4722 replies to this topic

[Nev]

And now I currently in the middle of building my own 3" system for my new engine

 

It would be interesting to hear what other designs/findings you make Al. Are you gonna merge your 2 streams into 1 box/stream ?  

[jim61]

Not sure if this is of interest but old school 2 stroke baffles had ( the ones I have seen ) small indents in the perforated sections to " scoop " into the exhaust gas flow and divert a percentage of gas into fibreglass wadding without actually obstructing overall diameter that much. Watching with interest👍

[oakmere]

Mr titan that not what Nev has done though! Nev it will be interesting to see what pressure you measure 👍

Edited by oakmere, 12 December 2016 - 10:39 PM.

[Mopeytitan]

Mr titan that not what Nev has done though! Nev it will be interesting to see what pressure you measure �

I know I was just saying

[siztenboots]

[Nev]

Not sure if this is of interest but old school 2 stroke baffles had ( the ones I have seen ) small indents in the perforated sections to " scoop " into the exhaust gas flow and divert a percentage of gas into fibreglass wadding without actually obstructing overall diameter that much. Watching with interest👍

 

I have done something similar with my turbulence strips, angled at 45 degrees in the centre of the pipe where the flow is least likely to reach the side walls. I had intended on installing about 5 of them, but when I tested with just 3 it already had a strong effect (of deflecting the gas from the centre of the pipe towards the sidewall).  

[Nev]

 

I'm not sure how he merges the 2 flows in that box, doesn't look like there is much room for pipework in there TBH. Even though it is a handsome piece of artwork and awesome welding I doubt it would drop the dB by 17 dB like mine.

 

As is often the case, people buy such things on how they look, rather than how they perform. Is there any info on noise reduction on it ?
 

Edited by Nev, 13 December 2016 - 10:45 AM.

[siztenboots]

just something that was on facebook this morning, i think its german

 

tbh, I would have made the high flow section a straight run and entered the silencer directly opposite the tailpipes

 

https://www.facebook.com/motorkrep/

[Nev]

There are just so many ways to tackle the designs, but it takes lots of R&D and some measurements to actually find what works well.

 

R&D = time + money + tools + patience. So it is rarely done, which is why commercial suppliers just offer the basic straight silencer design.

 

I have no doubt there are better ways than what I tried, I know that Josh (my aerospace engineer friend) thinks I should have installed my passive flapper valve system. Maybe he was right, I did make the thing anyway yet didn't install it, as I was keen not to introduce any more complexity + risk into the design.

 

Once my bung arrives, I'll see what back pressure readings I get. If the readings go though the roof, I guess I could build another variant with the flapper in, but it would be another £200 in materials and 20+ hours.

 

Edited by Nev, 13 December 2016 - 11:38 AM.

[mbes2]

When you starting a group buy ?

[FLD]

  In an airbox it would create a mild resistance and serve no purpose. In an exhaust it creates a mild resistance and serves a 2 dB purpose. QED.   [/quote] That's quite an assumption. Are you sure glass in the inlet would have no effect on intake noise levels? Sent from my iPhone using Tapatalk

Edited by FLD, 13 December 2016 - 07:53 PM.

[Nev]

 
In an airbox it would create a mild resistance and serve no purpose. In an exhaust it creates a mild resistance and serves a 2 dB purpose. QED.
 
[/quote]

That's quite an assumption. Are you sure glass in the inlet would have no effect on intake noise levels?


Sent from my iPhone using Tapatalk

 

Oh yes, it would reduce intake noise (probably quite well, as it is high pitch noise), but what I meant was that in my particular car it would serve no useful purpose (as there is no noticeable intake noise anyway).

 

If anyone was genuinely thinking of putting g/f wadding into their air filter box they'd have to very seriously considered what was going to stop it getting sucked into the engine and ruining it... I suspect whatever solution that was would add a lot of resistance to make it unviable.

Edited by Nev, 14 December 2016 - 09:50 AM.

[Mopeytitan]

That's because your intake is in the boot above your really loud exhaust

[Nev]

That's because your intake is in the boot above your really loud exhaust

 

I don't think I ever got much intake noise even when I had the airbox in the OEM position.

