I posted this to the DIY plenum porting, but I think it'll get more views here.


I haven't seen anyone remove material from bottom of the runners. Where the bottom of the plenum matches up to the actual intake runners. The turn is narrow, so what if you removed the shaded area to keep the same diameter down to the oil blow by hole? Effectively widening the turn and allowing more air to flow down.

Has anyone tried this before?

 

https://my350z.com/forum/intake-exha...-plenum-8.html

Boar needs moar bore.

 

Ah ha, I had seen that thread but did not know that was at the end of it. Well, good to know I was on the right track see where his paint marks landed.

 

Wow, thats a huge difference.

 

Ya, this seems like this should be a lot more popular NA mod. Granted this would cause your Z to be down several days having to take apart everything down to the actual runners. I was thinking of just doing the bottom of the lower plenum. But as sparco stated, bore needs more bore. So you can't do one and expect much gain, but definitely doing both yields good gains.

Looking at that dyno shet at the bottom, I'm really amazed at how well the TQ stayed up all the way to about 5800-5900 before it gradually fell. And those numbers were achieved on an 04 5AT.

 

How does the meeting point between the lower intake and head look? Should the head be ported also or does it match up well?

 

what were the results of this mod? Did you dyno this against a pre-modification state? In theory (yea, yea, yea - I know we dont live on a sheet of paper - hence why I'd want to see a dyno) this won't increase power output. The intake manifold runners neck down (decrease cross-sectional area) to increase velocity of the intake charge. A faster intake charge will fill the cylinder in a more efficient manner. But by all means, if you saw an increase in power than that's pretty cool!

 

You can still keep velocity up while enlarging everything to get more in there. Results are on the board and it's 5-10hp. What folks tend to not realize is that mods like this don't make big power on their own but partnered with a full exhaust and a tune and it'll be better. Add forced induction into the mix and it gets even sweeter.

 

I (respectfully) disagree about enlarging everything and maintaining velocity, but understand this is your mod so I am happy you got some gains out of it - and in reality it does neck down a little once it gets towards the bottom there. And I agree with you that it's the culmination of a few steps in the right direction!

A guy helping me with my build wants me to revise my greddy 18g kit into a psuedo LS1 intake and he brings up some really good points on how inefficient the OEM intake and greddy's post-turbo through throttle body piping is. All I have is time!!

 

There is a fine line to walk for sure when porting stuff out but if your runners are choking the engine from being to small then you can have all the velocity you want but it won't matter because you can't get enough air in. Open everything up a bit and you'll still maintain your velocity and increase your volume. Go to large though and velocity will drop and hurt things. Gasket matching everything though has historically been beneficial on nearly all engines so I'm comfortable in doing it. Plus like I said, it's been done before on these engines and gains have been shown so it obviously works.