Kerry Posted 17August, 2009 Report Share Posted 17August, 2009 Ever since I've had my 2.7 he has always let out a backfire on rev over-runs, (when I say "always", maybe 3-5 times on a one way trip over the Black Spur driven in "spirited" mode) I have asked those who have worked on him and I seem to get the old "Ah, they all do that" type answer. He has had three different mechanics (at different workshops) give him a tune up, and with varying degrees he has let one go on the over-run. Now I don't mind... the paintwork above the exhaust outlet was well scorched long before I gave him a bit of stick, and although it gives my dearly beloved a reason to cast a scornful eye and a cats bum mouth as we approach the roundabout, I quite like it! The question is... is it really that harmless, or am I going to be left with one of those trick cigars that MAD magazine might use!? Kerry Link to comment Share on other sites More sharing options...
blacklotus99 Posted 21August, 2009 Report Share Posted 21August, 2009 Ever since I've had my 2.7 he has always let out a backfire on rev over-runs, (when I say "always", maybe 3-5 times on a one way trip over the Black Spur driven in "spirited" mode) I have asked those who have worked on him and I seem to get the old "Ah, they all do that" type answer. He has had three different mechanics (at different workshops) give him a tune up, and with varying degrees he has let one go on the over-run. Now I don't mind... the paintwork above the exhaust outlet was well scorched long before I gave him a bit of stick, and although it gives my dearly beloved a reason to cast a scornful eye and a cats bum mouth as we approach the roundabout, I quite like it! The question is... is it really that harmless, or am I going to be left with one of those trick cigars that MAD magazine might use!? Kerry Ah, they all do that! The MFI is meant to be run fairly rich on these cars so you will always get the popping and banging on the overrun. Exhaust type and SSIs makes a difference to how how loud the bangs are! Link to comment Share on other sites More sharing options...
Kerry Posted 22August, 2009 Author Report Share Posted 22August, 2009 Cheers Ben, as you know I quite like a bit of popping and belching! Welcome aboard. Kerry Link to comment Share on other sites More sharing options...
jnr356 Posted 6February, 2010 Report Share Posted 6February, 2010 if you read the original owners manual(mfi?) it clearly states that these engines are prone(or words to that effect)to backfiring i have set these cars up on a dyno ,all new engine and mfi etc set the tuning with all factory calibration protracters ,loaded as per factory w/shop specs,etc,etc all perfect , drive the car runs perfect give to owner,oh theres a slight backfire on over run, recheck everything scratch head for a few days then read the owners manual boy was i stoked as i said ,car was perfect that was over 20 years ago Link to comment Share on other sites More sharing options...
Kerry Posted 7February, 2010 Author Report Share Posted 7February, 2010 SWEET! MFI- yes. With the exception of frightening grannies at the roundabout, I'll continue to enjoy IGY's irreverent pops and burbs! Cheers, Kerry Link to comment Share on other sites More sharing options...
tazzieman Posted 23February, 2013 Report Share Posted 23February, 2013 Ah, they all do that! The MFI is meant to be run fairly rich on these cars so you will always get the popping and banging on the overrun. Exhaust type and SSIs makes a difference to how how loud the bangs are! Indeed , having just put the SSi's and a Monty muffler on yesterday , I have noticed a little pluffing on the overrun - just a hint and quite retro. It was probably there before but got muffled down. Exhaust pop is fine , intake pop is not! Now , I just got to get me some some turbo flames on decel Link to comment Share on other sites More sharing options...
cyberpunky Posted 23February, 2013 Report Share Posted 23February, 2013 I used to get a nice little burble on over run but now I have changed the cat back, it is gone. I prefer the note and smoother transition into boost of this exhaust, but I do miss the burble Link to comment Share on other sites More sharing options...
Harvs11 Posted 23February, 2013 Report Share Posted 23February, 2013 Crackle'n'pop on over run; just one of the many sounds of a 911. Not such a bad thing, kind of fun to get it to crack by quickly backing off the go pedal in second. Link to comment Share on other sites More sharing options...
T-Man Posted 23February, 2013 Report Share Posted 23February, 2013 I think you guys are a menace with your loud exhausts disturbing all us civil folk. Link to comment Share on other sites More sharing options...
PAC-MAN Posted 24February, 2013 Report Share Posted 24February, 2013 Noise is beautiful Thing. Link to comment Share on other sites More sharing options...
