Help! Constant backfiring

DJ626 · 01-28-2003, 10:08 PM

I recently installed my up and down pipe, after, i noticed sometimes a loud pop noise would occur after letting of the gas and putting the car in nuetral. Ive heard of this before so it didnt bother me...however, now it happens every time i let off the gas and its really getting annoying.....any input is appreciated....thanks in advance.

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cmaj7 · 01-28-2003, 10:35 PM

What you are experiencing is afterfire, not backfire. A backfire is an explosion in the intake manifold.

If you have no cat's you will get afterfire. It's very common in turbo applications because the engine tends to run richer when on boost. Running rich adds an element of safety by cooling things down thus, reducing the likelihood of detonation(very very bad).

Afterfire is caused by a small amount of unburnt fuel which ignites when it hits oxygen in the exhaust. If you are running a non recirculating BOV it will excacerbate the situation. As will anything that makes the engine run richer.

The only way you will eliminate the sound of afterfire is run with a cat.

I, and many others here, actually love the pop sounds from afterfire as I downshift and brake.

krillz · 01-28-2003, 10:37 PM

if you dont mind me asking, whats your exact inatake/exhaust setup?

DJ626 · 01-28-2003, 10:37 PM

Thanks....just wanted to make sure its normal as it has begun to occur more often....

krillz · 01-28-2003, 11:36 PM

whats your exhaust set up?

rex n effect · 01-29-2003, 07:36 AM

I have a cat, but i still get a muffled after-fire from time to time with a turboXS exhaust, especially before the cat is warmed up.

mlambert · 01-29-2003, 09:02 AM

this is one of the perks of a turbo car

JayGold · 01-29-2003, 09:10 AM

Currently catless TXS Stage 4= afterfires at 2,000rpm's all the time. The best is to be sitting at a light, blip the throttle, and hear the afterfire...while all the surrounding drivers look worried

thebusiness999 · 01-29-2003, 10:49 AM

ALL HAIL THE AFTERFIRE, IT IS YOUR GOD!!!

Yes, I like my afterfire too...

whiterabbit · 01-29-2003, 03:34 PM

i dont get much popping and i am running catless. Is there something wrong with my exhausts or something?

I want some popping

DJ626 · 01-29-2003, 03:54 PM

My set up is:
Helix down pipe
gruppe s up pipe
TXS BOV
Intake resonator mod
HKS carbon ti cat back

Eric SS · 01-29-2003, 03:55 PM

Mine definetly started afterfiring after I installed my turbo and got a high flow cat. It is normal

Eric

Chunky_Chicken · 01-29-2003, 08:12 PM

I experienced an increase in afterfiring after swapping to an Ultimate up-pipe and Bosal down-pipe. I'm also running a straight pipe.

I absolutely love the sound and can actually make it fire repeatedly while decellerating if I rapidly tap the gas pedal slightly around 3000RPM (just for fun ofcourse, it is pretty loud so I only do it in industrial areas). I had one fella ask me if I was running antilag!

-Pete

krillz · 01-29-2003, 09:13 PM

i love this thread

DocDetroit · 01-29-2003, 09:52 PM

Yes, I too am one of the people who was a little dissapointed with the afterfire I got when I went completely catless. It is not nearly enough!

I love that sound.

I was driving behind a SRT-4 neon (manufacturer car driven by an engineer) and that thing had some vicious afterfire. I can't believe it comes from the factory with no mufflers! It sounds very good though. I talked to the guy, and he said it was a pre-production car, but it was very close to the production spec.

Does anyone know if I'll get more afterfire when I upgrade to STi injectors and a fuel pump? I imagine that when you jump off the throttle the ECU quits looking at the O2 sensor for fueling (because you're running like 24:1 A/F ratios at that point). So it must just use static injector pulse width values for the off-throttle state. If that's the case, bigger injectors should cause a richer off-throttle condition. Or am I way off base? Hmmm... I can't wait to test my theory

zacek · 01-30-2003, 04:23 PM

getting a hybrid BOV such as the APS or the GFB will reduce the frecuency of those afterfires considerably.

whiterabbit · 02-02-2003, 01:05 PM

when you guys say often...how often is often?

SFastWRX · 02-02-2003, 02:17 PM

According to dictionary.com,

back·fire
n.

1. An explosion of prematurely ignited fuel or of unburned exhaust gases in an internal-combustion engine.
2. The backward escape of gases or cartridge fragments when a gun is fired.
3. A fire started in the path of an oncoming fire in order to deprive it of fuel and thereby control or extinguish it

...

Source: The American Heritage® Dictionary of the English Language, Fourth Edition

...and...

