Baffles

[AllanB]

A few days ago someone posted something about a baffle they had made "a first effort" as they put it and I can't find it. It looked as though it was quite well worked out as it resembled a stock/aftermarket part, not the usual bodges they do here.

I am looking to build a baffle for my NV400 and wondered where you got the science from.

I have read a lot on the internet of what needs to be done, but almost nothing about how to do it.

Ideas?

[Happy Grumpy]

Ideas?

Go to a Thai metal shop with photos from the internet and your bike.

[ktm jeff]

Allan , the info you seek , CB 300 f forum , page 32 . Exhausts are still something of a black art and you may have to have a few made , with different baffle volumes , to get a good one , that sounds right , and gives smooth results . The internal volume of the header pipe , and its diameter , and length , needs to work in conjuntion / harmony with the internal volume of the silencer / muffler . The muffler needs to be divided into ( sound ) chambers , in order to create negative pressure waves / pulses , that bounce back up the header pipe , pulling out the next lot of exhaust gasses , which , in turn , helps pull in the next intake charge . You will need to input many stastistics of your engine and your desired power output type ( power or torque ) and desired rev range . Without some serious mathematical calculations , you may be best having a few made and giving each one a try .

[AllanB]

Allan , the info you seek , CB 300 f forum , page 32 . Exhausts are still something of a black art and you may have to have a few made , with different baffle volumes , to get a good one , that sounds right , and gives smooth results . The internal volume of the header pipe , and its diameter , and length , needs to work in conjuntion / harmony with the internal volume of the silencer / muffler . The muffler needs to be divided into ( sound ) chambers , in order to create negative pressure waves / pulses , that bounce back up the header pipe , pulling out the next lot of exhaust gasses , which , in turn , helps pull in the next intake charge . You will need to input many stastistics of your engine and your desired power output type ( power or torque ) and desired rev range . Without some serious mathematical calculations , you may be best having a few made and giving each one a try .

Thanks, that is kinda what I planned on doing, there is a guy in Khon Kaen who has reasonable prices. When I bought the bike it had a straight through exhaust which failed the Thai MOT (lol) and ran really rough, but then there were other problems which are now fixed. At that time I had one made which was very quiet, but very restrictive, so I messed around with it quite a bit and it is buggad now.

So I think I will get 3 made all different designs.

Ideally I am looking for 3 features.

1. A so called "quiet baffle" design like yours which gives a nice low exhaust note.

2. A smoother running engine from the V-twin.

3. Some back-pressure, which coupled with a better air filter, will richen up the mixture and, I believe, maximise torque, even at the cost of a couple of horsepower.

This may all take a while, but the baffle is easy to fit and remove, if a little messy, when the soot gets everywhere.

[eeeya]

I've made several baffles and I can tell you its a black art. I made more than 20 modifications until I got it right for my bike.

Its quiet but slightly loud when I open it up. Sounds a bit farty though from exhaust pressure coming out of the rivets of the slip on exhaust.

The simplest explanation I can give is its a fine balance between choking the engine and letting it breathe too much.

For a 2 inch exhaust get a 1 to 1-1/4 inch pipe, weld up the back on it. Drill a few holes in the body of the pipe. Insert it into the exhaust (welded end goes in first) Ride it. How's it feel. Remove baffle pipe again.. Drill more holes.. Ride it again. Etc etc.

Too many holes will eventually let too much exhaust through and power will be lost. Too few holes and it will choke the engine and power will be lost. As for achieving a desirable tone.. Good luck with that (unless you like a raspy dirtbike sound)

If your getting someone to do it get a few made and go buy a drill.

Better still go see Mr ebay

As for soot.. Should be clean as a whistle when removed

Better off just ordering a long and short one from eBay first. These are adjustable and might be an easier fix than running back and forward to a welders shop

Edited September 2, 2015 by eeeya

[taninthai]

You do like to complicate things ,as poster above says measure the opening of the end of exhaust and then onto eBay.

[ktm jeff]

If the OP wants to build a baffle / muffler from scratch , which i believe to be the case , then he will need to design a muffler , ( or buy one ) , including internal chambers , then try different baffle "inserts" for fine tuning .

[AllanB]

This guy in KK can build me a slide in baffle for about 400 baht, so 3 will be pretty cheap and as has been said opening up and shutting flow down will find something close to what I want.

If not I will buy a couple more, since I cannot get the stock item.

.....oh and some Fairy liquid to clean my hands....literally a black art.