[Mikethebear]

I'm considering replacing the stock airbox with a pod filter. My question is would this really improve the bike's performance by allowing more air in? Would water get into the system? I watched a video where someone removed the airbox to allow more air in on the track.
This is our stock airbox.

And this is what i'm considering.

Naturally there would be fitment issues I'd need to work out.

So if you think there are reasons not to do this, please let me know. Last thing I want to do is ruin my bike.

 

[Joeboo]

Yes it will get more air, but what's the point if you don't add more fuel.
It will also allow more heat to enter,you want cold air for more power. Not hot air,more water when it rains & more Dust & dirt.
Just my 2c

 

[Mikethebear]

Yes it will get more air, but what's the point if you don't add more fuel.
It will also allow more heat to enter,you want cold air for more power. Not hot air,more water when it rains & more Dust & dirt.
Just my 2c

So I would burn more fuel? That's fine with me.
Or do you mean that I would need to find a way to increase the amount of fuel the bike mixes with the air it pulls in?

This guy tried something similar:
http://www.kawiforums.com/ninja-250r/115443-removing-factory-air-box-installing-aftermarket-air-filter.html

 

[sendler]

The big difference will be that you are eliminating the long tuned runner in the airbox which will shift the power band higher up toward redline. You would probably need a fuel computer and a dyno tune to get the best out of a pod filter.

 

[don'tpanic]

It will make the bike noisier, too. But you won't care about that until you have already damaged your hearing, at which point it will be too late.

But the engine was designed with the tuned intake and exhaust for best power over a wide band of RPM. Unless you are going racing, I wouldn't even consider it.

 

[sendler]

Every bike is too noisy. Never ride above 40 mph without ear plugs.

 

[Wynne G Oldman]

I personally wouldn't use them on a road going bike. I had them on a RD250E I bought, years ago. When it rained, the filters got wet, which gave a similar effect to putting the choke on. I don't think they will filter the air as well as the standard filter either.

 

[sendler]

The stock air filter in the CBR250R is huge for a 250 anyway. It is as big as the filter in my Honda Fit.

 

[MotoMike]

... So if you think there are reasons not to do this, please let me know. Last thing I want to do is ruin my bike.

In addition to the reasons mentioned by others, invalidating your warranty would have to be at the top of the list of reasons not to do it.

If you want to give your motor a little more air you can always just remove the air box access cover.

 

[Mikethebear]

In addition to the reasons mentioned by others, invalidating your warranty would have to be at the top of the list of reasons not to do it.

If you want to give your motor a little more air you can always just remove the air box access cover.

I hadn't even considered that. I think I might just leave the airbox alone.
Thanks guys.

 

[CBR_Dave]

So I would burn more fuel? That's fine with me.
Or do you mean that I would need to find a way to increase the amount of fuel the bike mixes with the air it pulls in?

This guy tried something similar:
Removing the factory air box: Installing an aftermarket air filter : KawiForums.com Kawasaki Forums: Kawasaki motorcycle forums

The ECU wouldn't provide enough fuel to go with the extra air offered by the pod, so it would run even leaner than it does now (the CBR250R is quite lean as it is). You'd need a PC to add more fuel on top of what the ECU allows.

Dave

 

[Mikethebear]

The ECU wouldn't provide enough fuel to go with the extra air offered by the pod, so it would run even leaner than it does now (the CBR250R is quite lean as it is). You'd need a PC to add more fuel on top of what the ECU allows.

Dave

Sounds like it would be too much money and work for a minimal result.

 

[msvec]

I agree with CBR_Dave, the ECU definately runs the mixture lean for fuel milage. After only 3500 miles the valves were pitted when I took the top end apart. To be fair, I did put an Arrow slip-on at about 2000 miles but was still surprised about the amount of pitting.

Instead of putting a pod filter on, you might consider the DNA filter which is supposed to flow more air.

Check out: http://www.cbr250.net/forum/cbr250-performance/2592-dna-high-performance-air-filter-released.html

 

[Soul Searcher]

A Calm Day or a Tornado, Decisions, Decisions.

Greetings Mikethebear,

Just some information to Think About.

Here is a little Test to consider about your Air Flow Concern.

When the ambient air Temperature is at 0 deg F. Your cbr will Start and Operated to it's Full Potential, if the engine is allowed to warm up Properly. Their is more Gas being supplied to the engine in this Condition, as opposed to operating the cbr in 80 deg F Condition, @ 10,500 rpms in 6th gear. The Fuel System hasn't reached it Full Potential Yet.

Another little Test. Take a stop watch. Record how much time your cbr spends above 70 mph in 6th gear. This is the Speed, where the cbr's engine requires the most Air. To increase the Air Flow into the engine, you will have to increase the cc of the combustion chamber along with the intake system. Valve size, lift, duration, etc, etc.

