Decat install blog post

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Nigel B
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Perhaps it's just me then? Laugh Strange. 
 

Peter, it must be the growl from your roller barrels, drowning out the exhaust noise! Thumbup

aerobod
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With the standard re-packable R400D silencer filled with Acousta-fil and no cat, I need earplugs all the time, Also, I can't pass noise regs set to <93dB at 15 metres at certain events I attend,  without an additional SuperTrapp exhaust silencer over the end of the tail pipe that I can fit or remove in a couple of minutes. The car does sound good and revs very freely with the catless exhaust config, though.

James

R400svn
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Well just removed track day exhaust frrom the 420 and put a side exit on and what a difference. Much better noise, nice flames and if say it feels quicker or certainly freer reving. Just the length of the trackday exhaust must cause some restriction 

aerobod
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For noise reduction on the track, those of us at the events I go to that are above the noise limits have elected to use either a removable or semi-permanent solution using SuperTrapp or similar discs.

My R400D requires 18 discs to give 5 to 6dB of attenuation, but also have a greater exit cross section between the disc pack than the pipe diameter itself, to eliminate any appreciable power loss.

My homemade device weights only half a kilo (including cone deflector and shield to prevent damage to the rear wing from hot exhaust that exits at 90 degrees to the normal flow). It uses 4 Allen bolts on the back to clamp two half-moon sections behind the rolled exhaust tip lip. Most people just have the SuperTrapp adapter either clamped with an exhaust clamp or welded on to the exhaust tip, removing the discs when not needed. Much lighter and cheaper solution than an add-on rear exhaust addition:

James

CtrMint
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I wonder if that would work on the 620R, letting me replace the rear exit for a side exit and also pass noise regs?

Caterham 420R S3 Lotus Toxic Green,  Caterham 620R S3 Exocet Red. Blog: https://www.caterham7diaries.com
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Although the supertraps are effective as regards noise they do affect the power, we did test on the rollers many years back.

Alan.gilford
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Hi R400svn, what was the part number for the silencer you fitted ? I have the rear exit exhaust and RBTB on a 420r. Just wanted to check the length is the same with the rear exit collector pipe.

Thanks Alan.

R400svn
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Hi Alan. I have an Sv but dont think the silencers are different but maybe the collector pipe might be. 
i purchased the polished 7 inch silencer re.380X0006A

i just looked at a couple of side picks of standard cars with the normal cats and the pipes a pretty similar length. I did notice when fitting it does not sit over the collector pipe quite as far as the old silencer but enough all the same. 
well worth changing over Sounds so much better. 
Only thing for me is i lime the look with the rear silencer. 

aerobod
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Although the supertraps are effective as regards noise they do affect the power, we did test on the rollers many years back.

It depends on the tradeoff of number of plates vs noise reduction.

With the standard 12 plates with the 2.5" SuperTrapp the power loss is noticeable on the R400D, feels like about 15% or so, but not measured accurately. I would estimate 6 to 7dB noise reduction, but not measured with the standard noise gear at the events. With 18 plates I'm loosing less than 2km/h at 160km/h on the track on a short straight with a 70km/h entry, which would equate to about 2% power loss / 4bhp. WIth 18 plates I dropped from just over 93dB to 88dB at 15 metres on the same day and same autocross course where I had to be under 93dB after receiving a warning.

With 12 plates the cross section of the gaps in the entry to the plates (0.5mm thick plates with 1mm gap between them) is 77% of the exhaust cross-sectional area, with 18 plates it is 116% of the area. I think 24 plates would be the maximum that would be possible to use, for 155% of the exhaust cross-sectional area and perhaps about 4dB of noise reduction.

James

James B
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Replying to #16

"I wonder if that would work on the 620R, letting me replace the rear exit for a side exit and also pass noise regs?"

Mark - I'd be confident that a Raceco would work well on your 620R.  I've got them on both my R500 and CSR and they are very effective.  And lightweight.  And look cool...

James