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On high rev changedowns I can hear a distinct "pop" coming from the exhaust (SS Backbox)
While I love it - My wife keeps saying - "whats that noise - your car sounds rough" What do they know - eh?
Anyway - what is it?
Is it un-burned fuel or something & is it OK like this or should I get it looked at.
Must admit though - does sound cool....

Ro

 

I'm not an expert...

I think this is a sign of the car over fuelling itself, the pops are a common characteristic of the SS Back Box.

Over fuelling is OK, shows a healthy 'rich' engine.

Hopefully Pete or somebody more knowledgeable will confirm the above.

I have an SS BackBox on my 94WRX and would like a few more than the very rare pops from my exhaust.. want to swap!



[This message has been edited by Tim (edited 04-02-2000).]

 

I too think its perfectly ok.
brrrrrrm change gear pop, brrrrrrmmm change gear pop, but on saying that this morning- I blipped it a little to spin up and then gave it some coming out of a turn and the damn thing didnt move very quick- it was being retarted?
eased off straight away - changed up - and it was back to normal. Still get a pop every now and again.

 

Got SS backbox, downpipe and blitz induction on my STi. Pops and farts like you wouldn't believe. Sometimes makes people jump going thru villages/high streets! Wife thinks it sounds stupid. I agree they know nothing. Sounds how Subaru would want it too I reckon.

 

Hi Guys,

The popping is unburnt fuel in the exhaust gasses exploding when it comes into contact with the air at the backbox. Fun on heel-and-toe downchanges where the ecu doesn't seem to cut back the fuelling much as you declutch and rev the engine without any load!

Tim, I assume that was a typo about the healthy overfuelling "lean" engine...

Moray

 

Yea it sounds superb and in the dark people following may see flames being spat out of the exhaust.

 

Thanks Moray... you learn something everyday!

 

A friend and I went for a cross-country jauntlast night, and he was amazed (only had his car for a day!) to see blue flames shoot from my exhaust.
He couldn't really say when they appeared, but said they appeared several times.
When would flames normally appear....when changing gear, lifting off the throttle quiclkly to slow down, or both of these?

Stef.

 

Any of you guys with excess poping have aftermarket blow off valve, the externally venting type?

I dont hav one, but heard it can cause engines to run too rich in some situations, e.g. changing gear.

I only get slight popping on overrun, no flames yet; that's with Tanabe exhaust & down pipe (no cats).

Just a thought...

Andy

 

Stef...

such pops and (if your lucky flames) can be induced by heavy acceleration and then backing off - leaves unburnt fuel in the system....probably won't do your engine mounts much good mind.

The other way is blipping the throttle on downchanges (to just match or slightly overmatch the revs)

Alternatively...fit a vent to atmos blow-off valve and screw up your fueling so it does it all the time (remember my car at donno last year ?)

Ask Mr. Jay/Firefox how we woke up the passenger of another car whilst stuck in a traffic jam on the way back from the pod last year...blipped the throttle to 2,000 RPM whilst stationary and then BANG...oh my god...it was loud...needless to say...BOV is not on new car and has been sold.

Ian.