Would open airbox only lead to lean?

[Grove]

Hi all,

If my only "power" modification is an open airbox, eg the MNNTHBX one, would I be running leaner and is this an issue I should be concerned with?

My understanding is that the stock ECU doesn't compensate for much, but I don't know how much exactly.

I don't intend to modify anything else in terms of power (not even dropping in a non-OEM air filter).

Just looking for a bit of added sensory/ auditory feedback.

Thanks in advance.

 

[green_bread]

The bike seems to run lean from the factory. Yes, removing the lid alone will cause it to run more lean. Is it something you should worry about? I dont know... but it will definitely cause the bike to run more lean than with the lid and I would expect more surging at low speeds, etc.

 

[Deleted member 452]

Tried it and it was painfully lean (even with the Akra map). Remove the airbox lid, install a K&N filter, and PCV W/map from Chad at ktmperformance.com- You won't regret it.

 

[Grove]

Thank you!

 

[cornerslider]

Tried it and it was painfully lean (even with the Akra map). Remove the airbox lid, install a K&N filter, and PCV W/map from Chad at ktmperformance.com- You won't regret it.

+1 on what this guy said.... It will make you're bike all that it was meant to be....


Sent from my iPad using Tapatalk

 

[zaster]

Tried it and it was painfully lean (even with the Akra map). Remove the airbox lid, install a K&N filter, and PCV W/map from Chad at ktmperformance.com- You won't regret it.

What he said

 

[Muckabucka]

probably a good way to ventilate your piston crown if you like doing things like that.

 

[Grove]

probably a good way to ventilate your piston crown if you like doing things like that.

Would ventilating my piston crown help my engine run cooler?

 

[Muckabucka]

Yes, because you would be pushing and coasting everywhere.

 

[xlenduroman]

I have the Akra no cat map on my Duke. No other mods done yet. I knew from reading that removing the air box lid would be to lean, so I thought I would just remove the snorkel. That alone is still to lean. It killed the mid range and ruined the power delivery of the bike. It sucked bad so I put the snorkel back on. I did remove the little air damn in the air box and didn't re install it, that seems to be OK to my un tuned ear and butt dyno.

 

[simpletty]

Tried it and it was painfully lean (even with the Akra map). Remove the airbox lid, install a K&N filter, and PCV W/map from Chad at ktmperformance.com- You won't regret it.

Tell me what is your basis that the bike ran "painfully lean"? I have the Akra map and carted pipe and did the airbox mod with k and n. Been running all summer hard with no indication of "lean". Why does a bike have an O2 sensor? Last time I checked it was to check for the amount of oxygen in the exhaust, the telling the computer to compensate the fuel mixture to adjust for a lean or rich condition. I'm confused as to what proof you have to things being lean? Why doesn't the ecu compensate for the so called lean condition? Makes zero sense to me as to why in a modern fuel injected system the computer wouldn't compensate if it was a bit lean. Why can I add a cold air intake to my car? Seems with everyone's reasoning here the car would run lean and blow up as well.... I'm still running mine as is and it has not given any indication of running any different. It actually runs a bit rich at idle indicated by a bit of black smoke when you wick the throttle. I disagree that it runs lean, I guess the answer will be if it craters the motor....

 

[CDN Duke]

Tell me what is your basis that the bike ran "painfully lean"? I have the Akra map and carted pipe and did the airbox mod with k and n. Been running all summer hard with no indication of "lean". Why does a bike have an O2 sensor? Last time I checked it was to check for the amount of oxygen in the exhaust, the telling the computer to compensate the fuel mixture to adjust for a lean or rich condition. I'm confused as to what proof you have to things being lean? Why doesn't the ecu compensate for the so called lean condition? Makes zero sense to me as to why in a modern fuel injected system the computer wouldn't compensate if it was a bit lean. Why can I add a cold air intake to my car? Seems with everyone's reasoning here the car would run lean and blow up as well.... I'm still running mine as is and it has not given any indication of running any different. It actually runs a bit rich at idle indicated by a bit of black smoke when you wick the throttle. I disagree that it runs lean, I guess the answer will be if it craters the motor....

