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Old 05-15-2000, 03:57 PM   #1
Kilumanati
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Member#: 987
Join Date: Feb 2000
Location: Twin Falls, Idaho
Vehicle:
2000 Impreza 2.5 RS
Blue Ridge Pearl

Question Weapon R = Backfire?


I recently installed a Weapon R intake with
custom cold air extension on MY00 RS, and
since then the car has backfired about 3 to
4 times! It usually happens when shifting
up into second or third gear after charging
pretty much to redline. If any one knows
wh please let me know.
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Old 05-15-2000, 04:42 PM   #2
NYRS
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Join Date: Jun 1999
Location: Levittown, NY, USA
Post

I could be wrong but the backfiring could be caused by the length of the custom pipe being too long. This would allow more fuel to build up without the addition of air because it is taking too long to get to the throttle body after you "goose" the throttle. On the 00' w/o MAF the engine is reading vacuum, not airflow so the engine will sense no vacuum and add fuel without there being any air in the motor. Try shortening the pipe and see what happens. Like I said though, I could be wrong?
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Old 05-15-2000, 04:54 PM   #3
TamiyaRS
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Join Date: Dec 1999
Location: Newport Beach, CA
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I have experienced the same phenomenon occasionally in my '00 RS w/weapon R intake. Not big, nasty blow-your-muffler-off backfires; just an occasional pop when I back out of the throttle to shift. I think this is just a function of the MAP system not compensating quickly enough when the throttle is closed and making for a momentarily rich mixture. I can't imagine that it is much of a problem...
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Old 05-15-2000, 07:58 PM   #4
ShaneW
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Member#: 226
Join Date: Sep 1999
Location: Fremont, CA
Vehicle:
1999 Impreza 2.5RS
Rally Blue Pearl

Post

Did you reset your ECU?

ShaneW
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Old 05-15-2000, 09:03 PM   #5
Reciprocity
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Location: Alameda, CA
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2012 dcrawford died
for your sins

Post

Perhaps it is not actual backfire...but the sound from the un-even headers venting. Try doing a search on "backfire" and you will come across the thread.

I hear it too, a soft "pop!" when I get off the gas after a hard run up the revs. But I noticed it from the beginning, and I only have the home made intake.

D. Crawford
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Old 05-16-2000, 09:28 AM   #6
TamiyaRS
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Post

Yup, I reset the ecu. BTW...put the stock box back on and reset the ecu today, (car is going in for warranty work and I don't want to hear any BS about modifications), and the popping is gone.
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Old 05-16-2000, 07:14 PM   #7
tulit
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Chapter/Region: E. Canada
Location: Toronto
Vehicle:
09 STi
White

Post

I dont think you guys are getting backfires. A real backfire is what good old Uncle Buck got. You'd definately know when it was backfiring :-)

Its just similply due to the design of the headers and how exhaust gases from either side of the engine collide.

The reason you might not notice it with the stock intake is because the engine is running the correct mixture. An intake on any RS will either make the engine a bit too rich (98,00) or too lean (99).
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Old 05-16-2000, 11:13 PM   #8
direwlf
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Chapter/Region: W. Canada
Location: Calgary, Alberta, Canada
Vehicle:
1999 Impreza 2.5RS
Silverthorn Metallic

Post

Yeah. Sounds like it is dumping raw fuel into the header, hence the pop noise. That can be kinda hard on your cat.
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Old 05-17-2000, 12:58 AM   #9
Kilumanati
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2000 Impreza 2.5 RS
Blue Ridge Pearl

Post

Well I guess I am sort of glad to here that I am not the only one with that problem. The backfire isn't that loud, like something from Uncle Buck, but definitely noticeable at times and barely a pop at other times. I did reset the ECU and my extension runs from vent in the bumper into fender well and about an inch into the engine compartment and into Weapon R, not that long total, but definitely more piping than stock.
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