K&N Air Filter Queries and Doubts

[devils_friend]

Re: K&N Air Filter Queries and Doubts

A fuel injected engine does not necessarily flow more air-fuel combo than one with a carb. The R15 engine has a higher compression ratio (CR) at 10.4:1 compared to the 9.5:1 of the FZ. The R15, hence can produce more power with the same amount of air & fuel. However increased CR means more heat, which is too much for an air-cooled engine to handle, so its reserved for liquid cooled engines.

You getting it wrong brother. The CR of R15 is 10.4:1, this means that, for 10.4 units of Air you need 1 unit of fuel to help gain the required CR. Same goes for all the bikes. Generally for FI biked the CR will be on higher side.

TVS Apache RTR FI is air cooled bike. It dosent matter if the bike is 150cc or 200cc. The bike can be FI or Carb depends on how the company wants to position the bike in market. Pulsar 200NS is liquid cooled but with Carb.

Hope you get the point.

Cheerz!!

How does high compression allow more air?

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Explained above

Cheerz!!

[sniper]

Re: K&N Air Filter Queries and Doubts

Compression ratio is the amount by which the air-fuel mixture in the engine is compressed to during the compression stroke. So 10.4:1 means that 10.4 parts by volume of the mixture is compressed into 1 part before ignition.

[rx100.7050]

Re: K&N Air Filter Queries and Doubts

Compression ratio is the amount by which the air-fuel mixture in the engine is compressed to during the compression stroke. So 10.4:1 means that 10.4 parts by volume of the mixture is compressed into 1 part before ignition.

Exactly!! It's not the mixture of Air and fuel.

[gyan_recl350]

Re: K&N Air Filter Queries and Doubts

Compression ratio is the amount by which the air-fuel mixture in the engine is compressed to during the compression stroke. So 10.4:1 means that 10.4 parts by volume of the mixture is compressed into 1 part before ignition.

Some addition to it. It is actually the ratio between the (volume of the cylinder)+(combustion chamber) when the piston is at the bottom of its stroke, and the volume of the combustion chamber when the piston is at the top of its stroke.

You can also view itas total volume above the piston when piston is at BDC: volume above piston when piston is at TDC.
So when piston is at BDC and suppose there is 1040cc of air/fuel mixture and when piston is at TDC then the compressed volume of air/fuel mixture is 100cc then ratio is 1040:100 or 10.4:1 .

Hey I am asking my question again from my previous comment: "Then would we get any performance gain or not using them? I mean using SRF inside the Air filter box"

[sniper]

Re: K&N Air Filter Queries and Doubts

The K&N SRF filter in the stock air box will give you more power as it allows more air through it compared to a stock filter. Stock air boxes have small intake openings to reduce intake noise, so I suggest a few extra holes in it.
SRF filters though a bit low on power compared to direct fit-on-carb conical filters, are hassle free, last longer & have much longer cleaning intervals.

[gyan_recl350]

Re: K&N Air Filter Queries and Doubts

You getting it wrong brother. The CR of R15 is 10.4:1, this means that, for 10.4 units of Air you need 1 unit of fuel to help gain the required CR. Same goes for all the bikes. Generally for FI biked the CR will be on higher side.

This definitely is not CR buddy. It is not air-fuel mixture ratio. A good idle air/fuel ratio still remains 14.7:1 (AFAIK) regardless of compression ratio and we do not need some parts of air and some parts of fuel to achieve a particular CR.

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The K&N SRF filter in the stock air box will give you more power as it allows more air through it compared to a stock filter. Stock air boxes have small intake openings to reduce intake noise, so I suggest a few extra holes in it.

OK. Now how about it when I use SRF but do not drill any holes? And would it drop the mileage a bit (with or without holes, in both the case)?

[sniper]

Re: K&N Air Filter Queries and Doubts

K&N does not claim any improvement in mileage. Though I've lots of my clients who get better mileage after fitting a filter. Mileage will depend more on your riding style & the overall condition of your bike. Whats the point of improving performance if you are going to ride below 60kmph to save fuel?

[gyan_recl350]

Re: K&N Air Filter Queries and Doubts

K&N does not claim any improvement in mileage. Though I've lots of my clients who get better mileage after fitting a filter. Mileage will depend more on your riding style & the overall condition of your bike. Whats the point of improving performance if you are going to ride below 60kmph to save fuel?

May be you did not get my question and also we do not always redline or ride over 60 and definition of improvement is not always riding above 60 or hitting the top speed. Improvement in low end torque can also be an improvement or just a better acceleration can be as well. One would still ride at 60 but may be he/she reach there fraction of a second or a second earlier, even that can be an improvement. And neither did I ask how much would be mileage improvement instead I asked how much would be drop but you replied other way around.
And asking you as you seemed to know a bit about K&N, so that does not mean I am behind fuel saving. May be I am, may be not. That is irrelevant here.

I am asking in general how much mileage drop one can see/observe.

[sniper]

Re: K&N Air Filter Queries and Doubts

My bad. No offense intended. The mileage is usually slightly better with a SRF K&N & may go down by 2-5kmpl in case of conical filters. There are too many variables to get a right figure. Hope this helps.

