Get your super hero on!

I noticed a while back that upon deceleration I was getting a nice back fire. So I got to thinking could I do more with it? Could I get a fireball every time? Finally, how could I accomplish this? The answer: flamethrower.

For those of you wondering, I am not talking about the flamethrower you saw in one of those World War II movies starring John Wayne. I am referring to the flamethrower hot rodders have been using for years now with one key difference. They had show cars, and they had no issue washing their cylinder walls and rings with fuel to get their desired effect. While my car does look okay, performance is first. I do not what a show car but I do like some flash. So what if I could fire ball on deceleration at my whim. Hmm, okay.

As you know, if I can build it, I will. Especially if: it is from spare parts, negates the need to purchase a hundred dollar plus item, and the outcome is silly.

(Editors’s Note: It may seem like my build quality decreases in a few of my upcoming posts, but what has actually happened is I am limited by my tools. My tools are currently in a moving crate thus I have access to random or cheap hand tools. So for all those hand tool challenged as I am, have fun, as you can do this too.)

Parts list:
Random wire 18-16 gauge
S13 coil(any coil will work, but you will need to determine ground, trigger, and 12+ ACC)
crimp on connectors (some for relay, two small ones for the coil or if you have the coil plug)
5 prong relay (fuse is already installed in factory wiring)
Your brain
My write up with Diagram

First, you need to know what prongs are what of a standard five prong relay.

This is a recycle of someone else’s image but breaks down the five prongs of a “standard” Bosch style relay. I referred to this image a lot.

Next, is the image that lays the ground work for the system. A big thanks to Deschane for drawing this up for me and simplifying my life.

s13 flamethrower diagram

THE Masterplan.

All I want to show in this picture is the tiny Scosche crimp on connectors at the top of the package. You won’t need a fuse unless you want redundancy and you can use an old junk spark plug.

That is all I can think of for pre-do-it-up information. First start by locating a place for your coil and spark plug within the limits of your spark plug wire. I mounted my coil just off the spare wheel well using the two factory plastic screw in deals and mounted my spark plug as on top of the exhaust as room would allow.

Coil location. If you use the same mount style you will need to ground the case via a wire to bolt location on the chassis. More on this when I break down the coil.

I mounted my plug here. I just drilled a whole slightly smaller than the thread and cranked it in there. The spark plug wire tension also holds it in. Later I will helicoil the hole, but for now… meh.

Coil wiring. This is where you will need the tiny crimp on connectors I showed earlier if you don’t have the harness plug. The S13 240sx external coil is a ground firing unit. All you need to know is that the Red wire is 12+ ACC, the Blue wire in the plug hole is the Trigger, and the blue wire attached to the self tapping screw in the coil case is ground. The coil is case grounded. This means the coil mount points are what ground the coil for operation. I would also like to point out you don’t need some crazy 10-12ga wire like every online know-it-all thinks you do. 16-18ga is fine and is what is in the factory harness. If this was the fuel pump wiring mode I would go thicker as it runs constantly.

If you have the plug for the coil you won’t need the tiny crimp on connectors.

The Relay. Umm, yeah, about that. I used all red wire leading into the relay which isn’t impossible to do just more confusing. Engine coil trigger = 30. Coil (-) trigger = 87. button>ground = 86. ACC (+) = 85. I used the labels given in Deschanes diagram to try to keep things straight forward. Here is what I actually hooked stuff up too:

Here is the relay which isn’t gonna help you run your lines as I used all red wire…hahahahaha.

Coil trigger = green distributer wire on 95 s14 = 30

Locating this trigger wire on other model cars shouldn’t be hard. You just need the low voltage signal. Most will come from around a cam/crank angle sensor or distributor. Use the safe pin trick as you can see in the image, it will save you stripping a bunch of wires that may not need to be and it is fast. Just don’t hold onto the pin with a running car as you will probably get a shock. Also just strip a bit of this wire back don’t cut it. Then wrap trigger wire around and solder.

Coil (-) trigger = trigger wire on S13 coil = 87

Blue wire in picture coming from plug opening.

Button>ground = Brown wire out of clutch interlock switch plug = 86

(It should be noted that I put a master on/off switch in this wire so the system is off while normal road driving.)

The safety pin is in the brown wire during testing. It is wired tight now. Also just strip a bit of this wire back don’t cut it. Then wrap trigger wire around and solder.

ACC (+) = cigarette lighter power, orange/brownish wire = 85

I used spade connectors and just plugged them into the cig lighter plug.

So when you have all this done but before you drill you exhaust test your system. If it doesn’t work and you give up, wouldn’t you rather not have a 1/2 inch hole in your tail pipe. To test do as I did in the picture with electical tape and have someone watch the plug for spark while you depress the clutch pedal.

The tape won’t melt as you are gonna depress clutch, start the car , check for spark, turn off car.

There you have it. As you can guess catching a fireball on film is a matter of luck or high speed camera which I running short on both. For now, my deceleration could be richer for better effect and I am thinking about changing my “on” button (interlock/86 wire) to the gas pedal when not depressed. Why? The time when the car makes the best natural fireball/backfires is in gear and off gas. At a later date, I may supply some fuel into the exhaust via a fuel pump and lines but for now I am contented.

Until next time…

One reply on “How To: MINTY, FLAME ON!

  • Sean

    Another way to do this is to buy a car with a rotary engine, those things shoot fireballs like nobodies business. In all seriousness though, thanks for this write up, its a pretty neat little system you rigged up there. It looks pretty simple, so i plan to try it myself soon.

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