KTM Duke 390 Airbox Upgrades: What you need to know!

If you are considering upgrading your airbox and want to know more than just changing the filter and airbox lid then here are my thoughts on what you can and what you should consider
Further information on my website: www.motomirius.com
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Now, I’m just a normal guy who likes working on bikes; I’m not a qualified mechanic but I’ve spent a lot of time working on bikes and most of the servicing you see is directly from the manufacturer workshop manuals. I like to show you interesting things you can do and that I’ve done with my bikes, but I can’t promise you that anything I show you will work on your bike as not everything is always exactly the same. Be careful not to harm yourself, anyone else or your bike and always be aware that if you have a warranty then changing or working on your bike can invalidate it - they do love an excuse not to have to pay out. If you have any doubt then talk to a qualified mechanic or engineer and make up your own mind.

[@MattTofield]

Thank you, I have learned so much from your video.

[@MotoMirius]

Glad it was helpful!

[@JerryR390]

In my case i modified a Bajaj 200ns, fitted a 390 engine on it, i had no space for either air boxes NS nor 390, so i run the 390 intake runner plus an air filter and modded exhaust i have a power commander to add more fuel, my engine is 2015 and had blown about 4 headgaskets. Now im sourcing a 2017+ cylinder and head to benefit from the updated design on coolant flow and i also have a bigger radiator fitted. There is a version of the 200 NS that is fuel injected maybe i can use the air filter from it since is the same chasis than my carburated NS.

[@MotoMirius]

Sounds like you are having a lot of fun. Sounds like a great project!

[@realzeti]

Thank you for wealth of information in this regard. I have KTM 390 Adventure, and was considering filter upgrade to DNA (for lid) and KTM internal filter. My concern is if the top DNA filter will be sucking the water if raining, even though it is covered by the seat. Also, if I should be concerned while water crossing. Thank you much

[@MotoMirius]

It will depend partly on the type of filter - a foam filter tends to be better at water resistance. Also depends on your river crossing - doing it at speed can be problematic but probably not worse than heavy rain at speed. But if it's deep enough to cover the seat then you risk the rear intake going underwater anyway. A lot is technique - a steady speed creates a bow wave effect which leaves the bike in less water - the problem is then a sudden loss of speed where the water rushes back in and drowns the bike. So the answer is that it depends!

[@kawabungatortueninja]

In the air box there is 2 tiny holes at the front bottom, do you know what for?

[@hunterssports]

Every one gets this wrong. That port at the base of the air box, its a matched diameter for the intake port. If you open up the box, excluding forced induction eg ram air, turbo, supercharged you will reduce intake velocity that results in loss of low speed power and torque. Thats why the engineers build it this way for basic aspiration. The dyno runs show this experience.

[@MotoMirius]

It's balanced approach. Fortunately, the dyno work has been done on this bike, so there is an established modification path.

[@jamesboreham9002]

@@MotoMirius is there a part number for the air box link pipe inside the air box itself? The one that goes to the throttle body?

[@MotoMirius]

@@jamesboreham9002 I'm sure there is but you will need to check with a dealer who can ask KTM directly.

[@Usiris23]

I was curious if you think modifying the snorkel would mess up anything? I’m trying to make more room in my under seat compartment for a bigger tool kit and noticed that the snorkel runs through it, on the bottom right hand side. Was thinking if I could just dremel out that section or snorkel to allow more space? And the air box would still be pulling from clean, dry air. I’m not looking for an performance improvements cause I’ve already got the 2 stage filters in, just more space. Thanks in advance 🤘🏽

[@MotoMirius]

It will probably be fine, so long as you leave it drawing from under the seat - you don't want to pull the full snorkel because then it drawing from the bottom of the air box which is hot and wet.

[@fordesignphreshair1453]

Thanks for your videos. Does the 390 /401 Airbox Cover replace the DNA/K&N FILTER or is it in addition to the DNA/K&N FILTER

[@MotoMirius]

The airbox lid filter replaces the airbox lid - it has nothing to do with the air filter - which it is very important that you still have.