 

[bockscar]

Coming from the world of DIY EFI and having experience converting several engines to Megasquirt (MicroSquirt, actually), I feel I can provide some feedback on the whole "More Airflow means Lean A/F Ratio". Here's how an EFI brain works:

1. Air (Oxygen) comes in through intake
2. Injector squirts fuel into the intake port and mixes with the incoming air
3. Spark fires - Boom - Combustion happens
4. Exhaust exits through the exhaust manifold (or pipe, in our case)

Step number 4 is the single most important step of all modern EFI brains because of the good'ol O2 sensor. The O2 sensor is the sensor that tells the ECU that it is injecting the correct amount of fuel (or in some case, ignition advance or retard). That's because the ECU directly controls the injectors on time. Our engines use a MAP sensor (some engines use a Mass Airflow Sensor, some engines use both) and the MAP sensor (along with the Intake Air Temp Sensor) allows the ECU to calculate the incoming air density. So in a nutshell More Air == More Fuel.

Though it is not nearly as simple is that. There are many constants that come into play such as port size, fuel pressure, fuel injector flow rate and etc. I don't know enough about our engine to know exactly where the constraints are but I am pretty ******************** sure that switching out the air filter isn't going to lean out the A/F mixture. If the ECU is functioning property, it should recognize that there is more air incoming and inject more fuel (assuming the fuel pressure is adequate).

 

[roadster]

I must confess that I have tried this on several single cylinder engines and getting it to work is not easy. The entire standard system is tuned for a certain intake characteristic and taking it off means that some parts of the rev range will suffer. I have overcome this using either a restrictor at the carburettor mouth or, in the case of fuel injected engines, a housing around the cone filter.

I currently run a 400cc Piaggio as well as the Honda. The Piaggio ( unlike the CBR) has a very restricted and also low mounted air intake and I have succeeded in improving this with much trial and error. The main benefit is that I have no more concerns about riding through flood water which has been a feature here in the last few years. I have also improved the performance but with variable pulley automatic transmission you have less need for engine flexibility.

I have no plans to try this with the CBR because I suspect there is little to gain and much hard work involved. One of the magic things about the CBR is the spread of torque combined with a willingness to rev well above peak power. I wouldn't want to compromise that.

Regards Roadster

 

[sendler]

The main thing that will change when installing a pod filter on the CBR250R is not so much by reducing flow restriction as the stock filter has huge area already. But comes from eliminating the long, tuned intake runner which is in the air box, following the filter. Eliminating this runner would change the resonant length of the intake which could get rid of the suck out at the top of the power band above 9,500 rpm which is seen in the dynos. Whether or not the fuel map has any data points to use with this increased manifold absolute pressure remains to be seen. A logging, wide band fuel controller would be a good idea to go with it so you could see what is going on with the mixture and correct it.

 

[BBRMotosports]

Best way to make power by removing the airbox would be to run a velocity stack, not a clamp on filter. And like stated above it will need to be tuned for it.

 

[bockscar]

If you're not familiar with how the inside of the airbox looks, here's a diagram. I've put red arrows to highly how many angles the intake air has to move through the airbox before it reaches the throttle body:

From the opening of the airbox to the runner to the throttle body, I counted 4 angles the intake air must travel through before running into the intake manifold. If you know much about exhaust flow, you'll know that any time the exhaust has to maneuver through a restrictive bend, it increases resistance. While the same could be said about the intake, since the overall intake tract is so short, I'm not sure if that matters a whole lot in our motors.

As to the comment about the overall size of the intake, the outlet from the air box to the throttle body is perfectly matched; it's not larger or smaller than the throttle body. The inlet for the airbox is slightly larger (by about 1/3). This was probably designed as such to compensate for the parasitic draws from the airbox (PCV, SASS, EVAP).

 

[sendler]

Close. More or less. Of course the air comes through the filter and fills the entire clean side of the air box so it doesn't have to follow only the tightly turning arrows that you show to get into the tuned runner. The runner is there to make a tuned pipe which oscilates at given frequencies to form a torque bump from 3,000 to 4,500 rpm and again at 6-9,000 rpm at the expense of a suck out at 5,000 and 10,000. Eliminating the runner will shorten the wavelength/ increase the frequency of the intake standing wave and reduce the tuned effect due to the now reduced ratio of length to area. You will tend to lose the bump at 3 and 6k in hopes of making more power above 9,500 as was shown in the dynos from the race winning CBR250R team. Adaptation of the stock fuel computer via the O2 sensor is pretty much global which may not be able to adapt to rpm specific changes in fuel demand. The MAP sensor will see what is going on but I don't know if it will have enough control range to make the new mixture. You may need a fuel controller.
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http://www.cbr250.net/forum/cbr250-performance/1309-race-winner.html
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