Coanda effect

[GasSavers_RoadWarrior]

I'm figuring on messing with a Coanda surface under the back end driven by exhaust flow. Back of envelope figures suggest about 15lb of thrust at 60mph plus any drag reduction benefits.

Edit: BTW that's for a 3L V6 auto spinning at near 3000rpm, a 1.6 4 banger with a 5 speed turning at 1500 would be about a quarter of that.

[VetteOwner]

[QUOTE=red91sit;93741]could act like a gently sloping boat tail at the right angle! But more importantly, it's also a low pressure zone sucking up exhaust fumes... a bad thing...

/[QUOTE]

yea... hence why with a leaky chevette hatch seal and the front windown cracked or down it sucks up the exhaust into the car...

[red91sit]

haha, i know how that goes, I've got massive exhaust leaks, from the header on back... Luckily i have a "No ventilation" button for around town which does a remarkabley good job of stopping air from entering the car. The skunk button.

[Hateful]

Well, just to give it a try I removed the key cylinder from the trunk and mounted a 12 volt 8" fan( made for mounting on dash of trucks) to the inside of the trunk lid facing the key hole. There doesn't seem to be much coming out of the limited opening( possible that more forced through other small cracks) but I suspect more is pulled out at speed by drag.I'd been averaging between 36 and 37mpg so far on this tank.Today I drove on interstate at up to 75mph with no coasting in neutral( still saw the 9999 and few times). Over the 115miles round trip I averaged 39.8mpg. I don't know how much was the fan or how much were the other recent mods said not to be worth while. Anyway my car stayed cooler with the extra air and I didn't need to sweat nor turn on the A/C. I'm considering drilling additional holes where the Chevy bowtie is now as I can put it back on if I change my mind. Maybe another fan or two.

[GasSavers_SD26]

Well, who's tested the Ram Wing?

[GasSavers_RoadWarrior]

Originally Posted by SD26

Well, who's tested the Ram Wing?

No-one who's done rigorous testing...

Fuel expands 1% per 1C rise in temperature, if you fill your tank with gas from underground tanks at 15C, and let the vehicle sit in 20C temps while you fix the Ram wing on it, and say you get 400 miles to the tankfull... then you go on a 25 mile test run... with 5% expansion purely from atmospheric heat, you'll only get as much gas in as it uses in 5 miles, say about a quart... wow a quart for 25 miles! That's 100mpg! This is without expansion that might happen when the fuel runs into a warm engine bay to the regulator, and then 90% of it gets returned to the tank at low throttle openings.....

But of course... these devices never work for a FULL tank of fuel, because the ECU tunes it out*, or the gas additives poison the system...

A similar critique applies to certain products that claim "scientific mileage testing" or something like that for this technique.... and those use a fuel heater! Although to give them credit they do tell you to test the unmodified vehicle that way first... but still... fuel heater....

(*This does happen of course for some things, but it can also be used as a lame excuse for faulty testing)

[lunarhighway]

i once thought about placeing plastic tubes between the roofline seal of my rear hatch to enambe air to escape from the interior, but tubes where to weak and where crushed by the hatch. so i gave up on it.

shoudn't be to hard for production cars to set up their ventilation vents in this fashion. two birds in one stone i'd say

[GasSavers_RoadWarrior]

Some of them do, or have done, I've had cars with vents in the C pillar, then with the flow through ventilation flaps from the base of the windshield open, they should have been bleeding air from high to low pressure behind the car. In my minivan, I can open the flow through vents and crack the rear windows. Some trucks have slide open windows on the back of the cab, could be used with flow through ventilation....

[Greybrick]

Originally Posted by ZugyNA

Basic idea would be to take some of the high pressure air at the front of the car and transfer it to the back?

With all of the various mods done by some on this forum have any installed front intake vents and used flexible fume or hvac ducting to transfer some front pressure to the rear of the vehicle to break up part of the tail drag.

http://www.flexibleducting.co.uk/pro...application=29

http://www.novaflex.com/productcart/...?idcategory=16

.

[fowljesse]

My Mercedes SLC has vents between the rear 1/4 windows, and the rear window. It's a great design, but the car wasn't built for FE!