"Blunion05 drives a pink S2000 (USER WAS BANNED FOR THIS POST)" (6speedhaven) 09/15/2013 at 01:15 • Filed to: BBQ EXHAUST SAUCE

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If a car spits flames out of its exhaust, is it spitting and shooting flames or is it backfiring? I understand backfiring is actually an undesired result, but can the term apply to a car shooting flames anyway?

TeamJeep > Blunion05 drives a pink S2000 (USER WAS BANNED FOR THIS POST) 09/15/2013 at 01:24

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I think they are two different things. To be a backfire is an actual explosion outside the combustion chamber, as where exhaust flames are an extremely rich mixture where both gas and exhaust fumes get expelled through the exhaust, and the gas lights on fire. I just made all that up but it sounds decent.

6cyl > TeamJeep 09/15/2013 at 01:36

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As best as I understand it, this is pretty much accurate. The reason this happens so often on super cars is that most of them are either mid engine or have side pipes. Either way this means a much shorter exhaust system than an average car. The shorter exhaust means 2 things:

1) the temp at the tip of the exhaust is higher

2) if ignition occurs in the exhaust the chances that it will have burned out by the time it reaches the end is lower

NoblesseObligeZERO > Blunion05 drives a pink S2000 (USER WAS BANNED FOR THIS POST) 09/15/2013 at 01:39

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That cant happen on cars that are built for production (catalytic converters, mufflers) back fire happens when you are slowing down and down shifting on a racing straight pipe car..... basically it a drastic change in rpm... if you rev to high then immediately let go of the gas this will this is just for show.. Lamborghini did a muffler modification to make it happen on the Aventador... you can make any car do this just change the muffler to allow it do happen

Squid > Blunion05 drives a pink S2000 (USER WAS BANNED FOR THIS POST) 09/15/2013 at 01:53

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As others have stated it is just an excess of raw fuel that wasn't completely burned up in combustion. On high horsepower machines you are better off having a richer mixture to use as a safety margin. Also at high RPM's the pistons are moving so fast that the fuel mixture is still burning when the exhaust valves open. Backfiring is bad generally, and tends to break things. Turbo cars that have a well insulated exhaust system can also throw flames because all the heat is getting directed out through the tailpipe opening.

Blondude > Blunion05 drives a pink S2000 (USER WAS BANNED FOR THIS POST) 09/15/2013 at 01:54

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Wouldn't backfiring happen if the valves don't fully close before combustion resulting in the explosion escaping to the intake or exhaust manifold whereas spitting flames is the unspent fuel suddenly getting oxygen and igniting when it leaves the tailpipe?

gmporschenut also a fan of hondas > 6cyl 09/15/2013 at 02:04

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Also these types know of ways of getting around emissions so no Cat.= less restriction. Correction: seeing its Russia they probably don't have emission testing.

WarShrike > Blunion05 drives a pink S2000 (USER WAS BANNED FOR THIS POST) 09/15/2013 at 02:09

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Also more prominent on mid/rear engined cars at full tilt. Shorter path from exhaust valves to the tips. More heat in it, plus remains of fuel in system = flames as it hits fresh atmosphere. I believe it is even more prominent after cats are deleted and all that fun stuff.

It's hell on the bodywork too lol!

gmporschenut also a fan of hondas > TeamJeep 09/15/2013 at 02:10

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Yep. When i first got my project car running i thought it was awesome how after i let off the gas it would go Putt putt putt. Well I found out why. I had replaced the barely functioning injectors the previous owner had on the engine and hadn't noticed that he had the fuel pressure set as high as it would go.

LorenII > Blunion05 drives a pink S2000 (USER WAS BANNED FOR THIS POST) 09/15/2013 at 02:16

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Coolness factor +1 Batman point.

jrollincoal > Blunion05 drives a pink S2000 (USER WAS BANNED FOR THIS POST) 09/15/2013 at 03:33

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Psshh, you call that call that flame? How bout flame on demand? Riddle me this...or not, b/c the answers obvious. Cummins4LYFE

Dirty Harry Callahan > Blunion05 drives a pink S2000 (USER WAS BANNED FOR THIS POST) 09/15/2013 at 05:20

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The .gif there is showing a mixture that is rich enough to have used all the oxygen in the air to react and now that it has reached a fresh source of oxygen, it can finish oxidizing. It requires that the mixture be rich enough to use all of the oxygen and be hot enough to continue to oxidize once fresh air is introduced. This can be assisted by having the combustion temperature so high that the nitrogen wants to oxidize further reducing the amount of oxygen left for the fuel to react with.

Leadbull > Blunion05 drives a pink S2000 (USER WAS BANNED FOR THIS POST) 09/15/2013 at 09:37

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The question's been answered, so I'm just gonna say that your GIFs make me wet.

samssun > Blunion05 drives a pink S2000 (USER WAS BANNED FOR THIS POST) 07/19/2014 at 05:55

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Backfire usually means combustion is still going on when the intake valves open, so the engine is literally firing back through the intake, which doesn't typically end well.

Flames out the exhaust, like you see during a shift, aren't part of the combustion stroke, but instead an over-rich mix (too much gas and no oxygen left to burn it) going out the exhaust until it finds fresh air to burn with.