Is 42mpg too low a goal?

[Istas]

aerohead: This is why I was thinking those airtabs might actually be a benefit in this situation. The two reports on airtabs that MetroMPG pointed me to were done on an '06 Camry and an '03 Prius, both smoother cars than mine. But even if I do try them (and really, given the design of the aluminum vortex generators, it shouldn't be too difficult to mock up some of my own on the cheap to get at least a rough guideline), I'm going to wait until I have my MPGuino installed and calibrated before I even think about testing VGs.

(I don't trust that picture either, even I'm not sure if it's level, and at any rate I get the feeling my camera (which is more than a few years old) warps pictures.)

Also, getting cfd software running will help too.

A rear spoiler off the edge of the trunk seems like it'd be really easy to do. Also, I get the impression that adding that sharp transition at the trailing edge of other parts of the car would help as well? like on the sides of the rear bumpers? (it's rounded there too)

[RobertSmalls]

Mmm, gorgeous car. Just a few comments:

On the 1995+ Legacy, there is no speedo cable. Since very little else changed from 1994 to 1995, I'm guessing you don't have one either. I actually have a spare instrument cluster from a 1995, but I don't think it'll do you any good.

For CFD software, if you're willing to pay thousands, SolidWorks Cosmos FloWorks (not FloWorks Express, which is pretty much a teaser) is easy to use, but it doesn't have as many features as I'd like. Sure, you can do simulated wind tunnel testing, draw streamlines over your car and all that. It can report the force exerted on a single surface by the flow. But it wasn't able to tell me the Cd of the model I drew, and I really couldn't get it to quanify the difference between my model with and without mirrors or wheel skirts.

OpenFOAM seems like a respected open-source CFD toolbox, but you'd better be a computer programmer to get it to run. You'll also need to be running Linux, in a VM or otherwise.

What speed did you do the tuft testing at?

[Istas]

The speedometer will sometimes be responsive showing changes in velocity, but sometimes it will stick, then suddenly drop (or rise) 10 or 20 mph. McTimson said earlier he thinks it'd be weird for an electrical signal to be sticking (though I'm thinking the instrument panel might be at fault in that case), but I really don't know one way or the other what's in there. However, cruise control was an option on first gen Legacys, so whether it's cable driven or electric, I'm -hoping- there's a VSS somewhere that will give a consistent, reliable signal. Confident enough that I'm going to be getting a pre-assembled 'Guino.

I have Ansys CFX 11.0 installed on this computer, as well as SolidWorks 2007 for 3D modeling. There's still so much I need to learn in both, though, that I haven't even yet figured out how to put anything I create in Solidworks into Ansys for testing. Haven't given up yet though. (encouraging that there's an Ansys menu option right in Solidworks).

The tuft testing was done around 60-70 mph (speed limit is 70). It was hard to remain consistent because it's really the only road for traffic in the area, so I had to keep moving fast enough to not get passed in a passing zone (which would then mess up airflow in front), but there were also cars pulling out in front too. It wasn't the most controlled of tests, but I now know some things I didn't have any idea about before.

[bgd73]

that car in maine bent in half a decade ago.
what is up with the brown scoobs anyway.best give it the mismatched paint before no paint at all, the ecu could fry in a thunderstorm (resistor R1 goes first).

anyhoo, do you know this cars mechanics, is it the only subaru in history with the backwards firing order? (it came in that generation legacy). 189k miles with an egr hooked up best be letting that engine get as much air as possible....I am quite serious. keep a window open on the long run. In fact this car is disturbing to think about. Go find a loyale and weld the rust out ..you'd be better off buddy.

[Istas]

Tell you what, bgd73, you buy me a car with decent power that still gets over 30 mpg on the highway, that'll last me 4.5 years and 94,000 miles, and I'll drive that when this Legacy quits on me.

[QuickLTD]

I see you said something about aluminum VG's. I could not find any info on the aluminum ones ( I am tired its almost 1am). I went looking for the ones on the Mitsu EVO. They are a totally different shape than the ones most people try on here. I would think this is a better shape because Mitsubishi actually owns a wind tunnel or two as opposed to the company who makes those other ones. LOL I have been wrong before though LOL. I think the back of your cabin has a similar angle to the EVO.

[Istas]

Took me a while to find them. They may not be aluminum, I may have gotten that incorrect. However, they are metal, and very simply constructed:

Fuel Savers

I remember reading about the evo's VGs, that they worked when as tall as the boundary layer and angled 15 degrees off from the direction of airflow, or something like that. If I recall correctly from the comparison I read (I've read too many pages over the past couple of weeks to remember where I saw it), the metal "fuelsavers" are inferior to the airtabs in their actual effectiveness... But still, both the "fuelsavers" and the mitsubishi VGs are a simple enough shape. It wouldn't hurt for me to mock up some cheap ones and tape them to my roof to see if I can manage to make something that does anything at all.

However, I will not even bother with this until I get my 'Guino installed and calibrated.

Yeah, they do have a rather steep window and short trunk, don't they?


I got the tuft testing videos up on youtube, but for some reason the framerate when uploaded is abysmal. Coupled with the bad image quality I don't even want to link them.

[Istas]

Just ordered an MPGuino. Here's hoping I have a VSS wire, hah hah.

[QuickLTD]

Oh yeah I remember seeing those in another post. Good Idea to wait for instrumentation so you can document, document, document, compare and document. You are really researching this I see. Keep up the good work. I would tuft the rear window when you try the different styles of VG if possible.

keep up the good work
Dean

[Istas]

Of course, QLTD. Tufting's fun. Thanks for the encouragement.