102 replies to this topic

[Graeme Lambert]

How soon for results fezzasus? We talking weeks or months for stuff to be ready on this one?

[smiley]

 

I'm not planning on doing this more than once, so I think rather than cobbling together some pieces of exhaust and seeing what happens I'm going to bite the bullet and come up with something decent from the start, maybe even a bespoke or custom system.

 

The Tullet manifold will be staying though, and i don't think I'll be moving above 2.5inch diameter with the rest of the system in a bid to keep the noise down. As you say it will handle 280ish bhp anyway.

 

 

If you don't track, the 2.5" 200 cells tullett cat section, and backbox will do just fine.

Just some nice earplugs for long travel is advised. (i always got mindbending headaches over 1 hour of driving)

(and as i understand it, UK tracks are much more forgiving on noise then euro tracks with your static tests)

 

You may need to ask tullett for the improved cat solution, as the stock NA tullett ones seem to melt on SC's. (happened with a few)

Edited by smiley, 17 December 2013 - 10:47 PM.

[Graeme Lambert]

I thought the cat melting problem was down to CS mapping overfuelling? Was hoping that properly calibrated standalone would negate such a problem.

[smiley]

I thought the cat melting problem was down to CS mapping overfuelling? Was hoping that properly calibrated standalone would negate such a problem.

 

A belgian guy melted his on a stock stage II, running obdtuner this summer.

The default NA one is cheap, and melts. I believe you can ask tullett to weld in a hjs cat (or whatever better quality they advice for more money), but they are more expensive.

 

The main problem is your high horsies in combination with a track friendly exhaust.

That's no easy goal, as you may have read from various people now.

Edited by smiley, 17 December 2013 - 11:17 PM.

[Graeme Lambert]

 

 

Techieboy?! Calling Techie!

  Funnily enough I did think of Matt when posting

 

You need to take a whole car approach, especially if you're running undersized pulleys (which means a decent enclosed air filter or better yet the standard airbox) and understand that it's drive-by limits that are the problem and not static limits. But, get one thing straight in your mind from the very start, the Z22SE and a supercharger in combination do not make for a "sporty" (whatever the fcuk that is) noise. Forget whatever a VSE or Larini sounds like on an NA car, they sound sh!t (and often offensively loud) for 98% of the time once you fit a supercharger. There is no character to the noise, it's just a wall of noise. I've been through 6 or 7 systems and combinations of systems on my car, after binning the original VSE in my first few weeks of ownership, in the quest for manageable noise levels and it's still not there yet. Where I'm currently at is with a modified full Tullett 3.0" system and manifold with the super high temp stuffing. From the very start, this was too loud and meant a failed noise test at Bedford and Combe (no great loss). Static tests were and have never been a problem at any track I've been to. I went straight back to Tullett's and they agreed to adapt the system to allow for a de-cat silencer (also with super high temp stuffing) to swap in for the cat. This helped a bit. It knocked a couple of db off the overall levels and sort of changed the tone of the exhaust. It also meant for a near silent idle (once the car had warmed up) and low 90db's static tests at 4500rpm. However, this system still got me an instant black flag at Donington when I decided to see what happened when I didn't short shift down the pit straight (98db drive by, right above the track). After that, I convinced myself that maybe the stuffing had broken down and been blown out after a couple of years and plenty of trackdays so removed the system to repack it. Slight problem, packing was totally intact. In fact, it was so intact, I'm not sure it had even expanded fully to do it's job properly (which means it's either too tightly packed, or the exhaust gases aren't hot enough to melt the bindings to allow the expansion). Decided at the very least I needed to get some db reducers to go in the tailpipe. But the Tullett fits the car so well, there was no easy way to attach db reducers in a tidy but secure way (at least not the ones I knew worked properly). We were shortly off to the Le Mans trackdays and I couldn't face another 400 mile drive with the shitty exhaust noise so decided to get medieval on the exhaust. As the back box and tailpipe section (one piece on the 3.0" system) was off the car, I decided that I was going to get the tailpipe section split into two pieces so that the tailpipes were removable and get a number of different tailpipes made up. So I ended up with the original twin exit, a single 3.0" exit which stuck out about 1.5" further from the rear clam so I could easily install a db reducer and finally, the horrible "Cliffie Droop" single tailpipe that I could swap as needed (I also had an add on droopy section to fit the single straight tailpipe but lost that somewhere). A local custom exhaust place did that lot for me and when I went to collect the bits, I had a little brain fart and asked them if they could block the lower tailpipe of the original twin exit tailpipe which they did by blocking the lower pipe where it splits from the main tube and the upper tailpipe section. Due to my hatred of the way any of the other options looked, I elected to refit the exhaust with the modified twin tailpipe to keep the standard looks. To my surprise this actually dropped another couple of db off the static and drive-by tests we did before and after. Still by no means quiet but it definitely helped and made the schlepp to Le Mans a bit more bearable. For the same trip, I also fitted the biggest enclosed induction kit I could find (after giving up on a UK manufacturer adapting a Focus WRC system for me) and that really did help by knocking off some of the higher pitched SC whine from the undersized pulley. Not sure what difference that made in isolation to overall sound levels but I reckon it knocked the induction noise back to something more like the original Stage 2 SC setup and certainly made things more pleasant in the car. Lee basically did a similar thing a few weeks back which by some miracle got him on at Bedford (I still don't think I'd get on there for long if I tried). When/if I ever get the interest in the car back, it's going off to a motorsport exhaust place for them to do some proper frequency analysis on the car (was meant to happen earlier this year but I couldn't be arsed with it) to see where the largest problems are and to see whether i) they can either adapt the system to attenuate those spikes with a quarter wave resonator or two or ii) build a totally new chambered rear box(es) to do the job properly. Hoping for the former but expecting the latter.

