Trying for 12 mpg on a MoHo

[frankiejoe]

Originally Posted by RoadWarrior

That's the 3 1/2 inch at the back rise plus the assumed 1/4 inch spacing. That should allow "full coverage" still where the air tumbling off the leading edge of the first strip in the group just misses the trailing edge of the last strip in the previous group.
3 strips were considered optimum when used on sailplanes in the '70s, to promote a strong turbulation effect, most of the air gets "pumped" three times into nice tight and small energetic vortices....

Ah So! I'm beginning to "get" it. I'll set it up this coming week and give it a good test on my upcoming trip still a week away. I'll post my results on this thread when I get there. Thanks for your patience.

[ZugyNA]

http://www.fuel-saver.org/Forum/showthread.php?tid=550

Originally Posted by frankiejoe

With an overall average of 9.5 mpg, I managed to make 11 on a trip from Texas to Colorado last year. Did that by not going over 60 and a good coat of paste wax on the front. This year I want to beat that record and wonder if any other forum members have had success. Im driving a 30 ft. aerodynamic Airstream Land Yacht with a 7.5 liter Chevy gasser with Allison automatic. Should I try 55 mph, pulse and glide, dropping into neutral on downhills, all of the above, or what suggestions can you give me.

[occupant]

The sad part is I drive a mere 3-ton Suburban and get no better than 11mpg at any speed, with the same 454 but a 3-speed TH400 automatic.

Maybe I should trade it for an old Winnebago Brave or something...at least I could ask the wife to grab the wheel so I can pee, and never stop except for fuel.

[frankiejoe]

Originally Posted by RoadWarrior

That's the 3 1/2 inch at the back rise plus the assumed 1/4 inch spacing. That should allow "full coverage" still where the air tumbling off the leading edge of the first strip in the group just misses the trailing edge of the last strip in the previous group.



3 strips were considered optimum when used on sailplanes in the '70s, to promote a strong turbulation effect, most of the air gets "pumped" three times into nice tight and small energetic vortices. I guess the additional momentum transfered by the fourth and fifth strips had negligible further effects. I guess it's kind of redundant anyway to go with the extras. Sizing is a question of scale of the vehicle, on a longer, taller semi-trailer for instance you'd probably need 1/2 inch x 18 inch devices to perturb the boundary layer enough. On minivans and SUVs 1/4 x 6 inch devices would be adequate. Personally I'd go with the 12in length if you can only find 1/4 high strip and 8 inch if you can find the 3/8 high. It is kind of educated guesswork on my part, I've run the actual numbers before, and got a feel for the ranges, but don't have the books available at the moment to run them for the precise dimensions of your vehicle. But stuff like this you can be 25% off either way and get 90% of the results.

ROAD WARRIOR you are brilliant! I got up to 11.5 at 65 MPH on level ground. Didn't do squat up in the mountains but had some other problems with the MH so sorry for the delay in posting my results. The main thing we were all in awe of is great big semis were passing us constantly and we did not even know they were there! The proof this experiment worked was that every time we were stopped on the side of the road, trucks would pass and we were jostled around like an earthquake. But as long as we were moving, no upset whatsoever! I have extolled the virtues of your genius to everyone who wondered about the dirty strips of weather stripping on the back of our rig. Thank you is not enough so THANK YOU! THANK YOU! THANK YOU!

Frankiejoe

[almightybmw]

Got any pictures of your success? I'd really like to see this, as my parents have an old 454 Ford 28' class C, which they've never broken 10mpg in.

[thisisntjared]

simple mods would be tire pressure and wheel covers. i would imagine on something much heavier than a car, that tire pressure would do a lot.

remember though, 1mpg is more than 10% of an increase.

[GasSavers_RoadWarrior]

Woohoo congrats!

I guess from 11mpg at under 60 to 11.5 at 65 is somewhere around 5-10%. Shame they got dirty looking though.

I installed turbulation strips on Marvin the minivan before a summer trip in August, and was also enjoying a large reduction in sway induced by passing trucks and better crosswind stability. However, "mountains" or just hilly country bit into the FE for that trip, and those and driving conditions may have conspired in the demise of Marvin's tranny shortly after, as well as an O2 sensor problem. This meant that I was unable to determine clear gains from them on him, but they sure as heck made driving feel a bit easier. What might have hurt the tranny was hot weather driving on gradients where the speed of traffic was causing him to go on and off the TC lockup a lot. Anyway, it started complaining after I got back, then failed almost completely and he's waiting for a swap now. I would like to think they're worth similar gains on him, in fact I did pull close to 26mpg with a slipping tranny, so when he's better they might show up.

Wile-E being a wagon could probably also benefit, however, I only just got him back together and FE is all over the place due to winter, still trying to find his new baseline. Also haven't had good enough weather to stick them on. Getting fed up of getting tossed around in him though, so might put some on at first opportunity whether I've got solid figures to see the mpg differences or not. I'm going to avoid going across his roof with them though because of how his tailgate curves down, I mainly want to tuck air in around the sides. I may either use turbulators or a rear deflector on top of him in future when I find a suitable spoiler for the hatch to separate the air off it about halfway down.

Sharp eyed folks might like to look for a styling feature on the '08 up Dodge Grand Caravan, there's a crease in the rear pillar, I think that is a "trip strip" turbulation feature to bend air round the back. Some French cars of the 70s had a break in the rear roofline that was similar. Some sedans/coupes are also featuring creases ahead of and around the rear light clusters, I think this may be a similar thing also.

[thisisntjared]

i saw the pics of the gliders, but do you guys have pics on how placement on autos?

[GasSavers_RoadWarrior]

No installed pix here, but here's how I'd do them on your WRX...



Note this is not to scale, use placement and spacing mentioned in post above, however, place them in the areas indicated, you can neaten up the arrangement of them. I deliberately left gaps at the top of taillight/bottom of window level and at bottom taillight/bumper fillet, because Subaru may have done some careful work with flow around those areas and we don't want to mess it up. Also we'll leave the top of the roof alone because we'll assume Subaru knew what it was doing with the spoiler. This is about the placement that Wile-E will get when I get round to him.

You could also have single or triple vertical strips on the sides at the rear or the areas indicated if that would look tidier, or you only get a 6ft roll of stuff. Try and find the "closed cell" type of draft strip as this will not hold water like the spongy type.

[thisisntjared]

nice choice on the cherry blossom (sti's color to those who don't know) strips! i was actually thinking about doing it to my wifes fit since that is the car we use for the highway driving. its also black so i can get away with a lot more with the strips.

are the nearly horizontal strips more efficient in generating turbulence?

also how do angle the fence type strips in a delta formation? like this:

|\\
| \ \
| / /
|//