DIY Track Silencer for Exige 380/410
Discussion
I've had a few people ask me for details of my home made track exhaust, so I thought I may as well do a detailed post about it for people to copy or use as a basis for their own designs.
I knew when I bought the 410 that it would be too loud to take on track as standard. But once I had the car I really didn't want to change the standard exhaust. I love the Jekyll and Hyde nature of it between quiet and loud mode. I looked for add-on solutions but the only thing I could find was the Komotec dB eater. This was an option but I couldn't find any real feedback about it. It also was quite expensive and didn't look as if it would reduce the noise significantly.
I decided to have a go a making my own add-on silencer. I only really had two design criteria when coming up with it. 1) It must not be restrictive or increase back pressure. 2) It must be quick and easy to fit / remove. On top of that, cheap would also be nice. Good looking? Well, no, that was never going to happen. If you care about how good you look on track, you should probably stop reading now!
There are three main components used in the exhaust:
A universal silencer. This is a straight through design and of the same bore as the main exhaust system, so no restriction at all.
A 90 degree elbow. This is direct the exhaust gasses / noise towards the ground and help with the drive by readings.
A reducer piece. This is to allow the add on to slide inside the existing exhaust pipe.
The silencer is this one: https://www.demon-tweeks.com/uk/jetex-universal-exhaust-silencer-243999/
Options as follows: Material: Aluminised Steel. Size: 3 inch. Case shape: Round. Case length: 250mm
The 90 degree elbow is this one: https://www.demon-tweeks.com/uk/jetex-tight-exhaust-bend-244008/
Options as follows: Material: Mild Steel. Size: 3 inch.
The reducer is this: http://www.everyexhaustpart.com/cart/76-2mm-3-od-to-69-85mm-2-3-4-id-exhaust-reducer-expander.html?search=69.85ID-76.2OD
Options as follows: NOT slitted. (both ends) Material: Aluminised Steel. Reducer length: 6 inches.
I then cut down one end of the universal silencer ready for the 90 degree elbow to be welded on later.
The next stage was (for me) the most annoying and time consuming. The larger end of the reducer piece will fit perfectly inside the new universal silencer. But the other end will not fit inside the Exige tailpipe. I bought that particular reducer because it was the closest I could find at the time. To get it to fit I gradually ground down material from the outside until it would slide in and out of the Exige tailpipe. You want it to be a reasonable fit, but not too tight.
I measured the inside diameter of the Exige exhaust at 73.25mm. My ground down reducer end up with an outside diameter (OD) of between 72.5 and 73mm depending on where you measure. This is where somebody else doing it could save some effort. Either try and obtain a custom reducer with an OD of around 72.5mm, or just ask an engineering company to stick the reducer on a lathe and do it. It would take them only a couple of minutes.
Once that is done, the reducer pushes fully into the universal silencer and is welded up. (note that in the photo below I've just temporarily rivetted it in place)
That is the track silencer itself done.
The final stage is how to safely mount it. One way would be to drill a hole in the bottom of the Exige exhaust and then bolt it in place. I wanted to avoid this if possible, so I came up with a fixing bracket using 1.5mm thick mild steel plate which I got from ebay. This but could be done more neatly now that the final dimensions are known, but I made a 'bridge' which I could bolt different bracket designs to:
You can see at the end of the bracket there are two small holes. These are to attach exhaust springs to. Here's looking from the end:
The springs used are 85mm exhaust springs like this: https://www.ebay.co.uk/itm/165155566861?hash=item267409f50d:g:iYIAAOSwq1NfItQo
The bracket design itself is not too critical. You could do similar to me, or weld it, do whatever works for you. The important bit really is where those two holes end up in relation to the pipe which goes inside the Exige exhaust. To help with that I took a few photos with a ruler as a reference. As long as its within a couple of millimeters or so it should be fine. The springs allow a bit of variation.