No entry found for afterfire.

This event of unburnt fuel exploding in the exhaust has been called backfire since the internal combustion engine was invented. There are uncountable references to it in all manner of literature. I really have no idea where this "afterfire" term or the elitist attitude in its use came from, as I had never heard it before I registered for this board, although it sounds like a term they might use in the UK.

I did manage to get two useful hits (of the two hundred or so I scanned) in a google search, one being a reference to seeing the misnomer in a John Deere catalog, and this, from womenatthewheel.com's "Garage-ese 101":

Afterfire - the engine continues to fire after the vehicle has been turned off
Backfire - loud popping sound from the engine or tail pipe

Gonz · 02-02-2003, 07:39 PM

Quote:

. I really have no idea where this "afterfire" term or the elitist attitude in its use came from

Amen, to that.

Quote:

Afterfire - the engine continues to fire after the vehicle has been turned off

Let's hope they just keep calling this "run on " or " dieseling" as always, and not make up even more unnecessary and confusing words.

thebusiness999 · 02-02-2003, 07:53 PM

lol, that's kinda funny...

So who made up this afterfire term?

01-28-2003, 10:08 PM	#1
DJ626 Scooby Newbie Member#: 23975 Join Date: Sep 2002 Location: Mipitas Vehicle: 2002 Impreza WRX WR Blue Pearl	Help!...constant backfiring.... I recently installed my up and down pipe, after, i noticed sometimes a loud pop noise would occur after letting of the gas and putting the car in nuetral. Ive heard of this before so it didnt bother me...however, now it happens every time i let off the gas and its really getting annoying.....any input is appreciated....thanks in advance. * Registered users of the site do not see these ads.

01-28-2003, 10:35 PM	#2
cmaj7 Scooby Specialist Member#: 12677 Join Date: Nov 2001 Location: Florida Vehicle: 2002 Subaru WRX WR Blue	That's normal What you are experiencing is afterfire, not backfire. A backfire is an explosion in the intake manifold. If you have no cat's you will get afterfire. It's very common in turbo applications because the engine tends to run richer when on boost. Running rich adds an element of safety by cooling things down thus, reducing the likelihood of detonation(very very bad). Afterfire is caused by a small amount of unburnt fuel which ignites when it hits oxygen in the exhaust. If you are running a non recirculating BOV it will excacerbate the situation. As will anything that makes the engine run richer. The only way you will eliminate the sound of afterfire is run with a cat. I, and many others here, actually love the pop sounds from afterfire as I downshift and brake.

01-29-2003, 10:49 AM	#9
thebusiness999 Scooby Specialist Member#: 3767 Join Date: Jan 2001 Chapter/Region: SCIC Location: back in Los Angeles! Vehicle: 2008 BMW 135i !!! Jet Black	Useless post... ALL HAIL THE AFTERFIRE, IT IS YOUR GOD!!! Yes, I like my afterfire too...

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01-28-2003, 10:37 PM	#3
krillz Scooby Specialist Member#: 29874 Join Date: Nov 2002 Location: new york Vehicle: 2002 wrx mblackp	if you dont mind me asking, whats your exact inatake/exhaust setup?

01-28-2003, 11:36 PM	#5
krillz Scooby Specialist Member#: 29874 Join Date: Nov 2002 Location: new york Vehicle: 2002 wrx mblackp	whats your exhaust set up?

01-29-2003, 07:36 AM	#6
rex n effect Scooby Specialist Member#: 15289 Join Date: Feb 2002 Chapter/Region: SCIC Location: from santa barbara to Carp Vehicle: 02 wrx sedan PSM & grey '11 TDi daddywagon	I have a cat, but i still get a muffled after-fire from time to time with a turboXS exhaust, especially before the cat is warmed up.

01-29-2003, 09:02 AM	#7
mlambert Scooby Guru Member#: 13831 Join Date: Jan 2002 Location: 99 problems but a bitch aint 1	this is one of the perks of a turbo car

01-29-2003, 09:10 AM	#8
JayGold Scooby Specialist Member#: 7074 Join Date: May 2001 Chapter/Region: MWSOC Location: Illinois	Currently catless TXS Stage 4= afterfires at 2,000rpm's all the time. The best is to be sitting at a light, blip the throttle, and hear the afterfire...while all the surrounding drivers look worried

01-29-2003, 03:34 PM	#10
whiterabbit Scooby Specialist Member#: 16755 Join Date: Mar 2002 Location: yo mama's house	i dont get much popping and i am running catless. Is there something wrong with my exhausts or something? I want some popping