 

 

Literally only just seen this now Matt - obv missed it while browsing this on my phone previously.

Thanks for the info.

 

Agreed that the Z22/B207 is unlikely to ever sound properly Sporty (as such), I just want an exhaust note that is at least 'involving'.

 

Also that drive bys are the crucial measurement, and that induction is certainly one of the biggest problem areas. And that I see a single tailpipe does help with the sound.

 

G

[Mangham54]

Has anyone identified which part of the sound spectrum is the peak and tripping the noise sensors?

 

If so would there be anyway of attenuating the sound to move the problematic 'notes' into something more agreeable?

 

/ I might be talking absolute dog sh*t here - but surely there has to be a way to soften the exhaust note appropriately - even if it was to fit a dummy turbine in the exhaust system to chop up the airflow / pressure waves.

[FLD]

Has anyone identified which part of the sound spectrum is the peak and tripping the noise sensors?

 

If so would there be anyway of attenuating the sound to move the problematic 'notes' into something more agreeable?

 

/ I might be talking absolute dog sh*t here - but surely there has to be a way to soften the exhaust note appropriately - even if it was to fit a dummy turbine in the exhaust system to chop up the airflow / pressure waves.

 

I dont think this has been done yet, its what techie has been on about doing though.  Once you know this you can make (pay stupendous amounts to have made) a proper resonator system to silence these frequencies.

[fezzasus]

Has anyone identified which part of the sound spectrum is the peak and tripping the noise sensors?

 

If so would there be anyway of attenuating the sound to move the problematic 'notes' into something more agreeable?

 

/ I might be talking absolute dog sh*t here - but surely there has to be a way to soften the exhaust note appropriately - even if it was to fit a dummy turbine in the exhaust system to chop up the airflow / pressure waves.

 

It's the intake. I moved to an enclosed filter and it made a massive difference.

[Zoobeef]

So, what would a 3 inch tullet system with a decat and single exit be like?

[fezzasus]

So, what would a 3 inch tullet system with a decat and single exit be like?

 

Isn't Matt running the same thing?

[Zoobeef]

Which is what I thought and he said it wasn't too bad. But according to this thread itll drown out jumbo jets :/

[Andrew aka Stuwy]

I have a 2.5 miltek system with tubby back box and its very quiet.. only st 2 and z22 though

[Mangham54]

 

Has anyone identified which part of the sound spectrum is the peak and tripping the noise sensors?

 

If so would there be anyway of attenuating the sound to move the problematic 'notes' into something more agreeable?

 

/ I might be talking absolute dog sh*t here - but surely there has to be a way to soften the exhaust note appropriately - even if it was to fit a dummy turbine in the exhaust system to chop up the airflow / pressure waves.

 

I dont think this has been done yet, its what techie has been on about doing though.  Once you know this you can make (pay stupendous amounts to have made) a proper resonator system to silence these frequencies.

 

 

fcuk me... I got something right!

 

Think I need to have a lie-down.

[techieboy]

Yep, quarter wave or Helmholz resonators. Simple length of additional tube (blocked at one end) welded almost anywhere along the length of the existing system tuned (in length) to match whatever the problem frequency is. This then bounces an exact out of phase soundwave back into the exhaust to "cancel" out the problem frequency (like noise cancelling headphones). Obviously only works if there's a particular problem frequency otherwise I guess you end up with the equivalent of a spiders web of pipework. They're also on really effective at certain engine rpms (so really easy to tune one to ace a static test but probably not as effective over the full rev range).

 

It's also something that some Jap engines run on their intake pipework, so might be even more effective at killing some of the SC whine forcing it's way back out of the inlet once the pressure is too high in the inlet manifold.

 

I've been way too reticent about getting some proper spectrum analysis done as I didn't want to go too far down the 2.2 litre engine route if I then binned the Z22SE for the B207 which might be slightly different or even went down the hybrid Z22SE/B207R route. I did try some rudimentary measurement with a spectrum analyser app on the phone but there's just too much noise going on to draw anything useful from (except that it apparently breaks every Health & Safety at work noise guideline).

 

The exhaust on the right looks like it might have two resonators on to address two problems

 

[Graeme Lambert]

Bringing this one right back from the dead.

 

Plans have changed slightly, and power is going to be incresed considerably. Still stands that I want a quiet(ish) 2.5-inch system though.

 

Current thoughts are Dave Hardwick and the place Matt has made mention of above. Any others I shoudl be looking at for this.

 

I'm also thinking, silencer decat, single exit pipe (probably dummy one to maintain visuals of original design) and the largest backbox that can be comfortably squeezed in there. Mated to the 2.5-inch tullet tubular manifold. Will also have a 'quiet' air filter.

 

G

[Nev]

Has anyone ever opened up a OEM VXT back box and measured what the diameter of the pipework is inside it please? Id be keen to know please.

[Exmantaa]

Search... (posting from Vocky I think. Way way back in time.)

 

@ Graeme; Define "power is going to be incresed considerably".

Are we talking 330-350 SC horsies from a Harrop-ed B207?

Edited by Exmantaa, 31 October 2014 - 01:22 PM.

[Graeme Lambert]

Search... (posting from Vocky I think. Way way back in time.)

 

@ Graeme; Define "power is going to be incresed considerably".

Are we talking 330-350 SC horsies from a Harrop-ed B207?

 

Nail on head with power Exmanta

 

Hoping someone isn't about to tell me I need a 3-inch system...

 

G

[CocoPops]

Haha good luck. That many horses running around means noise!

[vocky]

If you want a 2.5" system with 330-350 bhp then you need a decent 4-1 manifold, forget about using any 2.5" aftermarket manifolds and get a long custom version and downpipe / cat section made, similar to the Tullet 3" manifold.