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NeilBlanchard 06-10-2008 08:05 PM

Scion xA aero mods

I've been testing some aero mods -- using good old duct tape, for the moment.
Simple stuff so far, and it seems to be quite effective: my best tankful average last year was 41.8mpg, and with some improved driving techniques, I got 43.5mpg on a tank. After covering the upper grill, I've got a new best of 45.5mpg. Then I covered the fog light recesses, and it's looking much better still!

The 45.5mpg tank was ~239 miles at the half tank -- and this tank is sitting at ~275 miles at a half a tank left! :D So if I do only 200 miles on the second half tank, that could be ~47.5mpg! Heck -- I might be on course to do almost 50mpg?! Incredible, if that's how it turns out.

[Edit: I ended up with 46.4mpg, partly because my last commute up Route 3/93/95 and on Route 117 was pretty clogged with stop and go traffic...]

So, I'm going to be trying to construct an even sleeker nose -- if I can form some planes to kick the air flow out and around the front wheels, and keep the required cooling (today was very hot -- near 100F and it worked fine!), then I could be exceeding what I thought this car was capable of.

millenniumtree 06-10-2008 08:29 PM

The truth will come out in 4-5 tanks.

My mileage swings up and down by almost 10mpg on each tank, depending on when the bloody pump shuts off the nozzle. I don't take the risk of topping off repeatedly like some. I do slow the pump down when I know it's nearing the top though - makes for a little more consistency.

I'm quite interested to see what sort of improvements you can make. I've got an xB and may be in the market for a replacement car for my aging civic.

Daox 06-10-2008 08:34 PM

Can't wait to hear what the next tank is Neil. Looks like its comming along well.

Thats some huge variance millenniumtree! My tanks in my Matrix vary about 3 mpg (40-43) and there are two different people driving it.

MetroMPG 06-10-2008 08:34 PM

Neil: that's encouraging. A 1.7 mpg gain works out to a 3.9% increase.

I did a number of non-rigorous "A" (5 controls) - "B" (2 grille block) runs and saw an average 2.9% gain @ highway speeds.

digitaldissent 06-10-2008 08:44 PM

looking good, I think I will just tape over my fog light spots like you for now.

I got a little bump with the upper grill block too, wonder if it will last

pawilkes 06-10-2008 08:56 PM

I didn't see much improvement on my grill block but that could be for many reasons. One questions I have is this, is it better to block the upper grill or lower grill? I have a Subaru Outback with the lower grill blocked and the upper grill open. I chose to do the lower one cause it was a bigger opening but it may be at the stagnant point anyhow so the blocking the upper grill may be better for smoothing flow over the hood. any thoughts?

Daox 06-10-2008 09:05 PM

Thats the general consensus. If your going to block one, the upper helps more with aero.

MetroMPG 06-10-2008 09:11 PM

You're right on: all else being equal, better to block the upper opening and send air that's already above the stagnation point over/around the car where there's less drag. Feed air that's below the stagnation point through the radiator, since it was going to end up in the turbulence underneath the car anyway.

pawilkes 06-10-2008 09:20 PM

sweet, i'll have to try that. I think it will make for a prettier mod too.

NeilBlanchard 06-10-2008 09:26 PM


I blocked the upper one because it is flush (the lower one is recessed) and it helps the air flow up over the hood. Also, the standard upper grill is more closed than mine is, so I felt more confident going without the cooling air. And there is the slot just above the bumper, too.

It worked perfectly well today in very slow/stopped traffic on Route 128 with the temps in the upper 90's.

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