01-29-2003, 03:54 PM	#11
DJ626 Scooby Newbie Member#: 23975 Join Date: Sep 2002 Location: Mipitas Vehicle: 2002 Impreza WRX WR Blue Pearl	My set up is: Helix down pipe gruppe s up pipe TXS BOV Intake resonator mod HKS carbon ti cat back

01-29-2003, 03:55 PM	#12
Eric SS Sooby Guru Member#: 1914 Join Date: Jul 2000 Chapter/Region: SWIC Location: 2013 335i, 2011 G37 coupe Vehicle: 2000 2.5RS w/ EJ22T swap and N20. gone. : (	Mine definetly started afterfiring after I installed my turbo and got a high flow cat. It is normal Eric

01-29-2003, 08:12 PM	#13
Chunky_Chicken Scooby Specialist Member#: 9782 Join Date: Aug 2001 Location: Toronto, Ontario Canada Vehicle: 2002 E46 M3 Laguna Seca Blue	I experienced an increase in afterfiring after swapping to an Ultimate up-pipe and Bosal down-pipe. I'm also running a straight pipe. I absolutely love the sound and can actually make it fire repeatedly while decellerating if I rapidly tap the gas pedal slightly around 3000RPM (just for fun ofcourse, it is pretty loud so I only do it in industrial areas). I had one fella ask me if I was running antilag! -Pete

01-29-2003, 09:13 PM	#14
krillz Scooby Specialist Member#: 29874 Join Date: Nov 2002 Location: new york Vehicle: 2002 wrx mblackp	i love this thread

01-29-2003, 09:52 PM	#15
DocDetroit Scooby Newbie Member#: 24977 Join Date: Sep 2002 Location: Waterford, Mi Vehicle: 2003 WRX Blue	Yes, I too am one of the people who was a little dissapointed with the afterfire I got when I went completely catless. It is not nearly enough! I love that sound. I was driving behind a SRT-4 neon (manufacturer car driven by an engineer) and that thing had some vicious afterfire. I can't believe it comes from the factory with no mufflers! It sounds very good though. I talked to the guy, and he said it was a pre-production car, but it was very close to the production spec. Does anyone know if I'll get more afterfire when I upgrade to STi injectors and a fuel pump? I imagine that when you jump off the throttle the ECU quits looking at the O2 sensor for fueling (because you're running like 24:1 A/F ratios at that point). So it must just use static injector pulse width values for the off-throttle state. If that's the case, bigger injectors should cause a richer off-throttle condition. Or am I way off base? Hmmm... I can't wait to test my theory

01-30-2003, 04:23 PM	#16
zacek Scooby Specialist Member#: 19467 Join Date: May 2002 Location: Chatsworth, CA. Vehicle: 02 WRX WR Blue	getting a hybrid BOV such as the APS or the GFB will reduce the frecuency of those afterfires considerably.

02-02-2003, 01:05 PM	#17
whiterabbit Scooby Specialist Member#: 16755 Join Date: Mar 2002 Location: yo mama's house	when you guys say often...how often is often?

02-02-2003, 02:17 PM	#18
SFastWRX Scooby Specialist Member#: 13379 Join Date: Dec 2001 Location: Los Angeles Vehicle: 2002 WRX I am Oz	According to dictionary.com, back·fire n. 1. An explosion of prematurely ignited fuel or of unburned exhaust gases in an internal-combustion engine. 2. The backward escape of gases or cartridge fragments when a gun is fired. 3. A fire started in the path of an oncoming fire in order to deprive it of fuel and thereby control or extinguish it ... Source: The American Heritage® Dictionary of the English Language, Fourth Edition ...and... No entry found for afterfire. This event of unburnt fuel exploding in the exhaust has been called backfire since the internal combustion engine was invented. There are uncountable references to it in all manner of literature. I really have no idea where this "afterfire" term or the elitist attitude in its use came from, as I had never heard it before I registered for this board, although it sounds like a term they might use in the UK. I did manage to get two useful hits (of the two hundred or so I scanned) in a google search, one being a reference to seeing the misnomer in a John Deere catalog, and this, from womenatthewheel.com's "Garage-ese 101": Afterfire - the engine continues to fire after the vehicle has been turned off Backfire - loud popping sound from the engine or tail pipe

02-02-2003, 07:53 PM	#20
thebusiness999 Scooby Specialist Member#: 3767 Join Date: Jan 2001 Chapter/Region: SCIC Location: back in Los Angeles! Vehicle: 2008 BMW 135i !!! Jet Black	lol, that's kinda funny... So who made up this afterfire term?