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Old 07-27-2002, 09:54 PM   #1
Scooby Newbie
Member#: 21857
Join Date: Jul 2002
Location: Boston, MA
1987 Barbie Corvette
Yeah Baby

Question custom intake

so i was thinking of how to build an intake for my car, which is a my99 2.5RS, and i figured since it already has the hood scoop, that's the coldest source of air. but there's the question of the mass air sensor... so i was thinking take the sensor and connect it right off the intake manifold, and remove the whole big thing in the middle, then put a cone filter right right off the sensor, which would end up right under the scoop. but what are the three hoses coming off the central part of the air box? can they be removed, are they important, can they be bypassed? or something... so would this all work or something, cuz that would be way cheaper than buying an intake, and if my calculations are right, be just as good or better. thanks. seize ya

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Old 07-27-2002, 11:09 PM   #2
Scooby Newbie
Member#: 16571
Join Date: Mar 2002
Location: Saint Charles, IL
2000 Impreza 2.5 RS
'90 Honda Civic si hatch


The three hoses are a means of the valves "breathing"... from What I understand. They can be bypassed by removing the hoses completely and replacing them with small K&N style filters suitingly called "breather filters". This modification is frequently called "Venting to atmosphere".

As far as mounting the air cleaner directly on the throttle body, Several people have done this and I cant really comment on it's effectiveness. However by mounting the filter on the TB, you are exponentially increasing the risk of hydro-lock. Water in the intake manifold can cause SERIOUS PROBLEMS and SEVERE ENGINE DAMAGE. The other thing to think about is what will happen in the winter with snow and what not. I say just save up your pennies and get a real intake.

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Old 07-27-2002, 11:26 PM   #3
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Join Date: Aug 2001
Chapter/Region: MWSOC
Location: My member# is lower than yours
05 Saab 9-5 Aero


The three hoses are for the Positve Crankcase Ventilation (PCV) system. Crankcase air is pulled into the intake from a hose that tees into one of three on the air intake. The other hoses are there to allow fresh air to enter the engine to replace the air sucked into the intake. The system helps prevent oil leaks and prevents hydrocarbon emissions in the crankcase from being vented to the atmosphere. (The PCV system was the first emissions control ever introduced, it made it debut in 1963) This is esentially a closed system.

If you don't pull the fresh air in after the MAF sensor, it can't be measured along with the rest of the incoming air, and the engine will run lean at idle, as up to 20% of the engine's air consumed at idle comes through the PCV system.
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