My OEM GPF is back on, so we're all properly legal again here now. Next on the list of things to be removed are the 200Cel Sports Cat and the 3" Flexi that I had fitted about 4 months ago (another £400 to be spunked in labour charges). This'll leave me with a completely stock 'front-end' with only the GPF-Back exhaust system modification ... and some £2K poorer.
Loud and deep outside. Just too loud in the cabin. I should have some parts being sent up soon so that I can swap out the resonated mid-pipe and do some testing.
@Tankdave Yeah, it was difficult to capture properly. I just used my Blackvue dashcam audio which was the only thing that I had that was recording at the time. The video sample was immediately after the GPF-Back system had been fitted, with me joining the motorway as I was on my way home, so obviously I was on a 'positive' throttle as I went up the slip road.
No, it’s the mid-pipe. This sits after the GPF, in front of the back-box. If you look at the ‘Ver1’ photo you can see a long straight pipe in the box to the left of the V1 resonated mid-pipe; that goes onto the GPF, then the mid-pipe, then the dual chamber back-box.
Hi Biscuit, why will you sell the flexi ? I think it's ok. At the moment I have the flexi pipe + mid GPF delete + oem back GPF installed, no sports cat, and it's fine. Not too loud at all and there is no drone at all. I get more pops & bangs, that is louder, indeed, but not overly. Now it sounds like an i30N I think. Because a new Kona N's sound is much softer in terms of pops & bangs not as wild as i30N, not at all.
I now want the engine end (Cat, flexi and GPF) back to stock for both Warranty and insurance compliance. I can survive with the modified 'GPF-Back' exhaust system as it's area that generates most of those extra dB and it is acceptable under my insurance.
Yes that drone sound I had on my Fastback with that same exhaust, it bothered the shit out of me….finally had it replace…all good now.Update: That's the resonated GPF-Back system now fitted.
The garage had issues with the fitting of the upgraded Valve Spring, which wasn't seated properly and was causing a rattle like a penny in a bean can! So when I got home I contacted RPM for advice, then an hour on the freezing tarmac outside my house saw me sort it out.
The other odd rattle now comes from the valve flap just inside the pipe - when it's closed and there's pressure behind it (at idle or running), sometimes it will oscillate a little against the mating surface which causes a 'ping ping ping' sound. The flap is easily reached and a little poking into the exhaust tip and prodding at the flap will often stop it making the noise - I'm hoping that once it gets a bit of carbon around the tube and the mating surfaces get dirty that it will soften the sound further.
POSITIVE: The sound is lovely in Eco/Normal and better in Sport. Unfortunately, I just can't accelerate hard unless I'm wearing ear defenders (see below)!
Not so positive: There is a serious amount of DRONE after this upgrade! It's like a sound weapon! The air in the cabin just vibrates with this deep noise that builds as acceleration does, to a level that is physically painful to the ears and makes you feel ill.
It's been suggested by Daniel at RPM that there may now be too much flow, given that I have a 200cel Sports Cat, 3" flexi, GPF Delete (resonated) and now their full 3" back end (with resonated mid-pipe). One option might be to add another resonator on the straight pipe after the GPF delete or make the current one bigger.. I have also thought about putting the original GPF back on, which would be the cheapest way to reduce the flow rate and hopefully lower the cabin noise to pre-vomit levels...
You can get a feeling for the sound in this Dashcam footage I recorded on the day of fitting. The deep booming and buzzing isn't distortion as you might think - you can tell this from the clarity of the indicator sounds and the satnav instructions also being transmitted into the cabin - the noise you hear is like being sitting next to the bass speaker at heavy metal concert!
Warning: The below video may make your speakers vibrate with the Bass levels. Earphones are suggested.
link to dashcam footage.
No it will not resolve the issue, because the source of drone is the RPM GPF Back. The other 2 things you mentioned (and the mid GPF delete you didn't) just make it louder but they won't resonate at a specific frequency or frequency range melting your brain down. Poorly designed product if designed at all. Actually I was luckier than you, he never sent me a resonated pipe as he promised, neither a fixed resonator so I couldn't waste my time and money with installing/deinstalling/testing it. The droning has gone only when I removed the RPM GPF Back, the other 3 things could be still installed. No problem at all.View attachment 22725
Guess I'll just have to wait until June for the removal of the Sports Cat and 3" flexi downpipe to see if that resolves the issue. It still sounds great externally though
Possibly a small difference in tone (a little more Bass in the cabin maybe) but, not noticeable difference in loudness. The cabin air still vibrates with sound on a hard throttle. The mechanic said to me "I don't know how you can tolerate the noise, it's just far too loud" - this is from a guy that runs an Audi RS6
Yeah I know what you are talking about. Btw I was able to abide the drone for 15-20 minutes in the city. The problem comes when you drive longer. And also big problem is the cold start in the morning. At cold start the valves are open for about 30 seconds (even in normal mode I donno why), that means insane morning wake up alarm for the neighbours, they hated me.Possibly a small difference in tone (a little more Bass in the cabin maybe) but, not noticeable difference in loudness. The cabin air still vibrates with sound on a hard throttle. The mechanic said to me "I don't know how you can tolerate the noise, it's just far too loud" - this is from a guy that runs an Audi RS6
