Cobalt Coupe Aero Mods

[OKXXFE]

So according to some info I found 'round here that I think may have originally been posted by Aerohead (?), the cooling system or just the engine bay in general is responsible for about 30% total aero. drag. By blocking off just my upper grill I achieved (conservative first estimate) 10-15% increase in FE. It will be interesting to see if fully isolating the airflow from around the engine will actually increase my overall FE to anywhere near the theoretical 30%. I know I have a whole lotta work to do in fabricating what I want and also the testing testing testing.
Does anyone know if the SGII or UG can compile select data for a spreadsheet? The easiest way I know to determine if variables are effective is to show it on a graph and plotting by hand is super tedious.

As it's Sunday, I think today is a good day for cardboard mockups and a trip to the hardware store! don't tell my wife...

[4drturbo]

Hopefully it is worth it in the end! Like the ideas.

[OKXXFE]

Well, big non-news to the folks here I'm sure. Cardboard and duct tape do not hold up that well for highway speeds. Engine coolant temps stayed alright till the tape let go, then of course the board that the tape was supposed to have been holding covered about 2/3 of the radiator on a 80*F afternoon. So the top piece had to go, then the bottom folded in a funny way so it went as well.
But, this was just a testing of concept and seeing if my template could work. I think I'll snoop around for some not-yet elected crooks signs for mock-up v1.5 and some zip ties.

The weather is supposed to be nice this week, so I might have time to take a little more pride in my work with the car as I will be riding to work for the week. The bike is still setting the bar for mpg's, though it's now obvious that a better power to weight ratio is far less important than aerodynamic drag at least for highway speeds. Still 50mpg@65mph and I get to be outside!

[freebeard]

Roll down the window and stick you hand out.

There's a reason why 100-mph tape costs 10x as much as duct tape.

[OKXXFE]

Originally Posted by freebeard

With your partial bellypan, hold the front edge in some sort of slot so that it can't droop down and turn into an air scoop. That's a failure mode.

Looking at the underside of my engine compartment, I don't have much room to work with. The front bumper to the radiator is my largest gap, and a partial belly pan from there to behind the radiator takes me almost to the oil pan. Good news is my radiator is fully enclosed in a shroud, so ducting the exhaust air from the fan should be only a minor challenge. I think I will use the stock valence piece to make a template for whatever material will be the front pan.
This morning was more duct taping and thinking about what I am doing more thoroughly, time to see how it does for the morning commute!
Ambient temp is ~70*F with wind @20-30mph from the South (strong headwind)


Have a wonderful morning!

[aerohead]

Originally Posted by OKXXFE

So according to some info I found 'round here that I think may have originally been posted by Aerohead (?), the cooling system or just the engine bay in general is responsible for about 30% total aero. drag. By blocking off just my upper grill I achieved (conservative first estimate) 10-15% increase in FE. It will be interesting to see if fully isolating the airflow from around the engine will actually increase my overall FE to anywhere near the theoretical 30%. I know I have a whole lotta work to do in fabricating what I want and also the testing testing testing.
Does anyone know if the SGII or UG can compile select data for a spreadsheet? The easiest way I know to determine if variables are effective is to show it on a graph and plotting by hand is super tedious.

As it's Sunday, I think today is a good day for cardboard mockups and a trip to the hardware store! don't tell my wife...

The experts would tell us to treat each vehicle on a case-specific basis as far as numbers go.
In the past,messengers suggested that a production cooling system would be responsible for about 12% of the overall aerodynamic drag.Hucho,in the mid-1980s suggested that the drag of a carefully designed cooling system drag could be reduced to 2% of the overall drag.
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Fiat published an SAE paper in the 1980s,based on wind tunnel studies of a 1/2-scale model with very detailed underbody.
Their tests showed that completely blocking off the cooling system didn't necessarily eliminate the cooling system drag.It might reduce under-body drag,while increasing upper-body drag.They did mention that this phenomena warranted further study.So this is the exception to the rule.************
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We do know that positive thrust was achieved in the North American P-51 Mustang cooling system do to heat flux air expansion.
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Walter Korff,aerodynamicist for Lockheed, tested the system diagrammed ,and demonstrated low drag.(so something as close to it should pay dividends).All NASCAR race cars use Korff's inlet geometry and airtight ducting.
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A look at the 1978 Pininfarina CNR 'banana' car illustrates the pains Dr. Alberto Morelli went to to design a low drag cooling system.(he could easily have spent a $100,000 in wind tunnel time just to develop the extractor vents,which blend the cooling system air at matched-velocity to the surrounding flow as it emerges).
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The 1987 Oldsmobile AEROTECH,closed-course LSR racer demonstrates careful attention to heat-exchanger airflow.
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We might want to think of mpg increases on the order of 6% for a perfect system.

[redneck]

Originally Posted by freebeard

Roll down the window and stick you hand out.

There's a reason why 100-mph tape costs 10x as much as duct tape.

I use Gorilla duct tape. $9 a roll at Lowes or Home Depot. I have not had any problems as long as the surfaces are clean. The Gorilla tape has been on for nearly half a year with little or no problems. However, 3M duct tape does not hold up. It wrinkles up in the sun and loses it stickiness when cold.(not very sticky to begin with) Plus, it tends to disintegrate quickly.

