Messing about with back box's

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appletree
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Post Thu Dec 03, 2009 8:55 pm

Been modding my exhaust again to give a bit better grond clearence.

the first one cought on the front section, the second one cought on the section under the rear beam as i'd left alittle to much clearence between them so ive mad it agin and got some decent clearence, the second one used to catch on country roads were the road was slightly dished.

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any way while i was messing around under there i noticed the back box had changed coulor is some strange places, both ends but not in the middle, so while it was off i cut the end and had a look inside.

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here is what i found ish... the gas has to change direction 180* twice to get out and were it changes direction is were its changed colour.

The red tubes are perferated and wrapped in wadding, the inlet being the top and the gray line being the flow of gas.

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The exhaust note has aways been abit raspy and resonating since the box was fitted and even more so now the bigger charger is fitted although its not bad sounding when it gets up there, i think its probly the gas going streight through the rest of the system ( no boxes ) and then hitting the back plate of the back box and bouncing back.

so to prove a point ive bought this cheapo cherry bomber thing for £55 of ebay to see what difference it makes to the sound, besides being stupily loud winkeye

Bit of a size difference
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Has any one made there own exhaust back box before and what construction was it? i think if the cherry bomber changes the note to a better one i'll make a stainless one with more packing and a 3"90* bend pointing down like a new derv style

Any thoughs on this tip style.

Somthing along the lines of this but possibly alittle more down swepped.

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M42 Supercharged 285bhp + M3 6speed box
GeoffBob
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Post Thu Dec 03, 2009 9:36 pm

Yeh, I've made cherry bombs before. Easy to do so long as you know how to weld. I usually just pack them with high-temp glass fibre.

This thread here should be of some help to you.

Also, take a look at http://auto.howstuffworks.com/muffler.htm
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baptie0
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Post Thu Dec 03, 2009 11:36 pm

Here is my creation, its 3 inch stainless perforated tube, straight through and I packed it with stuff called acoustafil.
sounds pretty good.
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appletree
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Post Wed Dec 23, 2009 5:07 pm

Just to up date this thread.

heres the cherry bomber ready to go on, nipped in to work and made up a short shection of pipework to join to my current middle section.

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heres two shots of it fitted to the car, dint look to bad either with the slightly smaller tip and with a nifferent design.

With this fitted it ment that this was the only silencer in the whole system, yep, nearenough streight through.

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Just to point out the axle stand isnt supporting the car on the driveshaft the weight is on the big jack behind the stand and it was put there just incase!

I new it was going to be loud and i only fitted it as an experiment to see if it changed the yone of the exhaust which it did, it also acording to the arse dyno lost power there was a definate dip in the acceleration.

short vid (turn your speakers down!)
[youtube][/youtube]
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You should never underestimate the predictability of stupidity

M42 Supercharged 285bhp + M3 6speed box