[@fordesignphreshair1453]

@@MotoMirius thanks for the clarification

[@benzinschnueffler187]

What about sealing off the original intake and put on an open airbox lid, the engine should get more air but not too much I guess

[@MotoMirius]

You could seal off the original intake but then you are just reducing the capacity of the system to pull in air - you'd need a good reason for doing that such as customising the build of the bike where you'd have to accept the compromise. If you have too much air capacity, it will simply not all be used. If you have too little - then you run short.

[@tinks43]

Good points David & another Suzuki in the stable?

[@MotoMirius]

Thanks Dave. Just a visitor as I can't keep it with the ULEZ expansion

[@juanposada9319]

If I run stock filter and FuelX Lite, should I go for Coober or DNA lid? Any significant differences that makes one better than the other? Cheers!

[@MotoMirius]

It's your choice. DNA flows more air and as a result the intake noise is much louder - some people love this, some really hate it so whether it is better depends on which side of the fence you sit! Personally I run the DNA but I have run the foam type quite happily.

[@aratare1880]

I've got a 2016 Duke 390. Since it draws air from the top, would you recommend removing the lid on top with the snorkel?

[@MotoMirius]

Yes, you can get replacement air filters designed to work with the lid removed.

[@Paulie3051]

Not sure where to message directly. Do you have a video on what is the best camera or most reliable to attach to a motorcycle?

[@MotoMirius]

I don't have a video. There are cheaper alternatives, but the ones used by the professionals (the people who can't afford to lose a shot) are the gopro and the insta360. Swings and roundabouts to both. Camera attachments are separate but can be used on both.

[@nikoschorianopoulos2737]

Very nice video ! I wanted to ask if I put full decat pipe with akrapovic slip on and remain the stock chamber. Also put dna filter and dna air box lid what piggyback do u recommend to me on a duke 390 2022 model with the exhaust under the engine ? I would prefer an AutoTune one for this set up if it’s possible!

[@MotoMirius]

Thanks Nikos. You have two main options for autotune - the FuelX Lite which is the entry level option but RaceDynamics say it will be OK. Or for a more advanced piggyback the RapidBike Evo - the exclusive version is cheaper. You could go for the RapidBike Race if you want it to also autotune the ignition as well as the fuelling.

[@MotoMirius]

@@sonny9608 No that is completely wrong. The big advantage of RapidBike is that it unlike the PowerTronic and Power Commander does not require connection to a computer. This, and the fact I am Apple based, is why I use RapidBike.

[@MotoMirius]

@@sonny9608 Because FuelX only controls the Lambda. Evo also reads other sensors so it's autotune map is more accurate. In this case, you get what you pay for. I'm strongly considering upgrading my Evo to the Race version because this also alters the ignition map. This goes back to my old video on choosing an ECU. If you have only made a basic modification to the bike then you only need a basic device so the FuelX Lite is OK. But if you heavily modify your bike then...

[@MotoMirius]

@@sonny9608 I find similar issues whenever I access an Italian manufacturer website, so I think it's a cultural isse - they all seem to present very badly and key information just isn't there. Which is a shame because the Dimsport products are excellent

[@panos_an7307]

Hey. It is always fun watching your videos. Can I ask for your opinion? I have a KTM Duke 390 21 with a full system Austin Racing GP1R and DNA Filter. Whats the best solution for the bike so it doest "dry up". Remap with a program? Or use a Fuel X power electronics to do the job? Thank you!

[@MotoMirius]

Thanks. It depends which route you want to go - I did a video on this a long time ago. Do you want to plug a device in and monitor how your bike is running then modify the map or pay someone to do it for you, and then keep checking to make sure it's right as the weather and temperature changes - where you live will tend to dictate which solution you go for - are you going to use a dyno as part of this - what software does the dyno operator use, how will you find a dyno operator who is good at what they do? Are you going to use someone remote who can update and send you a map - do you know how good they are? Or do you simply want to plug in an autotune unit - the factory ECU is an autotune unit and let it do it's thing? It will never be as accurate as an up to date map but it will be more accurate than an out of date map.