After all of that, this is the finished welded product. (With a bit of high temp black paint to make it look slightly less rubbish)
To attach it to the car you simply slide it inside the existing tailpipe. You then hook one end of the spring behind the Exige tailpipe (the side towards the front of the car) and then pull the other end through the holes on the bracket. A spring puller tool like this makes that easy: https://www.amazon.co.uk/Exhaust-Vehicle-Springs-Removal-Installation/dp/B0953W1NH2/ref=asc_df_B0953W1NH2/?tag=googshopuk-21&linkCode=df0&hvadid=534929732553&hvpos=&hvnetw=g&hvrand=6627173027298517969&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1006893&hvtargid=pla-1389651189987&psc=1
This shows a close up of how it's installed:
And that's it. Takes about 30 seconds to fit / remove and needs no tools other than the spring puller.
And finally, here's how it looks on the car:
Ok, so it's not pretty. But is it effective?
On my first day at Snetterton I initially went out on track without it fitted. As soon as I started to push a little harder I got black flagged for noise. 94dB drive by with a 92dB limit. I fitted my track silencer and had no more issues for the rest of the day. So all I can with any certainty is that is reduces drive by levels by at least 2dB.
At Donington Park I fitted it straight away as I've heard they can be quite strict. All I can say is that I had no issues all day, even when passing other cars on the straight where the microphone is.
Cadwell Park, well they actually let me 'pass' the noise test with a warning to 'be careful about noise' without the add-on fitted. So you would definitely be safe there WITH it fitted.
My final track day at Snetterton was the first time I'd actually had a proper static noise test all year. I told them the rev limit was the higher sport/race limit of 7000rpm as I wanted to get a 'worst case' reading for future reference. I think they told me told hold the revs at 5250rpm. My static result was 99.9dB, which I believe is quite a bit lower than a standard car would make.
In summary - circuits with a 105dB static and 92dB drive by should be fine. Donington is fine. I reckon Brands Hatch would probably be ok. Bedford Autodrome MAY be possible, but I wouldn't count on it. Goodwood and Thruxton are probably still off limits.
Overall I'm really happy with it. Yes it looks a bit funny, but it means I get to keep my standard exhaust (which I love) on the car the whole time. It also cost less than £100 in parts, which is a hell of a lot cheaper than a new exhaust.
I knew when I bought the 410 that it would be too loud to take on track as standard. But once I had the car I really didn't want to change the standard exhaust. I love the Jekyll and Hyde nature of it between quiet and loud mode. I looked for add-on solutions but the only thing I could find was the Komotec dB eater. This was an option but I couldn't find any real feedback about it. It also was quite expensive and didn't look as if it would reduce the noise significantly.
I decided to have a go a making my own add-on silencer. I only really had two design criteria when coming up with it. 1) It must not be restrictive or increase back pressure. 2) It must be quick and easy to fit / remove. On top of that, cheap would also be nice. Good looking? Well, no, that was never going to happen. If you care about how good you look on track, you should probably stop reading now!
There are three main components used in the exhaust:
A universal silencer. This is a straight through design and of the same bore as the main exhaust system, so no restriction at all.
A 90 degree elbow. This is direct the exhaust gasses / noise towards the ground and help with the drive by readings.
A reducer piece. This is to allow the add on to slide inside the existing exhaust pipe.
The silencer is this one: https://www.demon-tweeks.com/uk/jetex-universal-exhaust-silencer-243999/
Options as follows: Material: Aluminised Steel. Size: 3 inch. Case shape: Round. Case length: 250mm
The 90 degree elbow is this one: https://www.demon-tweeks.com/uk/jetex-tight-exhaust-bend-244008/
Options as follows: Material: Mild Steel. Size: 3 inch.
The reducer is this: http://www.everyexhaustpart.com/cart/76-2mm-3-od-to-69-85mm-2-3-4-id-exhaust-reducer-expander.html?search=69.85ID-76.2OD
Options as follows: NOT slitted. (both ends) Material: Aluminised Steel. Reducer length: 6 inches.
I then cut down one end of the universal silencer ready for the 90 degree elbow to be welded on later.
