Silencers

[erictharg]

OK - so we all know that the stock factory silencer is borderline for any event where noise is checked. Since the new cam I'm now officially over 105 dBA, which is not good. I've got Thermal Velocity packing and two small perforated half moon deflectors fitted but I've reached the limit of what the small stock silencer can do.
As an interim I've ordered a stock Jetex oval silencer that is somewhat bigger in volume (more like a 6.5" x 4" oval, ilo the stock 5" x 3") and is cheap enough at £42. But I'd like someting a bit prettier and I suspect lighter.
The Eleven can easily take a longer silencer. 24" or 26" long would be possible. I'm thinking 4.5" / 115mm round and longer would be the most elegant and lightest. Anyone out there played around with alternatives? Any recommendations? AA silencers in Stafford qouting £200 for a repackable mild steel 5" x 20". That's too much for a basic piece of kit for me. I'd sooner mess about and make up the 4.5" x 24" concept myself.
Adam - any idea where you got the longer oval you run?

[adamwilkinson]

From memory ours is about 8" dia. and around 30-36" long (i think). Aluminium outer with steel end caps and ss perforated pipe within. Allymally on here made ours i believe.

[jonclancy]

Indeed - I was 99.9db at our recent track day.

I love the stock silencer - it's a thing of beauty. Pity it's about 10db to loud!

[jonclancy]

I've just emailed Simon Westwood to ask who makes the stock silencer and if there is any chance of re-speccing the kit exhaust to make it more track friendly.

I'll pass on any info when I get it.

[jonclancy]

BTW, how about a silencer body folded to follow the lines of the pontoon? Need to go and study my car to see if this might actually work, or if the space available is too small.

[LA 11 builder]

I would look into some of the mufflers used on large motorcycles, like a Hyabusa or the like. Also there are some older BMW mufflers that are square (4cyl. Bikes) or triangular (3cyl. Bikes) that might fit into the pod. Anything off of a 1000+cc bike should flow enough for any A-series.....

Food for thought.....

[Westfield 129]

The muffler I received with my RHD car is a motorcycle unit. It's pretty quiet when compared to the Maniflow I am using on my LHD car.

On one of the local 11s, we replaced the 14" muffler of the same type I have on my car, with one of the same type that was 18" long. No change in the loudness, but the tone was a bit lower.

The latest motorcycle units have catalytic converters built in, so they might be VERY expensive, and the after market accessory mufflers are just loud.

The really quiet BMW mufflers that might work have the converters built in, so they would not be applicable. Same for the latest Hayabusa mufflers, though some after market bike muffler might work.

Perhaps if the exhaust pipe is pointed down.

There are other kit cars in the UK that probably run into the same problems. Caterhams use side mounted mufflers, and maybe one of those would work.

[jonclancy]

Guys, I have received a very helpful reply from Simon at the Factory regarding this. You were barking up the right tree with talk about motorcycle silencers.

I've copied his reply below. Hopefully there is an easy fix to the problem. I'm sure the "louder" cans will have a market on the Boardroom, to lessen the pain of forking out a wad for a nice new one.



"I will speak to our exhaust manufacturer and see what he can do. The silencer on your car is the same as the silencer we use on the Honda Fireblade cars.
What I was thinking that we could use the silencer we fit on the Hayabusa powered car which is similar but longer, downside is we would need a reducer as the silencer input is bigger that the manifold fitted to your car.

Let’s see if the manufacturer has any ideas."

[jonclancy]

CROSS-POSTED to both forums and both lists.

Folks,

As some of you have found, the stock XI silencer that comes with the kit is marginal when tested for noise limits for track work.

My own experience was that the 100dB(A) / 4500rpm / 0.5m limit for my recent track day was only *just* achievable. Other drivers are up to around 105dB(A).

I contacted Simon at the factory regarding the set-up, and enquired whether it was possible to offer a slightly quieter option in the same style and quality as the current silencer.

I have posted this to the two XI forums and two Yahoo lists for your consideration and discussion.

Is there a demand for a longer silencer as a kit option? Do XI drivers who have not partaken in a track-day, let alone racing, see this as an issue at all?

Please feel free to discuss and state whether you might be interested in a quieter version. I’ll collate the numbers and feedback from you all and send it back to the factory for further consideration.

Best wishes

Jon

P.S. Having tracked No 42 this Summer, I can highly recommend you try it out. Best hundred quid I have spent in a long while!!!



Edited discussion points:

Noise levels on the limit.

XI will fit a longer silencer box no problem.

Compliant levels might encourage more owners to try out at a track day.

Prefer not to try and bolt on an extra silencer section for the day.


Current silencer is same as that fitted to Fireblade powered cars. Hayabusa can is longer but has lager diameter inlet.

Could manufacturer use Honda input on Hayabusa box?

We need to know if there is a demand for this – manufacturer would need to make a batch of 5 silencers to make it economic for buyer. One-off would be VERY expensive.

This is the first time this issue has been raised. (Comment, probably due to face most XI never see the track).

Not going to see the kit silencer re-specced, as it would be an extra cost and kit price has been help at under £10K since 2009. Would need to be offered as a kit option at extra cost.

[LA 11 builder]

Regarding the cost, I was thinking of sourcing the silencer from a moto wrecking yard or CL. These stock systems are routinely replaced by aftermarket products by many people.