 

I think it's the S/C kidz that find it a genuine problem myself (rather than the T/C kidz).  

[Nev]

It's actually sunny here, so I'm off soon to test my new front springs and see if I've re-set the ride height correctly to avoid bump stop. I will put some small tie-wraps around the coil-over struts to see how close to the bump stops they are pushed and then belt down an average B-road.

 

I might also mount my tiny Chinese camera in the wheel arch to review the footage. It will give me an idea to see what scope I have to give more of the available strut travel to droop (instead of bump). I have a favourite "test" hump back bridge that helps test the droop factor !

 

I have been told that roughly 60% of strut travel is best allocated to droop, but TBH I find it's the other way round and 60% is best allocated to compression. This might be because I run soft springs (and have a slightly heavier VX than most) and the compression travel is "eaten" up more than on a car with stiffer springs.

 

Edited by Nev, 14 December 2016 - 10:13 AM.

[Nev]

Lightly vigorous 60 MPH B-road caused about 60% of the available strut to be used, ie there is a 40% reserve before the bump stop will engauge. I could deffo feel the extra 50 Lb of spring strength, and not in a good way really.

 

I'll wait for the roads to dry some more and try to hammer it a bit more and review the tie wrap.

 

The steering also felt less "darty", probably due just to the 1/4 turn nip I made to one side of the steering arm to reduce the toe out.

 

My lambda sensor seems to either be foooked or not plugged in correctly as the readout on the dash was going mental (mainly staying on 22 AFR even when accelerating, which is clearly wrong).

Edited by Nev, 14 December 2016 - 11:28 AM.

[The Batman]

Might have a possible air leak around the lambda bung

[Nev]

Might have a possible air leak around the lambda bung

 

I think positive pressure in the exhaust usually means no extra oxygen/fresh air gets to the lambda sensor as any leaks would spew exhaust gas out (rather than fresh air in), but I suppose it is possible.

 

Also my welds on the bung were pretty good TBH (almost professional!), so if there is any leak it would be the 3 bolt flange (which doesn't currently have a gasket as it's on order).

 

I will fiddle with the loom plug first, that might be dirty and not fully pushed home as it was awkward to get to.

Edited by Nev, 14 December 2016 - 11:36 AM.

[Jocke_D]

 

Might have a possible air leak around the lambda bung

 

I think positive pressure in the exhaust usually means no extra oxygen/fresh air gets to the lambda sensor as any leaks would spew exhaust gas out (rather than fresh air in), but I suppose it is possible.

 

Also my welds on the bung were pretty good TBH (almost professional!), so if there is any leak it would be the 3 bolt flange (which doesn't currently have a gasket as it's on order).

 

I will fiddle with the loom plug first, that might be dirty and not fully pushed home as it was awkward to get to.

 

 

I'd humbly say you are wrong. The exhaust gases are pulses that both push out exhaust gases but also suck in fresh air.

I support this with the fact that I failed this years MOT because my Lambda reading was outside the limits (to much oxygen). I found a small leak just before the muffler, fixed that and then it passed.

[Nev]

 

 

Might have a possible air leak around the lambda bung

 

I think positive pressure in the exhaust usually means no extra oxygen/fresh air gets to the lambda sensor as any leaks would spew exhaust gas out (rather than fresh air in), but I suppose it is possible.

 

Also my welds on the bung were pretty good TBH (almost professional!), so if there is any leak it would be the 3 bolt flange (which doesn't currently have a gasket as it's on order).

 

I will fiddle with the loom plug first, that might be dirty and not fully pushed home as it was awkward to get to.

 

 

I'd humbly say you are wrong. The exhaust gases are pulses that both push out exhaust gases but also suck in fresh air.

I support this with the fact that I failed this years MOT because my Lambda reading was outside the limits (to much oxygen). I found a small leak just before the muffler, fixed that and then it passed.

 

 

Well, my gasket is coming from China, so it might be a few months before I know if the joint is leaking.

 

Edited by Nev, 14 December 2016 - 12:08 PM.