Windtunnel through the front trunk!
 

I recently had the experience of my tach gauge popping out of the dash while driving and then I got a rush of air through the gauge. Is it correct that all this air is flooding the trunk?

It's kind of ironic because I got hardly any movement through the tiny fresh air vents in the dash.

what speed were you going?
Same issue here, air pressure behind dash, although having a gauge pop out would be interesting... maybe it's the air coming in from the fresh air intake.
My speaker insert in the dash will float out when I get up to 100 mph....it's not bolted down (73 911).

Even with a fresh hood seal, you will get air into the trunk area, especially at speed. You would think they would have done a better job sealing out the air, but that is not the case. Shimming the seal may help some- the front bumper to body seal and the cross strip behind it on the long hood cars. You can't do too much as the hood fit will be affected
Any holes in the front trunk area should be closed off to reduce this unwanted air too

Pull out the carpeting on the floor; maybe you'll find this is the problem:

http://home.earthlink.net/~jaegan23/...911/Rust01.JPG

If I were you, I'd pop the hood and take a good look at the fresh air intake assembly and check to see that it's firmly attached to the grill and that all of the hoses are firmly attached and not ripped. You've got a lot of ram air effect coming into that grill and if the fresh air blower isn't firmly attached or you've got a breach in the system downwind of it you would more than likely get a wind tunnel effect into the trunk and dash area instead of into the fresh air system. You did mention that your fesh air movement through the grills is almost non-existent.

good point on the fresh air- don't forget the drain on the fresh air too- about 3/4" round on the passenger side bottom

you sure your hood was all the way latched? There have been times that my hood was at the first catch but not all the way down. I would get way more air through my dash vent and elsewhere.

I was doing freeway speeds - 70-80mph. And no I don't have Fred Flintstone floor boards. :-)

Yes, I'm sure the hood was latched all the way. The seal on the tach is shot because it's a lose fit when I popped it back in. Still I was surprised by the amount of air rushing through the round hole. It was a lot - 10 times more than any normal air vent even with a fan on full blast.

Scott, thanks for the tip on checking the fresh air intake assembly. Sounds like that could be the problem since, yes, I get hardly any air through the regular fresh air vents.

Anthony,

I experienced a similar result when I had my speedo out to be repaired. I was amazed at how much air flow there was though the speedo hole. A nice fresh blast of air. And there is nothing damaged or missing from my car, and the hood was closed completly. You'd think Porsche would leverage that air flow. Even the supposed more refined Carreras don't get enough air in the cockpit.

jw

I can get the speaker cover on the dash to levitate at around 80mph.

This is due to the fit between hood and hood seal. My latch is adjusted to accomodate the thickness of the hood bra. With it installed, air flow through the trunk is minimal. Without the bra installed, there's quite a lot of air pressure inside.

There's no air flow path into the trunk via the normal vent system unless a hose is broken. Even then, with the interior vent door open, I doubt there'd be enough trunk air pressure to kick the tach out.

Sherwood

Lot of places where air can enter the trunk area...and we wonder about fogging up the instrument lenses , too !

Don't forget the goop around the shock struts, once the OEM stuff is removed and you had your car aligned. Most leave that area free afterwards...

And all the variious grommets for wires and such...check the integrity of this too.

- Wil

That could explain my air flow. My hood latch is also adjusted to accomodate the bra.
jw

For Sale: Near mint early 911S in excellent shape. Minor surface rust only on belly pan. Easily restored to concours...:rolleyes:

Repair bill for the above wood work?