I had the Akra map applied on delivery and found the bike to surge at partial throttle. After installing the MNNTHBX lid and DNA Race filter, it got considerably worse. I did do the ECU reset but while it worked ok initially on first short ride, later in the same day it got worse so I put the lid back on the airbox. I then added PCV, aftermarket exhaust and removed the lid again. It doesn't surge anymore (plus has way more power in midrange etc).

 

[simpletty]

I had the Akra map applied on delivery and found the bike to surge at partial throttle. After installing the MNNTHBX lid and DNA Race filter, it got considerably worse. I did do the ECU reset but while it worked ok initially on first short ride, later in the same day it got worse so I put the lid back on the airbox. I then added PCV, aftermarket exhaust and removed the lid again. It doesn't surge anymore (plus has way more power in midrange etc).

Ah ok. I did the pipe and akra tune about a week after I bought it. Did the filter and air box mod about a week later. I was down for quite a while with an ecu failure but have about 1500 road miles on the bike and about 400 since it's been converted to track use only. Never have had any issues with running. Has plenty of power from bottom right through to redline. Maybe I'm just lucky.

 

[xlenduroman]

^ My 390 Duke is my 3rd new efi bike in my garage. I have the ability to tune the others. I agree with what others have stated on this forum, the mighty 390 is lean, especially so with any mods, even with the factory Akra map. Fueling needs addressed, and the stock ecu isn't capable.

If you bought your 390 new and did all those mods in the first couple of weeks, I am assuming you were still breaking it in. If so then you probably didn't get a feel for the 390 power delivery. With your mods, I am guessing your power delivery is linear with maybe a wake up on top? Regardless... trust the info on this forum. You are leaving a lot on the table by not giving it the proper fuel for your mod, and you may be rolling the dice with your motor longevity.

 

[KTMGene390]

Tell me what is your basis that the bike ran "painfully lean"? I have the Akra map and carted pipe and did the airbox mod with k and n. Been running all summer hard with no indication of "lean". Why does a bike have an O2 sensor? Last time I checked it was to check for the amount of oxygen in the exhaust, the telling the computer to compensate the fuel mixture to adjust for a lean or rich condition. I'm confused as to what proof you have to things being lean? Why doesn't the ecu compensate for the so called lean condition? Makes zero sense to me as to why in a modern fuel injected system the computer wouldn't compensate if it was a bit lean. Why can I add a cold air intake to my car? Seems with everyone's reasoning here the car would run lean and blow up as well.... I'm still running mine as is and it has not given any indication of running any different. It actually runs a bit rich at idle indicated by a bit of black smoke when you wick the throttle. I disagree that it runs lean, I guess the answer will be if it craters the motor....

Modern motorcycles are equipped with O2 sensors primarily for emissions reasons. However, there are two kinds of O2 sensors: narrow band & wideband. Stock the 390 is equipped with a narrow band sensor which tells the ECU if the bike is rich or lean from its programmed base map of 14.7:1.

Basically, it's a yes/no switch but can't tell the ecu how rich or lean just that its rich or lean and the ecu adjusts fueling to try to achieve the base map settings. On the other hand a wideband O2 can tell you precisely how rich or lean thereby allowing you to achieve a target air fuel ratio e.g., Dynojet Auto-Tune, Bazzaz Z-AFM.

When you make intake or exhaust modifications the engine will run even leaner than stock and the ecu's limitations will not allow it to compensate for this. Reflashing the ecu or installing a piggyback unit is the only way for the bike to run to its full potential. The stoichiometric AFR is 14.7:1, gas engines make best power running slightly rich.

I.e., reflashing the stock ecu helps but the maps available are limited. It's best to install a piggyback unit like the PCV in addition to flashing the ecu.