I Liquid-Cool My Amplifier

[Blacklane]

I have a black roadster with an aftermarket amplifier mounted in the trunk. My wife and I love to take long drives and listen to good music, but in the hot summer, the amplifier often goes to thermal shut-down, leaving us in silence. My amp is 80w x2 plus 240w x1 Class D, which is not over-sized. I considered adding a fan to cool the amplifier, but the real problem is that the trunk gets too hot with the sun above and the muffler below. So based a little on this thread http://forums.bimmerforums.com/forum...5519-Hot-trunk
I decided to liquid-cool my amplifier.
It turns out that the computer guys have been cooling CPUs with liquid for years and have developed a whole host of components, all of which run on 12 volts, the same as hard drives. It also turns out that the standard 120mm fan and radiator size is a perfect fit for the vents in the trunk behind the wheels.
I found a 120mm radiator and a high-volume (184 cfm) fan. I found a pump that fits in the trunk corner well. I found a coolant reservoir that mounts behind the trunk lining at the tail light. And I found some cooling blocks that match my amplifier power transistor area. With all of that, I created a liquid-cooling system that draws outside air through the radiator. This air exhausts out the other side of the trunk where there is another vent that is out-going-only. The pump then pumps the cooled liquid to the cooling blocks mounted on my amplifier where the power transistors are.
Electrically, I wired a relay to the amplifier white wire (turn-on sense) which turns-on the fan and pump when the amplifier is turned on. I might add a temperature sensor to this circuit to only turn-on the fan and pump only when needed. I've also considered adding a fan to the opposite-side vent which would blow outward to further reduce the trunk temperature, since I'm currently heating the air as it's being drawn into the trunk through the radiator. However, currently I can feel a lot of air blowing out of the trunk from the out-going vent.
I had to make mounting brackets for the radiator and one for the reservoir, but the only mods to the car were the 5 small holes for those. Since the pump is at the bottom of the corner well in the trunk, I decided the best way to mount it was by using simple foam blocks. It looked difficult and pointless to install screws at its base. I could only fit 3 mounting screws for the radiator.
I wonder if I should have mounted the radiator on the side away from the muffler, but I chose the muffler side since it was un-used space and could be easily hidden. I can reverse the fan to blow outward if I find the air in the trunk is cooler that the outside air coming from near the muffler. I would also have to remove the flapper thing from the opposite side to allow air to enter the trunk there. Currently, air is only allowed outward there.
I made a cut-out in the trunk liner for airflow and once it is installed, the entire system will be virtually hidden. The cut-out is in a place that should not get blocked by luggage nor allow things to fall into it. I might add a screen at some point.
There was no mounting provision on the cooling blocks I used. I disassembled the amplifier and measured where I could safely drill. Then I drilled and tapped screw-holes to hold aluminum bar stock that holds the cooling blocks. I added heat-sink compound behind the cooling blocks.
I bought most of the parts on-line through e-bay, FrozenCPU.com, and Koolertek.com. The coolant is a type of propylene glycol/water mix with anti-microbial. It has a freezing temperature of -35 F. It took a little less than one 700 cc bottle to fill the system, even with long tubing runs to the other side of the trunk. It needs to be replaced every few years. http://koolance.com/liq-705-liquid-c...ty-700ml-clear
Radiator.jpgRadiator mounts.jpgRadiator mounted.jpgPower Transistors & Cooling Block.jpgComponents Installed.jpg

[Blacklane]

More Pictures.Amp&Cooling.jpgPlumbed&wired.jpgLiner Cut-out.jpgVent Hole.jpg

[Randy Forbes]

Daniel (dwm) removed the finned aluminum heat-sinks on the back of his amplifier, and cut a bar of copper to bolt into their place. Then he had me mill it out to provide a zig-zag coolant flow path, and sealed it with a piece of Lexan over the top. He converted his BMW Mobility kit to house a VFD-controlled pump and reservoir, and mounted a pair of radiators w/fans (similar to yours) to the trunk vents.

I don't have any pictures readily available of the whole finished installation, just of the block being milled...

[BMWBergy]

Kudos to all for their creativity and resourcefulness.

My current Class-D has been fine with no cooling. Actually, I've never had to use water cooling on any amp (yet) in my life, going on about 20 different amplifiers - including a competition-grade stereo running at 0.5 ohm back in college.

[Bear Grylls]

that is pretty dang cool I give you props for ingenuity

[spacecowboy]

You could eliminate the reservoir with this Swiftech model.

MCR120-QP-RES.jpg

[Blacklane]

I considered that radiator model, but I didn't think I had enough room down in the well for a pump and the hoses that are on the bottom of the radiator. As it is, I'm using several elbows and creative loops in the plumbing make it fit. But as I said, there are a lot of products readily available, so there are many ways to assemble this. I am using a Swiftech pump, and their products are top-notch.

[dkindig]

Nice! Haven't had problems with thermal shutdown, but had thought of using PC fans over the vents to improve air circulation. Great job on the water cooling!

[Blacklane]

Daniel (dwm) removed the finned aluminum heat-sinks on the back of his amplifier, and cut a bar of copper to bolt into their place. Then he had me mill it out to provide a zig-zag coolant flow path, and sealed it with a piece of Lexan over the top. He converted his BMW Mobility kit to house a VFD-controlled pump and reservoir, and mounted a pair of radiators w/fans (similar to yours) to the trunk vents.

Yep. That's where my initial idea came from. However, I don't have the ability to mill out a block of copper.

- - - Updated - - -

Nice! Haven't had problems with thermal shutdown, but had thought of using PC fans over the vents to improve air circulation. Great job on the water cooling!

I was actually quite surprised at the airflow out of the trunk on the opposite side with this set-up and the trunk lid closed. I crawled under the car behind the tire and could feel the breeze flowing out. I have to admit that this fan is not silent, but that wasn't a primary concern in the trunk. I can hear it turn-on when the amplifier powers up, but it's not noticable while driving.

[fmcfad01]

TIL there is another reason to be happy about being a coupe owner.

This will never be necessary.

[spacecowboy]

I considered that radiator model, but I didn't think I had enough room down in the well for a pump and the hoses that are on the bottom of the radiator. As it is, I'm using several elbows and creative loops in the plumbing make it fit. But as I said, there are a lot of products readily available, so there are many ways to assemble this. I am using a Swiftech pump, and their products are top-notch.

I'm pretty sure there is also a QP model that doesn't have permanent barbs, so you can put any type of fitting on there you want. I use a triple QP myself, & also use swivel fittings. Not having to deal with a reservoir made the decision easy. The thicker fans create more pressure to move air through the radiator versus the thinner fans. CFM is only part of the equation.

[lennium]

Heading into 1st summer here with a amp in the boot, was wondering if I would have probs with heat, thanks for the ideas if I do!

[badvlvo]

I've never had any thermal shutdown issues that would require liquid cooling any of my amps.
I have a Zed Leviathan going in the trunk soon, and I'm not worried about the heat.

[lokijibber]

What an awesome project. Kudos for the effort. Amazingly, I never had issues with my amp shutting down. It does get VERY hot back there though.