'06 Impreza 2.5i Wagon vibration

[Larry Renger]

Interesting you should mention aerodynamics.

First, I came across a guy with a hopped up SPI. He said that a roof spoiler might be the fix.

Second, it was chilly here (oooooh! 60 deg) in the morning and the shaking didn't happen. Two possibilities, first the air would be more dense, and second, the tire pressure drops 1 psi for every 10 deg according to my tire guru.

I have ordered a set of Pirelli tires, and will get them on this weekend. More late breaking news as it happens!

[freakray]

I don't see how it can be an aerodynamic issue - my WRX Wagon doesn't shake.

The roof spoiler a fix? Is he referring to the Wagon roof spoiler or the roof spoiler on his STI?
If he's talking about his STI, I just hope he understands the function of the roof vane.
On the Wagon, I can't say I notice much difference that it makes.

[SabreKhan]

I do notice that the roof spoiler makes my wagon look faster, and that's worth 10hp right there!

I was thinking that the aero of the '06 was really the only thing significantly different from the '04, that's why I threw that out there. Also, 1psi shouldn't cause a vibration (nor should 4 or 5). Especially if you've had the tires balanced, since they're supposed to check the air pressure before they balance.

[freakray]

Originally Posted by SabreKhan

I was thinking that the aero of the '06 was really the only thing significantly different from the '04.

Please tell me I didn't actually read that

What about the different turbo, engine, suspension, transmission, wheels, brakes.....I can keep going.

[SabreKhan]

I just assumed the 2.5 N/A was relatively the same as the 2.5 N/A from last year. Have they really upgraded all that much stuff? (I know they didn't put a turbo on it, and we've already discussed the wheels).

[SabreKhan]

After further research, it turns out that Subaru also changed the valve timing on the N/A motors and re-routed the exhaust a little... still nothing that would cause a vibration based on mph.

[freakray]

Blah, yeah, no turbo...we can only wish

[Larry Renger]

In the parking lot at work, I noticed the Saab version of my wagon. It does have an overhanging lip from the top of the roof which would give a cleaner air "break" over the top. Should be much smaller vorticies than the smooth curve of my car. Hmmmm!

BTW what is N/A with regard to the engine?

[SabreKhan]

Naturally Aspirated, as opposed to Forced Induction (superchargers and turbochargers).

[Larry Renger]

You know, it is kind of funny that the 2nd car I tested had the same vibration, but nobody else seems to have ever noticed it. You would think SOMEBODY else would have complained.

Even my wife finally could feel the vibration once I turned it on and off a few times by changing speed. Very strange.

Maybe it's the hemorroids increasing my sensitivity?

[Larry Renger]

New tires, problem solved! I got a set of Pirelli Nero Zero M+S rubber installed, and the shake is gone. Anybody need a set of Potenzas? Cheap!

[Jay!]

Hahaha! That's completely retarded, but I'm glad to hear your problem is fixed.

[freakray]

The curse of the Bridgestone Potenza RE92 strikes again.....

Smart move to get rid of them.

[SabreKhan]

RE92's were great tires for learning to autocross my WRX. They were grippy enough to use the AWD correctly, slippery enough to teach me the car's weaknesses, and crappy enough that I didn't mind burning them to the ground.