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Looking to keep out salt and slop from engine bay. Anybody modify a GD plastic undercarriage tray to fit 1st gen legacy? thanks

I wanted to buy the whole STI plastic tray setup which covers most of the bottom of the car but I didn't know if it would fit or not. No salt here but I bet the aerodynamics would be a lot better with those pieces.

You know I haven't looked at any of those under trays, any pictures online of what's all part of it.

Following this as I'd like to know myself, but for the same reasons as Kimo: aerodynamics.

I am going to pick up a GD one locally for cheap and see if I can make it work some how some way. Josh, hard to find a pic. Theres some images on ebay.uk...but I don't know if those are the same as the usdm cars.

Well take lots of pictures when you get the GD one and during your fitment process.

I think silver03 is just talking about the engine panel but I believe there are other panels that cover the rest of the undercarriage as well.

The engine one is the one that would make the most difference for aero or, of course, keeping the engine clean. It's something like 10 or 15% of the total drag that comes from an unmanaged engine compartment and that's why you'll find the fromt undercarriage panels on almost any newer car. But, I'd also like to make a panel that covers the sloppy transition from undercarriage to rear bumper.

After reading about aerodynamics it makes me wonder if what I want to modify will even help, if not hinder the car. For instance if you were to block off most of the area below your engine, how well would a TMIC work afterwards? Maybe it would work better because there would be less pressure from below or maybe that air rushing underneath creates a vacuum in the engine bay that sucks air in the scoop and through the intercooler. Without actually measuring pressure differences before and after it's kind of a shot in the dark. There's been many many people who added a scoop to their car thinking it would force air in to their intake or intercooler when in reality it created a hole which the air flowed out instead of in and I bet in their head they were thinking,"Yeah I can really feel the difference!"

The device to measure this pressure difference is a magnehelic gauge preferably 0-1" - 3" h20. I think I might buy one and play around with it.

so you mean to say this doesnt allow air to come in when driving?






when you run a tmic, you most likely have the shroud to go from the hood to the tmic. this allows any air when driving to be forced into the tmic.

Turbulence is what you get in the engine compartment. The most efficient way to cool would be to duct the exiting air from the heat exchangers up through the hood behind the leading edge. That is a low pressure area that helps pull air through more efficiently than the turbulent slop in the engine compartment. TMIC will always be inefficient because of rising heat from the engine and no way of effectively routing the air through. Unless you completely sealed off the engine compartment, preventing air from escaping and allowing the heat to rise, I'd be amazed if you saw a difference. In theory, if you could manage the airflow well enough, you could extract air from the engine bay more efficiently with the block by rushing high speed/low pressure air past extraction vents. But it's all such an ugly mess under there that it would be remarkable if you could get it to work even at a set speed on a perfectly smooth road.

sqc151 wrote:so you mean to say this doesnt allow air to come in when driving?






when you run a tmic, you most likely have the shroud to go from the hood to the tmic. this allows any air when driving to be forced into the tmic.

That would be ideal but still isn't true. It will only flow that way if the pressure is higher in the scoop than it is below the TMIC.

I will post some pics. But the piece I am referring to is merely the plastic under engine piece. Intital mock up doesnt look to bad. My dremel and I have a little work to do, but not as much as you might think. As far as aerodynamics...its an L wagon....mostly want to keep road salt and grime out.

yea sorry, i was joking around with kimo.
ok back on topic. im sure a gtspec undertray or stock plastic piece will be fine to keep grime out from the engine bay.