbers have been certified by the Society of Automotive Engineers (i.e. SAE certified). A new voluntary power and torque certification procedure developed by the SAE Engine Test Code committee was approved March 31, 2005. This procedure (J2723) ensures fair, accurate ratings for horsepower and torque by allowing manufacturers to certify their engines through third-party witness testing.
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[Motor31]

If your automatic transmission keeps shifting up and down while towing you are abusing the engine and transmission. Drop the OD if that is the case. If it holds the load in OD at the speed you want and the temps (transmission and engine) are normal you are good to go. You DO have a transmission temp gage right?

[RodeWorthy]

Mike, not sure who you are addressing your remarks to. For me, there is no 'hunting' or continuous shifting. The transmission will eventually drop down out of 6th gear if the grade is steep enough to warrant it. It will usually stay there until the grade has been cleared. If there is a signifcant grade or series of grades it is a simple matter of enabling tow/haul mode which keeps the transmission out of 6th gear. Speed retardation on the downgrade is greatly enhanced in this mode as well. Engine and transmission temps are nominal. Transmission temperature monitoring is a stock item and reported through the Driver Information Center. I believe this method is optimum for my setup and the speed I drive. Staying low in the power band saves fuel at the same time the engine is operating near its peak torque. The truck is responsive and I am satisfied with the fuel mileage.

[GlennWest]

do you boon dock a lot? Noticed those solar panels and battery pak.

[RodeWorthy]

Glenn,
The solar panels and controller are new this year. The batteries and inverter were optional factory install. We did some boondocking last winter (pre-solar install) in the SW and we enjoyed it. Thought we would enjoy it even more with less dependency on generator(s). We have not given it an extended test yet but I believe our limitation, if there is one, will be battery capacity. We will return to AZ this winter and plan to test the system extensively while boondocking. We will also enjoy full hookups when we want to do that. We don't boondock a great deal. We live in the East and there is less opportunity for that than in the Southwest. Most use we get around here is keeping our batteries charged while the rig is in storage. It was a fun project. I did all the work myself and learned a lot.