Increased air in tires to sidewall max -> +10% mpg

[xBiffx]

You can read his build log here and judge for yourself:

http://ecomodder.com/forum/showthread.php/aerocivic-how-drop-your-cd-0-31-0-a-290.html

I believe more recently he swapped the engine for a VX engine (with lean burn), but here is his fuel log with the original 1.5L non-VTEC engine the car came with:

Note that even at the start he was pretty significantly beating EPA numbers.


Now, mind you, my car stock is rated for 61 highway but I find the numbers really conservative, at least in the summer. Simply turning off the A/C results in beating that significantly. It's parked out front right now with "88mpg" showing on the display, which was the result of 33 miles of 65mph driving and 17 miles of 50mph driving, with a few stop signs and traffic lights, though admittedly I've done a few (invisible) modifications too.

Thanks for the info. Now it makes more sense.

Another thing your post made me think of:

If my calculations are correct, when this baby hits 88 miles per gallon, you're gonna see some serious shit.

 

[soccerballtux]

Increasing tire pressure is generally the first (and easiest) way to improve mileage, and is well documented at giving ~10% over at Ecomodder.

You might enjoy this diagram:

^ Only the most hardcore/crazy do some of these things, but every bit it adds up. Basjoos, the owner of "aerocivic", has done all of these modifications and has documented his vehicle as capable of 95mpg when cruising at 65mph on level ground. The EPA rating is 34/40.

Personally, I run higher tire pressure and have done a bit of smooth paneling under my car (it also protects from salt), and in the winter I run a partial grille block. My car came from the factory without an alternator, smooth wheel covers, and wheel skirts.

what's he get at 80mph?

 

[soccerballtux]

No way in hell that he gets that MPG with only those mods. That's an increase of nearly 150% without even touching the thing that drinks the gasoline.

what else do you think the gas energy goes to? you have tire contact patch friction, tire rubber flexion drag, and coefficient of drag. there's literally nothing else when you're rolling along on the highway.

I have 215/45/17 profile tires and run at the max PSI too. I get another 10% or so.

 

[xBiffx]

what else do you think the gas energy goes to? you have tire contact patch friction, tire rubber flexion drag, and coefficient of drag. there's literally nothing else when you're rolling along on the highway.

I have 215/45/17 profile tires and run at the max PSI too. I get another 10% or so.

I know most of it has to do with aero but taking a civic, something that has decent aerodynamics to begin with, you aren't going to get that much of a change by just changing the aerodynamics. Now, if you took a brick moving down the highway, like my F-150, and just did aero adjustments, I think you could see a lot more potential change.

 

[Yuriman]

what's he get at 80mph?

95 mpg (US) at 65 mph
85 mpg (US) at 70 mph
65 mpg (US) at 80 mph
50 mpg (US) at 90 mph

I know most of it has to do with aero but taking a civic, something that has decent aerodynamics to begin with, you aren't going to get that much of a change by just changing the aerodynamics. Now, if you took a brick moving down the highway, like my F-150, and just did aero adjustments, I think you could see a lot more potential change.

He brought his Cd from 0.31 to 0.17 (measured). For comparison, a Prius is ~0.26, a 1st-gen Insight is ~0.25, and a VW XL1 is ~0.19. Considering the mileage these other cars get, it's a wonder his isn't higher.

I'm sure he also moved to LRR tires, increased the pressure, and got rid of a lot of parasitic drag items under the hood (like hydraulic power steering).

As far as the engine goes, Honda's VX engine is nearly as efficient as a TDI.

 

[soccerballtux]

I know most of it has to do with aero but taking a civic, something that has decent aerodynamics to begin with, you aren't going to get that much of a change by just changing the aerodynamics. Now, if you took a brick moving down the highway, like my F-150, and just did aero adjustments, I think you could see a lot more potential change.

that's not what I asked. I asked where else you thought the energy was going at steady state cruise on the highway. Reality is a closed system, it doesn't just disappear.

random aside: My car's coefficient of drag is about 0.45, about as bad as your truck.

 

[soccerballtux]

95 mpg (US) at 65 mph
85 mpg (US) at 70 mph
65 mpg (US) at 80 mph
50 mpg (US) at 90 mph

wow. that's the COD speed-exponent taking control

as much as I like going 80, I would have trouble saying no to 65

 

[soccerballtux]

now if only he applied his skill to his eating habits and wardrobe...

 

[Yuriman]

now if only he applied his skill to his eating habits and wardrobe...

Hah, for sure. There are some strange folks on that site.

 

[shabby]

Higher pressure reduced your chances of hydroplaning because of the reduced contact patch.

Ok so no hydroplaning, what aboot stopping in the rain with a smaller contact patch?

