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What the difference between a 4 port and a 6 port intake. Can someone please explain?
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One intake system uses 4 ports - 2 primary, 2 secondary.
The other uses (you guessed it) 6 ports! https://www.nopistons.com/forums/pub...IR#>/smile.gif 2 primary in the centre iron, and 4 secondaries (2 per rotor). They did it to use an intake manifold with a rotating sleeve which would increase intake duration at higher RPMs. The lower secondary port (on the rear or front iron) is always open and the upper port is closed at low end and opens at high end. They've been doing it since the 80s. When did Honda come out with VTEC anyways? |
Originally Posted by ColinRX7' post='890718' date='Dec 24 2007, 12:20 PM
One intake system uses 4 ports - 2 primary, 2 secondary.
The other uses (you guessed it) 6 ports! https://www.nopistons.com/forums/pub...IR#>/smile.gif 2 primary in the centre iron, and 4 secondaries (2 per rotor). They did it to use an intake manifold with a rotating sleeve which would increase intake duration at higher RPMs. The lower secondary port (on the rear or front iron) is always open and the upper port is closed at low end and opens at high end. They've been doing it since the 80s. When did Honda come out with VTEC anyways? |
Personally I would remove the whole intake system and pull the sleeves right out of the motor, and clean them up.
You should be able to see the diaphragms turning linkages on the lower intake manifold which connects to the sleeves inside the block using forks which are not permanently connected to the sleeves, they just force the sleeve to turn when the diaphragm is charged. 86-88s use exhaust back pressure to charge and I forget what the 89-91s do to charge. The only reason they're not permanently connected is so that you can easily remove/install the lower intake without screwing around trying to disconnect the LIM from the sleeves. That being said, you can rip apart the intake and pull the sleeves out of the block (literally pull with one finger), and clean them up to reduce friction which translates to proper operation of the sleeves. It might seem like a complex system but it's actually brutally simple. |
Here is a 6 port intake gasket layed over a 4 port intake manifold.
The red lines show the 4 port outline. https://www.nopistons.com/forums/gal...1_179_6263.jpg |
Originally Posted by ColinRX7' post='891004' date='Dec 29 2007, 12:49 PM
Personally I would remove the whole intake system and pull the sleeves right out of the motor, and clean them up.
You should be able to see the diaphragms turning linkages on the lower intake manifold which connects to the sleeves inside the block using forks which are not permanently connected to the sleeves, they just force the sleeve to turn when the diaphragm is charged. 86-88s use exhaust back pressure to charge and I forget what the 89-91s do to charge. The only reason they're not permanently connected is so that you can easily remove/install the lower intake without screwing around trying to disconnect the LIM from the sleeves. That being said, you can rip apart the intake and pull the sleeves out of the block (literally pull with one finger), and clean them up to reduce friction which translates to proper operation of the sleeves. It might seem like a complex system but it's actually brutally simple. |
Both of my cars did at idle, they were S4s.
You'd be surprised what a little moisture and time can do to a car that has low mileage. |
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