Brumby Boy Posted April 18, 2005 Share Posted April 18, 2005 since putting a 2 " mandrel hiflow exhaust with a hiflow lukey muffler with a set a extractors and minus the cat on my EA81 powered Subaru Brumby, there has been a Popping/backfire type noise every time i get off the gas. Also when backing off (at night) my friends have seen a foot (at least) long flame out the exhaust tip. i have done no other engine mods to my ute. this is realy annoying, but everytime i talk to the boys at work (key motors subaru workshop) they tell me this is a normal traight of this engine design but i still believe that there has to be more to it than that. PLEASE HELP ME. Quote Link to comment Share on other sites More sharing options...
4x4mudrat Posted April 18, 2005 Share Posted April 18, 2005 Lukey turbo muffler and a resonator might help. A foot of flame?!? Quote Link to comment Share on other sites More sharing options...
Brumby Boy Posted April 18, 2005 Author Share Posted April 18, 2005 Ok 6" at least i found out my cos was exadurating. but yeah there was definatly a flame i think it might be running to rich?? should i play with my mixture screw or shiuld i play with the jets or needle? when i get a bit of cash im gunna get a webber and build a custom manifold. Quote Link to comment Share on other sites More sharing options...
4x4mudrat Posted April 18, 2005 Share Posted April 18, 2005 Custom manifolds are very tricky to do as they contain a water jacket and the thermostat. I don't think that playing with the mixture screw is the answer to your problems. Quote Link to comment Share on other sites More sharing options...
SuBrat84 Posted April 18, 2005 Share Posted April 18, 2005 ... there has been a Popping/backfire type noise every time i get off the gas. ... My ea81 (84 brat) does this too.. but it is stock exhaust (intermediate pipe and muffler are Walker) original cat though. I am curious about it.. but it doesn't do it very often. Usually just if i reallly get on it to 4000+ rpms and then let my foot all the way off the pedal. Quote Link to comment Share on other sites More sharing options...
85Sub4WD Posted April 18, 2005 Share Posted April 18, 2005 it sounds like the air injection system is acting up - do a search, and you will find lotsa info on it! - I had mine make noise when it was carbed, but never shoot flames!!! it is still possible though... Quote Link to comment Share on other sites More sharing options...
ausubaru92 Posted April 19, 2005 Share Posted April 19, 2005 Yeah, mine is worse since I put a new exhaust on, (1.75" equal length primary pipes, 2" straight back to a mercury hi-flow muffler, gonna add a hot dog) Pops and crackles on deaccleration, and if i rev high then deaccelerate, i get a real loud crackling and a bang occasionally I've welded shut the air injection flange, and my exhaust gasgets dont leak, is this problem only associated with carb cars???? brumby boy? .... im curious,.. how did u design the extractors? Quote Link to comment Share on other sites More sharing options...
555Ron Posted April 19, 2005 Share Posted April 19, 2005 Mine is the same. The mechanics i've talked to don't know. Its worse when its cold, and what my manual says is the Anti-Backfire Valve hisses at me on deceleration... i've replaced it with no success. I want it fixed, but i don't know where to start. Quote Link to comment Share on other sites More sharing options...
Brumby Boy Posted April 19, 2005 Author Share Posted April 19, 2005 I didn't build them, i bought them from a performance shop when i baught my tacho. Mine is also worse when it is cold and it is very bad when i rev it past 4000rpm. Anit-back fire valve? Air injection system? Quote Link to comment Share on other sites More sharing options...
555Ron Posted April 19, 2005 Share Posted April 19, 2005 I didn't build them, i bought them from a performance shop when i baught my tacho. Mine is also worse when it is cold and it is very bad when i rev it past 4000rpm. Anit-back fire valve? Air injection system?Yeah. You'll find the AB valve (as you look from the front of the engine) on the left hand side of the chasis between the air intake and the windscreen wiper bottle. The air injection system is driven by a reed valve on the rear right hand side of the engine. (left cylinder bank). Its plumbed into the y connecting pipe on this side only. Its connected to the AB Valve somehow, so this is good news for me at least... i've been trying to figure what the ************ this thing has to do with the price of eggs in China! This is all extremely new to me. But it's function is to put oxygen into the exhaust to help the cat converter to function. From what i've read, the AB valve should suck in air, and mine is blowing air out... this may be why its complaining. Again, i've not found much, but this is so far my understanding... I'd be interested to know what your AB valve is doing. Mine is hissing and rattling on deceleration... perhaps we have the same problem. If you find a fix, could you post it in here for me? If i find anything else i'll let you know... Quote Link to comment Share on other sites More sharing options...
subie94 Posted April 19, 2005 Share Posted April 19, 2005 my 86 gl had a bad anti-backfire valve on it an so when ever i let off the gas when the engine was at about 3000...BANG!! just like a shotgun:banana: plus i was told that i had some flames coming out the back.so maybe it is the anti-backfire valve that's causing your troubles. Quote Link to comment Share on other sites More sharing options...
Brumby Boy Posted April 19, 2005 Author Share Posted April 19, 2005 Yeah ill have a look tomorrow cos i dont feel fike doing it at 11:10pm and post it to let you know. dose the AB valve work all the time or over certin RPM? Quote Link to comment Share on other sites More sharing options...
