Yamaha FZ-09 Forum banner

1 - 3 of 3 Posts

·
Registered
Joined
·
393 Posts
Discussion Starter · #1 ·
Took the DB insert out of my Akra today, and OMG its loud! Its OK when up the revs a bit but extremely deep when in lower revs. A couple of people on a UK forum have modified they're inserts which seems to give a sound somewhere between having the insert in and having it out. Was thinking maybe I'd do this but can anyone see any adverse effects that might arise from doing it? The thing that concerns me is that when the insert is in (in stock form), the gas has a nice smooth exit as intended, but with a modified insert in place the gas kind of has a flat surface/wall it now hits which could maybe force it back the wrong way hampering the flow and maybe causing a loss in performance or a heat build up?

Stock insert (item #6):


Modded insert:
 

·
Super Moderator
Joined
·
5,734 Posts
I'm certainly not an engineer, but it looks like all that was done was to shorten or cut off the "extra length" on baffle part that sticks into the can. As long as the total opening size is the same, in my opinion it really shouldn't matter. I guess if you really got down to flow dynamics and someone did a calculation, there might be a bit of difference.....but again, I'm not an engineer so maybe someone on here can offer a more detailed/final answer. I do know that if you change the amount of flow through an exhaust system without changing the fueling, you will either richen or lean out the A/F ratio, depending on whether you restrict the flow or open up the amount of flow. Opening it up will lean it out, restricting it will fatten or make it a bit richer.....then it's time for a fuel controller of some sort/brand and a dyno tune for a map for that setup.
 

·
Registered
Joined
·
393 Posts
Discussion Starter · #3 ·
I'm certainly not an engineer, but it looks like all that was done was to shorten or cut off the "extra length" on baffle part that sticks into the can. As long as the total opening size is the same, in my opinion it really shouldn't matter. I guess if you really got down to flow dynamics and someone did a calculation, there might be a bit of difference.....but again, I'm not an engineer so maybe someone on here can offer a more detailed/final answer. I do know that if you change the amount of flow through an exhaust system without changing the fueling, you will either richen or lean out the A/F ratio, depending on whether you restrict the flow or open up the amount of flow. Opening it up will lean it out, restricting it will fatten or make it a bit richer.....then it's time for a fuel controller of some sort/brand and a dyno tune for a map for that setup.
Thanks, its a tricky one as we'll never know if the guys at Akrapovic made the db insert that shape/length to get the flow right or get the required db limit. Soon as I get a chance I'll be getting it dyno tuned anyway as you should with a more open pipe so maybe I'll modify the insert and leave it fitted when its tuned.


Sent from outer space
 
1 - 3 of 3 Posts
Top