cone cfm

[Kodeblue]

OK, I have been searching for a while now and have not found what I am looking for. I am getting the CAi and want to know what size cone to put on. There is a theory to calculate for how many cfm is required. Anybody know what I need?

2000 Grand Am SE
3400

[UNCTYPE-S]

why do you need to do any calculations? all i did was buy a 5 inch KnN cone with i think a 3 inch flange. something like that, but i never had to do any calculations to find it.

[Kodeblue]

The reason for the calculation is to get the maximum performance out of your CAI. Some people just throw on any cone. I do realize that the 5" is the way most are going by I forget what cfm is needed.

[The Old Guy]

Check out this thread:

http://www.grandamgt.com/forum/showthread.php?s=&threadid=11873

Especially this statement:

Originally posted by StarFire
I disagree with that statement completely, our Engines require nothing more than a 5" cone. Our engines don't take in enough air to warrant it...the bigger of a cone you go, the more low end you loose (resulting in a mushy feeling to the pedal). If you stick with a 5" you will notice it, but it's not super bad. However if you get a 3" cone, you will not notice the loss... I believe when using K&N's calc. for filter size, our cars only need something like 3.2" filter (which doesn't exist)...

So unless you are going to do some major mods...I wouldn't go over 5". Even with the 5" I lost some good low end power to the car, however upon installing the GMS MAF, I've gained it all back (while keeping and slightly increasing the mid/upper).

I personally wouldn't put a 7" cone on our cars, but it's whatever you want to do!

I'm personally trying out a 4" round K&N.....4" base instead of 5" on the cone filter....the cfm is definately smaller.....but I don't know if it's going to be close enough to a 3" cone. :confused:

[Greed4Speed]

Again, if an engine only requires a certain CFM, how would a different size filter matter? The engine can only take in as much as it needs or can. If this is the factor, then why does a little larger TB, MAF, or intake ports allow more power??? You think because you have a larger filter the pistons will draw in more air than the engine can handle? No. They just have less resistance in the airflow to overcome. Isn't this what the MAF is for anyway?

I've only seen CFM calculations used for carburated engines where the CFM also indicates the amount of fuel.

[Kodeblue]

OK, I don't understand what you are saying there. It seems you contradicted yourseld. The engine does need an X amount of air. If you have a 2" cone on for example, will it get all the air it needs? No, it will not. So that brings me back to my question. What size cone will allot the correct amount of air?

[Greed4Speed]

What I am saying is that you can't go too large on the air filter. The limiting factor is elsewhere in the engine.

Yes, too small will matter. It's like trying to run a race while breathing through a straw.

You have to follow the thread that was brought up.
Sorry.

[The Old Guy]

You can debate this all day......but the proof is actually in testing different size cones. Just remember.....I'm dealing with a stock 3400 with no mods other than a CAI......if you change your MAF, intake manifolds, exhaust etc. it'll change the situation.

I ran my cold air intake using a 5" cone..result as most of you with a CAI have found....car definately runs better but has a low end loss.

Same car....same intake......4" cone.....low end loss is not there, 0-60 times were better and I still have the high end.

it's not in what the "pistons will handle" it's the air/fuel ratio that gets thrown out of whack.

I was at Summitt Racing yesterday when I picked up the 4" cone and talked to some of the guys I know there.....they say the loss may be in reaction time of the MAF.....it doesn't have time to react to the overload of air drawn through the intake when you punch it at 0 and by the time you reach around 5 MPH it makes it's adjustment. Remember.....the air has to pass through the MAF before the sensor can pick it up....so initially your A/F mixture may be off until the computer makes the adjustment.

No dyno tests to prove it, but you are dealing with physics not just technology so it makes sense.

[StarFire]

...and the answer is...suction!

Think of it this way, smaller filter, less "available" air. Bigger filter, more "available" air.

Now, think of it this way.

Take your hand and cup it in a "C" or "O" fashion. Now put it up to your mouth, try to suck in air while opening and closing it. Now you will notice that when you close your hand really small, it's harder to get in air. When you open your hand really wide, you can get in more air, but it's actually harder to pull in the same amount of air (providing your lungs are the stopping point for the amount of intake). Now if you find that middle ground where you can suck in a good amount of air, you will notice that the air travels FASTER into your mouth (creates like a rushing senstion). This is basically the same idea.

The engine can only pull in so much air, but it's not pulling the total amount in at all points. This is where you throw your torque curve off with the CAI. The smaller filter sub 4"s, is pretty much the right amount, it will make it easier for the engine to pull in air for the low RPMs while still freeing up the resistance for the upper RPMs too.

I think that makes sense, I dunno, feel free to tell me I'm wrong. :)

I think it all has to do with the laws of physics. Crazy people making up laws that can't be broken! What's up with that!? lol

[The Old Guy]

Originally posted by StarFire
[ Now if you find that middle ground where you can suck in a good amount of air, you will notice that the air travels FASTER into your mouth (creates like a rushing senstion). This is basically the same idea.
[/B]

Exactly!!!! The purpose of a CAI is to get the correct amount of cold air in.......at the correct velocity. Velocity is the key.....why else do you think any good CAI is made of mandrel bend pipe with no restrictions......sure a dryer hose will get cold air in but at what velocity????