Modifying the stock intake tract for more power (cleaner air)

[s30series]

So currently, the intake track sits like this :



It "sucks" in air from underneath the rear seat. Not a lot of clean space there or an open air to draw air in.
I'm thinking about modifying it to suck in air from underneath the bike...something like this:



To do that, you'd have to cut an oval hole in your underfairing and obviously cut the stock intake track. The intake tract is very pliable so this should be pretty easy.


Then, I was thinking about fabbing up a sort of "cover" (the green part) to protect the opening from debris kicked up by the tire. This part would simply screw into the underfairing via sheet metal screws. It would be made out of ABS/carbon fiber....maybe even 3D printed. It will have some holes at the bottom to get rid of any moisture that gets in it.

Thoughts? Opnions?

Here's a shot with the seat removed. You can see the intake tract is shortened, and not in the way of anything. I think it would be very beneficial.

 

[Treachery]

I'm not an air-movement physicist, but I suspect that any rear-facing inlet you try will actually lead to less air in, as that's an area of negative pressure. Something routed forward might help. I've not seen the inside of the airbox, but others have suggested that some gain might be had removing restriction there.

 

[emeglasson]

Have you considered removing the 'snorkel' and cutting out the sides of the airbox to allow better, more direct flow? I'm referring to the triangular pieces on the sides, between the frame. Was considering doing that to mine, but haven't done it yet.

 

[s30series]

Yeah I've thought about that a bit. The airbox already has the inlet pointed aft anyways (as the top picture shows). This was just my first idea on how to make it work. My friend and I were actually also thinking about a naca duct for the side, but we're still trying to figure it out.

As far as the triangular pieces on the side, that is the bottom of the airbox, past the filter. The top cover (pre-filter) i extremely small and there is no room to really do anything to it. Unless you just completly cut a bunch of holes in it and let it suck air from under your butt!

I might mount a gopro down there and some pieces of string/yarn and go for a ride. I can't imagine there is that much air running up the tail to cause a neg. pressure area. Maybe, but no way to tell without testing.

Whatever happens if you've taken your rear tail off and seen the way the stock airbox sucks air in, we can all agree it's poor design to get good airflow. A ram-air setup would be awesome, now I just need to figure it out. Maybe a naca-duct on the side with a 90degree bent inlet pipe......hmmmmmmm

 

[guzz46]

I took the snorkel off, this was when I had the stock muffler, and if anything I think it actually lost a bit of power, so I put it back on again.

 

[mr-fabricator]

Have you considered removing the 'snorkel' and cutting out the sides of the airbox to allow better, more direct flow? I'm referring to the triangular pieces on the sides, between the frame. Was considering doing that to mine, but haven't done it yet.

Im with u on this one , snorkle was ditched , air box lid peppered with 25mm hole saw and the side of the tray cut off so the only plastic remaining is the bottom to stop tyre debris , works a treat imo

Regards lee

 

[ryandalling]

I had a dyno done on the bike, and it runs lean... It's getting too much air. I think you may need to adjust the fuel map if you give it any more air.

 

[mr-fabricator]

Just ordered a AFR guage , its always on my mind about the modifications we do and the effects on fueling , will strap it on for my next track day and see whats going on , i thinknim over fueling now as im sucking air away from the air box . Will test it out , revert back to a closed air box and compare . Im running the powerdynamics piggy back so may be able to adjust things .

 

[s30series]

Just ordered a AFR guage , its always on my mind about the modifications we do and the effects on fueling , will strap it on for my next track day and see whats going on , i thinknim over fueling now as im sucking air away from the air box . Will test it out , revert back to a closed air box and compare . Im running the powerdynamics piggy back so may be able to adjust things .

Keep us updated. The power dynamics will def. let you adjust the fuel delivery.

Also can you post what you ordered?

