Exhaust Backfire?

[XSquareStickIt]

I was wondering for a while what causes Exhaust Backfiring. All I know is that it happens because unignited fuel ends up in the exhaust pipes and ignites there.

But that then begs the question, how DOES unignited fuel end up in the exhaust of a car? I remember it happening often enough in GTPSP with just about any stock FD RX-7, especially on the downshifts. In GT5 though, it never happens with any stock FD RX-7 I've tried. The premium ones (1991 Type R and 2002 Spirit R), the standard ones (1992 Type RZ, 1997 RS-R, 2000 Type RZ). However, readily happens on the RE Amemiya street tuned RX-7, along with the 787B. Other non Rotaries I actually drive (OMFG WHAT) like the Viper ACR does it often too.

Am I mistaken in saying that higher power cars do Exhaust Backfiring more often? Or is it how you shift? Or how you tune the car, and what parts you use? I'd really love to take pictures of Exhaust Backfiring from a stock FD. Of course, that's a horrible task to undertake as well, but first things first...

What causes Exhaust Backfiring IRL and in GT5? Thanks in advance!

 

[GODfreyGT5]

Look at a video or diagram of how an engine works (pistons, valves). Fuel, and air are ignited, and then sent to the exhaust from the same 'chamber', but through a different valve that they came in from [3 valves per cylinder- Air,Fuel,Waste] (The rotating camshaft triggers these to open, worth looking at). So if fuel doesn't get ignited, it goes out the way that any other 'waste' goes from the engine, out the exhaust.

I'm no expert, but that's the basic idea.

 

[seanneedscar]

^^ and there is more un-ignited fuel in an engine that runs rich, which rotary engines do, because they are a bloody stupid engine to be put in a production car

 

[gamerdog6482]

Which leads to the question of why it gets ignited after exiting the chamber.

 

[Shoe67]

Which leads to the question of why it gets ignited after exiting the chamber.

Exhaust is hot? Maybe

 

[BobbyBRAKEaNek]

Exhaust is hot? Maybe

Ding. Ding. You will receive 10 paint chips and 10 museum cards for your answer. Lol

 

[Shoe67]

Ding. Ding. You will receive 10 paint chips and 10 museum cards for your answer. Lol

You serious

 

[RoadRocket77]

^^ and there is more un-ignited fuel in an engine that runs rich, which rotary engines do, because they are a bloody stupid engine to be put in a production car

It's a great idea... kinda like a 2-stroke. super small but packs the power of an engine twice the size. It's an extremely precise engine. if the timing is off by a millisecond... it will backfire. the only thing with these engines is they tend to burn oil... speciffically older rotary engines. the new ones don't burn oil as bad as last gen designs. They just run better at speed. they love to be wound out. lug out a rotary and it will run like crap. drive it like you would run a chainsaw and the engine is perfectly happy.

 

[leexr2i]

Anti lag on turbo..
en.m.wikipedia.org/wiki/Antilag_system

 

[Dlyte]

Anti lag on turbo..
en.m.wikipedia.org/wiki/Antilag_system

Yeah the anti lag system or backfire kit (initial d) I sweet, I'm gonna have to get one for my Prius!

 

[MisteRsw20]

My FD IRL backfires espesically when downshifting after hard acceleration. Does it even more when the engine is still warming up. Its caused by fuel ingniting in the exhaust, but since im still using a catalysator in my car there is no flames coming from the back. If you would want flames you would need a straight midpipe that replaces the catalysator.

 

[dxm8975]

I don't think the way of tuning the car has something to do with the frequency of the phenomenon arising, because I already checked out an enemy car ignting backfires several times from the exhaust in the tail even it remains without undergoing through any degree of tunings.

And I doubt the horsepower of the car is concerned with it either, since when I see them emitting backfires I discovered that even a light weighted car with a very tiny horsepower ignites the fires as it makes a stop at the portal of a corner...

I've been curious at how the backfires happen and had a test drive a couple of times with some cars, and insofar as I confirmed through my eyes on the run is that a car is likely to ignite the fires whenever I changed the shift gear especially when I deccelerate with the car at the entrances of every curve, but I didn't see much when I accelerate after passing through the sections, so I have no idea what exactly is the cause, but the way of shifting the gears can be counted as one of the reasons for that.

 

[Dlyte]

I don't think the way of tuning the car has something to do with the frequency of the phenomenon arising, because I already checked out an enemy car ignting backfires several times from the exhaust in the tail even it remains without undergoing through any degree of tunings.

And I doubt the horsepower of the car is concerned with it either, since when I see them emitting backfires I discovered that even a light weighted car with a very tiny horsepower ignites the fires as it makes a stop at the portal of a corner...

