So why should I change from the stock muffler?

[fatenhappy]

I suppose its getting on towards a week now since fitting up the new cat delete to 'F3T' ... So today progression took me a little further down this road so at least now I get to make some adjudged decision about 'his' exhaust! ...

The stock muffler was dropped off today. Then I started to have a really close look at both the spec and uninterrupted / unobstructed through put possible of what I reckon it's capable of! I don't know probably all up it took no more than 30 minutes for the initial observations and measurements.

While doing this I also took a bunch of photos which I have since annotated so everyone can share the same.

I would suggest the numbers can't be fudged as they are proven mathematical formulae applied directly in relation to hard measurements. In the most part I used both internal or external micrometres as appropriate ...

So here are the actual stats ...

1) The standard 'long' muffler that I had fitted to the 2017 F3-T is 720 mm from tip to tail. There is one inlet with an I/D of 1.65" (42mm) ... There are twin outlet exhaust pipes each of 1.27" I/D (32mm).

2) The cat delete exhaust I have fitted has an exit / entry into the muffler (that can be any muffler) of 1.95" (49.63mm)

By measuring the maximum internal diameter of any section of either inlet air tubing or outlet exhaust, its possible to 'theoretically' work out the maximum rate of flow of gases for the same. That's even (supposedly) irrespective of the horsepower or pressure applied.. The caveat to this is, the maximum rate of flow is generally accepted to be 115cfm per sq inch of area ... These flow rates are also generally noted with a reference to sea level and ambient temperatures are assumed.

What are the restrictions and limitations of the thru put for this muffler ..... So for the inlet to the exhaust; (which I have chosen because it has the smallest cross sectional area in total of just 1.62" or 42mm) for the mufflers thru put. By applying simple maths, the maximum gases it can pass are when @ 245.89 cfm of thru flow. Converting that we come up with an engine being at 111.77 hp max flow applied. Now remember back to where I said I was also looking for any point or points of internal restriction. As it turned out, there is or are 'baffles' or a physical point of restriction approximately 1/3rd the way back from the exhaust tip ... Well that too is going to restrict the thru put of these gases even further. All I am able to deduce there is by applying a flexing length of thin material, it definitely faces a restriction at this point. And, I tried entry from both ends and both times found the same approximate point of restriction. The only way I know of to tell what is actually there would be to use something like an arthroscope or similar, which I don't have. My point here is if there is a manual restriction it will be a major restriction to the thru put of exhaust gases. In my own mind, I just can't see how even this number could be achievable.

What is the potential thru put then from the newly fitted cat delete: ... For this we simply do as we did previously and measure the outlet of the cat delete's I/D at its narrowest point. So 1.95" or 49.63mm ... If you do a quick comparison straight away right here between the stock mufflers inlet diameter that I had just taken off and this cat delete outlet's capability, immediately we can see a whopping <7mm choking difference in diameter right at the entry point to the (rear) muffler. You'll see in just a second just how dramatic this becomes ... This time when we do the maths our max applied flow rate comes up to 343.43 cfm, of thru flow, which converts to 156.11 hp maximum flow applied under the same conditions ...

Unbelievably almost ... that's in excess of 40% difference of potential .... So right there is my answer. After all I am looking to free up the thru put of gases or at least the potential for them to be unlocked as we go along..

So what's on for my next crazy adventure ... Why buy a manufactured muffler at up to a grand a pop? ... Why don't I have a go at building my own ? I already know the minimum diameter I require ... I also know I must quieten down the exhaust as well, but I am also looking to not restrict it 'too' much ... Hope you enjoy the photos attached ...

[Peter Aawen]

Hey Fatenhappy, great work on that lot; the bad news is that over here in Aus, our F3's get to run exactly the same stock muffler as the 1330 RT's; but over there in Nort America, they get a whole different selection that they can choose from!

[fatenhappy]

Hey Fatenhappy, great work on that lot; the bad news is that over here in Aus, our F3's get to run exactly the same stock muffler as the 1330 RT's; but over there in Nort America, they get a whole different selection that they can choose from!

All good Pete ... I have what I have and I am happy with it, so that's what I have to work with as the starting point ...

The later just came to me this arvo when doing this other stuff as to why not have a go at building a 'performance' or and 'straight thru' type muffler ...

I have seen some of the deborturous crap by 'some' back yarders ... I know I can do way better and if not, I'll happily swallow my pride and go buy a production silencer!