Aeromod hopes dashed.

[Fat Charlie]

Today I did my first oil change since coming here. What a disappointment! I was savoring the wait, dreaming of grille blocks and underbody panels. I got zip. Subaru did what they could for this rig's aero, and there isn't much I can help with right now.

The grille? Upper and lower all face right into the radiator. Until I get more used to its temperature range I don't dare reduce it, especially going into summer.

Fog lights? Those things are maybe 1/4" from flush, and small. Even just a clear two liter soda bottle, clear RTV and five minutes with scissors wouldn't make economic sense.

Underbody? I'd probably be wasting my time. There's a nice front belly pan that I'm quite familiar with after six years of oil changes, and it ends right before the suspension. Behind the suspension the floor panels are smooth as far as the eye can see, with a centerline channel for the exhaust. I didn't bother backing onto the ramps to see about diffuser possibilities because I was just so depressed. With this underbody an air dam would just increase FA.

Wheel skirts are always a possibility, but I'd really rather wait until my fabrication skills get better. I'm not worried about being laughed at, I just don't want my car to attract much attention. It sometimes moves with a sense of urgency.

Exterior mirrors? Not happening, I can't get rid of them. In fact, I wish they were bigger.

So for aero I'm looking at maybe spats ahead of the tires, maybe side skirts and maybe a chin spoiler to clean up what's under the lower grille. That seems to be my biggest hope. There's an inch or so of the bottom that directs air down- extending a flat plate flush with the belly pan forward maybe four inches to scoop air into the lower grille might help a bit, maybe even enough to block the upper grille. It's also the only thing I can think of other than small tire spats that might actually help the underbody air flow.

Don't even suggest a boat tail. I'm nowhere near being in that league and with two kids and two dogs I need that hatch all the time.

So basically I'm whining tonight. The factory did a good aero job and my mileage is really just my own fault. I was hoping to pick up another MPG or two for free: an afternoon's work is a lot easier than working for it every mile every day. Sigh.

[euromodder]

Originally Posted by Fat Charlie

The grille? Upper and lower all face right into the radiator. Until I get more used to its temperature range I don't dare reduce it, especially going into summer.

Most of the cooling usually comes from the lower grille.

Do you have something like a ScanGauge so you can see the actual temperature, rather than the car's own temp meter ?
My 90% upper grille block increased water temps by only 3 - 5° C - invisible on the car's thermometer.

Find out what temp your thermostat opens at, temps should not go much higher than that - and not stay well above that for long.

With this underbody an air dam would just increase FA.

It could still work.
Air going underneath will still cause drag. You could still benefit from a moderate air dam - even though it will increase frontal area.
Try it, and see what it gives.

It sometimes moves with a sense of urgency.

LOL.

[jedi_sol]

Do you have any pics of the underside? Maybe we all can think of other ideas?

[Fat Charlie]

Euromodder- Temp is one of the displays on my Torque dashboard. You're right with the OE gauge. All it's good for is letting me know when I can turn on the heat in the winter. It looks like I have a 192 degree thermostat, I seem to run at 194 most of the time. I've seen it up over 200, though, but I'm going to wait until I get more comfortable with it before I start playing with the radiator.

Jedi- not yet. It'll probably be next week at the earliest because I'm heading going to be tied up for the next several days.

Thanks for the good cheer, guys.

[shorttimer]

I kinda feel for you. But to be cheap on gas, you're really going to have to be light on the foot. And that's not exactly what they had in mind when they designed the car, turbo n all. It will require an immeasurable amount of discipline. I think, in your case, the scanguage may be of value. I say this because I also live in a complete dichotomy. I try to stretch every drop of fuel & then I'm just a road racing fanatic. Especially MotoGP. About 10 years ago, I was given a non running Moped, which only took 1/2 hr or so to get going. I live on a mild hill & had been doing hypermiling this whole 10 years before I knew what it was called. With coasting downhill I'm getting way over 200MPG. For the Moped I have only spent $20 on gas this year, so far. I don't have to commute for work. Yay! I do have a van and cringe when I have to put the key into the ignition, which has only been on one trip so far this year and about $150. My license & insurance are eating me alive, which is usually 3X the cost of gas, and that's after I told them I was only driving less than 2000mi a year. I've got zero tickets or DUIs. My freeway legal bike is a Kawi EX250 & you know, from reading our forums, that some guys are regularly getting mid 90s mpg. I'd strongly recommend one of those if you can afford $1500, give or take, + $120/yr for insurance. Restraint on a MC is sooooooo hard for me to do, cause they sound so sweet at around 14 grand. But, like you, I'll learn.

