NmexMAX

iTrader: (22)

I got my VI yesterday and was looking insede it and noticed that the first 2/3 of the short runner walls are nicely polished, and about 1/2 way down into the end of the runner, it becomes rough again. I was wondering if any gains would be acheived by machining the other half of the short runner to match the rest of it?

Any thoughts?

speedtrip

The first 2/3 of the short intake runners are probably machined to allow unrestricted movement of the butterfly valves. It would be my guess that polishing the remainder will do nothing. The short runners and the pod on top are tuned for a resonance effect. The long runners bring the air to the engine.

When the variable intake butterfly valves are activated it allows the pressure wave created by the piston as it moves down on the intake stroke, to an open plenum volume (the pod on top of the VI). This plenum reflects the pressure wave back as a compression wave which forces more air into the cylinder.

NmexMAX

iTrader: (22)

yeah nissan knew what they were doing.......

speedtrip

I like our simple 4th gen VI's. It works just as good as the variable runner length hoopla in the 5th gens.

Keven97SE

I thought about doing this to my MEVI as well but ran out of time to do it, so never got around to it.

Based on the dyno I performed on my extrude honed intake manifold, the resonance rpm increased ~400 rpms due to the EH process (torque peak #1 went from 3300 to 3700, peak #2 went from 4600 to 5000). The EH process definitely shifts the boost to a higher rpm. You *may* see an improvement in high rpm torque (ie HP) by doing this to the MEVI, but you may also lose more than you gain by making 5000-5500 softer. I don't know. I seriously doubt it'll do much. It may be worth spending an hour or two hand-polishing the lower section, though. Aluminum is very easy to polish by hand. You should be able to get a very smooth finish by using several different sandpaper grits.

JsL

iTrader: (5)

I know you won't get any gains, but get the VI cover, that thing looks soooo tight!!!!!

NmexMAX

iTrader: (22)

Yeah, the cover is really nice, and adds a very stock appearance to the entire engine bay. I remember when Mr Cranman and I went to the dyno, the guys over there asked it it was an aftermarket intake manifold, and I'm pretty sure if he had the cover they wouldn't have asked, maybe, but I do like it, and am thinking of getting one.