[blod5]

Bit of an odd one, or thats how it seems to me.

My 335i has a BMW performance exhaust as well as recently having the VRSF downpipes fitted.

Absolutely love the sound and not sure if this is the same with others running this set up, but the car gets about 50%+ louder right at the top revs (before redline)

Another point to mention, I have unplugged the valve 'thingy' in the boot to keep it open.

Anyway, was driving around like normal then got to a hill, I was going up it at quite low revs and all of a sudden the car got way louder. The burbles turned in to pops on the over run as well as exhaust note and turbo whistle getting louder.

This lasted for a few minutes of driving, then I stopped for 5 minutes or so to wait for a friend and then it seemed to go back to how it was a short while after that.

Not really bothered if it stays how it is now as its loud enough but also don't mind if it were to stay like that either.

Could this be that value opening up as I were going up a hill?

Any suggestions?

[ajsalida]

Well I am not sure this is any help but I'd want to rule out something like an exhaust leak in the system right away. Either right at the turbos/DP, at the DP/exhaust join, and then at the new muffler location. Look for soot or signs hot gas has been leaking out, obviously could be a safety issue esp. if inside the engine compartment.

IIRC the PE exhaust requires cutting the old muffler off and clamping a new one on, I'd start there and check clamps etc. then move on upstream and check DP/exhaust bolts and then V-bands on the turbo flanges make sure everything is tight and not leaking.

If you disconnected the correct connector to the flap, it should stay open all the time.

[E92Carlos]

My car used to do this before i put in the jb4 , i am not sure exactly what causing it to get louder but i know exactly what your talking about. Crusing at low speeds the exhaust will all of a sudden get louder and deeper as soon as you punch it it goes back to normal right ?

I am guessing the ecu is trying to save gas or something , not really sure.

[Asps91]

This happened to me. I always though maybe the wastegate was getting stuck or something momentarily and changing the note.

[PNWN54]

I experience the same thing when the engine is being kind of lugged up the hill or is in a bad rpm range on certain gear. If you coast and tap the gas pedal right after that the exhaust doesn't just burble but it will sounds like a loud whip lash or gun shot. I'm not sure what causes this effect on the exhaust but it doesn't seem to upset the car too much. I try to avoid this and downshift to make it easier on the engine.

[blod5]

Yeh you guys seem to know exactly what I mean. Hasn't done it since which has almost been a week. Will just keep an eye out and planning to get a JB4 in the coming months anyway

[mex2309]

Originally Posted by blod5

Bit of an odd one, or thats how it seems to me.

My 335i has a BMW performance exhaust as well as recently having the VRSF downpipes fitted.

I have PE exhaust but not DPs yet. I'm concerned it'll be overly loud after DPs.
Can you describe how much louder the exhaust is w/ DPs? 25% louder?

[Jeff@TopGearSolutions]

I never heard of this issue but apparently it's common. If you don't have a tune, I'd start with that just to make sure you are safe. The first thing I was going to mention was to log your vehicle to see what's going on, you'll need a tune to do that.

[blod5]

Originally Posted by mex2309

I have PE exhaust but not DPs yet. I'm concerned it'll be overly loud after DPs.
Can you describe how much louder the exhaust is w/ DPs? 25% louder?

I dont regret one bit getting DP's

On a cold start up it is very loud, if you live near neighbours that moan about sound, they won't be happy ill tell you that. You can rev it very slightly to a higher RPM and hold it there and funnily enough it actually gets quieter. I do this if I need the car to be quieter whilst I wait a minute or so for it to warm up. Luckily my car is kept in a underground so no worries there.

Driving along it definitely louder but not ridiculously louder. Sounds a lot more beef'd up. Actually sounds a bit like my old V8 M5 on low revs. Like I mentioned, right at the top end, the exhaust note gets super loud which is where I want it to. I think at that pitch it vibrates the exhaust pipe a lot which is why it gets so much louder (in a good way that is) The burbles get slightly more noticeable but not a lot.

[PNWN54]

Originally Posted by Jeff@TopGearSolutions

I never heard of this issue but apparently it's common. If you don't have a tune, I'd start with that just to make sure you are safe. The first thing I was going to mention was to log your vehicle to see what's going on, you'll need a tune to do that.

This only became noticeable after downpipes went on with PE Modded mufflers(used BMW clamps). To me it seems normal, engine increases throttle upon an incline, which in turn creates louder exhaust. More throttle= more exhaust noise = awesome

Here's my most recent log via MHD running Stage 2 OTS map. Mods in signature:

http://datazap.me/u/rockroll335i/sta...og=0&data=4-21