555Ron Posted April 19, 2005 Share Posted April 19, 2005 Yeah ill have a look tomorrow cos i dont feel fike doing it at 11:10pm and post it to let you know. dose the AB valve work all the time or over certin RPM?Hehe. I did at 10:30pm. I must be more keen then you. Though i just got a hand full of grease and couldn't see much, so i wouldn't recommend it. (however, i would recommend cleaning up after your CV boot goes... yucky molly grease) The AB Valve is connected to the Carbi/inlet manifold and i think it may only do stuff on deceleration. I think it lets more pressure into the manifold, though again, it doesn't make sense to me and i'm not too confident. Quote Link to comment Share on other sites More sharing options...
Brumby Boy Posted April 19, 2005 Author Share Posted April 19, 2005 Yeah that cv grease is some good s*#t hay And i like to keep my neibours happy i annoyed them enough when i built my sub box the other week and my exhaust isn't very subtle. Quote Link to comment Share on other sites More sharing options...
ausubaru92 Posted April 20, 2005 Share Posted April 20, 2005 2 quotes from my Gregories manual.... "The Coasting Bypass Valve is a vaccum actuated device which meters additional Fuel/Air mixture into the inlet manifold during deceleration to assist in the complete combustion of the mixture" "To prevent a temporarily rich mixture from entering the engine and then igniting in the exhaust, the AB valve is used. The AB valve supplies additional air to the inlet manifold when vaccum is high, eg. on rapid deceleration" I dont think i have a CBV. My AB valve sucks in air on deceleration through the bottom and produces a hissing sound. I believe this is normal. Is the Backfiring a carb only problem or does it happen to EFi Subes as well? Brumby boy.... please describe your extractors, i am very curious cos i made some of my own,... 1 & 3/4 pipe, 72cm long equal length joined in a central collector with a total volume of 0.9 ltr per pipe. have u got pics? Quote Link to comment Share on other sites More sharing options...
karinvail Posted April 20, 2005 Share Posted April 20, 2005 http://www.ultimatesubaru.org/forum/showthread.php?t=33253 My car was also popping terribly, shotgun sounds, and fire out the tailpipe..... Quote Link to comment Share on other sites More sharing options...
555Ron Posted April 21, 2005 Share Posted April 21, 2005 http://www.ultimatesubaru.org/forum/showthread.php?t=33253 My car was also popping terribly, shotgun sounds, and fire out the tailpipe..... Karinvail, did you do the fix with the $20 valve? I would like to see it assembled on the vehicle. I don't understand what parts to put where...:-\ Quote Link to comment Share on other sites More sharing options...
555Ron Posted April 21, 2005 Share Posted April 21, 2005 Ok, Subaru said this genuine part is $540. I could get an entire engine for that money! And to add insult, it may not even fix it!! Quote Link to comment Share on other sites More sharing options...
85Sub4WD Posted April 21, 2005 Share Posted April 21, 2005 Ok, Subaru said this genuine part is $540. I could get an entire engine for that money! And to add insult, it may not even fix it!! see about getting one from a JY ( http://www.halspartsandservice.com ) or plug the holes up - I think there is also a repair article here http://www.usmb.net/repair/?CurrentDirectory=FOLDER_3f29ddceb73856.77194796/&FileType=Article&File=ARTICLE_3f3c62be2ef9f8.91773347.art that addresses how to fix it Quote Link to comment Share on other sites More sharing options...
Ru_ Posted April 21, 2005 Share Posted April 21, 2005 Just a though here boys but it seems like your on the right track with the AB valve. Try installing a dashpot. The EA82 turbos come with them to pretty much hold the throttle open for a split second when you hop off of the gas....thus letting air in to burn the extreme rich condition on deceleration. I have seen my spfi backfire pretty good with a stock exhaust on it. but that is really pushing it. I'd have to say that SPFI's and Carbs would be the worst becsuse of the HUGE intake distance between the injection point and the engine. That's alot of room for the fuel to fill up. On the MPFI's the fuel is injected right onto the valve, therefore less fuel sitting in the intake. On the EA82T's I think the dashpot is basically for turbo overboost due to quick throttle snapping. I have an 88 GL-10 and the dashpot has been taken out. I have a BOV on so I feel I don't need a dashpot. That being said, it doesn't backfire. It could be the turbo in the exhaust or whatever, I don't know. All I can say is under full boost, when I hop off the gas, the Wide band o2 jumps to about 10:1 mixture, then down to nothing, and no back fire. Meh. If your looking for a cheap fix, see if ya can make a dashpot fit. It might just do it. Quote Link to comment Share on other sites More sharing options...
karinvail Posted April 21, 2005 Share Posted April 21, 2005 Karinvail, did you do the fix with the $20 valve? I would like to see it assembled on the vehicle. I don't understand what parts to put where...:-\ Mine might be different than yours, the pipes that lead to the manifold from the ASV's - we plugged them off at the manifold. Didn't cost a penny (used scrap sheet metal to cap the holes.) I still get popping on deceleration, but the exhaust shop said it's because of the bigger than stock tailpipe (2 1/2" now with the new muffler - it used to be 4" though, so it's a LOT better now, LOL). Quote Link to comment Share on other sites More sharing options...
Brumby Boy Posted April 22, 2005 Author Share Posted April 22, 2005 i talked to the boys at work and they all concluded that the reed valve in the air injection system must be cloged up. also that the exhaust has not enough back pressure. so when i get some cash ill be making new extractors and exhaust out of 1.75mm stainless pipe and a new cat with a 2" performance muffler and hopefully it will come out with the deep sound im looking for without the poping and crackling!! sorry i inspected the AB valve and this has nothing whatsoever to do with the noise. Quote Link to comment Share on other sites More sharing options...
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