[@panos_an7307]

@@MotoMirius I would definitely choose my bike to be safe and running on a safe mode. Do you believe it is an option to get the bike on a dyno and then plug the Fuel X and compare it? It is way difficult to trust someone my bike

[@MotoMirius]

@@panos_an7307 I'm going to assume you mean the FuelX Lite. This is an autotune product so learns as it goes, so I don't think it's going to work if you just plug it in on the dyno, it may reset when unpowered. You can put the bike on a dyno and see how it is running, then fit the FuelX, ride it for a few hundred miles and put it back on the dyno to see what has changed.

[@panos_an7307]

@@MotoMirius Yes thats what I meant. So will the Fuel X autotune ECU encounter the dry up of the engine; Sorry for getting you busy, do you have a personal email;

[@MotoMirius]

@@panos_an7307 Contact form is on my website. But if I were looking to pay for dyno time I would instead be investing in the RapidBike Evo or Race and not going the FuelX route.

[@BMF-NJ]

I went to Ktm last week to ask about a bigger fuel injection they don’t recommend it not they will tell me, I have the dna lid filter and have a slip on and have the fuelx lite I have the decat which I haven’t fitted as I’m not sure if this mod will be ok with the fuelx lite and I want to swap the stock filter in the box k&n can you tell me if I do these two add on top will it be ok for fuel x lite

[@MotoMirius]

KTM are not likely to recommend changes to the bike unless they are a specialist dealer such as Grey Area KTM in the US. According to Race Dynamics, those changes are OK for the FuelX Lite. If you do further mods to the airbox then your issue may be the capacity of the fuel injector which no software changes can overcome. You could try discussing with Grey Area KTM - not so much about the FuelX but about when you should consider upgrading your injector. In my opinion, if you are heavily modifying the bike then a more comprehensive fuel management system such as the Rapid Bike Evo Exclusive may be something to consider.

[@PaIeRider]

I have a fuelx lite and am going to add an airbox lid filter. Is there much benefit to upgrading the stock air filter as well?

[@MotoMirius]

Depends on the type of airbox lid you are adding - the highflow versions then probably not so much, but a foam filter then you might want to.

[@PaIeRider]

@MotoMirius great, thank you 😊 definitely adding a high flow dna or k&n lid filter, I did wonder about redundancy there. Cheers, love the channel!

[@goat34]

How can foam from a DIY lid get sucked into your throttle body/engine if you have the KnN or DnA filter there also?

[@MotoMirius]

Have a closer look at the airbox. Air goes in at the bottom at the back, up through the filter and only then past the lid (unless your bike is an RC or 2016 or older). So it can't be trapped by the filter since it is AFTER the filter.

[@goat34]

@@MotoMirius ahh. Thank you! Only my 3rd day with this machine,so still learning about it. Thanks for all your info too. 🤠

[@ThrottleAddiction]

What affect does the open style lid have on the sensor in the bottom of the air box? The lid mod almost eliminates air passing the airbox sensor.

[@MotoMirius]

Sensor is ambient air temperature - which is why it's at the bottom of the box and out of the direct airflow, so very little effect.

[@ThrottleAddiction]

@@MotoMirius Ahh, okay. I thought there may have been airflow velocity measurement taken as well.

[@MotoMirius]

@@ThrottleAddiction nothing that complicated on this bike.

[@Wolf-cl5tg]

A question out of topic. Can you do a swap of KTM 390 speedometer onto a KTM 250? I know it is possible but I have only watch a video of that in Hindi. But I don't understand Hindi.

[@anuppokharel703]

You can swap but the speedometer won't work and the mileage counter and trip counter also doesnt works

[@MotoMirius]

As Anup comments, it can be done but there are some issues. The issue with the post 2017 390 is that it is a CANBUS system so it is no longer just a matter of connecting wires. I have seen a dongle made in India which is claimed to allow the lights to work but again not in English so hard for me to interpret.

