[ACRGLASS]

Has anyone found a rear air deflector for the Promaster? I found the patent for the DeflectaShield design that we've had on many older vans, and installed on many customer vehicles as well over the years. Of course, Deflecta is gone, and this style wouldn't work on the Promaster. However, the much older aluminum styles or something like them could possibly.

We're after keeping the van clean of dirt, debris, snow and ice, but the obvious benefits in mileage should also happen when reducing that vacuum in the square rear end. It was sure noticeable on our older vans, it has to be on this high top as well.

The deflector only has to stick up about 3/4" above the roof top to catch enough air to solve the problems on the older style vans and vehicles.

http://www.google.com/patents/US5338088

Any suggestions?

 

[grnd0]

Air tabs.

 

[ACRGLASS]

Thank you, interesting reading, and product.

 

[ACRGLASS]

After a lot of looking, we've discovered a few things regarding the accumulation of dirt on the rear of the van on dirt roads, specifically.

First, the HVAC OEM system in the van.

Every vehicle typically has a fresh air intake at the bottom of the windshield beneath the cowl and wipers. It's usually on the passenger side, and is on the Promaster. What we noted was a dusty dirty smell of dirt in the van when driving down country roads. We noted the buildup on the rear, and it creeping in the joints in the weather seals on the rear doors, but not enough to account for what we were "smelling" or "breathing". We found that the above mentioned air intake has a very large drainage tube to allow rain water to expel out of the main HVAC intake to the ground, and it exits right behind the right front tire. Dirt was actually being sucked up that drain tube, and we could smell it, even though the HEPA filter was trying to stop it.

Hitting the "recirculate" button stopped the problem, but created another. With out positive pressure coming in the front, the rear door dust problem coming in around the weather strip joints became MUCH worse. I don't know yet if I can relocate that drain tube exit point, but one certainly CAN NOT plug or dampen it in any way. Water would come into the cab in a car wash or heavy rain. Over my decades in the auto glass industry, I've seen tons of cars with water problems due to things like leaves plugging those drains, and most cars have one on each side, the Promaster has only the one.

So now, thanks to a very nice gentleman and Mfg I won't mention just yet without their permission, I have an initial potential prototype of a rear air deflector that could work on any van of the Promaster style, and may similarly duplicate what DeflectaShield did with thier's years ago. Hopefully a rear air deflector can solve both issues, and with our older van styles we had the DeflectaShields on, it improved fuel economy as well by eliminating that suction on the rear of a van/square rear end vehicle.

It may take a while, but I'll post our progress as we make it.

 

[cutndry]

I'm going to try to use an air dam under the front bumper for some better aerodynamics. A combination of front air dam and rear air deflector might be just the right combination. Here's an article on aerodynamics for pickup trucks talking about a combination of factors to improve aerodynamics, not just limiting the improvements to one area.

http://media.gmc.com/media/us/en/gmc/news.detail.html/content/Pages/news/us/en/2013/May/0516-gmc-pickup-aero.html

 

[Wowbagger]

Does anybody have any experience with Airtabs on a Promaster?

 

[RDinNHandAZ]

See http://www.promasterforum.com/forum/showthread.php?t=49993
Save your cash until a nice top deflector becomes available IMHO. I doubt even that will have any noticeable effect on mileage but might keep the back windows cleaner. Few here have found a significant mileage loss or any gain from any top addition or other addition. Perhaps waxing the van will do as much (an old racer trick).

 

[Brian P]

I'm going to try to use an air dam under the front bumper for some better aerodynamics. A combination of front air dam and rear air deflector might be just the right combination. Here's an article on aerodynamics for pickup trucks talking about a combination of factors to improve aerodynamics, not just limiting the improvements to one area.

I did this but it's too early to see if there's much effect on mileage. Initial impressions are that it's not worse, and it might be a percent or two better (which is about all I would expect). For the investment of about $5 and some time fiddling with it, there's not much to lose if it doesn't work ...

I used lawn edging (home depot) and made some 90-degree brackets from a piece of aluminum angle. I screwed the brackets to the existing screws that secure the bottom of the bumper (plastic) to the support - if you look up from underneath at the bottom of the bumper, you'll see them. Then the lawn edging is bolted to those brackets. If you're smart you can get the bolts along the front to be hidden behind the van's existing little rubber flap on the bottom of the bumper, and a dab of black paint takes care of the ones on the side that are outside of where that flap is. I also used a piece of threaded rod to fit inside the bottom edge of the lawn edging to hold the bottom edge in shape.

I also blocked off the top half of the grille - the top half of the "Ram crosshair". Piece of 1/8" black plastic zip-tied to the backside of the cross-bars of the grille through strategically placed holes - done. You will have to unbolt the center part of the grille in order to get in behind it to do this. If you want to do this together with the air dam ... do this one first (which is not the way I did it). Life will be much easier for removing that center part of the grill if you don't have an air dam attached to the bottom of it!

Don't block off anything below the crossbar where the Ram emblem sits. The pipe with the metal fuzz on the outside of it in there, is the transmission oil cooler ... you don't want to mess with the airflow around that.

I don't live in a hot desert climate, nor do I do heavy towing, nor am I stuck in traffic jams a lot with the air conditioning on ... your mileage may vary. If your situation is potentially testing the limits of the cooling system (mine is not), you may not want to do the grill block.

 

[Swoop]

I did this but it's too early to see if there's much effect on mileage. Initial impressions are that it's not worse, and it might be a percent or two better (which is about all I would expect). For the investment of about $5 and some time fiddling with it, there's not much to lose if it doesn't work ...

I used lawn edging (home depot) and made some 90-degree brackets from a piece of aluminum angle .
. . .

Brian,
It has been close to a year since you posted about your air dam modification. At this point, do you think it has been beneficial?

