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  #16  
Old 01-13-2008, 02:24 PM
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I'm not personally fond of the extrude hone procedure and it's "benefits". We've used it a few times on different motors and did not gain anything appreciable that makes the cost of the process worthwhile. I too agree that ceramic coating the intake plenum will yield greater results. Doing so has for me in the past on many aircooled 911's

Second a perfectly smooth surface doesn't help flow any and actually hurts it in some cases due to the loss of the boundary layer(layer of air that "sticks" to the inner walls) Air flowing across a perfectly smooth surface vs a boundary layer has greater friction, this has been proven time and time again. Adding the ceramic coating inside the manifold would most definitely yield a better surface than the super rough OEM surface, but not as bad as going with an extrude hone that damn near polishes the inside. I think it's one reason why the extruded hones DON'T make any appreciable power, at least in my experiences.

And finally, I'd leave the TB's alone. They'll flow more air than the motor could ever really need right now. Only thing I'd ever change would be to convert from a butterfly setup to a flatslide valve setup to eliminate the air obstruction of the butterflies and shaft at WOT but even that's going beyond what most would ever really use.
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  #17  
Old 01-13-2008, 04:55 PM
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Ok Tom, went through your locker. I think I will just contact Outlaw and have them make me a set!

Also, to others who have responded, I'm definitely not trying to say "I know it all why hasn't this been done before?" More like I just haven't read anything about it on here and I wanted to know if it was worth it. Thanks for everyone's response so far! They are appreciated.
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  #18  
Old 01-13-2008, 05:29 PM
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Quote:
Originally Posted by Boxersix View Post

Second a perfectly smooth surface doesn't help flow any and actually hurts it in some cases due to the loss of the boundary layer(layer of air that "sticks" to the inner walls) Air flowing across a perfectly smooth surface vs a boundary layer has greater friction, this has been proven time and time again. Adding the ceramic coating inside the manifold would most definitely yield a better surface than the super rough OEM surface, but not as bad as going with an extrude hone that damn near polishes the inside. I think it's
From a fluid mechanics perspective, you actually want a slightly rough surface on the intake side to "trip" the flow and get better mixing of the air-fuel. Smoother on the exhaust side is okay.

-Bill
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  #19  
Old 01-13-2008, 05:54 PM
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Originally Posted by SVXRide View Post
From a fluid mechanics perspective, you actually want a slightly rough surface on the intake side to "trip" the flow and get better mixing of the air-fuel. Smoother on the exhaust side is okay.

-Bill
Exactly. The optimum surface prep is around a 400grit comparable. Just enough to optimize a good boundary layer for velocity and turbulence level for atomization
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  #20  
Old 01-13-2008, 09:06 PM
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So wouldn't it be good then to have the intake itself as smoothe as possible to increase velocity,and then leave the "stacks" with the factory finish since that's where the injectors are? Seems like it would help smoothe airflow until the point where are and fuel mix and then the extra velocity would create extra turbulance and increase combustion effeciency.
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  #21  
Old 01-13-2008, 09:25 PM
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So wouldn't it be good then to have the intake itself as smoothe as possible to increase velocity
Not really, as the smoother the surface the less of a boundary layer you have. This of course has a fine line you need to follow as obviously if it's too rough then you're just messing with flow and are right back to the beginning. For example, when I port heads they all get a final blast finish in the port with a 4-600grit(pending head material) after all the port and sand work has been done. I have shown people at my shop with a CNC ported head with two ports, one polished and one 400 grit soda blasted with the blasted port having a higher velocity than the polished port on my flow bench. This is of course on the intake ports. Exhaust ports just get ported and sanded as a boundary layer there makes minute effects in exhaust velocity.
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