Flipz

Evening all,

It all started a week ago when my JapSpeed exhaust started rattling, sounded like it was hitting the sub frame or something - I looked underneath the car and all was well, not hits and it just sounded like it was coming from inside the exhaust itself. Everyone refused to believe me and said it was a heat-shield or something, so I popped my OEM exhaust back on. Low and behold - no rattle. Ebay exhaust, meet my friend - the bin.

I've been wanting to get rid of the CrapSpeed exhaust for ages anyway and pretty much decided on the Tanabe Medallion Touring, but just can't really justify the expense at the moment when I'm (supposed to be) saving for my wedding.

The main reason I wanted a new exhaust was to quieten the whole thing down, no drone when cruising and a nice note at WOT. The misses moans like crazy and it wakes her up every morning it's a nice day and I decide to take it to work.

The obvious choice ended up being to modify the OEM exhaust with a UK exhaust mod, heard loads of them (online and in person) - think they sound great, quiet, deep and drone-free. So, today I picked it up from the shop today after having the mod on the mufflers along with the centre silencer and resonator removed.

The car sounds quite nice at tick over, deep note and rumble but not a big fat drone like the old ebay exhaust, so that's nice. The issue comes when driving it, it's so freaking loud!!! I mean, really bloody loud, and severely obnoxious! There's a dual carriageway by my mates house and he could hear me from inside his house, over half a mile away. It sounds great from inside the car (if you like that level of exhaust noise - I do to some extent, but it's not what I want for this car, at all), but as soon as you let off the accelerator, cue major horrific rasp. How on earth has this happened???

A few things to note:
- I have all the mods in my signature
- There's no cat
- The workshop used 32mm tube for the muffler mod

So I guess this is all a VERY long winded way of asking - If I only put the cat back in, will it really hold back the noise that much, or have I made some horrible mistake by pairing up my mods with a UK exhaust mod? Anything else I can do to throttle this horrible rasp and reduce the volume?

Chuck S

No surprises here since you removed the primary muffler (resonator) in the mid pipe and bypassed much of the exhaust at the rear. My understanding of the so-called UK exhaust mod is it bypasses part or all of the muffler (depending on the diameter of the tubing used).

Here's the stock muffler. The UK Mod bridges the intake on the upper left and connects directly to the output pipe down the center.



Sound level with this mod is controlled by the diameter of the bypass pipe which sends some noise directly out the tailpipe.

The OEM cat also muffles sound a bit so the combination adds noise. Easiest test is to refit the cat and see how it sounds. I suspect you'll have to refit the primary muffler (resonator) too. And I'm guessing you removed the little resonator pipe sticking out the side of the mid pipe too.

Quibblers will (correctly) argue the resonator is not a muffler. It just cancels out certain frequencies. Cancels? Muffles? Same effect.

-- Chuck

martin j

Not having heard this I suspect that you may have overdone it by removing the centre box and the resonator at the same time, I personally would have gone one stage at a time and then have been able to judge when enough was enough, i'm sure someone who done that been there will be along soon to correct me (or agree, shock horror), at least you may be able to rectify it if you wish.

Nottm_S2

You can buy a stock exhaust for peanuts as people arent that fussed with them, there's one in my shed for an 01

So you could reverse it that way. it really depends what the garage did.

i did an exhaust mod on an M3 and it made it pretty loud and sounded good without being silly (stock they dont even sound like a v8)

Flipz

Oh boy, this is frustrating. I definitely agree, I should have done it one stage at a time. I should be able to get the mid-silencer back from the garage and have it refitted. Probably cheaper than modding another exhaust (maybe). I think I'll try the cat first but I suspect this won't make the difference I want it to.

edi57

I have a standard OEM exhaust, virtually new condition, happy to sell for not much if you'd like it.

I did the UK exhaust mod, 38mm. I still have the cat, mid section and resonator, just the 38mm link pipes added before the silencers.

I was surprised at how muted the car still was. It's not really much louder at all. Anyone who didn't know any better could easily believe that it hadn't been modified. The difference is that the car has a mildly sporty note to it. For me, it's perfect. It's not over the top, just really pretty sensible.

kw_21

Personally I think the exhaust mod and a decat is all you needed. Very nice tones all through the rev range and certainly not obnoxious.

Mike RT4

^This .

Car sounds a little deeper, a few more dB (92 at 6000rpm), no drone and quiet as stock at steady state throttle.

unclefester

It doesn't bypass the exhaust silencer, it just provides a secondary more free flowing route for SOME of the gas to go via. That's why it's quiet at low RPM and louder at higher RPM without being offensive.

Chuck S

See the photo I posted earlier of the stock muffler cut open. The central pipe leads to the outlet at the bottom center of the photo; all the muffling is done between where the exhaust enters in the upper left of the photo and before the exhaust loops back around to the outlet pipe.

The UK Exhaust Mod runs part of the exhaust directly to the muffler outlet without going through the section that muffles the sound. Call it a by-pass for want of a better word. The amount of exhaust bypassing the muffler section of the muffler depends of the diameter of the bypass pipe. I'm guessing the muffler input pipe is about 50mm ID so a 38mm ID bypass is sending almost 80% directly out the exhaust outlet without going through the muffler part of the muffler. Change the math as you need to. For example of the inlet is 60mm a 38mm bypass will still be sending 63% straight out the back.

-- Chuck