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Discussion Starter · #1 ·
My goal is to get this CRV up to a consistent 30mpg on the highway. I love getting good fuel economy, and the 2nd-gen CRV is a frustratingly blocky shape which works against that! In this thread, I'll be chronicling the efforts to improve my car's highway economy. Lots of aerodynamic tweaks for the fuel economy geeks, basically.

The hardest part will be measuring; I don't do a lot of highway driving so there will probably be a lot of time between measurements. I'm going to estimate mpg impact if I have any confidence in my estimate; some changes, however, are likely tiny.

Here are my guidelines: I want this to be something that the average person can easily do. I won't change anything major on the drivetrain or alter the suspension. And I want it to be reasonable, too. I'll accept that if I use A/C I'll certainly be below 30mpg, but I'm not going to accept going 55mph on the highway just to get my numbers up. Time is important, too! :)

So, here's the first step:

"What?" you're thinking? Tire pressure. The sticker on the car recommends I think 26mpg; but the sidewall will accept much more than that, so I put it at around 30psi or so. This lowers rolling resistance, but also increases noise and ride harshness somewhat - it's a tradeoff. Estimated improvement over stock: ~1 mpg

Next step: fill in those little styling indents which serve no functional purpose.

Black duct tape is invisible from 20 feet away. I am worrying, a little, that these might discolor the bumper. They might come off soon; I think they have no impact.

Next step: this is one I've been working on for a long time. This is the third try!

The CRV in 2004 left the front tires open to the air. Why? Either for rugged looks or for better clearance. Either way, that big gap would be filled in for the 2005 model year, indicating to me that Honda saw a reason to plug that big hole!

That's my attempt. Finally, it seems sturdy enough to hold up. Sorry for the dirty car. You can see that I've extended the air dam no further down than stock; you can make the argument that I should have gone further. Estimated improvement: ~0.5mpg

So that's where we stand right now. Got some more stuff to do, too, when I have the time. Feel free to comment, advise, ask questions or even just tell me it's pointless. :)

 

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Discussion Starter · #2 ·
Here's some more tiny tweaks!


Rear wheel deflectors.


Most all new cars have them these days. However, like the front wheel design, there isn't much commonality between manufacturer as to how big these should be. Mini puts them well ahead of the wheel; Toyota has ones just in front of different sizes; BMW uses small ones. So as to whether htis one's optimal, I've really no idea.

You can see, actually, how aerodynamically "dirty" the car is underneath.

Last, taped over the weird divots molded into the front bumper. I'm sure those are there for a reason; but I can't imagine what, so I'm assuming it's just styling.



And on it goes :) ... so far, I'm just mirroring design features that are common on new cars which simply weren't used a decade ago to get the car more slippery.
 

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Discussion Starter · #3 ·
First "trustable" highway readout was yesterday: 26.3mpg, using 3000rpm (63.5mph) over 200 miles.

To me, this is frustratingly low, given that I drove slowly. :/ There are a few explanations, but I'm not sure how much of an effect they might have: 1) The MA to NH route does have a positive elevation change; 2) about 30 miles was actually in stop&go traffic, which usually gives me about 17 mpg. However, I don't like to make excuses - the reality is that part of your driving has to involve hills & rush hour, meaning you shouldn't really count them out! :)
 

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I think what you're doing can be a very fun and informative project. A few comments.

  • What is your baseline MPG?
  • What year is your CR-V? Update your profile. :)
  • The piece you have before your rear wheel is not going to do anything for you because it will bend in the wind and probably rub into your tire.
  • Placing duct tape across the front bumper/under tray could be causing even more if an aero drag than the actual openings are causing. The leading edges of the duct tape would be kicking up "dirty air" where the openings could be potentially allowing air to pass through the engine compartment or even underneath the V which could potentially cause downforce. By forcing the air over or under the front the way you are might not be the best thing aerodynamically.
 

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Discussion Starter · #5 ·
Good comments, thanks.

For all of this stuff, it's accurate to say "this might not be an improvement." You can't really know until you've tried it, and there's a few things working against knowing for sure: I can't test anything in a wind tunnel and the real world has a lot of variables. For example, changes in gas mixture make a huge difference: typically I was getting 27mpg in the summer, 24 in the winter, so that alone is going to obscure nearly any small changes I might make to the body shape.

All I can say is, I THINK all these things should help - and I didn't just make them up; they're techniques used in more modern cars.

For example:
Front wheel deflectors: 2011 Kia Sportage has them almost identical to what I made (ie, they actually look tacked-on!)
Real wheel deflectors: Toyota RAV4

The rear wheel deflectors are actually pretty strong; they're not bending back. They key is to fasten them securely. That was a problem I had with the fronts early on.

I have a 2004, and I'll try to update my profile.

Interestingly, the current CRV has some strange stuff going on at the bottom edge of the front bumper - there are two little flaps and I've no idea what the purpose is!
 
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