OKXXFE

But, this was just a testing of concept and seeing if my template could work. I think I'll snoop around for some not-yet elected crooks signs for mock-up v1.5 and some zip ties.

Go to Lowes or Home Depot and buy a 4x8 sheet of 1/2" foam insulation with foil on one side and plastic on the other. Costs less than $10, can be cut with a sharp razor knife and bent or twisted into any shape desired. It can also be painted or fiber glassed on the foil side if desired.

I'll be posting soon in my boat tail thread to show what is possible using 1/2' foam...

>

[OKXXFE]

So my cooling system seems to do just fine when heading into the wind, and I do see some improvement in fuel consumption into the wind with the grill blocked off. However, with a 20-30 mph tailwind and 90*F, I don't think I am getting adequate flow through my radiator as I consistently see my coolant temps over 200*F which I am not comfortable with. I haven't had a problem per-se but it has gone as high as 212*, which I then rolled down a window and blasted the heater, I am NOT GOING TO DO THAT ALL SUMMER!
The grill block is coming off for afternoon drive home, though I think my partial belly pan/radiator scoop does help some and I will be pursuing a more appropriately engineered and permanent solution with ABS or fiberglass.

*What do ya'll think of a Detachable Nose Cone that would cover the upper grill, and hopefully channel high pressure air directly into the flux-capacitor? The top portion of this scoop/nose would continue the line of the hood to about 10-12" out front and be only as wide as the top of the lower grill opening. Could be made of High Density Foam and fiberglass over?
I couldn't look any worse than the 'Cuda RoadRunner....right.

I'm also dreaming of a Plexi or PolyC rear glass cover starting from the roof glass transition down to the edge of my low rise spoiler. Like a hatch for a coupe.

@Aerohead: That Aerotech I is the most beautiful shape I have ever seen on wheels, why in hell didn't they just do that in Aluminum and sell it? I'd have bought one.

[aerohead]

Originally Posted by OKXXFE

So my cooling system seems to do just fine when heading into the wind, and I do see some improvement in fuel consumption into the wind with the grill blocked off. However, with a 20-30 mph tailwind and 90*F, I don't think I am getting adequate flow through my radiator as I consistently see my coolant temps over 200*F which I am not comfortable with. I haven't had a problem per-se but it has gone as high as 212*, which I then rolled down a window and blasted the heater, I am NOT GOING TO DO THAT ALL SUMMER!
The grill block is coming off for afternoon drive home, though I think my partial belly pan/radiator scoop does help some and I will be pursuing a more appropriately engineered and permanent solution with ABS or fiberglass.

*What do ya'll think of a Detachable Nose Cone that would cover the upper grill, and hopefully channel high pressure air directly into the flux-capacitor? The top portion of this scoop/nose would continue the line of the hood to about 10-12" out front and be only as wide as the top of the lower grill opening. Could be made of High Density Foam and fiberglass over?
I couldn't look any worse than the 'Cuda RoadRunner....right.

I'm also dreaming of a Plexi or PolyC rear glass cover starting from the roof glass transition down to the edge of my low rise spoiler. Like a hatch for a coupe.

@Aerohead: That Aerotech I is the most beautiful shape I have ever seen on wheels, why in hell didn't they just do that in Aluminum and sell it? I'd have bought one.

*In the past,some GM products had 'normal' coolant operating temps as high as 255-F.A service manager at a local Chevy dealer might be able to tell you over the phone what to look for.(Remember,GM tests their cars at Furnace Creek,Death Valley,California,at idle,with all accessories on,in 120-F or so heat.They have very robust cooling capacity).
*As to the nose,it would help get your duct length closer to the height of the radiator.Also,it would lower the stagnation point which is very good for low drag and lift.Ideally,the nose would be vertical,or slightly canted backwards with the air dam integrated right into it.Just like NASCAR.You'd need to watch your approach angle clearance (16-degrees) so it doesn't scrub or worse.
*The rear backlight area is where the money is.The current 2nd-gen Insight has a fine contour to mimic.Rear visibility is something you'd have to make an executive decision about.Many backlights are intentionally 'fast' just to aid in outward vision.A rear camera system compensates.Selective reflective Mylar coating would help with solar insolation effects.The answer is to do gold vapor deposition as NASA does on their space suit helmet visors.Kinda difficult for mortal men.If you get the roofline up to 'Kamm' specs,then she's a candidate for tail,which should get you into 50-mpg territory.Easy.

[roosterk0031]

200 dF is nothing, my Stratus fan didn't kick on till almost 220, I haven't noticed at what temp the XFE rad fan turns on. It's really not pressurized (other than thermal expansion that there is no way to avoid) till 212, but they hit max pressure of the radiator cap 50+ times before hitting operating temp due to thermal expansions begins which is almost instantly. Used to be one of first performance mods was to swap to a lower temp t'stat. Ecomodder swap in a higher temp one. I'd go 205 without a 2nd thought, if the rad fan didn't turn on before that.

Pull the fuse on the Power steering, save some amps and save gas, steering kind of twitching anyway. Real easy ABA test.