[@oli1472]

Do you need to remap if you're just changing for a K+n filter. No lid mods

[@MotoMirius]

Typically this will be fine.

[@Paulie3051]

2024 KTM 390 out already. When will you post a video of it?

[@MotoMirius]

I need to do that now, but I'm away for the next couple of weeks so I can't film

[@Antimortem]

👍

[@sugonmadyik6222]

im want to modified my ktm making a Ram air system, remove my air box and connect inlet to front ram air direcly to get fresh air thus increase performance, is it posible?

[@MotoMirius]

Anything is possible. Ram air can be a catch 22 because it also has the potential to introduce turbulence into the intake which can reduce air flow as well as introduce water and particulates - so you need to make sure the system is well designed. Given the capacity of the bike, I'm not sure you will gain much, but I'd be interested to hear how it works out!

[@boostego1268]

The red bull Ktm race bikes use ram air to greet effect

[@MotoMirius]

@@boostego1268 Yes, because professional racing teams spend more money on that installation than your bike cost with professional engineers and dozens of hours testing. The system can produce more power but like any system, if poorly implemented can reduce power. If you take a professionally designed system and install it then yes, you can obtain more power. But... race teams also don't care too much about long term engine life since winning is the whole and only point of racing so installing a race system in a street bike may not be optimal in terms of filtration. So, as per my previous comment, it depends on exactly what, how and why you intend to do it.

[@sugonmadyik6222]

what if im not removing the air filter to remove dust away from combusing in engine. but i think air filter will reduce the air speed incoming from ram air.@@MotoMirius

[@Dannyfr33sh]

The foam on my coober lid came apart, went into the TB as you mentioned and stalled my bike and had to get a tow home. Now I’m looking for tutorials on TB removal and can’t find one. Do not use coober lid. Not worth it

[@MotoMirius]

If you are using a foam filter lid, it's important to make sure that when you remove it, you can see where the foam has been squashed against the top of the air filter - if the glue lets go then this should be enough to hold it in place until you can stop the bike and remove it - it should start getting louder if there is an airbox leak. To remove the TB you will need to pull the tank and with this out of the way you will have the access you need - there isn't much to the removal, but as usual, it's a bit tight in there - unplug the electrical connections and then remove the clamps and wiggle it out. Good luck!

[@handymadandyddd1900]

what about gen 1

[@MotoMirius]

I don't have a gen 1 but most of the same comments apply. The big difference with the gen 1 is that the airflow goes into the top of the airbox and not the bottom as it does on the gen2, so there is a different air box lid modification and you can even remove the airbox lid (but better to replace with a proper filter).

[@handymadandyddd1900]

@@MotoMirius I’ve replaced the air filter with k&n I will see how it runs with no airbox lid

[@jordyquiroz5649]

My 2019 390 threw its first check engine light because my friend did some 12 o clock wheelies Oil ended up in the air box.. happened at 8000 miles I rode it down the mountain I was like 40 miles from home. Cleaned up my air box changed the filter and she has been all good. 14000 miles now

[@MotoMirius]

Sounds good. Yes, high wheelies will blow some oil into the airbox- if you do it a lot you can reroute the hose - but then it will drip somewhere else in normal riding.

[@cmbscx1084]

Great informative video. I always find it comical that there are smarter people than the engineers who designed it. Put a good filter in the bike and call it done. These are not race bikes, with cams, ported heads etc so the gains will almost never be known, felt or understood by the average rider, myself included.

[@MotoMirius]

These upgrades are more for fun than to expect any massive increase in performance. The RC with the same engine actually has a racing series so this is a racing engine - the RC has a different airbox of course.

[@atncozkan5162]

İts been discussed before.390 engine at top makes 44 hp.you cant get more of it.simply buy a duke 690

[@MotoMirius]

Why buy a 690 and not just go straight to 1290? I think you are missing the point. It's not about the power, it's about modifying your bike - there is a massive car and bike modification scene that people love and spend lots of money on, even if to you, it makes no sense.