Fire Suppression System

Well, its time to get ready to race.  I’m going to NASA comp school at the end of January.  I’ve had a fire system for a few months, in inventory.  Since I have the rest of the year off, I’ve been working on the install.  I bought the SPA Technique 4L alloy manual pull system.  It comes with 6 nozzles that spray in a 90 degree cone pattern.  The idea is that 3 nozzles go in the engine compartment and three in the driver’s cockpit.  However, the Miata has the gas tank directly behind the driver.  So, I decided to place one nozzle in the trunk aimed at the exposed portion of the gas tank and the filler neck.

All of the mounting brackets are handmade out of 1/16” thick 1.5×1.5 inch aluminum angle.  I cut them all to shape and then formed them over some roll cage tubing scrap using a clamp and a hammer.

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I placed two nozzles in the driver’s compartment.  One at that apex of the A-Pillar aimed straight down.  The 90-deg cone will ensure that everything from my knees to my chest is covered in fire suppressant.  The second nozzle I placed down low, aimed at my ankles.  Again the cone will cover from my upper shins to my toes.  It will also spray the entire floor pan and the lower portion of the firewall.  I couldn’t place the framing square in the foot box for a photo, but I did measure where the cone will cover.

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In the engine, I decided to place 3 nozzles.  One on each side of the engine mounted on the firewall.  You can see the left sided nozzle pretty easily, below.  Its the small red thing just above the intake manifold.  The exhaust side nozzle is harder to see in the picture below.  Its located just above the brake booster (round black thing), and just below the two brake lines that are angling towards the firewall.  Finally, there is a third nozzle that is mounted on the left side above wheel well.

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Here is a better close-up of the exhaust side nozzle.  It is aimed down and forward in oder to spray as much of the lower engine block and manifold as possible.  In the event of thown rod, the engine case could crack and spray hot oil all over the manifold, quickly catching fire.  Even though the nozzle is tilted down, it still sprays the top of the valve cover.  Further, you can see in the second photo the framing square which represents the horizontal spray pattern.  The nozzle still covers the entire length of the engine, and even gets down onto the transmission bell housing.

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Next is a close-up of the intake side firewall nozzle.  It is located up as high as I could mount it, and aims down directly at the fuel rail.  This is where high pressure (40psi) fuel is fed to the injectors.  A failure here would spray lots of fuel very quickly all over the engine.

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finally, the last nozzle is located directly to left of the engine, and spraying directly at the fuel system.  The input and return fuel lines are located here and are very high pressure (~60psi) coming directly from the fuel pump, the fuel regulator and all of the soft fuel hose is located within the spray pattern of this nozzle.

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I decided to mount the tank over the right-rear wheel.  This places a little bit of weight (~12 lbs) over this wheel, which is the lightest corner of the car.   We will find out of this is a good idea or not.  it was a bit of a bear to get the mounting holes drilled, and nuts on the bolts.  I ended up using a right angle drill and a stubby drill bit to drill the holes.  Even still it was a tight fit, and I couldn’t put a lot of pressure on the bit.  So, it took a while to it to go.

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The SPA system supports two mechanical pulls.  So, I’m mounting one on the dash for the driver, and a second on the passenger side of the main hoop of the roll cage for access from outside the car.

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Next up is running all the plumbing, and finishing all the final touches of the system.

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