Russ Posted 24February, 2013 Report Share Posted 24February, 2013 i was reading this before my drive this morning sad that it didn't happen in my car then i was making noise in the tunnel it did it wonder how long till it destroys the CIS box (although i assume the germans are one step ahead of my thought process, and that's why the air filter straps are rubber so they have some give in them) Link to comment Share on other sites More sharing options...
tazzieman Posted 24February, 2013 Report Share Posted 24February, 2013 i was reading this before my drive this morning sad that it didn't happen in my car then i was making noise in the tunnel it did it wonder how long till it destroys the CIS box (although i assume the germans are one step ahead of my thought process, and that's why the air filter straps are rubber so they have some give in them) Intake backfire is different from exhaust backfire. The latter is better thought of as afterfire. Both may be caused by mixtures out of whack or timing issues. CIS engines are set up a little rich to help with warmup and reduce the risk of burning valves. A little afterfire is normal. The intake backfire on the other hand , is a no good situation! Link to comment Share on other sites More sharing options...
StevepGT3 Posted 24February, 2013 Report Share Posted 24February, 2013 One of the most endearing features of Fister stage 3`s is guaranteed pops and farts on overrun , the ones that I get on full throttle upshifts were a bonus Link to comment Share on other sites More sharing options...
T-Man Posted 24February, 2013 Report Share Posted 24February, 2013 What are Fister Sage-3s??? Link to comment Share on other sites More sharing options...
StevepGT3 Posted 24February, 2013 Report Share Posted 24February, 2013 Souvlaki with triple garlic sauce Link to comment Share on other sites More sharing options...
T-Man Posted 24February, 2013 Report Share Posted 24February, 2013 Souvlaki with triple garlic sauce That'll always increase the back pressure!!! Link to comment Share on other sites More sharing options...
Harvs11 Posted 24February, 2013 Report Share Posted 24February, 2013 I think you guys are a menace with your loud exhausts disturbing all us civil folk. Not at all T1. It's an early warning system for the kids playing in the street so they can scatter before I turn the corner Link to comment Share on other sites More sharing options...
tazzieman Posted 24February, 2013 Report Share Posted 24February, 2013 I can hear an exhaust sound thread coming on! Will be soon... Link to comment Share on other sites More sharing options...
wasserkuhl Posted 24February, 2013 Report Share Posted 24February, 2013 they all do that sir. however leaks in the exhaust system will make it louder and more noticable. removal of the muffler and replacing the gaskets, along with muffler gasket goo ( not muffler putty ) can reduce this. but. why? me likes the pops and bangs. thats what makes these old school 911s rock. All it is, is fuel burning in the exhaust that didnt burn in the chamber. downside? burnt valves if you potter around. always drive them longer than 39 minutes. always take them to 6k. always clear their throats. simples. Link to comment Share on other sites More sharing options...
T-Man Posted 24February, 2013 Report Share Posted 24February, 2013 they all do that sir. however leaks in the exhaust system will make it louder and more noticable. removal of the muffler and replacing the gaskets, along with muffler gasket goo ( not muffler putty ) can reduce this. but. why? me likes the pops and bangs. thats what makes these old school 911s rock. All it is, is fuel burning in the exhaust that didnt burn in the chamber. downside? burnt valves if you potter around. always drive them longer than 39 minutes. always take them to 6k. always clear their throats. simples.Wise words Wasser, but why 39 minutes? Link to comment Share on other sites More sharing options...
Uncle Posted 24February, 2013 Report Share Posted 24February, 2013 I wasn't happy with the coughs and bangs from the B&B system so I've done something about it. I added a turbo and fuel injecion that I can add 2% open injector on overrun to make sure I get bigger pops/bangs/flames. Link to comment Share on other sites More sharing options...
tazzieman Posted 24February, 2013 Report Share Posted 24February, 2013 We will be a little on the nose let alone the ears when all these ghastly hybrids and electrics start to take over the roads. But who cares? I certainly don't! Link to comment Share on other sites More sharing options...
StevepGT3 Posted 24February, 2013 Report Share Posted 24February, 2013 I wasn't happy with the coughs and bangs from the B&B system so I've done something about it. I added a turbo and fuel injecion that I can add 2% open injector on overrun to make sure I get bigger pops/bangs/flames. MMMMMMMM Flames Link to comment Share on other sites More sharing options...
withers Posted 24February, 2013 Report Share Posted 24February, 2013 I can hear an exhaust sound thread coming on! Will be soon... Yes... you could all do that with your go pros! pointing/mounting the go pro off the back of the rear lid or on the side of the rear fender.. then taking off as quick as you can. Would record the visuals and sounds! Link to comment Share on other sites More sharing options...
T-Man Posted 25February, 2013 Report Share Posted 25February, 2013 I wasn't happy with the coughs and bangs from the B&B system so I've done something about it. I added a turbo and fuel injecion that I can add 2% open injector on overrun to make sure I get bigger pops/bangs/flames. MMMMMMMM Flames Yep, sign me up for that mod!!!!!!!!!!! Link to comment Share on other sites More sharing options...
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