aero-mods,installment#9(internal drag)
 

Note from Darin (admin): this installment is part of a series posted by Phil (aerohead) about the effectiveness of various aero mods - usually with quotations and citations to source data.

See the Aero mods data index here.

End note.

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More debris from the library. As always, it's a mixed bag spanning a few decades. The numbers should stand on their own merits, as they come from the big-boys. My own tidbits are courtesy, Southern California Timing Assoc., official timers for all F.I.A. land speed records. Images will come later, sorry! Many of the vehicles can be found through GOOGLE Images.

There's not a lot of info, so this will go pretty quick. Thing is, people have thought about these things and "looked into it". As George Santayana said, "those who refuse to learn from the past are doomed to repeat it." There's no reason why any ecomodder should waste time going down a trail that's been thoroughly flushed out.So here we go,and I hope it helps.

Internal-Drag

1938, windtunnel tests on the Adler/Jaray (on the car lots in Germany) demonstrate that blocking the grille achieves a 15-percent drag reduction, dropping the Cd from 0.38 to 0.32.

Walter Korff, in his recipe for a Cd 0.21 passenger car suggests that an idealized cooling system,with airtight inlet and outlet ducts properly positioned, can cut drag by 7.7-percent.

1963, Kelley and Holcombe, of GM suggest "The ideal circuit for an engine-radiator internal flow system requires a smoothly edged, clean intake opening that leads to a completely enclosed diffusing duct, permitting the velocity energy to be converted to pressure energy with low losses, minimum pressure drop across the radiator, and is directed into a contracting duct that exits the air at a convenient low pressure. It should be possible to accomplish the engine cooling job with little or no net loss in an efficient system."

1973, CAR and DRIVER's Pinto picks up an added 0.40 mpg with an optimized grille-block.

April, 1975, C and D's aerovan Dodge picks up a 3-percent drag reduction with optimized grille-block.

1975, Dr.Alberto Morelli designs all the best features into the cooling system of the CNR "banana-car", cooling system losses are cut to 0.008. Morelli observes losses in production cars up to 0.1. On CNR, an air-tight 4:1 diverging inlet duct, and four, air-tight converging exit ducts are positioned on the car such that air bleeds into surrounding air at same velocity.

1986, Fiat windtunel studies of large-scale models show cooling system drag at 6.9-percent. Sealing the system only cuts drag by 1.2-percent, as upper-body drag increases.

1987, Bridgestone/Firestone Test Track, Fort Stockton, Texas,U.S.A., In closed-course, l and speed record attempt, GM tapes-off cabin ventilation NACA inlet to minimize aero drag. Driver, A.J.Foyt, can only tolerate 5-laps in the car at a time before being overcome by alcohol fuel vapors.

July, 1991, Bonneville International Speedway, Wendover, Utah, the Phil Knox, 1984 HONDA CRX, 1.3-liter experimental streamliner : air-cleaner deletion returns no measurable improvement to top speed ( internal-internal flow).

Hucho publishes that cooling system drag can me minimized to 2-percent,drag as high as 10-percent has been observed.

General note, all NASCAR teams use the Korff/Kelley-Holcombe/Morelli/American Aviation P-51 air-tight divergent inlet duct. Kamm and others, since the 1930s have used critically-cited exit ducts for the exit flow. Ford and GM PNGV cars use rear, quarter-panel heat-exchangers to dispense with front grilles altogether, for sub-Cd 0.17 bodies. The Olds AEROTECH uses "ideal" heat-exchanger inlet and outlet ducts, borrowing from aviation oil-cooler technology and probably has no drag at all due to thrust from expanding air mass.

Cooling system drag constitutes about 12-percent of overall aero drag and its been demonstrated that it can be eliminated. Its under the hood and out of sight, but its something to think about.

Another great post with some valuable stats. Thanks for digging through the stacks.

And Phil: good news! The forum upgrade did in fact include individual photo galleries. I will be testing it out, then importing the MaxMPG images to your gallery.

Hi,

A great example of this type of cooling is the Britten V1000 motorcycle:
http://www.nzedge.com/heroes/images/jkb-bathurst.jpg
The air enters in the small ducts in the nose of the fairing, and the (small) radiator is located under the seat, and the hot air exits out the duct "stinger" at the tail of the motorcycle.

This motorcycle is totally amazing btw: custom engine (producing 165 horsepower at 12,400 rpm -- with no need for counterbalencers) is a stressed member (it IS the frame, really!), the front and rear suspension are carbon fiber girders with the suspension travel provided by linkage, the wheels were handmade with a "skin & bones" carbon fiber structure, and the aerodynamics (dubbed "torpedo over a knife edge") was unusual and ground breaking.
http://www.nzedge.com/heroes/images/jkb-queenstown.jpg

Hi,

Another tie-in with this thread is the Crower 6-stroke engine:

http://en.wikipedia.org/wiki/Crower_six_stroke

Once it warms up, it injects water into the cylinder, which expands as steam, producing a second power stroke, and cooling the engine at the same time. There is no need for a radiator, or a cooling system, as such...

Wow.

pretty cool. I believe indy cars also use the engine as a stress member. Totally changed my thinking when I found out.:o

maybe this will help illustrate things a bit

(I will try and get option B setup on my car)

http://www.killrobot.com/images/rad_air.gif

version C
 

Version C is what Walter Korff,and the GM Research Labs guys were promoting back in 1963.This is also what Morelli did with the banana car,although he had exits underneath too.Kamm pioneered the principle in the 1930s,and this allowed the flow over the roof of the car to be good enough for the K-car form to work.Great image,thanks!

Be sure to read the AUTOWEEK article at the link further down the page.

“Especially an 18-wheeler, they’ve got that massive radiator that weighs 800, 1000 pounds. Not necessary,” he asserts. “In those big trucks, they look at payload as their bread and butter. If you get 1000 lb. or more off the truck…”

Offsetting that, of course, would be the need to carry large quantities of water, and water is heavier than gasoline or diesel oil. Preliminary estimates suggest a Crower cycle engine will use roughly as many gallons of water as fuel.

And Crower feels the water should be distilled, to prevent deposits inside the system, so a supply infrastructure will have to be created. (He uses rainwater in his testing.) Keeping the water from freezing will be another challenge.

The wiki article already mentioned that keeping the water out of the oil will be a big problem. It will be a HUGE problem. You can add piston rings, but that adds friction to be overcome. Any steam that gets by will condense in the oil, which will then have to be filtered out.

This (digitaldissent) is close to an idea i had a while back. It's a theory so here goes!
Hypermiling doesn't work an engine hard does it? So remove the radiator and install a custom built (tubular?) heat exchanger that the engine air intake draws air through. As it draws its air through the heat exchanger, the engine coolant is pumped around like in a radiator, cooling the coolant and warming the air to the engine. Then in the space the radiator was in, re-build the belly pan so it slopes up in front of the engine, to the underside of the bumper, thereby creating a pointy front end on the car and hopefully improving aero. The new "radiator" will need cool fresh air to maximise cooling and so that the air going to the engine isn't flaming hot! So an intake in the nose is used.
Does any of this make sense? I suppose the idea came about because of the drag a radiator places on a car. I thought maybe i could remove the rad. Then how was i going to cool the coolant? Simple: stick a radiator in the air intake. Does anyone here have a grasp of the approx heat output from an engine and how much of that heat could be directed back into the engine safely via the air intake?
This might not work at all but we've got to keep trying right?!
Maybe i'll try it before i de-commission the civic next year....

ollie

do a search on Smokey Yunick and look at some of his engines :thumbup: