Pro Stock John

iTrader: (34)

This is not an LS1 specific question.

So if you have a car that has a long air intake assembly, like 2-2.5 feet long, what would be better:

-Long CAI that stretches from the TB to the bottom of the car
-Short air intake that attaches a filter to the TB, with say just a six inch transition

I'm thinking the short ram will injest some hot air when not in motion, but that the long intake will have less air velocity...

What do you guys think?

Also for FI setups, I have heard that have long intakes with a lot of bends will significantly slow down incoming air velocity...

Keith

I have always heard that a restriction on the inlet side of a FI setup will be compunded once the air is compressed. I could see a long air intake assembly posing a restriction.

chuntington101

its all about how much air can you get down (or up in this case) that tube! a vacum is a pain in the *** as you can only have a maximum of -1bar (-14.7psi) acting upon the air! now the longer the intake track (to the SC/turbo/inlet valves) that great the resistance and thus a lower about of air can be moved by the vacum! this is why water pumps that are used to pump water out of deep wells are mounted at the bottom (in the well) rather than at the top!

on the other hand, there is F*CK ALL point in pulling hot air from behind a rad or intercooler as this air is less dense and thus will make less power!

so i think its a compromise bettween getting the cold air and the restriction of the piping!

Chris.

jyeager

If the intake piping is big enough, the length should be a non issue.

Pro Stock John

iTrader: (34)

But I have heard that regardless of diameter, a long intake tract can be problematic.

jyeager

Yes, it seems intuitively clear that it does. The question is whether it's one that could be measured on the dyno. If it were long enough (say 10') or small enough it sure would.
It changes the picture quite a bit if we are talking about your boosted car that sucks in a ton of air.

I'm only speculating, but if we are talking about air velocity in to the intake ports of the heads then a large intake tract say 4" in diameter shouldn't be an issue since you are running through a 90mm throttle body anyway.
Again, I can see that being different when your boost gets high enough though.

jyeager

John, you're the type of guy that I'd go to for advice, so this is only speculation designed to help you discover truth....So that being said, I can say that an application of the scientific method should answer this question pretty easily.

Try back to back dyno pulls with the 2 setups. If ventilation is good, hood up on the car, then you can do runs with the long intake, then runs without it. An improvement shows restriction.