modifying undertray?

[canyons]

Just wondering what you guys may have to done to increase ventilation through the undertray.... i want to keep the tray for stone protection but I want to slot it or drill it for airflow, then cover the openings with wire mesh.

thx

canyons

[theadmiral976]

Depends on which tray you are referring to. I would advise against modifying the front aluminum tray - it serves a structural purpose, helping to hold the fender linings and front bumper plastics in place. People on this forum have reported adverse vibrations and driving instability when driving without the tray - it is possible those same effects would happen with extensive modification. The other paper-like trays are less structural and more protective. But the transmission doesn't really get that hot, so I doubt you are talking about that tray.

If you are driving a stock BRZ, even the SoCal temps should be manageable by the car. If you have modified the car (e.g. unwrapped header, forced induction, etc.) or are frequently racing the car, I would recommend a dedicated oil cooler to help with heat soak. Or wrapping modified exhaust parts.

My main reason for my advice (not to modify the aluminum tray) is because one of the big advantages (in my opinion) of the twins is the low coefficient of drag. That aluminum tray is a significant part of that CoD measurement.

[humfrz]

^ ..........there ya go .........


humfrz

[Gunman]

Heat naturally goes up, so if you are wanting to let air out, I'd vent the top. Holes on the bottom will increase drag, and decrease downforce generally.

[ryoma]

the Beatrush undertray has more ventilation holes than the OEM one so you don't need to cut anything. http://www.kamispeed.com/Beatrush-Al...br.s564000.htm

[cdrazic93]

I would also reccomend making the side vents functional, as another route of ventilation.

[Calum]

Or you could old school. A few washers under the hood hinges.

[DocWalt]

Originally Posted by Calum

Or you could old school. A few washers under the hood hinges.

Sure, if you want to make the heat problem worse. There's a big high pressure bubble at the base of the windshield and as soon as you give that air somewhere to go like the engine bay you increase the pressure. That increase in pressure evens out the pressure differential across the radiator and there goes your cooling air flow.

[shiumai]

Where's the main outlet/exit for air entering the engine bay right now? The small gap at the corners of the hood/windshield?

[DocWalt]

Originally Posted by shiumai

Where's the main outlet/exit for air entering the engine bay right now? The small gap at the corners of the hood/windshield?

Out the bottom, around the trans. There's not much space for the air to go, which is why the hood lifts at high speed. The air is forcing its way past the edges of the hood.

[Poodles]

Originally Posted by Gunman

Heat naturally goes up, so if you are wanting to let air out, I'd vent the top. Holes on the bottom will increase drag, and decrease downforce generally.

Depends on the holes. If they're designed to suck air from the engine bay, you can actually increase velocity under the car and make downforce.

Though keep in mind this is stuff that takes an engineer to really get right...

[churchx]

"Heat naturally goes up" - BS. Warm air self rising by convection is very WEAK thus in most cases can be ignored, except maybe if car is stationary and fan is not moving. Most forms of active fanning (or frontal air push from car speed) are by order or two stronger then that. If and how vents will act at specific place is depends more on if there is high or low pressure on moving car on both sides of panel where extra vents are planned. It's better to rely on some aerodynamic modelling or real world testing how it will work on specific car in specific place.

[Gunman]

Originally Posted by Poodles

Depends on the holes. If they're designed to suck air from the engine bay, you can actually increase velocity under the car and make downforce.

Though keep in mind this is stuff that takes an engineer to really get right...

Which is why I said "generally". We have gained downforce with some holes on the Riley DP car, but it took wind tunnel, and cfd time to locate them correctly, something the average person won't be able to do.

[7 skulls]

I have done this using Run Cool Hood louvers (medium 9x14 inches). These louvers come with heavy duty rivets and aren't flimsy. I cut 2 slots roughly sized to the inner portion of the louvers using an aluminum blade on my jigsaw. Does it help with under hood temps?
I have oil temp and water temp gauges so using these as a guide: I would say yes there is a slight effect on oil temps. The cooler the air temp/higher speed, the more effect these have. In short, under tray venting does not hurt anything but will not have as large an effect on underhood temps as much as vented hood.