The next stage was (for me) the most annoying and time consuming. The larger end of the reducer piece will fit perfectly inside the new universal silencer. But the other end will not fit inside the Exige tailpipe. I bought that particular reducer because it was the closest I could find at the time. To get it to fit I gradually ground down material from the outside until it would slide in and out of the Exige tailpipe. You want it to be a reasonable fit, but not too tight.
I measured the inside diameter of the Exige exhaust at 73.25mm. My ground down reducer end up with an outside diameter (OD) of between 72.5 and 73mm depending on where you measure. This is where somebody else doing it could save some effort. Either try and obtain a custom reducer with an OD of around 72.5mm, or just ask an engineering company to stick the reducer on a lathe and do it. It would take them only a couple of minutes.
Once that is done, the reducer pushes fully into the universal silencer and is welded up. (note that in the photo below I've just temporarily rivetted it in place)
That is the track silencer itself done.
The final stage is how to safely mount it. One way would be to drill a hole in the bottom of the Exige exhaust and then bolt it in place. I wanted to avoid this if possible, so I came up with a fixing bracket using 1.5mm thick mild steel plate which I got from ebay. This but could be done more neatly now that the final dimensions are known, but I made a 'bridge' which I could bolt different bracket designs to:
You can see at the end of the bracket there are two small holes. These are to attach exhaust springs to. Here's looking from the end:
The springs used are 85mm exhaust springs like this: https://www.ebay.co.uk/itm/165155566861?hash=item267409f50d:g:iYIAAOSwq1NfItQo
The bracket design itself is not too critical. You could do similar to me, or weld it, do whatever works for you. The important bit really is where those two holes end up in relation to the pipe which goes inside the Exige exhaust. To help with that I took a few photos with a ruler as a reference. As long as its within a couple of millimeters or so it should be fine. The springs allow a bit of variation.
After all of that, this is the finished welded product. (With a bit of high temp black paint to make it look slightly less rubbish)
To attach it to the car you simply slide it inside the existing tailpipe. You then hook one end of the spring behind the Exige tailpipe (the side towards the front of the car) and then pull the other end through the holes on the bracket. A spring puller tool like this makes that easy: https://www.amazon.co.uk/Exhaust-Vehicle-Springs-Removal-Installation/dp/B0953W1NH2/ref=asc_df_B0953W1NH2/?tag=googshopuk-21&linkCode=df0&hvadid=534929732553&hvpos=&hvnetw=g&hvrand=6627173027298517969&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1006893&hvtargid=pla-1389651189987&psc=1
This shows a close up of how it's installed:
And that's it. Takes about 30 seconds to fit / remove and needs no tools other than the spring puller.
And finally, here's how it looks on the car:
Ok, so it's not pretty. But is it effective?
On my first day at Snetterton I initially went out on track without it fitted. As soon as I started to push a little harder I got black flagged for noise. 94dB drive by with a 92dB limit. I fitted my track silencer and had no more issues for the rest of the day. So all I can with any certainty is that is reduces drive by levels by at least 2dB.
At Donington Park I fitted it straight away as I've heard they can be quite strict. All I can say is that I had no issues all day, even when passing other cars on the straight where the microphone is.
Cadwell Park, well they actually let me 'pass' the noise test with a warning to 'be careful about noise' without the add-on fitted. So you would definitely be safe there WITH it fitted.
My final track day at Snetterton was the first time I'd actually had a proper static noise test all year. I told them the rev limit was the higher sport/race limit of 7000rpm as I wanted to get a 'worst case' reading for future reference. I think they told me told hold the revs at 5250rpm. My static result was 99.9dB, which I believe is quite a bit lower than a standard car would make.
In summary - circuits with a 105dB static and 92dB drive by should be fine. Donington is fine. I reckon Brands Hatch would probably be ok. Bedford Autodrome MAY be possible, but I wouldn't count on it. Goodwood and Thruxton are probably still off limits.
Overall I'm really happy with it. Yes it looks a bit funny, but it means I get to keep my standard exhaust (which I love) on the car the whole time. It also cost less than £100 in parts, which is a hell of a lot cheaper than a new exhaust.
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