 

[ChronoReverse]

Very generally, Friction is a coefficient dependent on the material and the normal force. So if you're not hydroplaning, there shouldn't be a huge difference.

 

[nerp]

what's he get at 80mph?

A few rattles here and there.

 

[Yuriman]

Very generally, Friction is a coefficient dependent on the material and the normal force. So if you're not hydroplaning, there shouldn't be a huge difference.

In practice it doesn't work that way, unfortunately. In wet conditions, outside of hydroplaning, the amount of braking you can apply before ABS kicks in will be reduced with higher pressure.

 

[tortillasoup]

In practice it doesn't work that way, unfortunately. In wet conditions, outside of hydroplaning, the amount of braking you can apply before ABS kicks in will be reduced with higher pressure.

Braking distance isn't going to be shorter with wider tires...

 

[Pulsar]

Braking distance isn't going to be shorter with wider tires...

Want to bet on that?

 

[reallyscrued]

You are going to wear down your suspension bushings so fast, I don't think it's worth it.

Your car's suspension geometry was designed with some mushiness in the tires in mind. Overinflating makes it much less mushy and you're having all the ball joints, strut mounts, control arm bushings, etc - take the brunt of the road inflections.

Hope you like a loose, creaky suspension.

 

[JEDI]

Braking distance isn't going to be shorter with wider tires...

um.. thought more surface area in contact w/road, the better the stopping on dry pavement??

You are going to wear down your suspension bushings so fast, I don't think it's worth it.

Your car's suspension geometry was designed with some mushiness in the tires in mind. Overinflating makes it much less mushy and you're having all the ball joints, strut mounts, control arm bushings, etc - take the brunt of the road inflections.

Hope you like a loose, creaky suspension.

lol.. my car has 200k miles (bought new).
I have never replaced the struts/shocks.

I don't hear creaking.

 

[tortillasoup]

Want to bet on that?

Yes, yes I do. Wider tires are for = Handling + heat dissipation

 

[MrPickins]

fleabag?

 

[RGUN]

Yes, yes I do. Wider tires are for = Handling + heat dissipation

.... This seems to go against every drag race vehicle setup I've ever seen. Perhaps someone should tell them to put the pizza cutters on the back.

 

[tortillasoup]

.... This seems to go against every drag race vehicle setup I've ever seen. Perhaps someone should tell them to put the pizza cutters on the back.

Wut? They use pizza cutters in the front because of aerodynamic losses and there is little load on the tires. There is no load on the front tires in a drag race which is why huge, wide tires are used in the rear. Don't forget the "burnout" they do on those tires prior to taking off.

https://www.physicsforums.com/threads/wider-tire-giving-better-traction-debate.330790/

 

[RGUN]

Wut? They use pizza cutters in the front because of aerodynamic losses and there is little load on the tires. There is no load on the front tires in a drag race which is why huge, wide tires are used in the rear. Don't forget the "burnout" they do on those tires prior to taking off.

https://www.physicsforums.com/threads/wider-tire-giving-better-traction-debate.330790/

You just posted an article directly opposing your position. According to your article, wider tires can offer more grip - presumably with a commensurate reduction in braking distance. Your statement also seems to support the point of view that wider tires help with grip... Are you not arguing the opposite?

 

[leper84]

How frequently do you see overinflated tires? I didn't think all that many people did it with road tires.

http://www.barrystiretech.com/sae800087synopsis.html

In this test, all tires showed less wear with higher pressure at 40PSI vs 30PSI, though with diminishing returns. Additionally, belted radials showed very little change in shoulder to crown wear with increasing pressure.

Every time gas prices spike, wait awhile and you start seeing people at 45-50 PSI with at least 3-4 32nds less tread in the middle. I don't know what they did in that test from 1980, but this is all stuff I've seen since fuel prices first jumped. I haven't paid too much attention to the load rating but I'm sure its more pronounced in a situation where the load rating of the tires exceeds the load rating of the car its installed on.

 

[tortillasoup]

You just posted an article directly opposing your position. According to your article, wider tires can offer more grip - presumably with a commensurate reduction in braking distance. Your statement also seems to support the point of view that wider tires help with grip... Are you not arguing the opposite?

That's not an article.... that's a message board discussing this issue. Also they never use the words "braking distance" anywhere so I know you didn't read anything on that page.

 

[soccerballtux]

You are going to wear down your suspension bushings so fast, I don't think it's worth it.

Your car's suspension geometry was designed with some mushiness in the tires in mind. Overinflating makes it much less mushy and you're having all the ball joints, strut mounts, control arm bushings, etc - take the brunt of the road inflections.

Hope you like a loose, creaky suspension.

and it's been fine for 60k miles and will continue to be fine.