Aerocivic - how to drop your Cd from 0.31 to 0.17

[freebeard]

Originally Posted by johnlvs2run

Did you do anything to create that suction, or is it already there on my car as well?

It's instructive to observe other vehicle's front wheelwells in the rain. You can see a forward rolling, outward expanding mist, but it varies from vehicle to vehicle. Ecomodders like to speculate about directional vanes in the hub, but fact is the skin friction on the tire is more effective. See Tesla Turbine.

Considering who's in the thread, and speaking as a VW Beetle owner, I'd like to say "Boat-tailed Civics/Insights are awesome."

[j12piprius]

Thanks for the feedback.

If I understand correctly, there is nothing that needs to be done to the wheel wells, other than the wheel skirts that help.

Upcoming projects for me, add adjustment to grill block, and wheel skirts.

[aerohead]

Originally Posted by johnlvs2run

Thanks for the feedback.

If I understand correctly, there is nothing that needs to be done to the wheel wells, other than the wheel skirts that help.

Upcoming projects for me, add adjustment to grill block, and wheel skirts.

*The volume of the wheelhouse affects drag.The absolute minimum has an advantage.
*If the wheels are exposed,they should be flush with the sides of the vehicle and have the convex,full-coverage covers.
*The rear face of the housing would be radiused and blended into the fender.
*I have no data on 'air-curtains.'
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*If the wheels are inset a bit,then skirts can be added which will not aggravate frontal area.
*Full-coverage wheel covers are still a benefit,as they reduce windage losses of the rotating wheels.
*Ford,with their 1984 Probe-IV concept car,had something like an inner ABS fender which contacted an elastic polyurethane spat,which would deform to allow for wheel flop.Ford claimed a 9% drag reduction for the system.
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*Some automakers have chosen to integrate engine cooling system air extractors into the belly pan centerline and abandon the front wheel houses as a passage for this airflow.A move which simplifies front skirts.
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*The articulated front skirts on AeroCivic are a proven,off-the-shelf design which incorporates the best of everything,minus the exotic materials and exotic fabrication requirements.And basjoos has some delicious numbers to go along with them!

[j12piprius]

Originally Posted by 3-Wheeler

I also have a small area for air flow due to a grill block, and recently drove on an 80F day up some 1/2 mile long hills by LaCross WI. The grill block was on the car at the time, and I did the following to keep engine coolant temps down:

The temp was mid 90's during my 125 trip, the particular uphill midway, 10 miles at 4% grade and 2 miles of that at 7% grade.

1) My speed averaged 40 to 45 mpg in 5th gear with light throttle, with a couple of brief interludes in 4th gear to maintain momentum.

2) Your comment about keeping rpm close to 3000 rpm is interesting, but seems counterintuitive due to more stress on the engine, a longer time going up the hill and seems it would put more stress on the cooling. Would going a lower gear at higher rpm actually help the cooling?

3) The higher engine speed also means higher coolant speed through the engine block, which keeps it cooler than lugging the engine up a long hill.

4) The engine was not lugging at all. I think the engine load was 70 percent.

5) My engine temp usually went to 206 on the hill, but the last time went higher, maybe due to having pulled the a/c fan fuse, though I'm not sure that would affect the engine temperature. I had previously disconnected the temperature sensor as a test and then plugged it back in, so I hope it's still working.

[skyking]

the higher RPM's do work, because the energy required is divided among more events. The heat is less concentrated, and as stated before the cooling system is running at a better flow for the heat.
I deal with this phenomenon with my Cummins-powered Dodge truck.
It makes huge amounts of torque at 1700, but the heat will build rapidly on a hill. If I get it to 2100 or so in the lower gear everything is cooler.

[kir_kenix]

Originally Posted by skyking

the higher RPM's do work, because the energy required is divided among more events. The heat is less concentrated, and as stated before the cooling system is running at a better flow for the heat.
I deal with this phenomenon with my Cummins-powered Dodge truck.
It makes huge amounts of torque at 1700, but the heat will build rapidly on a hill. If I get it to 2100 or so in the lower gear everything is cooler.

Yeah, I have seen this happen many times as well in diesels as well as gasoline engines. Recently I went with my father in law to pick up some Holstein bulls from Wyoming. We took his half ton Chevy and pulled his lead sled stock trailer (I offered to take the 1 ton and my aluminum stock trailer...but there is no arguing with some people). When loaded that truck would heat up even during slight grades, but shifting down always alleviated those problems.

3rd gear pulled something like 2600 rpm going up hill at 55, as opposed to 2100 in OD. Moral of the story was to leave it in 3rd and avoid watching the temp.

[serialk11r]

Originally Posted by aerohead

*The rear face of the housing would be radiused and blended into the fender.

When you say that, do you mean like this? (front fender) Is that really the best way to do it, considering how there seem to be a million different fender designs out there? For example in this one, the rear fender doesn't have that treatment.
http://img.netcarshow.com/Porsche-91...llpaper_04.jpg

Originally Posted by johnlvs2run

2) Your comment about keeping rpm close to 3000 rpm is interesting, but seems counterintuitive due to more stress on the engine, a longer time going up the hill and seems it would put more stress on the cooling. Would going a lower gear at higher rpm actually help the cooling?

Technically yes there's "more stress on the engine" as the engine would be pumping out more bhp before mechanical and throttle losses and burning more fuel, but because you're reducing the temperature that you're burning the fuel at, less heat will make it to the coolant.

[aerohead]

Originally Posted by serialk11r

When you say that, do you mean like this? (front fender) Is that really the best way to do it, considering how there seem to be a million different fender designs out there? For example in this one, the rear fender doesn't have that treatment.
http://img.netcarshow.com/Porsche-91...llpaper_04.jpg



Technically yes there's "more stress on the engine" as the engine would be pumping out more bhp before mechanical and throttle losses and burning more fuel, but because you're reducing the temperature that you're burning the fuel at, less heat will make it to the coolant.

Yes the Porsche is using the radius.Here's a link to the Ultralite.
Dozens of concept cars have used this.Scagglione of Ferrari may have been the individual to introduce the concept.
http://files.conceptcarz.com/img/GMC...V-10-GM-02.jpg

[Xist]

[ECONORAM]

Originally Posted by basjoos

That suction is developed by a wheel spinning within the close confines of a wheel housing. Having a skirt over the wheel well opening does help to increase that suction just as the housing around a squirrel cage blower helps to strengthen and direct its flow.

I get a small amount of cooling airflow through my radiator even with the grill block closed as some air leaks around the edges of the closed grill block. When climbing a long steep hill in the heat, I'll open the grill block and let the front wheel suction do its thing. Then when going down the other side I'll gradually close the block as the engine's heat production drops.

Bajoos, thanks for sharing the explanation. I don't run a grill block on the ECONORAM mule--testing gave me a negative result--but did put in an under drive crank pulley. In light of that, I may need to incorporate something similar to your wheel well venting at expressway speeds to keep things cool. Although, if I keep working on the aerodynamics perhaps I can push the cooling issue a little farther down the road (so to speak).

@ freebeard, good point. Maybe I'll watch some pickups similar to mine to see how the spray flies out. Or maybe I'll pull a MetroMPG and rig up a webcam and video my own wheel wells to account for the aero panels.

@serialk11r, take a look at the wheel wells of a RAM pickup. The entire wheel well is radiused. But it could probably use a little refinement wrt to the ecomodder realm...