35 replies to this topic

[nicollow]

Id be keen on a baffled decent DIA system. But £700 for one seems steep. Might see if someone can just modify my VXT one and up the u-bend diameter. Isnt that all that is being discussed?

[alexb]

Really interested. On my to-do list with some priority. Not sure yet if I want 2.5 or 3 inch

[Rosssco]

Id be keen on a baffled decent DIA system. But £700 for one seems steep. Might see if someone can just modify my VXT one and up the u-bend diameter. Isnt that all that is being discussed?

 

My exhaust is exactly like that - 2.5" all the way incl. U-bend, and merges down to a 2.25" for the turbo silencer just as it enters it.  

[FLD]

Id be keen on a baffled decent DIA system. But £700 for one seems steep. Might see if someone can just modify my VXT one and up the u-bend diameter. Isnt that all that is being discussed?

Price was a complete guess based on the price of a Tullet. I'll just wait to see what they say.

[Pipo]

Yeah it is the pipo one. Photobox fooked it up but managed to find a thumbnail on google (hence the sh*t quality)  

I still have the original drawing on my PC.  It will be my pleasure to mail it to anyone who wants it  

[smiley]

We still have it Pipo.

 

[Arno]

In a same vein the Toyota-Elise OEM silencers look like this from the inside:

 

 

Pretty similar. Just a little less chambers.

 

The SC'ed Toyota powered Elises use the same silencer, they just bring the exhaust out unsing a single pipe, but otherwise the construction of the chambers and such is pretty much the same.

 

Like all OEM silencers it's also double-skinned which also helps a lot with noise reduction as is prevents the noise from resonating the outer skin and getting transferred out of the silencer that way.

 

Bye, Arno.

[FLD]

Ok, we'd best get a consensus on the best design, size etc. I'd like to stick with my 3" Tullet down pipe and bend. This would be easier for the rest of the parts. Anyone care to offer guidance on design; oem, miltek, lotus etc. Needs flow and silence!

[Bargi]

If you're decat then put the largest pre-cat you can in its place. If I remember correctly Dave H made up an 18 inch one for my setup and by far made the biggest difference to sound levels. Sent from my SM-G950F using Tapatalk

[alexb]

Ok, we'd best get a consensus on the best design, size etc. I'd like to stick with my 3" Tullet down pipe and bend. This would be easier for the rest of the parts. Anyone care to offer guidance on design; oem, miltek, lotus etc. Needs flow and silence!

 

3". As far as the design goes I would stick with the NA, but increase the internal piping accordingly. The one thing to be aware of is that the internal connecting pipes will act like tuned ports, so just increasing their diameter might not be the best idea. That is especially true for the tail pipes. Perhaps the manufacturer can offer some guidance there.  

[FLD]

Yeah, resonances have crossed my mind. Brain melting maths with multiple chambers, pipes and revs.

[siztenboots]

put a helmholtz resonator on, no drone

[Baron Von Scubadaddy]

Something like these ....

https://www.google.c...P1JXb-4ci-4MzM:

 

would we have the space for it ??

[Arno]

put a helmholtz resonator on, no drone

 

True, but need to be sized/shaped corectly to work in the required frequency range/band.

 

They have a fairly limited frequency response window so won't just 'magically' fix all noise, but if you do manage to hit the area where a resonance peak is located they can work wonders to get rid of annoying buzzes and resonances.

 

 

Bye, Arno.

[Nev]

My home made one eliminated 95% of drone (without a resonator pipe), probably due to the exit of the initial gas into an expansion chamber being staggered along a 60cm perforated pipe (which breaks up any single frequency): https://sites.google...e-design-topics

 

My actual build steps are here: https://sites.google...jectives-issues

 

If the length of the perf pipe > the wavelength of resonance freq then the problem of "drone" is eliminated. I vaguely remember doing some calcs and my basic maths (which may have been wrong) at 3000 to 5000 RPM meant the perf pipe needed to be at least something like 40cm long.

 

I got my static test dB down to 100 dB(A) at 4500 RPM using 3.5" pipe everywhere, so it should be easy with 3" or 2.5" pipe.

 

If you have a look at my wool strand tests on the website, it revealed a lot (unexpectedly) about where the gas was at highest pressure (scroll down here: https://sites.google...gn/05-build-log). It was highest pressure escaping the first 3" of the perf pipe and at the end of the perf pipe (this was at idle).

 

GL with it, proper empirical R&D will take a lot of time. My time was free, but my project probably took me about 50 hours, so getting one designed and tested for £700 sounds like a total bargain. If it were me, I'd charge circa £2000 to design + make the first one.

 

 

Edited by Nev, 25 July 2017 - 07:45 AM.

[alexb]

As a wild guess, I'd say that nobody is going to do any research. That's why I would base it on an existing design that is known to work well. The 'only' thing to do is scale it appropriately. Ideally you would like to increase the size of the chambers, but packaging restraints don't allow for that. The other thing to be aware of is that some of the connecting pipes and certainly the tail pipes may be designed such that they act like a band pass filter on certain frequencies. By just increasing the diameter, you shift the frequency. Another thing that comes to mind is that gas temperatures may be a little higher than for the original design. That causes the wavelength to change.