If I made my own ghetto intake, would I get any real power?

[ivymike1031]

Originally posted by Bryan8412
thats dependant on my other questions that i wish someone knew: does a CAI take horsepower?

A cold air intake, in simple terms, is a long, wide tube with a filter at the end. It gathers intake air outside of the (hot) engine compartment, and delivers it to the next part of the air induction system (usually the carb, the throttle plate, or a slightly upstream component). A cold air intake is generally designed to be less restrictive than the factory intake that it replaces.

Whether or not it "takes horsepower" is a tough question to answer. If you interpret "takes horsepower" to mean "reduces brake output of the engine" then in general, no. There can be tuning effects, etc., that come into play, but in general, a CAI results in a higher engine output than the factory intake. If you interpret "takes horsepower" to mean "consumes otherwise useful energy" then technically, yes. It will take some amount of energy to move the air through the CAI. This amount of energy is typically less than what the factory intake required, but neither takes a whole lot.

[ivymike1031]

whether or not to use a CAI on a turbocharged setup is an interesting question.

Given the choice of taking your air from under the hood (hot) or from outside the engine compartment (cold), performance considerations will almost always push you towards the latter. Compressing cold air takes less energy than compressing hot air by the same ratio. This is the reason for using real* intercoolers, which go between the compressor stages on a turbine engine. Compressing cold air results in a cooler charge than compressing hot air, which may or may not be important, depending on the effectiveness of the intercooler. If the intercooler is already bringing the intake charge within a few degrees of ambient, then the charge won't get any cooler as a result of the CAI (but you could perhaps opt for a smaller intercooler). If the charge leaving the intercooler is considerably higher than ambient, then taking in the cold air initially will definitely help. So for the efficiency of the turbo, the cold air intake is always helpful. For charge temp & density, it's not always going to be important.

The other considerations in a design will occasionally outweigh performance. Packaging and cost are two big hitters, especially in the case of a retrofit. If the CAI costs too much to add, then forget it (I doubt that this will be the case). If a CAI cannot be packaged within the engine compartment in an aesthetically pleasing manner, or at all, then it might not be worth trying to stuff one in there. If the ducting is too complex or long, then a CAI might not work anyway (air will have time to heat up as it travels through the tubes). Most of the time it's a simple matter to duct your air in from outside the engine compartment, and the decision is simple ("just friggen do it!"). These sorts of points can be debated ad nauseum; I think the performance portion of this discussion is more pertinent.

*(the things on cars that are commonly called intercoolers are, in my opinion, more appropriately called aftercoolers. Some people count the compression stroke in the engine as a compressor stage, however, and thus justify the name "intercooler").

[sciguyjim]

Bryan,
I have no concrete examples for you or links either, & I know just a little about turbochargers. However, I do know science and my experience is telling me what's right and wrong here. That's why I tried to get my ideas across with simplified examples.

You asked "i wish someone knew: does a CAI take horsepower? and does it take "time" and slow the process a la a muffler?"
This is one of the things I tried to get across to you. CAI is free, it takes no work, no time, no muffler. If you take air from under the hood it's going to be hot. If you take a little tubing and run it to a place where it can suck cold air from outside the car you now have a CAI (cold air intake). Given the choice, why not take the cold air?

[Bryan8412]

Originally posted by sciguyjim
Bryan,
CAI is free, it takes no work, no time, no muffler.

Did you read the post above you?

But basically what it comes down to, is that for the most part it's unnessicary, but at certain times it may be useful, but rarely, and not worth the increased cost unless (a la the expensive audi) you're building a supercar and are going all out. So I guess we were both right, sometimes it's useful, sometimes it's not. Just depends on your application I suppose. Nice debate though

Thanks Ivy for the explanation. And you're right it's wierd, i was wondering why some places used aftercooler which was much more appropriate than intercooler, which physically would be very difficult to do in the "compressor stroke"

[ivymike1031]

Originally posted by Bryan8412
But basically what it comes down to, is that for the most part it's unnessicary, but at certain times it may be useful, but rarely, and not worth the increased cost unless (a la the expensive audi) you're building a supercar and are going all out. So I guess we were both right, sometimes it's useful, sometimes it's not. Just depends on your application I suppose. Nice debate though

That's not exactly the message I was hoping you'd take away from my post. What I meant to say was more like "do it unless you've got a strong reason not to." It will always help the compressor efficiency, and will sometimes increase the intake charge density too. Sometimes it will be very difficult to put in the CAI, otherwise go for it.

I've heard that most vehicles these days come from the factory with intakes positioned to ingest cool air, but I certainly haven't personally verified that information. I can think of a couple of examples of cars that don't seem to fit the rule.

[SaabJohan]

Originally posted by ivymike1031
I've heard that most vehicles these days come from the factory with intakes positioned to ingest cool air, but I certainly haven't personally verified that information. I can think of a couple of examples of cars that don't seem to fit the rule.

Most cars have the intakes placed so that can get cool air. Sadly many of theese intakes are very restrictive. So, some replace these original boxes with open air filter, and often the result is bad. In most cases the power decrease but sometimes problems like knocking can occur. All problems are not created by the hot air, like a miss calculating air mass meter as one example.

Bryan8412, Audi R8 use low boost pressure, and the fact that it uses two turbochargers don't change anything. The Audi uses BMC filters (which are large) but the box is a special for R8 made in carbonfibre.

[Bryan8412]

Originally posted by ivymike1031
I've heard that most vehicles these days come from the factory with intakes positioned to ingest cool air, but I certainly haven't personally verified that information. I can think of a couple of examples of cars that don't seem to fit the rule.

ok thanks for clarifying, I interpreted your post wrong as I didn't understand the part where the CAI takes up power (i neglected to see that you stated it uses less than factory, so it in fact takes up power but less than you took up before). So grendal and jim were right for the most part, thats interesting to know, learn something new everyday, thanks for ending the debate. So as long as it's practical to add a CAI in any application (natrually aspriated or forced induction) it's worth it? I see.

Originally posted by SaabJohan
Bryan8412, Audi R8 use low boost pressure, and the fact that it uses two turbochargers don't change anything. The Audi uses BMC filters (which are large) but the box is a special for R8 made in carbonfibre.

I'm not sure where is said two turbochargers changed anything, i was merely pointing out that upon looking into the vehicle and specifically it's intake I was unable to find a link that specifically stated the specs of the intake (cold air or not etc) and was requesting one to be found, but that information is useless now as we have established that CAI's are worthy for forced induction uses