Modifications started… but a question?

Viewing 8 posts - 1 through 8 (of 8 total)
  • Author
  • #37407

    Hi Everyone,

    I have started modifying my 2021 Vitpilen 401. Things I have currently done are as follows:

    1. Added an Arrow Pro-Race Nichrom Slip On Exhaust

    2. Replaced the mid-chamber pipe with a Comp Werkes Chamber Delete

    3. Pending (waiting on delivery) on a Stage 2 DNA Air Filter (as suggested in this group)


    So far the bike sounds like a weapon, and runs GREAT!!! VERY VERY HAPPY WITH IT!!!

    Next on the list (to be done at the same time):

    1. Rapid Bike Fuel Module or ECU (currently talking to a local dyno tuner for advice)

    2. Arrow Racing Header/Collector Pipe

    3. Modified Stock Airbox (intake runner modification)

    I will keep everyone posted on how everything goes…..


    What I am interested in finding out from the group is as follows:

    Question: Have any of you ‘just’ installed a slip on exhaust and a chamber delete and NO FUEL MODULE or ECU update? If yes have you had any issues? Mine is currently like this and runs like a dream, no stalling etc. Keep in mind I own a 2021 model Vit 401.

    The reason I ask is I initially planned on adding a Coober ECU, thinking an ECU or fuel module was all I needed, but when I reached out to their tech support team (who are VERY VERY HELPFUL) they advised that I would need more than a programable tuner to support a header and mid chamber delete.

    They have advised that, I would need someone to line up my intake and exhaust and said:

    “If you remove all restrictions from your exhaust, then you need different cam shaft to keep your mixture inside the chamber. As long as you have any kind of restriction on exhaust, you can use a Coober lm ECU”.

    Now, considering I have a 2021 model, and I CURRENTLY have the stock header which has a CAT in it, is that not a restrictor?

    If, simply keeping the stock header pipe, and then deleting the mid-chamber with a Comp Werkes pipe, is bad for the bike then I am curious how everyone else has dealt with this mod? Surely heaps of members have done this???

    I would have thought simply adding a fuel module, or programable ECU would be sufficient, but based on the Coober reply I would need to do more… the comment on the cam shaft has me confused…

    Have many others changed their cam shaft, off the back of a main header pipe swap and a mid chamber delete? Keep in mind I have a 2021 bike, which has a cat in the main header pipe (as opposed to earlier models which had a cat as a seperate pipe between the chamber and the header.

    Any thoughts from anyone would be greatly appreciated….

    Either way I am currently talking to a local motorbike dyno tuner, who will provide me with advice which I will share.

    Thanks experts.


    If the cat is in header. You should be good .


    Did you installed the slip on and the chamber delete at the same time?

    If not, did you noticed any improvements after adding the second mod?


    That is what I am thinking..

    I will add in the DNA Stage 2 air filter over the next few days and see what happens. I am also about to order a RapidBike Easy to hopefully get ahead of any fuel/air mix ratio issues… so far with just the Arrow Pro Race exhaust and Comp Werkes mid chamber delete is sounds and runs awesome.


    LuisLAN, I did them both at the same time! BUT I am 100% sure the mid-chamber delete has made a big difference. You can feel the bike breathe better, and it also sounds a lot more throaty/deeper! I am very keen to see if the DNA filter adds to this. In a week or so I will try put up a sound clip.




    I am running a Werkes cat delete, Fresco Ultra Shorty exhaust setup with K&N air filter, Coober air box cover, and Coober ECU.  Bike runs AMAZING!

    Had the same setup before the Fresco, but with a straight pipe exhaust instead. It lost mid range power.  Possiblity due to the lack of back pressure like you mentioned before.

    Also heat wrapped exhaust header and swapped to a 70/30 mix on water/coolant with Water Wetter to combat the hot temps.Fresco


    Sorry, slightly unrelated, Competition Werkes chamber delete on the 2020 onward (the one the header runs under the engine), does yours touch the side stand pivot? Or does anyone’s? Mine does. It’s not touching while the stand is up, but it scrapes as it swing up/down. Does yours do the same?


    JB, Yes, mine nearly touches it…. it did concern me slightly at first, but it is totally fine!

    I will try to take some pics.

    FYI for anyone interested. I have since added a RapidBike Easy and the bike runs so good!

    Very happy with it.

    Now just waiting for a silencer bracket to remove the rear foot pegs.

    I will post some pics soon.

Viewing 8 posts - 1 through 8 (of 8 total)
  • You must be logged in to reply to this topic.