Yes, It's probably been answered a thousand times...

[GScivic7]

I didn't know that having those secondary runners were bad for boost, how is that so? It's just a shorter path to the motor and more air + more fuel = more power. My motor has the same IM setup with the second set of runners and there have been a few people who have boosted these motors and haven't really complained about any problems with them. Care to inform the un-informed?

[hybridsol]

Originally Posted by GScivic7

I didn't know that having those secondary runners were bad for boost, how is that so? It's just a shorter path to the motor and more air + more fuel = more power. My motor has the same IM setup with the second set of runners and there have been a few people who have boosted these motors and haven't really complained about any problems with them. Care to inform the un-informed?

ok the longer smaller diameter runners are much more restrictive because of there square cross section. Meaning when you look from an end view, the shape of the primary runner is square not round or oval, they also add aerodynamic drag on the flow. Since square shaped runners have more surface area, the boundary layer between the air flow and the runner wall is stickier and creates more turbulent flow which disrupts the speed of the flow and the amount that reaches the chamber. The design of the B18c1's intake manifold dual stage runners is to provide more low to mid rpm torque with the longer, narrower square runners and then increase flow for the upper rpm torque gains by having oval (low drag) larger diameter (low restriction) shorter secondary runners open up, along with the primaries in an N/A setup. The result is a wider torque curve that sits at peak torque across a longer rpm range. The 8 runners have a combined greater surface area and would restrict a turbo's efficiency for filling the chamber. You don't need long primary narrow runners to build up more flow velocity in the low to mid rpm torque with a turbo. Since you aren't filling the chamber like an N/A engine, you are actually stuffing in the air. Also the b18c1's intake manifold's plenum is really too small for a turbo. You need an intake manifold with a larger plenum volume and 4 runners (not 8 runners) for less surface area drag that are larger in diameter and shorter in length, it makes them much less restrictive.

[Kven]

the b18c doesnt use dual runners; and i was never referring to using a turbo engine. the whole runner length/diameter has to do with flow and resonance tuning. heres a good writeup on intake manifold design: http://www.hondalife.com/modules.php...rticle&artid=2

[hybridsol]

Originally Posted by Kven

the b18c doesnt use dual runners; and i was never referring to using a turbo engine. the whole runner length/diameter has to do with flow and resonance tuning. heres a good writeup on intake manifold design: http://www.hondalife.com/modules.php...rticle&artid=2

....yes it does the GSR motor has dual intake runners.....

[hybridsol]

Originally Posted by Kven

the b18c doesnt use dual runners; and i was never referring to using a turbo engine. the whole runner length/diameter has to do with flow and resonance tuning. heres a good writeup on intake manifold design: http://www.hondalife.com/modules.php...rticle&artid=2

If your reffering to an ITR, that entire motor was built for high rev, right down to the piston skirts coated with molybdenum. its a lightweight high compression motor, and also is all about high rev. right down to its high CR. I know the american copy of it very well, the b18c5 I have one in a del sol. I don't think he has reffering to a jap spec ITR...... That can be pricey.

[Kven]

since he said b16b im thinking he is also talking about the jdm b18c :shrug:

[GScivic7]

ah, I have been enlightened thanks hybrid.