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Discussion Starter #1
Or ways to improve it? I've a K&N filter, but nothing else really.

I've been thinking about those long tubes for CAIs...wouldn't those reduce efficiency and throttle response? The way I think about it, air is elastic and doesn't come as fast as it is pulled all the time(hence volumetic inefficiency), and having to pull the air in that long tube causes an short-duration pressure drop due to air suddely being sucked on faster(pressure falls because the suction takes longer to reach the end of the tube where the difference can be replenished from) and a constant reduction in pressure due to increased friction with long tube-walls(though if they're very smooth, this'd be irrelevant)

Wouldn't a cone-filter HAI have better throttle response due to a much shorter tube?
 

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A HAI would have better throttle response because there is less of a pressure drop. A CAI will pull in cooler air though. So my thoughts on this: Choose which you want. Better throttle response with hotter air than the stock airbox brings in. Or cooler, more dense air with more pickup at highway speeds.
 

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Shame we can't just pull off the upper intake manifold, let air suck straight in. Just slap a K&N flat universal filter over the lower intake manifold. :p
 

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Now I feel like I'm back in my Calculous class. :) Small numbers by themselves don't matter much, its the effect of all of them together. But you may be right, looking more into the math, there really isn't much difference air-pressure wise between a HAI and a CAI.
 

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Disclaimer: I'm not a fluid dynamics expert but I'm pretending to be one now.

First thing, air is not elastic. It is a fluid and fluids do not stretch. Second, the length of the intake tube has no effect on volumetric efficiency. Volumetric efficiency is a figure that defines the ratio of air that does get into the engine versus the maximum amount of air that can be ingested by the engine. I'm going to quote some things from Automotive Engine Repair and Rebuilding, 2nd Edition by Barry Hollembeak and Don Knowles.

"What limits the engine torque and rpm on a typical car or light truck engine? There are several answers to this question. Probably the most important factor in determining the torque is the breathing capacity of the engine. After a specific engine rpm, the design of the air intake system, valve train, combustion chambers, and exhaust system limits the airlfow into the enigne to the point at which the pistons are moving so fast the air just does not have time to get into the cylinder. Under this condition, compression pressure and engine torque begin to decrease.
...
The engine's ability to produce pwoer is limited by its volumentric efficiency... Without the ability to breath, all other performance enhancements done to the engine are irrelevant.

In order to increase horsepower output, the amount of air compressed in the cylinder must be increased. Airflow is the main focus over fuel delivery because airflow is the limiting factor. Usually any amount of air delivered to the cylinders can be matched with the correct amount of fuel; however, the inverse is not true.

Therefore, if engine torque is to be improved and maintained to a higher rpm, the air intake system must be improved to increase the airflow into the cylinders at high rpm. Increasing airflow into the cylinders at higher rpm may be accomplished in many different ways, including:
- intake manifold design
- valve train design
- combustion chamber design
- exhaust manifold design
- increasing the number of valves per cylinder and/or the valve diameter
- increasing valve lift"

I don't know if anyone is actually going to read all that, but what it means is stuff like intake manifold porting and polishing, head porting and combustion chamber polishing and cc'ing, headers, camshaft, roller rocker upgrades, and more are what improve volumetric efficiency. I'm just trying to help here, so I apologize if I come off as a pretentious know-it-all because that's not my intent. ;)
 

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Well Pin, you are kind of right, and kind of wrong. First off, air is HIGHLY elastic. It also is a gas, not a fluid. The 3 states of matter are solid, liquid, and gas (ok, technically a 4th plasma state also :p )

Also, your definition of volumetric efficiency is somewhat right.....It really is a ratio of the pressure going into the cylinder versus ambient pressure. Super and turbo'd engines have a volumetric efficiency over 100% because the air is being pressurized and stuffed into the cylinder, so the pressure going into the cylinder is higher than ambient air.

Also, an engine VE changes through the powerband. And engine may have 85% efficiency at 2500rpm, but only 60% at redline. Just like the vulcan, plenty of low end grunt and power and fuel efficiency, but as we all know, it bogs like crazy on the top end. This bogging is 2 fold. 1) the air cannot get into the cylinder fast enough (and thus VE drops) and 2) the air cannot get out of the cylinder fast enough, so it takes more engine power to get the air out.

As for you HAI vs. CAI dilemna, the length of the pipe will hurt power a fraction of a percent and do just as little to throttle response. And, though the HAI may have a tenth of a second faster throttle response (at the most, likely far less than this), the density difference between 200* engine air and the nice 70* air whizzing by my fender is almost a 3 fold difference. You do the math.. ;)

-mobiuslogic
 

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I was confused, now that I think about it you can't pressurize liquids so I made a big mistake. Looks like I need to take physics again. :eek:
 

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ehh.. it's a Vulcan, it doesn't matter!!

Duratec sweetness it the only way to go with a bull..
 

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Originally posted by Noir04@Jun 5 2004, 06:12 AM
ehh.. it's a Vulcan, it doesn't matter!!

Duratec sweetness it the only way to go with a bull..
I second that :)
 

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That's all you two have to say here? Ridiculous.
 

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This is the first time I post outside ofthe EEC board, but I'd like to clairfy some things:

I know a lot of you are going to disagree with this but first: the first definition provided here of VE is correct: it is the ratio of air being flowed by the engine vs the displacement capacity.

Also, as you all know, an engine is simply a big air pump. Since the engine, on an N/A car, works on vacuum. you wil NEVER reach 100% VE (your car may read 100% VE if you log it with say autotap or what not, but I can explain that if someone brings up the point. On a blower car, it is not uncommon then to see VE over 100%, since you ar eno longer dependant on vaccum, but you are stuffing air in.

I have a way to monitor this real-time with my equipment, and just so you know, for the most part on these cars, the air intake, MAF, TB, etc. are NOT a restriction on a stock car. Thus, the only way you will really flow more air will be to add an aftermarket cam, or a blower, etc. Yes, I know someone wil claim that an agressive camwill actually decrease vaccum, but this is because it is in actuality letting in more air, tehre is more duration in the high end, or more lift (which is in essence free horsepower), etc.

A CAI and what not will not really make a difference in amount of air flowed (well it will, but only marginally, because there is very little pressure dop/restriction). Because it is not a restriction (see qualifying statement above), and neither is the TB on this particular vehicle (at all), at least, there is no pressure drop behimd them (see qualifying statements above). Yes, we have data for all of this. On a stock car, headers and exhaust willalso not increase VE, though they do add P in a way. The way this happens, is that since you eliminate some back pressure, the troque surve moves up, and since HP = TQ x RPM/5252, then if you do the math, you will see that you now have more HP (high end) but less torque down low...

The above arguments represent commonly dispersed myths. Part of the reason. We have data for all these claims.

As a side note, a pice of advice concerning re-usable air filters: Re-usable filters, such as K&N filters do improve flow a little, as discussed above (thought not much). However, when cleaning these filters, no matter how little oil you use, some of the oil will make it onto the hotwire on the MAF. This will cause a lean shift. If you are going to use a re-usable air filter, we recommend tossing it and buying a new one when it is time to clean. It is better to pay for a new filter than an new motor.
 
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