sac

The challenge: get some air flowing in the trunk of a Miata.

Currently, with a D7104 in there, the trunk is like an oven after 2-3 hours (no we don't often run the system that long, but on a weekend road trip it happens). And I will be adding 2 more amps to run the system actively, and those will not have the internal fans that the D7 has. So it is going to get hot in there...
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The plan: Cut several (4-6) 1.5" holes into the sheet metal that divides the trunk from the rear deck (just behind the seats where the top folds down). Install 3-4 fans to draw air in from the deck. Provide fresh air for those fans by installing a 1" high by 15" wide box that runs from the front of the rear deck (between the seats) to the sheet metal (at the back).

The question: Can I run 3-4 fans to pull the fresh air into the trunk, and leave 2-3 other holes as exhaust holes (not connected to the air box), with no fans there?

Because of all of the air blowing around the open cabin, I don't see a problem for the fans drawing air in through the air box to get sufficient cool air. The only problem will be getting the warm air out (avoiding pressurizing the trunk and preventing the fans from working efficiently).

Because the holes will only be 2-3" apart, in a straight line, and because the fans will not have dividers between them, I suspect that the air will flow between the fans as well as in and out of the trunk via the holes.

Has anyone ever tried something like this? Any thoughts? And has anyone tried crossflow fans?

Thanks.

[ July 12, 2005, 11:46 AM: Message edited by: sac ]

olskool005

have you ever thought of extending the vents from under the front seats to the trunk. And then using the fans to exhaust the hot air. that way you would be using A/C in the summer

Tzu

iTrader: (1)

hmm...thats a dilema.

If i am picturing it the way I think it is supposed to look like, it may work, but the intake and exhaust are on the same plane. What is to stop the air from simply being pushed into the trunk a couple inches down, and then move directly sideways where it is then exhausted?

To have efficient airflow, it has to follow a certain calculated path. Eg, push air into the trunk from the rear deck, and have exhausts at the back of trunk where they can run over your amps if they are mounted on the floor. This is the IDEAL way to do it, however, not exactly the most plausible.

Some people may say that "all holes should push air into the trunk to get maximum air over the amps. " however, I personally think that you have the right idea to have an exhaust since your trunk is sealed and little fans would be attempting to pressurize the trunk like you stated. It wouldnt work that way. Thus, i believe that an exhaust is necessary in your case.

hmm....so lemmie think here....

this is the best idea I can come up with a 2am.:

Cut all the holes you want in your rear deck, but put fans in ALL those holes pushing air into the trunk. Seal up any other holes you may have in your rear deck (most cars will have some holes to conserve some sheet metal).

Now, there should already be an "exhaust" hole in your trunk somewhere to allow the trunk lid to close properly. Somehow (not quite sure yet), you can route some PVC pipe around the trunk, beginning at the exhaust and ending at your amps. this makes a direct airflow connection between the stock trunk exhaust and your amps. I think a blow torch may bend PVC.

Doing it this way, ensures maximum air into your trunk. The exhaust PVC pipe that would be beside your amps would ensure that air IS flowing over your amps, thus cooling them.

Its a big job, but I have no doubt that it would work, and would be very impressive in my opinion.

just my .02 at 2am.

[ July 16, 2005, 11:55 PM: Message edited by: Tzu ]

sac

I think I found exhaust holes (4x5" holes leading from the rear quarter panel cavities to the passenger compartment, beside each seat). Still need to test this, but they should work well.

Thanks for the ideas. I have decided to run a pair of Papst crossflow fans (10" long each) over the amps' heatsinks just on the trunk side of the deck holes (the amps are mounted to the front wall of the trunk).

Tzu

iTrader: (1)

Just remember, there is a difference between running air over your amps and running FRESH air over your amps.

My amps are mounted just behind my rear seats with fans over them. Over long trips, i just fold down the seat and give them some fresh air because I always ride with my windows down.

Good luck with the build.