Its been said multiple times, but I have never read why.

Why does an intake result in a slight decrease in low RPM performance, but improve it during high RPMs? i.e. how/why does the intake change the distribution of power?

 

allows more air into the engine. Better the engine breathes.. the better the engine performs. Thats why in theory a good Cold Air Setup will allow colder air into the engine allowing the engine to run cooler. You can also think of Nitrous as a cold air intake in the artic region.

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Side note.. how you been.. long time you havn't posted

 

I believe it's all resonance related.

 

Loss of low-RPM performance occurs any time an airflow passage is widened... due to the idea that the stock setup is designed for low RPM performance, so widening it out tips it more for the higher-RPM's favor.
The reason this happens is airflow velocity--a certain unit volume of air will move more slowly through a wider passage than a skinnier passage. If the stock (skinny) passage is best for low-end torque, then widening it a little will make it work best at a higher RPM where airflow demand is higher.
Ultimately, the "torque" issue is decided by airflow velocity. Airflow velocity determines how much air will actually get into the cylinder for each intake stroke. Higher velocity results in more air reaching the cylinder for the short period of time that the intake valve is open. But it's important to note that with higher airflow demands (higher RPM and/or more load), the limited-sized passage can only pass so much air in a period of time, therefore when airflow demands increase beyond the passage's ability to supply, you end up getting less air into each cylinder, thus reducing torque. That's what happens when an intake designed for low-end torque is used at high RPMs... the engine doesn't produce much power because the opposite effect is happening--air is moving fast, but you can't get enough of it through the passage to produce a lot of torque in each cylinder.

 

jdm tYte yO!

 

http://vbxmaxima.8m.com/caivssi.html

 

I believe another advantage to "cold air" is it's more dense than warm air, and therefore cold air has more oxygen particles per cubic inch that flows into the combustion chamber.

The more oxygen you have, the more boom you have...(same goes with fuel of course, and you want the right mixture of fuel and air so you don't run to "lean" or too "rich"...) This is why if you go turbo (add more air) you should get larger fuel injectors.

An intake doesn't add enough air to make your engine need larger injectors like a turbo does.

-vq

 

Yes, that is the main theory behind the CAI's advantage over a WAI. Cold air = more dense, therefore for a certain amount of air velocity, you're packing more oxygen than if it were warm. Gasoline-powered engines throttle/meter their output by the amount of oxygen coming in (which in an NA configuration is always obtained via air), so more air == better.

 

You're on the right track. The higher velocity at the intake port results in higher "volumetric efficiency." That's the technical term for what you are describing.

 

They're right about the larger diameter piping not being as effective for midrange power due to lower velocity creating lower volumetric eff. However, drawing cool air from the fenderwell as opposed to hot air from the engine bay, means denser air containing more oxygen to burn. Additionally, using smooth, aluminum piping instead of kinked, accordian-shaped, plastic pipe usually reduces or prevents the loss in midrange while benefitting the top end as well.

 

Thanks , I learned alot !

 

This is another interesting article...
http://www.autospeed.com/cms/A_0629/...popularArticle
not totally applicable to our N/A maximas, but Im working on it.
I just got one of those Dwyer guages off of ebay for 50$ shipped, but the bastard sold me a dud. *i think im going to cry

 

probly already said...but gives more air to the engine...lets it breath better...more gains in the low rpms.....oh and nice sound too lol

 

99% of the time it doesn't...at least not enough to feel. I've never meet anyone who can "feel" an extra 3-4 hp to the wheels in a street car.

 

Uhm.. those who claim they can feel actually aim for 25-30hp from the intake..

Respect the butt dyno.