1987 300zx z31 build up - Gone. Hello Z32

[SILV14]

Yup!

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[boarderline]

well it has been awhile! I have gotten a wideband 02 sensor, AFC, and a tach adapter. Sadly the AFC I got was used and the circuit board is shot.. so I will be getting a SAFC 2 from Apexi. Hopefully I will be able to return the broken one so I dont loose out on 300 bucks. So I am hoping to be able to bring my car into the shop in a week or 2 to get the exhaust so I can install my wideband sensor and start tuning and driving! I am iching to drive it!

[boarderline]

here is the latest and greatest update! blew my turbo at the end of last year, also found that i had bad compression in cyl. 1. so this winter I started tearing down my block to do a rebuild and well I was at it I ported my head




















home made valve compressor extension

intake ports

before getting ported

after!


Next I will be tearing down the lower block and bringing it to a machine shop to get finished honed and get the head milled and cleaned up.

[SILV14]

Where are you taking your block?

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[SpooledupRacing]

Get in there and spend some real time sanding and smoothing out those runners. Just making them larger doesn't do much if they are all choppy.
Looking good though, just do it right, new gaskets new parts and no silicone!

[SILV14]

Actually the air doesn't care if it is smooth or rough. Fuel will slow when it gets close to the sides and turn back to liquid and that isn't what is needed.

Its like water skiing. The best time is smooth with ripples. Smooth as glass seems good, but there is a lot more friction.

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[SpooledupRacing]

I'm confused with your response. Look at ANY PROFESSIONAL port job. You need to have smooth transitions. You will get better performance with nice clean smooth runners.

[SILV14]

I know this is a terrible source, but it has good information
http://en.m.wikipedia.org/wiki/Cylinder_head_porting#section_5

It is popularly held that enlarging the ports to the maximum possible size and applying a mirror finish is what porting is. However that is not so. Some ports may be enlarged to their maximum possible size (in keeping with the highest level of aerodynamic efficiency) but those engines are highly developed very high speed units where the actual size of the ports has become a restriction. Larger ports flow more fuel/air at higher RPM's but sacrifice torque at lower RPM's due to lower fuel/air velocity. A mirror finish of the port does not provide the increase that intuition suggests. In fact, within intake systems, the surface is usually deliberately textured to a degree of uniform roughness to encourage fuel deposited on the port walls to evaporate quickly. A rough surface on selected areas of the port may also alter flow by energizing the boundary layer, which can alter the flow path noticeably, possibly increasing flow. This is similar to what the dimples on a golf ball do. Flow bench testing shows that the difference between a mirror finished intake port and a rough textured port is typically less than 1%. The difference between a smooth to the touch port and an optically mirrored surface is not measurable by ordinary means. Exhaust ports may be smooth finished because of the dry gas flow and in the interest of minimizing exhaust by-product build-up. A 300 - 400 Grit finish followed by a light buff is generally accepted to be representative of a near optimal finish for exhaust gas ports.

The reason that polished ports are not advantageous from a flow standpoint is that at the interface between the metal wall and the air, the air speed is ZERO (see boundary layer and laminar flow). This is due to the wetting action of the air and indeed all fluids. The first layer of molecules adheres to the wall and does not move significantly. The rest of the flow field must shear past, which develops a velocity profile (or gradient) across the duct. For surface roughness to impact flow appreciably, the high spots must be high enough to protrude into the faster moving air toward the center. Only a very rough surface does this.

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[SpooledupRacing]

Seems t be counter productive... I have always read, always hears you need to have a nice smooth port, I'm in no way talking mirror finish but not a chewed up port.

Regardless this mod on his motor will most likely only harm the bottom end and not produce any more power up top.

[boarderline]

Aarons right. The port its self is what gives you the biggest jump in performance. By polishing them up and making them PERFECTLY smooth will help a little but would only account for 1 maybe 2 hp. I am not too worried about that 1 to 2 hp. I did however take a sanding bit and cleaned them up a little. they are smooth to the touch