[NeilBlanchard]

Less air flow doesn't necessarily mean worse cooling. Especially if you form a duct that makes all the air going in the grill through the radiator. On some cars, the air comes *out* of the upper grill, or there is more than is needed. It is the stylists who determine the grill opening, not the cooling engineers.

I have down to about 20% of the original opening, and closed the openings that were venting air out before the radiator, and I have not yet overheated. The cooling fan may run a little bit more often, but not much.

[CFECO]

If you have manual transmission, you could try short shifting, and let the turbo's torque pull the car rather than higher rpm's. I don't know how Subaru sized the turbo, low end boost or top end power, that would make a difference. How's your tire pressures, they can make a large difference too.

[Fat Charlie]

I'm doing great with the right foot and the coasting; my last three tanks have been over 31 mpg, one (and the current one) over 32. Not bad for an EPA combined of 19 and an observed 22ish before this.

I like the ducting idea, Neil. When I do get to aero I'll have to use that. The intercooler has a good duct from the hood scoop, but the radiator is just hanging out on its own. More to think about...

CFECO- I've got a manual and the turbo doesn't do much until over 3500 or so. I'm behaving, keeping the revs low and watching the load. Tire pressures are only 5 psi over recommended, 4psi below sidewall. They're low profile and I don't want a blowout.

[superchow]

...I just don't want my car to attract much attention. It sometimes moves with a sense of urgency. ...

Heh, I like the way you put it.

In any case, maybe I have some constructive input being the owner of a '98 Forester. I have had excellent results with switching to 0% ethanol gasoline. It was an experiment, but here is my rationale (and correct me where my chain of reasoning fails):

1. "Normal gasoline" has a lower resistance to self-ignition because of the ~10% ethanol content.
2. Therefore the ECU cannot tell the variable valve timing to advance the timing as much as it theoretically could.
3. Therefore you get less compression within the cylinder and less torque.

For the last 5 years I have been running 91 grade gas or better in our long-termer Civic with great results. (The 91 means higher resistance to knocking, correct?) But even 91 grade gas has 10% ethanol...

I then found out that in our town we have one ethanol free gas station, so I gave it a shot even though it is "only" 89 grade.

Now the Subaru is happier revving at 1500 rpm as opposed to previously 1750 rpm. This has enabled me to drive 35 mph in 5th gear @ 1500 rpm instead of 4th @ 2000 rpm on level ground. It's almost like the car was designed to run on E0 gasoline from the start.

Here is the website I found my E0 gas station with: Ethanol-free gas stations in the U.S. and Canada

Even if you do not have the opportunity to sample ethanol free gas, I would suggest to try a higher grade of gasoline to be able to take advantage of the higher knock resistance. Even with the higher cost of gasoline at higher grades, the increase in mileage easily pays for the lower fuel consumption.

p.s.: If you check out my gas log, note that my daily driving is 95% city and suburban driving.

[jkv357]

Based on my knowledge and research on the subject, this is what I've determined.

You need to base your octane choice on the manufactures recommendation. If they say it will run on 87, use 87. Compression ratio is the major determining factor. Engines that require higher octane fuel typically have higher compression. If you run a lower octane fuel than recommended, and the engine begins to detonate, the "knock sensor" will retard the timing and stop the knock. Either way, you'll lose power and efficiency.

If you run a higher octane than needed you'll lose power and economy. You are looking for the lowest octane possible to just barely keep the engine from detonating - that's where the engine will burn most efficiently. Octane slows the burn rate in the combustion chamber, and doesn't "give" you anything.

(EDIT: a better description of what octane does would be: The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites.)

The only exception would be using a higher octane fuel that doesn't have Ethanol instead of a lower with Ethanol. In that case you'll get better mileage, but not as good as Regular without it.


Jay