[gyan_recl350]

Re: K&N Air Filter Queries and Doubts

My bad. No offense intended. The mileage is usually slightly better with a SRF K&N & may go down by 2-5kmpl in case of conical filters. There are too many variables to get a right figure. Hope this helps.

Makes sense. Thank you for the reply and now I see your signature below, you are K&N distributor and dealer and you say installer as well. Great

[abhi7013]

Re: K&N Air Filter Queries and Doubts

You cannot compare FZ and R15, both are different. R15 has Fuel Injection, so the amount of Air Fuel mixture going in the cylinder is more. This in turn produces more power as compared to a bike fitted with Carburetor. So, 150cc bike can be manufactured to produce power of 200cc bike and at the same time it can be manufactured to produce power of 110cc bike also.

Cheerz!!

So you say fi bikes take in more air than carb bikes? How is it so? And previous posts by fellow members clearly defines what is CR. Though it is high for r15, I don't see any relation between that and the amount of air/fuel intake.
But this statement of yours 'fi lets in more a/f mixture', has got me confused now.
Could someone clear it please?
Afaik, that's not the case. Else my zmr would be more powerful and it would not return me the excellent mileage figures that am getting now. Infact the carb'ed zma has a lesser FE. Going my your statement, this is opposite of it.
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[vvk1987]

Re: K&N Air Filter Queries and Doubts

So you say fi bikes take in more air than carb bikes? How is it so? And previous posts by fellow members clearly defines what is CR. Though it is high for r15, I don't see any relation between that and the amount of air/fuel intake.
But this statement of yours 'fi lets in more a/f mixture', has got me confused now.
Could someone clear it please?
Afaik, that's not the case. Else my zmr would be more powerful and it would not return me the excellent mileage figures that am getting now. Infact the carb'ed zma has a lesser FE. Going my your statement, this is opposite of it.
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Don't consider any of the above statements while reading the below written explanation

See in carburetor fitted bike you set a particular af ratio by adjusting af screw so this ratio remains same throughout the rpm range of bike whatever may be the environment condition or riding style until you change the af ratio screw settings


But in fi bike it has different sensors to sense the environment condition s & rpm
According to it the af ratio is calculated @ each & every second giving better af mixture(may be incresed ) with better efficiency

So in fi af ratio is not constant & in carburetor it's constant

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[devils_friend]

Re: K&N Air Filter Queries and Doubts

So you say fi bikes take in more air than carb bikes? How is it so? And previous posts by fellow members clearly defines what is CR. Though it is high for r15, I don't see any relation between that and the amount of air/fuel intake.
But this statement of yours 'fi lets in more a/f mixture', has got me confused now.
Could someone clear it please?
Afaik, that's not the case. Else my zmr would be more powerful and it would not return me the excellent mileage figures that am getting now. Infact the carb'ed zma has a lesser FE. Going my your statement, this is opposite of it.
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My bad, i am sorry that i could not write down my words properly. By more air i meant is that, the AF Mixture injected by FI system is of much higher pressure than Carb system. This helps in atomising the fuel at a quicker rate than normal system.

Cheerz!!

[abhi7013]

Re: K&N Air Filter Queries and Doubts

Don't consider any of the above statements while reading the below written explanation

See in carburetor fitted bike you set a particular af ratio by adjusting af screw so this ratio remains same throughout the rpm range of bike whatever may be the environment condition or riding style until you change the af ratio screw settings


But in fi bike it has different sensors to sense the environment condition s & rpm
According to it the af ratio is calculated @ each & every second giving better af mixture(may be incresed ) with better efficiency

So in fi af ratio is not constant & in carburetor it's constant

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Well, that's the role of the processor in the bike rite. Depending on the throttle position and the condition of the acceleration, the air-fuel mixture varies. I knew it. But my query is simple. Consider two similar 150cc engines. One with a carb and another with an fi system. Will there be a difference in the volume of air consumed by both these engines? If so, will the difference be so much that the free flow filter used for one engine, cannot be used for the other? My opinion is that the difference will not be so much that you'll have to use a bigger filter.
Dunno if am correct here. If am not then please do correct me

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[Bibhu]

Re: K&N Air Filter Queries and Doubts

Well, that's the role of the processor in the bike rite. Depending on the throttle position and the condition of the acceleration, the air-fuel mixture varies. I knew it. But my query is simple. Consider two similar 150cc engines. One with a carb and another with an fi system. Will there be a difference in the volume of air consumed by both these engines? If so, will the difference be so much that the free flow filter used for one engine, cannot be used for the other? My opinion is that the difference will not be so much that you'll have to use a bigger filter.
Dunno if am correct here. If am not then please do correct me

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The question you are asking has 2 aspects. First is volume of charge entering per intake stroke. Second is rate at which the charge flows overally ie: how fast a fresh charge enters and burnt gasses are expelled. Regardless of fi or carb, or cc if the bike flows faster it will consume more volume. Seen the same example, the r15 breathes through 4 valves and revs faster, so regardless of being the same displacement as a fz it will consume more volume regardless of the fact that it will take in simillar amout of af mixture as an fz due to the simillar displacement.

Adding a free flow makes sure that engine breathes more freely as the choking effect is reduced compared to the stock filter. A faster revving thus faster flowing engine would be able to use to better effect.

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