MODs to Akra db killer ???

[KEVINJSTANLEY]

Hi all
I have been running with the db out of the Akra...I do love it on town journeys however on a run it makes my head bang , now I could get ear plugs but I don't so I put DB back in.

IT IS FAR TOO QUITE.
So has anyone made mods to the db killer to give more noise, is it a case of some well placed holes drilled into the flat plate to allow more gasses out and hopefully noise.

any assistance would be good

kev

 

[addy]

http://www.motorcycle-talk.net/forum/mt-07-fz-07-modifications/369-removing-akrapovic-db-killer.html

Have a read of this thread, a few people trying different mods to the baffle. I personally cut the two inner pipes halfway and sanded down the large outer ring/plate to make it easier to get in and out and it's made a massive difference to the sound.

 

[KEVINJSTANLEY]

thanks Addy
I have done as you suggest and yes it is better...but not that grumble that I crave have you noticed that with the db in the bike at 80 mph just pulls better that with it out .

 

[da1kini]

thanks Addy
I have done as you suggest and yes it is better...but not that grumble that I crave have you noticed that with the db in the bike at 80 mph just pulls better that with it out .

yes, thats because the bike need a certain amount of back pressure to run right. With baffle out that pressure is reduced...

 

[FrostHazer]

yes, thats because the bike need a certain amount of back pressure to run right. With baffle out that pressure is reduced...

Back pressure works negatively,the lowest back pressure the best for the efficency of the engine. On the other hand if the exhaust gasses have a very high flow the engine runs lean so the fuel/air mix needs adjustment. So it will run much better if you take out the baffle ( lower back pressure and higher airflow) but increase the fuel% by a little in the injected mixture.

 

[Gee]

Took a hacksaw to my DB killer today and chopped off the swaged end, sounds a lot less obtrusive.

What a bugger trying to get the stupid screw back in tho!

 

[da1kini]

Back pressure works negatively,the lowest back pressure the best for the efficency of the engine. On the other hand if the exhaust gasses have a very high flow the engine runs lean so the fuel/air mix needs adjustment. So it will run much better if you take out the baffle ( lower back pressure and higher airflow) but increase the fuel% by a little in the injected mixture.

so...with the baffle is best cause you don't have to trim the bike at all....The akra system is made to suite the bike and therefore it runs better with the baffle in. No brainer.

 

[FrostHazer]

so...with the baffle is best cause you don't have to trim the bike at all....The akra system is made to suite the bike and therefore it runs better with the baffle in. No brainer.

I didnt said the opposite, i just said that back pressure isnt something that makes the bike run better, as many people believe.

 

[KEVINJSTANLEY]

Hi Gee and all

yes you are not kidding about that screw when you have chopped the internal twin pipe, lol

 

[Gee]

Kev,

Think i'm going to go down the local fasteners place and get a longer bolt and a washer, so that it sits on the exhaust outer instead of inside that recessed hole (thats what makes it bloody fiddly).Who cares if it makes a little mess of the outside of the exhaust because nobody can see it under there.

Will get a bolt with a normal bolt head instead of a allen head as this should be easier to remove/tighten if needed.

 

[da1kini]

I didnt said the opposite, i just said that back pressure isnt something that makes the bike run better, as many people believe.

No, but it need it to run as it should, not better just as intended. If you mod the exhaust or buy one not made for the bike the back pressure is changed. And then the bike does not run right.

 

[FrostHazer]

No, but it need it to run as it should, not better just as intended. If you mod the exhaust or buy one not made for the bike the back pressure is changed. And then the bike does not run right.

It doesnt run right cause the % of air compaired to the fuel is more than it should, with only an exhaust upgrade you'll have a better exhaust system with more airflow but the same amount of fuel in the air-fuel mix . If you want the max possible power for your bike you should modify it to have as low back pressure as possible at the rpm range you're using it more and you are interested it, but at the same time you should change air-fuel ratio.
If you dont want to change the air-fuel ratio for whatever reason (money i guess), is obvious that "stock" back pressure would have better results because air flow wouldn't be changed by much, so there wouldn't be a change in air-fuel ratio, so the bike would run good and very close to stock. That simple.
If you fit an aftermarket exhaust (especialy without baffle in) you decrease back pressure and the bike runs better (with ecu reprogrammed).

 

[da1kini]

It doesnt run right cause the % of air compaired to the fuel is more than it should, with only an exhaust upgrade you'll have a better exhaust system with more airflow but the same amount of fuel in the air-fuel mix . If you want the max possible power for your bike you should modify it to have as low back pressure as possible at the rpm range you're using it more and you are interested it, but at the same time you should change air-fuel ratio.
If you dont want to change the air-fuel ratio for whatever reason (money i guess), is obvious that "stock" back pressure would have better results because air flow wouldn't be changed by much, so there wouldn't be a change in air-fuel ratio, so the bike would run good and very close to stock. That simple.
If you fit an aftermarket exhaust (especialy without baffle in) you decrease back pressure and the bike runs better (with ecu reprogrammed).

or you could just by the akrapovic titan system made for the bike and leave the baffle in and then you would not need to change one thing because the back pressure is not affected. That is what I meant with my first post. Have no clue why you keep posting replys about changing or tuning ECu and stuff...
My first reply was to the guy buying a akrapvic titan and removing the db-killer and therefore affecting back pressure and then the bike would lose some performance...

 

[KennyNorge]

After riding 5100km with Akrapovic and Db-killer installed I decided to get some more sound.
The Akrapovic without db-killer is way to loud for my taste after 5min.
And this year sound pollution is HIGH priority for the police and the puplic roads administration, so got to keep the sound reasonable ;-)

Thank you all for sharing your methods
Looket at all your tips and went for the hole drilling. Starting with four 6,5mm holes and maybe adding more after giving it a good test

Had a quick spinn, sounds deeper on idle and more agressive with blips of the throttle. Don't notice big difference while riding, but got to give it some more time My wife have kept here Akrapovic orginal, so will test the bikes side by side tomorrow

 

[Gee]

Cut those flanged sections of the end of the inside pipes (last 20-25mm). Makes removal easier too.

 

[KennyNorge]

Cut those flanged sections of the end of the inside pipes (last 20-25mm). Makes removal easier too.

I was really considering it, but was affraid it would be to much. I grinded the innside of the flanged sections with a powertool, so removal is now easyer

 

[Donut]

I have cut down the inner pipes to:

a. produce more sound
b. make removal/replacement a lot easier.

I started with cutting about half way down the inner pipes and progressed to leaving about 1cm - the sound difference between the 2 mods is negligible, if any at all.

To make removal/replacement easier still I drilled a hole in the pipe and db killer (roughly opposite the original) and secured the db killer with an allen bolt/nut and spring washer which makes life a lot quicker and much less hassle to remove and re-fit.