I've been curious at how the backfires happen and had a test drive a couple of times with some cars, and insofar as I confirmed through my eyes on the run is that a car is likely to ignite the fires whenever I changed the shift gear especially when I deccelerate with the car at the entrances of every curve, but I didn't see much when I accelerate after passing through the sections, so I have no idea what exactly is the cause, but the way of shifting the gears can be counted as one of the reasons for that.

Honestly I think it's back pressure and engine timing with a free flow exhaust.

 

[seanneedscar]

It's a great idea... kinda like a 2-stroke. super small but packs the power of an engine twice the size.

Hence why I said, 'production car' ... i'm not doubting its performance in race car applications (or airplanes, for that matter, I think thats where it was used)

the only thing with these engines is they tend to burn oil... speciffically older rotary engines.

The ONLY thing?? They burn oil. (dont keep an eye on this, kaboom) They dont burn fuel. (bad gas mileage) They require high-rev's frequently. (bad gas mileage) the apex seals wear out (frequent rebuild required)

they love to be wound out.

^^ exactly, see point above. Gas is approaching 5 dollars a gallon. I dont want to have to redline my car all around town. lol

lug out a rotary and it will run like crap. drive it like you would run a chainsaw and the engine is perfectly happy.

Again, hence, 'production car' this is a daily driver, yet I can't lug it out or shift at low RPM?? GENIUS!!!!!

This brings me to the biggest point, Apex Seals. Depending on generation you can only get about 70k miles out of the engine before it requires a rebuild with new Apex seals. This is the worst part of all

Tell me its a good idea to put an engine in an otherwise reliable, japanese production car, that lasts 1/4 as long as a normal piston engine. If you are a rotary enthusiast and you think its fun to rip out your engine and rebuild it on the kitchen table every 5 years, well good for you. But from a business perspective, it was a mistake.

Look at the RX-8. this engine will last about twice as long as the FD's engine. But still, 150k miles out of a japanese car made in the 00's is laughable. I would be thoroughly surprised if a wankel rotary is ever used in a production car ever again.

RX-7's are amazing machines, have always been one of my favorite japanese cars. The FD on all points is a pure bred sports car. And the engine it has is a radical idea. But for a production car that people expect to be able to handle 10k-15k miles a year, its dumb. Find a slightly heavier engine, with similar output (maybe an F22 out of an S2000) and relocate the battery to the back. Problem solved 👍

 

[ryzno]

OK. I believe that PD has not fully tweaked this part of the program. I'll try to explain:
IRL oldschool cars: pre '96. Ran a program that was not really based around emissions, These trans. would stay in gear to help deceleration. eg I have a '91 Honda Accord EX.
In Sports Mode the trans engages harder and holds on to the gear longer like a MT, under deceleration it's the same.
Even when shes not in Sports Mode the shifts are not as strong but the trans will still hold on but not as long.(I know cuz half the neighborhood can hear me.)
So back to the point I belive that PD has not fully thought about trans.
All cars use the Speed Senor to determine the vehicles speed and uses the cam and crankshaft senors to determine RPM. So if you go with the ol skool look at it, when the car slows down the trans holds on to the gear turning the engine at the same time. The PCM (cars cpu) will continue to feed the engine the gas determined by RPM, but this gas is not needed because the engine is not under load. So with a catalytic converter that can reach 2000+ degrees and an engine thats pumping out extra gas and 02 and not to mention what happens in a CAT system. The remaining fuel will combust and create a Backfire. You can also get a LEAN backfire again i will not explain becasue of so many scientific principles.
Over the years of Automotive evolution OBD2 systems, Government Regs and Hybrids have changed these factors.
I guess PD has not accounted for this.

Good Racing

PS: I mean if you do not have a wheel setup with a clutch pedal, you will not be able to disengage the engine from the trans when you want. You can still have a backfire when disengaging when you chose. Anyways ask a real Technician and he will agree with my facts

 

[Smuttysy]

I was wondering for a while what causes Exhaust Backfiring. All I know is that it happens because unignited fuel ends up in the exhaust pipes and ignites there.

You mean like this?

(Spark plug wired up in the exhaust pipe will do it, as my brother proved, lol)

 

[rb26x]

Yes, it's the fact that when the engine isn't under load, it isn't using the fuel sent into the engine. My car backfires at revs as low as 2500 sometimes, and it backfires almost every time I heel-toe downshift. If I had not catalytic converter, I'd enjoy it much more though.

 

[jmtrvenom19]

Backfires happen when unignited fuel enters the exhaust and it ignited... the reason that happens is because if you bounce off the rev limiter or downshift when the RPMs drop the ignition is cut off but the fuel isnt allowing fuel to go right through the combustion chamber with being burned.. when the ignition is cut back on it ignites the unburned fuel that is in the exhaust and you get a back fire.