Board logo

How to fix on my 2nd inline silencer
bi22le - 24/6/20 at 02:00 PM

Hi all,

To overcome track day noise limits I had a secondary silencer made up. My plan of trying to fix it with ali straps and rubber has proved harder than first thought. The main reason is that the straps are the right length to tightly grip the silencer they are tough to wrap around and bolt up. I need to bolt the two together in a secure and easy way. Here it is just resting:

Unstrapped 2
Unstrapped 2


Unstrapped 1
Unstrapped 1



And this was my attempt. Basically as you see it. there are 4 straps in total, paired up and joined wih a single nut + bolt. The bolt is tight and they can still slide, although it was tight to get the bolt in to start off with. If I shorten the straps further it will REALLy hard to get the bolts through and tight. I need a clamp that I can fit seperately and then tighten up. Here you can see what I was trying to do:

Strapped 2
Strapped 2


Strapped 1
Strapped 1



Thoughts?


Deckman001 - 24/6/20 at 02:51 PM

Not really much help, but does your exhaust headers really need to be that long?

Here's mine from about 14 years ago pasenger side rear
pasenger side rear


For yours, I'd probably say fit the top silencer with similar bobbin av mounts to the side of your car, it'll get good stability, but will then need grommets to fill the holes when it's removed ?

Jason


steve m - 24/6/20 at 04:04 PM

Imho that double exhaust looks dreadful, and with the tight bend will sap power,

I would of used the original silencer , with a pipe going under the axle, and mounted the second silencer across the back under the tank and exit rewards

just my opinion,

steve


steve m - 24/6/20 at 04:06 PM

Also, I am sure someone will complain about the exhaust protruding so far out of the width of the car,
it looks dangerous

steve


bi22le - 24/6/20 at 04:48 PM

Thanks for your thoughts on how to mount the silencer Steve!



I am getting it rolling road next week so will see what the impact is, I also think it will knock power, but a car sitting in the pit because it's too loud is far worse.

Regarding it sticking out; I have seen a number of times, and been instructed to do so myself, been on track days where people have bolted in the end of their silencers quite long DB killers. They protrude further than this, and if a car is getting that close to me on a track day, I will be asking for them to be removed from the track.

This is a necessity not out of choice.

[Edited on 24/6/20 by bi22le]


adithorp - 24/6/20 at 05:19 PM

What engine do you have and what dB readings have you been getting (with original)?


Dingz - 24/6/20 at 06:23 PM

Quote 'I would of used the original silencer , with a pipe going under the axle, and mounted the second silencer across the back under the tank and exit rewards'
I suspect just putting the pipe on to exit at the back would make a lot of difference, I remember seeeing a car like that years ago and it was quiet.


bi22le - 24/6/20 at 06:47 PM

quote:
Originally posted by adithorp
What engine do you have and what dB readings have you been getting (with original)?


4age 20v.

I get 98db static but I don't know what drive by. As you may know though, the statics have been sticking around 98 / 95 but the drive by has been dropping.

When I was kicked off I think static was 98 and drive by was 85 IIRC. A big disparity with lots of noise expecting to be lost somewhere.

I had my TB sticking through the bonnet with a sausage filter on, so I have changed that too.


JimSpencer - 24/6/20 at 06:56 PM

Hi

I think you're going to really struggle to mount that - you need something solid to clamp the 'top' silencer to, the wrap around clamps just hold it, it's what they fix to that supports it?

Re the tight bend, I'd be more concerned what back pressure it might create, that is tight..

So

I'd suggest it's also not a fix for the problem, I'd suggest working out what's causing your problem as it does look like the 'bottom' can is fairly chunky, so it shouldn't be 'that' loud.. you might be better off trying to deal with the source of the issue rather than the end result?

Could be an exhaust design issue as mentioned above - if it is then that's not going to be cheap, so if all else fails I'd simply follow the herd, go to Pipe Werx (or similar) order a DB killer and then rolling road it to suit - it'll cause you way less headaches than what you're currently trying to do..

If a DB Killer isn't enough then you definitely have an induction or exhaust design issue IMHO.

HTH


adithorp - 24/6/20 at 08:47 PM

Can't understand how you're not able to get less than 98db from a 4a-ge. My R1 is less than that. Induction noise wouldn't help but you should have improved that with the airbox. When and how was your silencer repacked?


bi22le - 24/6/20 at 10:36 PM

Thanks for the replies.

The noise limits I had trouble with were drive by. I have not been on track for a few years but when I last got kicked off the difference between static and drive by was growing.

I may have solved it with my induction change. It will be a lot quieter at the front end for sure, compared to what I had before. The exhaust was an additional. If I have forked out 450 for brands GP and get a black flag for noise, I don't want to go home!

I am booked in with AtSpeed early next month to check how the new induction affects things and I wanted to check this exhaust set up too. I don't want to use it in anger if I can help it.


bi22le - 24/6/20 at 10:39 PM

So I had a bolt on DB killer. It sounded no different and I still got kicked off!

I repacked the silence quite some time ago with Acustafil, but I bet it's not that, the stuff does not degrade really. The Acustafil I removed to repack was perfect after about 5 years of track use so it was a wasted exercise really.


adithorp - 24/6/20 at 10:49 PM

How much acoustafil did you use? The online calculator is generally regarded as resulting in overpacking. Between 2/3rd and 3/4s the amount seems to give best silencing.


bi22le - 25/6/20 at 09:51 AM

quote:
Originally posted by adithorp
How much acoustafil did you use? The online calculator is generally regarded as resulting in overpacking. Between 2/3rd and 3/4s the amount seems to give best silencing.


It was some time back so had to remember, probably over packed though by the sounds of, especially if the calculator is high. The stuff I took out was quite loose in there, and it expands from new looking like you are not refitting enough.

I think I'm going to rig something up secure but temporarily for the RR session, I can then see what the impact of having it on is.


peter030371 - 25/6/20 at 12:11 PM

I've seen this type of thing on Westfields and Caterhams for a BH GP trackday.
https://forum.wscc.co.uk/forum/uploads/monthly_2017_10/received_10155085851152877.jpeg.062835398f1d206026f6ff706250e7bf.jpeg

and this https://forum.wscc.co.uk/forum/uploads/monthly_2017_10/received_10155085851092877.jpeg.5e13b06208c981c5feedfb22a16b0fc1.jpeg

The same day some had these https://www.facebook.com/221277681273020/photos/pcb.1821222317945207/1821222254611880/?type=3&theater

So your plan is not so daft


HowardB - 26/6/20 at 07:36 AM

JeffW had a good solution on his car,. there was a flexi coupler inside the wheel arch and then another silencer,.

I am not sure if he is still on here, his photo archive may still be around.

hth


peter030371 - 26/6/20 at 08:56 AM

quote:
Originally posted by HowardB
JeffW had a good solution on his car,. there was a flexi coupler inside the wheel arch and then another silencer,.

I am not sure if he is still on here, his photo archive may still be around.

hth


From memory I think he found that the tyre on that side ran a lot hotter than the other side and that was just on short sprints.


HowardB - 26/6/20 at 09:11 AM

quote:
Originally posted by peter030371
quote:
Originally posted by HowardB
JeffW had a good solution on his car,. there was a flexi coupler inside the wheel arch and then another silencer,.

I am not sure if he is still on here, his photo archive may still be around.

hth


From memory I think he found that the tyre on that side ran a lot hotter than the other side and that was just on short sprints.


That makes sense...