Custom air intake for 390 KTM big gains expeted !

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    If some people are interested “Gray Area KTM” is selling a new air box who show hudge gains at high rpm !

    Reffering to the manufacturer part number, the vit and the duke have the same air box ( the seller has checked), so it should fit for us !

    I ordered it already, i’ll keep u posted.

    ( !! You need a Piggyback to get the benefit of it and you may damage your motor without by running to lean)



    Definitely interested in this one. Did you already install a piggyback (or Coober or any other fuel controller) or will you be installing both at the same time? Do you know if there are special maps available to cope with the extra air? Did you consider going all the way and also adding a decat pipe?

    I find that the performance gains of an ecu only (whatever brand) are not really significant on small engines like the 401’s (just a personal opinion), but with an improved air intake we start talking serious business.

    If I look on GreyArea’s website, I am not sure to read the graphs correctly and I would be interested to compare the results with the stock engine, but it seems to me there is a lot more torque coming lower in rpms (as soon as 3.000 if I am not mistaken).

    Anyway let us know when you have installed this thing, I am sure all are pretty interested in the results.

    • This reply was modified 2 years, 4 months ago by Avatarelbastos.

    What mods are done to the airbox and what is the cost?


    rod frostrod frost

    Here is a thread from the KTM 390 Duke forum from a 390 mod using the same air intake etc. plus some other mod which may be compatible with the 401 (post 149 of 167)


    Thanks Rod

    I tried this and could not get it to work as smooth as i wanted to. The bigger injector may be  what i need to make it work.


    @Elbastos : For now my bike is modded like this :

    -DNA Air filter

    -Mivv suono pipe (decat), stock muffler

    -power commander 5 with a custom map made by a tunner ( first map for the Vit he said : Worldwide 🙂 (joking) ). My bike is also equip with something that cut the signal the from the lambda probe.

    The air box isn’t shipped yet so i couldn’t tell you anything about it 🙂 (look for CDN duke’s post on the 390 forum, he has tested it). Concerning the low rev, i’m affraid there’s no gain with this mod.

    If you’re looking for torque you should look on the ecu side (Cobber, PW5 etc…) and if you’re only looking for torque, i think you can stay with the stock parts (filter and exhaust). I will go for the coober in that case : from what i understood it is “tailored” for the stock bike.

    : I’ve seen that you have a cobber and work closely with them.

    From what i understand, the cobber is a fixed map richer than stock ?

    How the cobber can adapt the AFR with new parts ? When you say that the injector is the limiting factor, this is make me thinking that the cobber is able to send a signal that is using the full capability of the injector ?

    I a kind of a newbie in those parts and i tend to think that the PW5 offers much flexibility ?  ( and way less reliability )! I’m a bit lost !














    Just to say that this airbox has a shorter air intake inside. It makes a big difference, awsome top end ( the power grows till the rev limiter) and pretty unoticable loss in low rpms. (and it fits like a charm)

    • This reply was modified 2 years, 2 months ago by AvatarJeanfons.

    Hi Jeanfons

    How much hp are you making with your set up and what is your top speed.

    • This reply was modified 2 years, 2 months ago by AvatarVp-1.

    Hi Vp-1,

    Well the dyno tester didn’t gave me the result !! ( oh sorry i didn’t print them, he said….).  I really struggled to find a good dyno tuner here. ( i just installed a WBC2 auto tune on the bike).

    On the RC390 forum, another guy showed a whole 5 HP gains with also a larger injector (tuned graph before and after).  You can also find some tune results on the Gray area website.

    From what i’m feeling it really expend the range of the “usable” rpms. After 5500 rpm, it is a more agressive behaviour, the bike will pull more and more till the limiter. It’s a very nice feeling !

    It also changes the sound, you can hear the air being aspirated at high rpms!

    As for the top speed, i never push the bike that far yet. But i already push it to the rev limiter in fith and it came easily. I’m 99% sure it will hit the rev limiter also in 6th.

    I’m in 15X43 witch is still a bit short regarding my cruising speed (120 kph and i’m around 6k rpm). ( I think the best will be 16X44 or 15X41-42)




    can u tell me what model powercommander v u have? And did it fit perfect or did u have to do any modifications?


    better pics here from rc390 version

    I don’t know how they can claim such high gains, so it just increase more airflow ? how is this different than the airbox cover from coober.


    Yes it is really different ! The difference is inside, the tube inside is shorter, you can also ad the coober lid on top.

    This is still the biggest improvment to my bike so far in terms of performance



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