 

[cjwell]

Guys as you can see there is plenty to be had by modifying the lid/snorkel and replacing stock filter (and even more in it with "tuning"). The attached graph is same bike I collected data off of before pulling apart. The blue line is K&N filter installed with the snorkel/lid removed off the filter holder. The red line is same set up (Akra system, Akra map, K&N filter) BUT with the lid and snorkel installed as delivered. It makes good gains across the board, but is LEAN up to 7k. I would not recommend running this combo until a proper tuning solution is available. Like I say I should have a PCV mid May, and hopefully my new combination together and on the dyno shortly after. My "kit" will have a K&N filter included if needed and instructions on how to modify the lid... Sit tight I want all this stuff as bad or worse than you guys!

 

[A1VW2NV]

Subscribed!!

 

[Treachery]

Good stuff, cjwell! Eager to watch the development!


Sent from my iPhone using Tapatalk

 

[guzz46]

Did you dyno it when it was standard? because in the recent motorcyclist magazine shootout the RC 390 has 41.7 hp, which would imply that the K&N air filter, Akra system, and Akra fuel map don't really make any hp gains at all.

 

[ASM]

Did you dyno it when it was standard? because in the recent motorcyclist magazine shootout the RC 390 has 41.7 hp, which would imply that the K&N air filter, Akra system, and Akra fuel map don't really make any hp gains at all.

He did...I am not sure whether he posted it in some thread but he has a picture of it in his gallery. The dyno chart shows the bike with the stock exhaust and AKRA installed. Stock the bike makes 40.x on his dyno...

390dynodata - KTM RC 390 Photo Gallery

 

[guzz46]

He did...I am not sure whether he posted it in some thread but he has a picture of it in his gallery. The dyno chart shows the bike with the stock exhaust and AKRA installed. Stock the bike makes 40.x on his dyno...

390dynodata - KTM RC 390 Photo Gallery

Thanks, so it's only about a 1hp gain then, so much for the approximately +5hp claim quoted else where, so it appears you have to spend a lot of money just to get a small 1hp or 2hp gain on this bike, I was contemplating an air filter and Powertronics to go with my exhaust sometime in the not too distant future, but if I'm only going to gain a couple of hp then I think I'll save my money instead.

 

[cjwell]

Yes I have lots of dyno data in various configurations...The bone stock average run file is in my gallery. 40.6 hp STOCK. The Akra slip on claims 2.5 BHP increase I believe, I'm not sure where you saw 5hp. 5hp would be a HUGE gain about 12%, it instead is a more realistic typical 5% gain like another pipe/map combos. With the Akra system and Akra KTM map it made 41.2 hp which isn't super impressive albeit. BUT, the Akra map is overly rich on the stock air filter, lid and snorkel. With some tuning on the last dyno pic I posted (42.5hp), I think 43ish would be achievable. That would be a gain of 6% which is pretty darn good gains for 'bolt on' items. Every dyno is different, you can't compare my dyno Motorcyclists, or your local shops. It's a tuning 'tool' and for before/after that's it.

 

[Treachery]

I'm not sure where you saw 5hp.

KTM PowerParts catalog.

 

[guzz46]

I saw it here 404 - PAGE Not Found at SBKSTORE

Also as Treachery said, in the powerparts catalog, the font's a bit small, but you can read the original here https://www.flickr.com/photos/10430020@N08/16011743649/in/album-72157650020202361/lightbox/

 

[cjwell]

I don't think they lied intentionally, if anything they mixed/missed units.... 5% is to be expected. 5hp would be on a 750-liter bike. Sorry, if they misrepresented. Just my opinion though. I'm barely hoping for 10 hp over stock with piston, cams etc... That's a 25% increase in power . Somewhere I saw either in KTM or Akra literature a 2-3 BHP increase which is what I'm seeing.

 

[mr-fabricator]

Lets not forget its not all about peak power ,

Drivability . Usability and where the power comes in are all just as important .

Horsepower is how hard u hit the wall

Torque is how far u take the wall with u .

If i can get out of a corner quicker and pull strong enough then the guy behind me will never catch me by the end of the straight , 42hp and a bucket load of torque will decimate the competition .

The Yamaha R3 racing in malasia have engines 15 hp over standard ,( completly reworked ) get the ktm to 50hp ish and the torque will make up the rest .