If you’ve been to enough car shows, or ever played GTA V, then you’ll know that, with some tuning, cars can spit flames. The exhaust pops and bangs and a quick flash of fire shoots out, which does look really cool. But those pyrotechnic modifications may actually be destroying the engine, and cost a small fortune to fix.

How do people get a car to spit flames?

In order to get their car to spit flames, one must tamper with the onboard computer. The unit is responsible for controlling all sorts of things, from air intake to fuel injection and so forth. It’s fairly easy to buy tunes for cars, with Hondata being the most famous tuner around. Just purchase what you want, plug it into your car’s OBD2 reader, and modify the code.

To get a car to spit flames, the computer is instructed to let a little bit of gasoline into the ignition chamber before the exhaust valve closes. Sounds like gibberish, so allow me to explain. An engine ignites gasoline with a spark, and that explosion creates gas. The harder you’re pressing the throttle, the more exhausts are created, and vice versa.

When you take your foot off the throttle, the exhaust valve closes more because you’re not igniting as much fuel. However, tuning the engine to spit flames, the car is instructed to spit a little more fuel through the exhaust valve before it closes. And because the exhaust and muffler are hot, that heat ignites it into a puff of flames.

But as cool as it looks, tuning your car to send gas down the wrong pipe will, inevitably, destroy the engine.

How spitting flames for your exhaust is destroying the engine

For starters, liquid fuel isn’t supposed to flow through the exhaust pipes. That’s literally why the exhaust valve closes when fuel is being sprayed into the ignition chamber, and opens when only exhaust fumes remain. The first piece to wear out is that exhaust valve, which can get burned with excessive fire-spitting.

If those valves can’t close when fuel is ignited in the chamber, it leads to a lack of engine compression. The car’s performance will drastically dip, and the engine itself won’t operate properly. So your once cool performance car is now ruined by the tune you installed to make it cooler. Somewhat ironic, if you ask me.

And rest assured, tampering with your car’s onboard computer automatically voids the warranty. So if you want to tune your car to spit flames, you’d better start saving up.

How much is the repair bill?

This will depend on the car you’re trying to tune. And while a burnt exhaust valve is a common occurrence on tuned cars, it’s not an uncommon occurrence among regular cars. If you drive a fairly cheap car, think Subaru Outback, then you’re likely looking at a $1000 to $2500 repair bill.

But if you’re driving, say, an Audi R8 with a V10 engine, then things start to get pricey (after all, it’s got 10 exhaust valves, one for each cylinder. The Globe and Mail tells a story about an Audi that rolled into the dealership with low engine compression. After analyzing the car’s onboard computer, traces of aftermarket tuning were found, despite the owner attempting to hide them.

According to the report, the bill was somewhere around the price of a brand new Toyota Camry, which starts at around $25k. So if you really want to damage your engine for some flame-spitting fun, be my guest. Just know the consequences, and the costs, of modifying and tuning your car improperly.