Difference between short tube and long tube CAI?

6754 Views 13 Replies 10 Participants Last post by PLAZAMAN, Feb 14, 2003

Cyric

Discussion Starter · Feb 13, 2003

I've read so much about the Benfer CAI, and I am anxiously awaiting the one-piece unit. I'm a fiend for research before I make any decisions, and there is one piece of information that I have yet to see discussed (unless I missed it in the search I did).

What is the significant difference between a long tube induction and a short tube induction?

If you search E-Bay, there are many short tube (tube being about 6" and sitting in the empty bay where the stock air box would be mounted) for $30.00. There is also the ECIS intake with a heat shield.

Then there are the Benfer/Dinan type tubes, that stick the filter down below near the bumper. My logical assumption is that the colder air = better performance. But does anyone know what the actual difference is, and has it been tested?

The Benfer sounds like a great deal, but fitting it in my 330ci with Xenon sounds like a major undertaking.

Thoughts?

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Cyric

Discussion Starter · #2 · Feb 13, 2003

Anyone?

Have I repeated a question that has been asked a thousand times? I couldn't find anything in the search. If I missed it please point me in the right direction. Thanks!

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JetBlack330

· #3 · Feb 13, 2003

Great issues. I would like to know the answers to these questions as well.

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SBenfer

· #4 · Feb 13, 2003

Serbonze said:
I've read so much about the Benfer CAI, and I am anxiously awaiting the one-piece unit. I'm a fiend for research before I make any decisions, and there is one piece of information that I have yet to see discussed (unless I missed it in the search I did).

What is the significant difference between a long tube induction and a short tube induction?

If you search E-Bay, there are many short tube (tube being about 6" and sitting in the empty bay where the stock air box would be mounted) for $30.00. There is also the ECIS intake with a heat shield.

Then there are the Benfer/Dinan type tubes, that stick the filter down below near the bumper. My logical assumption is that the colder air = better performance. But does anyone know what the actual difference is, and has it been tested?

The Benfer sounds like a great deal, but fitting it in my 330ci with Xenon sounds like a major undertaking.

Thoughts?

Put simply;
The colder (thus denser) the air going to your engine, the more horsepower you will be able to produce. It is our feeling that intakes with the filter in the engine bay perform superbly until the engine heats up - after which point you're drawing in warmer air than if it were in the bumper. This is why we designed our intake to sit in a position where they would more consistently draw in cool air. In addition, there are a multitude of modifications you can further perform introduce a more direct flow of cold air into the bumper cavity.

-SB

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BimmerJustin

· #5 · Feb 13, 2003

Like what mods, exactly?

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Choson1

· #6 · Feb 13, 2003

The longer tube intakes are only longer cuz they want to draw in cooler air from somewhere outside the hot engine bay. Besides temperature, I don't think there would be any benefits to be gained from longer tubes.

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BimmerJustin

· #7 · Feb 13, 2003

That's not what I was asking. Or maybe I didn't clarify myself. What other mods besides a CAI and a high bore TB can you do?

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Dukes

· #8 · Feb 13, 2003

BimmerJustin said:
Like what mods, exactly?

Like superchargers and turbochargers.

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BimmerJustin

· #9 · Feb 13, 2003

oh...okay....those mods.

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Cyric

Discussion Starter · #10 · Feb 13, 2003

In addition, there are a multitude of modifications you can further perform introduce a more direct flow of cold air into the bumper cavity.

Since he mentions a direct flow of cold air into the bumper, I don't think he is referring to superchargers. I would imagine he means some other form of airflow (scoops, ducts) in the bumper area that would direct a flow of cold air into that cavity.

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topazmania

· #11 · Feb 13, 2003

Well, one could also argue that the longer tube provides more resistance to airflow, thereby reducing the internal pressure of the air entering the engine which would negate some of the effects of drawing in slightly colder air. So we are really arguing over like 2HP here.

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MooDogg

· #12 · Feb 14, 2003

As far as I know, there is no significant drawback to having a longer tube as opposed to a shorter one. The only drawback that I can think of is that of an increased likelihood of water ingestion to the engine.

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KevinJ_2k1_325ci

· #13 · Feb 14, 2003 (Edited)

Re: Re: Difference between short tube and long tube CAI?

I think you would need to go a step further to realize what the real differences are. SBenfer is correct except for the fact that if a short ram intake such as Conforti, ECIS, and SPP utilizes a heat shield to shield the air intake from engine heat thus it drastically reducing the effects of engine heat and negates any performance degredation from a short ram intake.

The same argument can be made for intakes such as Benfer, Dinan, Injen, and soon AEM. Since the air filter is not in the highest air pressure zone, the intake inlet behind the bumper will draw hot air when the car is stationary.

Here are the REAL performance differences between a short and long tube intake which I have stated in the past and most intake experts will state...The following information is quoted from BMW's "etm" technical manual:

"Short intake pipes or intake pipes with a large diameter have the effect of producing higher output values in the upper engine speed range together with lower torque values in the medium engine speed range. Long intake pipes or intake pipes with a small diameter develop high torque in the medium engine speed range."

Technically this means depending on certain conditions,

- short intake should produce more HP in the mid to upper range and lower Torque in the mid range.

- long intake will produce more torque in the mid range and less HP in the upper range.

So do you care to get more power or toque in the mid range or upper range, that should be your determination for short versus long intake.

SBenfer said:
Put simply;
The colder (thus denser) the air going to your engine, the more horsepower you will be able to produce. It is our feeling that intakes with the filter in the engine bay perform superbly until the engine heats up - after which point you're drawing in warmer air than if it were in the bumper. This is why we designed our intake to sit in a position where they would more consistently draw in cool air. In addition, there are a multitude of modifications you can further perform introduce a more direct flow of cold air into the bumper cavity.

-SB

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PLAZAMAN

· #14 · Feb 14, 2003

Stay away from Ebay Intakes. Cheap filters and cheap quality intakes.

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