New exhaust raspy sound at around 3000 rpm

by **Sheik Jabooti** » Thu Oct 11, 2012 7:22 pm

Hi guys,

Just got my new exhaust fitted last week. It's an Ultrex TBE but with my stock mufflers refitted. The sound is great under 2000 rpm...quiet but deeper than stock. Above 4000 rpm it sounds good too...not too loud but aggressive :twisted:

The problem is in the 2500-3500rpm range where it has a distinctly raspy sound. Not drony just raspy. Reminds me of the sound my LH Torana used to make when the mid exhaust pipe would fall off (but not as loud of course).

Any ideas on what's causing it and how to get rid of that rasp sound without costing a fortune or ruining the flow?

Cheers

(BTW. If anyone's interested I'm selling the 2 Ultrex mufflers brand new as I won't be needing them on my stealth back exhaust)

by **rooby** » Thu Oct 11, 2012 7:38 pm

Previous discussion on the topic for reference viewtopic.php?f=18&t=17379

by **Sheik Jabooti** » Fri Oct 12, 2012 11:33 am

rooby wrote:Previous discussion on the topic for reference viewtopic.php?f=18&t=17379

Yeah, I had read that...but they didn't seem to come to any firm conclusion in the end. My rasp is not so much an air noise, more an unpleasant exhaust note. It may be just that rpm range gives an awful pitch. Low rev's have a deep sound and as the engine gets faster the pitch raises. Above 4000rpm the higher pitch starts to sound sporty again. I think it's that 2500 - 3500 rpm range where it's neither deep nor sporty...just sort of raspy. In saying that, it does coincide with the turbo boosting range...which makes me start to think about the waste gate flap issue described?

Methinks I need an audio clip.

by **Sheik Jabooti** » Wed Oct 17, 2012 7:41 pm

raspy_exhaust.zip: Exhaust note; (469.03 KiB) Downloaded 487 times

OK, here is a sh!tty recording of the sound. Unfortunately it was from inside the car so it's not great but it does characterise the sound ok.

So is this waste gate flap or just a normal sound for a straight through exhaust with stock mufflers?

Any help or opinion is greatly appreciated

by **Sheik Jabooti** » Fri Oct 19, 2012 4:31 pm

It seems I'm having a conversation with myself...but for the benefit of others who may come after....

The more I research this the more it is sounding like wastegate rattle. Not having heard wastegate rattle before it has been hard to figure out but based on a tip from Matt (Kido Tuning) and lots of reading it matches perfectly to wastegate rattle. I would characterise the sound as a bad set of maracas shaken very fast. Various solutions include swapping the wastegate actuator to an after market one, bending the WG Actuator arm (apparently a Vin Tune speciality), adding a spring to the WG Actuator arm (not sure if that works on the subarus) and retuning the WG Duty Cycle.

Matt is over here next week tuning the car, so I will get the definitive expert opinion from him and post back here.

by **Stomps** » Mon Oct 22, 2012 12:20 pm

WTF?? Matt will be in Perth??

god dammit.. i should have booked in a tune.. grrr..

I couldnt really hear anything in the sound file, but if you are around either the Vic Park or Huntingdale areas, im happy to have a listen..

like i said in the other thread, i know what wastegate rattle sound like pretty well, having it on previous cars..

by **Sheik Jabooti** » Thu Oct 25, 2012 6:21 pm

The verdict from Matt was that it was just normal Subaru exhaust noise. I guess the new exhaust just made it louder and more noticeable. It's not pretty but this is one I could easily chase my tail on.

I might put the Ultrex mufflers back on to my stealth back exhaust and see if that makes it more "manly"...my guess it will be the same clattering sound but now just REALLY loud.

by **kennysti** » Thu Oct 25, 2012 6:33 pm

I have an ultrex cat back with a Phat DP, when I was running the prototype ultrex quads I had a very raspy note around the 3k mark, I've just changed back to the single tip 4" mufflers and it vanished instantly, all gurgle and awesome and no tacky vibration

by **agan** » Thu Oct 25, 2012 11:59 pm

I had the prototypes after kennysti - catback quads. There were kinda loud at 100km/h but got way too boomy after I installed a dump.

So I then took over torpedo's STI quads and has since then been vastly improved.

Not quote as burbly as ultrex (love the burble) but I guess I have to be practical about the drone - probably an auto box thing. I tried sound deadening all over the boot - not much change.

Plus I prefer music quality so keeping to the STI quads seem to be the best solution for now. And having an auto box probably isn't the best for drones.

Given that most gains come from the dump and centre pipe (or so I'm led to believe) I will probably keep to this setup for now.

by **Sheik Jabooti** » Fri Oct 26, 2012 4:28 pm

kennysti wrote:I have an ultrex cat back with a Phat DP, when I was running the prototype ultrex quads I had a very raspy note around the 3k mark, I've just changed back to the single tip 4" mufflers and it vanished instantly, all gurgle and awesome and no tacky vibration

Interesting. I didn't install the Ultrex canons as I was trying to keep it quieter. I might give them a go before selling them off. Somehow though, I think the straight through canons are going to be very loud.

by **Sheik Jabooti** » Tue Oct 30, 2012 5:02 pm

agan wrote:I had the prototypes after kennysti - catback quads. There were kinda loud at 100km/h but got way too boomy after I installed a dump.

So I then took over torpedo's STI quads and has since then been vastly improved.

Not quote as burbly as ultrex (love the burble) but I guess I have to be practical about the drone - probably an auto box thing. I tried sound deadening all over the boot - not much change.

Plus I prefer music quality so keeping to the STI quads seem to be the best solution for now. And having an auto box probably isn't the best for drones.

Given that most gains come from the dump and centre pipe (or so I'm led to believe) I will probably keep to this setup for now.

So I put the Ultrex canons on over the weekend and the clatter was gone just as Agan experienced. But following the same outcome it is damn loud...border line earmuffs mandatory. Effectively the Ultrex mufflers are a straight through design...kinda like a big resonator. It sounds great...really sporty...but requires the listener to be at least 3km away to not damage their hearing :wink:

I've decided to have fun for a week and put the stock mufflers back on as the noise in the wagon is out of hand. But it does give hope to the idea of installing a hotdog resonator to get rid of the clattering!?

Anyone interested in a set of Ultrex mufflers!? Only used for a few days! $250 + postage