 

[ACRGLASS]

Found myself re-visiting this issue this AM over coffee. Four years with the van, and still have not solved this yet. A really nice gentleman sent me a sample of a Bus rear wing/deflector, but I'm very hesitant because of the mounts. It's a **** of a unit, but the mounting to the Promaster has to be "fail safe", not "fail secure" in case you catch this thing on a tree branch so you don't take the rear of the van off.



I just want to get rid of the vacuum behind this van, at all times on the highway, but especially on a dirt road.



I know from previous experience posted above that Deflecta Shield's product did wonders on Astro and Express vans, and on an older Blazer I had.



Surfing around.....not finding much. I'm not interested in a "sporty spoiler" for looks only.

 

[KNDLKSTMS]

I rigged a 60" Yakima Slipstream cross bar that mounted to the 80/20 roof rails . Wing nutted a Gopro to record yarn taped to the back window and roof around the "wing". Moved it up/down , for/aft 'till the yarn "danced" . The dancing yarn meant air was filling in the vacuum . The sweet spot was about 1.75"high over the lights and camera proboscis .

 

[GaryBIS]

Does anybody have any experience with Airtabs on a Promaster?

This article claims to have wind tunnel tested airtabs on a Sprinter: http://www.airtab.com/Site/documents/an-expediter-and-his-airtab.pdf


Quite a nice improvement if true. The airtabs should also keep the back of the van cleaner as the energy they add to the boundry layer should keep the airflow attached longer.



This forum has a lot of discussion and some testing of ideas to improve aerodynamics of vehicles: https://ecomodder.com/




Gary

 

[dttocs]

I rigged a 60" Yakima Slipstream cross bar that mounted to the 80/20 roof rails . Wing nutted a Gopro to record yarn taped to the back window and roof around the "wing". Moved it up/down , for/aft 'till the yarn "danced" . The dancing yarn meant air was filling in the vacuum . The sweet spot was about 1.75"high over the lights and camera proboscis .

Sounds promising...

Can you share a picture or two please? I can understand how fore/aft could be done, but I’m struggling with how you achieved up/down. (Also, did you mean Yakima Jetstream? I think Thule makes the slipstream)
@GaryBIS, there has been a bunch of discussion about AirTabs at Sprinter Forum (one example) with no solid conclusions, and although Advanced RV reported some success, they don’t seem to have made them a standard recommendation.

 

[GaryBIS]

Hi,
Somewhat surprisingly you can buy a variety of vortex generators on Amazon: https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=vortex+generator
Prices all the way down to just over a buck apiece, good reviews on durability.
Some types of VGs could also be made easily with aluminum angle iron.



If you drive 12K miles a year and gain 5% in mpg (say from 19 mpg up to 20 mpg), with $3 per gallon gas, the saving is near a hundred dollars per year - about a 1 year payback. Plus about 700 lbs less CO2.

Seems like a no-brainer if it could be verified that it really produces the drag reduction.
Should also help with keeping back of van cleaner.


I'd definitely give it a try if I could figure out a way to test before and after fuel consumption that is believable.
Thinking about picking a level stretch of road a couple (or more) miles long.
Drive it several times in both directions before VG install and using the van mpg computer to estimate fuel consumption.
Then repeat on same stretch of road in the same kind of weather with same tire pressure etc. after VG installation.
Use yarn tufts with camera to see if separation is actually delayed.

Any thoughts on this method? Or, a better method?


A paper that discusses various type of vortex generators: https://csus-dspace.calstate.edu/bi...s_ChrisMugnaini_20151130_Final.pdf?sequence=1
The gains that they show on semi trailers is not as great, but I think the rounded corners of the PM make it a better candidate the VGs?



Gary

 

[ACRGLASS]

I'd like to see pics also please, KNDLKSTMS! TIA

 

[phil]

No idea of the cost,

http://www.seeiiairfoils.com/

 

[ACRGLASS]

I'm going to post a couple of photos of the aluminum "bus" deflector the gentleman sent me a actual sample of that we have NOT mounted. In the photos, it's just sitting up there on the van, balanced to not fall off on the camera housing. It does illustrate how I want something to work, based on what DeflectaShield did in the past on their designs that worked very well. BTW, it is 48" wide, for reference. Obviously, it would take some work to reinforce the mounts, if you used what they sent with it in any way. It reaches no structure in the van besides open sheet metal. If anyone wants this company's info, I'll get it for you, I was impressed to say the least with their efforts to help.



Oops, nevermind, I see Phil already did post it. http://www.seeiiairfoils.com/

 

[Swoop]

If you drive 12K miles a year and gain 5% in mpg . . . .
Seems like a no-brainer if it could be verified that it really produces the drag reduction.

5% sounds very optimistic to me. I would expect the effect to be in the difficult-to-measure range. Auto makers have been trying for years to improve fuel economy (while making over-sized, over-powered vehicles, because that's what Americans want to buy ). They would love something this simple and cheap if it really worked.

 

[jagarcia89]

Interesting. I have been having a hard time even finding a front deflector let alone a rear. I notice a pretty bad shake when I am approaching the rear of a semi truck. I wonder if this would help.

Let us know your findings!

 

[KNDLKSTMS]

I have trouble posting photos . I drag photos over and they disappear . I'm a bit technologically challenged . PM me your e-mail and I'll shoot you those Pics .I don't have any scientific mileage data but in theory it should work . Maybe even help with the buffeting following a tractor-trailer (truckers don't like being followed that close) .
I worked at a maintenance hanger for a while and they put VG kits on a few wings . Looked like they were about .750" tall and 1" long made from T aluminum .062 extrusion , and they had a slight curve to match the wing . I was told they made the wing work better at low speeds , 40mph to 80mph .