Civic hatchback aerodynamics

[SVOboy]

Send me a PM about the MID so that I don't forget about it, I should be able to loan it to you after winter break, which will be ending around the beginning of january.

[basjoos]

Originally Posted by theclencher

Yes, I know you can't judge aero by looking at it... but unless that pointier nose is somehow directing more air away from a "dirty" undercarriage I don't see how it can be improving aero. Generally, as long as the airflow going around the front end remains attached along the sides the bluntness or pointyness of it doesn't really affect drag in the 0 degree yaw condition. In fact I wonder if the increases in "frontal area" due to the added length of nose and tail when the car is yawed serve to increase Cd in crosswinds?

The great effect of that nosepiece surprised me too. I had installed it in preparation for my next mod (Re-scuplting the profile of the hood/windshield area) and didn't expect it to have the effect that it did. The only cause I can think of is that most cars have deliberately designed into them a high pressure area on the nose to help funnel air into the radiator openings. The pointier nose reduces the size of that high pressure area, and by placing the point low, diverts some of the air over the car that used to go under it.

[thisisntjared]

Originally Posted by basjoos

The great effect of that nosepiece surprised me too. I had installed it in preparation for my next mod (Re-scuplting the profile of the hood/windshield area) and didn't expect it to have the effect that it did. The only cause I can think of is that most cars have deliberately designed into them a high pressure area on the nose to help funnel air into the radiator openings. The pointier nose reduces the size of that high pressure area, and by placing the point low, diverts some of the air over the car that used to go under it.

yea i was going to say cross winds usually dont get passed 40mph and are thus not a great concern. cutting that high pressure system in front of the bumper should help a great deal...

also, i think you are correct in the assumption that the auto makers create the high pressure area to aid in cooling.

[Peakster]

Holy smokes! This is the first time I read this full thread. Basjoos, your aerodynamic modifications are INCREDIBLE! I'm definitely going to at least try wheel spoilers on my car after being inspired by you!

Just one year ago, I was driving a 1985 Pontiac Fiero with a Cd of 0.37 and that number shot to 0.41 when the headlights were popped up!

[GasSavers_Frank]

What inspiring work! Keep it up and thanks for posting!

[basjoos]

I've noticed that the nosepiece has made a change in the A-pillar vortex. When driving in the rain, the behavior of the water drops on the side window shows me the location of the drag-inducing vortex produced by the A-pillar. It forms a comma-shaped line of stationary water drops about 2/3 of the way up the glass where the bottom of the vortex beats upward against the glass, keeping the drops suspended and not letting them run down the glass. Since I added the nosepiece, this comma-shaped line of water has shifted upward and is now located 4/5ths of the way up the glass, which I believe if indicative of a smaller-sized vortex and hence less drag.

When I gassed up today, a guy asked me if my car was an experimental hybrid.

[onegammyleg]

Originally Posted by basjoos

So how much is a 17 year old car (1992) with 683,971 km on it worth anyway?

almost as much as a Big Mac ide figure

[GasSavers_Frank]

Something you may want to try sometime is to install larger diameter tires. This is an easy way to change effective gearing which will load the engine more for a given road speed. Lower RPM at a given load usually requires more throttle which means less pumping losses which means higher engine efficiency. Or something like that. Your efficiency improvements have reduced engine load; there might be more to have...

[basjoos]

My tires are one size over stock, mainly due to limited availability of my car's stock tire size. One problem with going to a larger tire size is that it also increases the ground clearance, which tend to increase drag as more air goes under the car.

[basjoos]

As I have progressively aero modded this car, its coasting ability has steadiliy improved. To the point to where I now drive it considerably different than I have driven any other car. Since any moderate downhill grade now produces a steady accelleration, any slight downhill is now a steady speed coast, and it takes a long time to lose speed when coasting on a flat grade; in any kind of slightly rolling terrain, I find myself spending a good chunk of my driving time in ICE-off coasting mode.