air intake equivalent length?

[igloonation]

K first off i'm not an engineer or a technician or even a student, but i have read a few things online pertaining to intakes.

Idk if this is an easy question to answer or not, but anyways i have an intake on my car right now (keeping things simple) it's 32 inches long and has a diameter of 3 inches.

I'd like to make my own intake and shift the power band a little bit higher 100-200rpm and I'd like to use either 2.5inch or 2.75inch piping. Now from what i understand inorder to shift the power band higher with a smaller diameter pipe i'd have to make the pipe shorter but what i don't know is "how much shorter?"

Also to keep things simple i'd like to not get into harmonics/acoustics/pulse waves, etc. I'm mainly just concerned with air speed velocity.

I want to be able to flow slightly more air with a shorter, smaller diameter pipe.

[igloonation]

K first off i'm not an engineer or a technician or even a student, but i have read a few things online pertaining to intakes.

Idk if this is an easy question to answer or not, but anyways i have an intake on my car right now (keeping things simple) it's 32 inches long and has a diameter of 3 inches.

I'd like to make my own intake and shift the power band a little bit higher 100-200rpm and I'd like to use either 2.5inch or 2.75inch piping. Now from what i understand inorder to shift the power band higher with a smaller diameter pipe i'd have to make the pipe shorter but what i don't know is "how much shorter?"

Also to keep things simple i'd like to not get into harmonics/acoustics/pulse waves, etc. I'm mainly just concerned with air speed velocity.

I want to be able to flow slightly more air with a shorter, smaller diameter pipe.

[Mikey Antonakakis]

You could just buy one of those adjustable powerbands, they aren't that expensive.

[TorqueWrench]

Check out Grape Ape Racing's website. Would post the link, but dont want to wait for approval. Technical papers have some pretty good calculations for ballpark answers.

[wagemd]

If you want to avoid harmonics and waves, it is going to difficult if not impossible to quantitatively answer that question.

What you can do that's quite a bit simpler is to just iterate. Start with your 32 inch intake and start chopping till you find what you like. Depending on how much time you have and if you have a real dyno available, you could start cutting maybe 1/2 inch lengths off at a time.

Keep in mind just changing that pipe might not make big (or even positive) changes to your power/torque curves. The whole engine package is usually tuned as a system on modern cars so changing the intake acoustics could end up actually decreasing power/torque if it's fighting with the exhaust.

Finally, its hard to say how big of a change you will see from modifying that pipe... If you really want to do much with the tune, you'd have to start modifying the runner length; which is a real pain on a production car.

Not to discourage you, just want you to know what to expect http://fsae.com/groupee_common/emoticons/icon_wink.gif

[igloonation]

yea after a bit of thinking i realized its hard not talk about harmonics/waves.

Although if we take the pure cfm of a 3inch diameter pipe 32 inches long would it be possible to figure out the needed length of a 2.5 or 2.75inch diameter pipe with a comparable cfm?

In case i'm wrong can someone confirm for me that shorter pipes flow better than longer pipes? Whether its because of friction or whatever.

[wagemd]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by igloonation:
yea after a bit of thinking i realized its hard not talk about harmonics/waves.

Although if we take the pure cfm of a 3inch diameter pipe 32 inches long would it be possible to figure out the needed length of a 2.5 or 2.75inch diameter pipe with a comparable cfm?

In case i'm wrong can someone confirm for me that shorter pipes flow better than longer pipes? Whether its because of friction or whatever. </div></BLOCKQUOTE>

It would probably be possible to find that length for a steady cfm value, but the number would be useless since the intake isn't a steady flow. If you just want max flow, you could tinker with some sort of short nozzle/diffuser setup.

To answer your question, a shorter pipe (comparable in all other ways: diameter, material, etc) will flow better because there is less pressure loss (an effect of the friction). This is only necessarily true in steady state however. Waves tend to mess with that as well.

If you dont want to look at the math (I dont blame you) your best option really is extra pipe, a hacksaw, and some drive time.

[igloonation]

this is kind of a side question, but i'm looking at going to school for mechanical engineering, to be at a level where i could design intake systems (meaning the entire intake from valve to filter) and exhaust systems would a 2 year diploma be enough or would a 4 year degree be enough even?

[wagemd]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by igloonation:
this is kind of a side question, but i'm looking at going to school for mechanical engineering, to be at a level where i could design intake systems (meaning the entire intake from valve to filter) and exhaust systems would a 2 year diploma be enough or would a 4 year degree be enough even? </div></BLOCKQUOTE>

I terms of raw knowledge, I really haven't leaned much of what my intake work required from classes (sadly). Some background such as "this is why flow cant go supersonic" was covered in class, but cant say I've taken much directly from coursework. Most of what I needed was self study. However, if your wanting to do power package design as a career, I would venture to say even a BS would be a tough sell to an engine builder.

[igloonation]

no i'm not really looking to work in the aftermarket industry, more automotive oem or race team engine designing.

[wagemd]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by igloonation:
no i'm not really looking to work in the aftermarket industry, more automotive oem or race team engine designing. </div></BLOCKQUOTE>

I bet its a lot harder to get into oem and race design. They have more resting on the final outcomes of your design. High school and college kids will buy just about any old cold air intake because its "cool". Race results and funding are to lose on the other hand (= grad school). Not sure how many forum members have made it out into the race car world beyond FSAE, but I imagine they would agree? If not let me know and Ill get my resume ready now http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Demon Of Speed]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by igloonation:
this is kind of a side question, but i'm looking at going to school for mechanical engineering, to be at a level where i could design intake systems (meaning the entire intake from valve to filter) and exhaust systems would a 2 year diploma be enough or would a 4 year degree be enough even? </div></BLOCKQUOTE>

A 2 year degree (at least in the states) is going to be pretty pointless for what you want. You spend the first 2 years getting the humanities, math classes and other elective out of the way. From my experience, even in junior and senior level classes it was the theory of the stuff that makes the car work, never directly designing anything for a vehicle (which is one the the reasons I love FAE). I am going to grad school for automotive engineering and now half the classes directly relate to designing cars, and the other half is indirect like the junior and senior level classes.