Aero-Modding the 4Runner - Page 3 - Fuel Economy, Hypermiling, EcoModding News and Forum

crashnzuk · 10-21-2013, 10:56 PM

I don't know if you read those hot rod articles that were posted or not. They stated that (from an aero standpoint) having a roof rack, or rear wind deflector individually was worse than running with both. You might try removing the deflector as well and see what happens.
Travis..

jeff88 · 10-22-2013, 01:24 AM

I seem to have missed those articles. Thanks for the insight. That is interesting that the aero would be worse the way I have it now, but I will try it again for a tank and see what happens. It may have to do with the crossbars helping the air flow over the deflector rather than through it. If the air goes through it, it creates more of a parachute. (I really have no clue, merely speaking out of the derriere.) I plan on putting a kamm on anyway, so maybe I will take off the deflector for a couple of tanks after this experiment and see what I get out of it.

crashnzuk · 10-22-2013, 01:34 AM

I think we have the same basic idea of the why. My brother has an Infinity QX4 (upscale pathfinder) that we pulled the cross bars off of. He says it's quieter inside, but his economy is the same as before. He really doesn't do any freeway driving with it though, all surface streets. I told him to pull the deflector off of it, but I don't know if he will or not.
Travis..

jeff88 · 11-11-2013, 03:01 AM

With just the crossbars off, I didn't really see any gain. Most tanks were 20.X, one was 21.X and two were 18.X and 19.X. With the results going back and forth, that leads me to believe that my commute/driving style played more of a roll the last 5 weeks than removing the cross bars. I don't know if the air foil being attached still was causing a parachute, hence the reason for no substantial gains; fix one area and make another worst. The cross bars may have indeed helped the air flow over the air foil, rather than try to go through it.

After about 5 weeks of going crossbar-less, I finally pulled the air foil off today. I've only driven about 30-40 miles with it off, but I can already tell the wind noise has dramatically lessened. On Friday, I wasn't feeling well, so I turned the radio off and realized how loud the wind noise was. Today after removing the air foil, I noticed the truck is a lot quieter. I'm hoping the lack of noise will translate into an increase in FE. Only time will tell and we'll see in the next couple of tanks.

One nice thing about having a gas guzzler is that you have to fill up more often, meaning you can see the results sooner!

jeff88 · 11-14-2013, 05:14 PM

I realized I forgot to add a pic of the foil-less 4Runner!

Before:

After:

I took off the foil and mounts and then reattached the screws back into the holes to plug them. If after a tank or two I see an increase, I will go get some washers to help waterproof it a little bit more.

DISCLAIMER: My back window does not roll down, so the benefits of the air foil to keep exhaust out of the cabin is void. I can't get exhaust in the cabin anyway!

jeff88 · 11-21-2013, 01:55 PM

Well I finally got through a full tank without the air foil on and the result was, well... meh. Tank MPG was 20.2, which is right at average. So at least for one tank, no measurably good results.

The average maximum temperature for the dates of this tank were 5° lower than the last tank dates. Would 5° effect my MPG so much that it would essentially nullify my mod?
10/30-11/9: 72°
11/10-11/20: 67°

aerohead · 11-23-2013, 03:09 PM

Yes,the fully-warmed-up equilibrium temp for all the lubricants is now lower,and pour-point viscosity will never be as low as before.The tires will have higher R-R,and the air density is up,given constant barometric pressure.
This is why the SAE does fully-warmed, back-to-back comparisons,same day,as quickly as they can reconfigure the vehicle.
The only test variable should be the shape of the car.

CFECO · 11-24-2013, 12:04 AM

Looking at the side of the vehicle, imagine the point where your speed increases to the point, where the air coming off the front grill makes a bubble, and comes back down at the top of the windshield. Above that speed and an attachment to the roof rack to match the template "Should help", below "that speed", the air will be interacting with the rack and causing drag.

jeff88 · 11-24-2013, 01:27 PM

Quote:

Originally Posted by aerohead

The only test variable should be the shape of the car.

If only I could control all the other variables!

It seems to be warmer this week, so we'll see how it goes in a few days. I wish there was a way to input the temperature into an equation to have a weighted mpg, for comparison uses.

Quote:

Originally Posted by CFECO

Looking at the side of the vehicle, imagine the point where your speed increases to the point, where the air coming off the front grill makes a bubble, and comes back down at the top of the windshield. Above that speed and an attachment to the roof rack to match the template "Should help", below "that speed", the air will be interacting with the rack and causing drag.

Thanks for the insight, but I'm not sure what you're saying. Are you saying it's a good thing to remove the roof crossbars?

CFECO · 11-24-2013, 02:50 PM

I think it is speed related. If your traveling faster the air would tend to go up the windshield and over the car, I think. At a slower speed it would tend to get into the rack more. Maybe you could build the upper half of an airfoil and mount it to the roof rack. Build it so the front matches the windshield angle and then becomes the "Template" from there to the rear, ending at the top of the tailgate.