maybe this is a dumb question

but has anyone had their mrev or lower plenum ported/polished, would any gain be seen by this on a NA application or is it pointless?

 

yes, i believe there are a very small gain on the high end. search on my350z, Tony from MD said something about it. i modded my stock lower plenum into a "MREV2 look-a-like" and port and polished it.

 

As with any parts you have to balance whether the $100 per HP gained is cost effective.............easy for poorly trained to actually decrease power [increased reversion] via porting.

 

MREV2 is ported.

Polishing it smooth won't help. Polishing it rough might help.

That's a nice job up there aleok - looks like a helluva lot o work though.

Q45 - why so pessimistic? I think the chances are excellent that even an untrained person, relying on good 'ol common sense, could get gains by porting provided the modifications are not extensive (i.e. just identify the most restricted area and make the holes bigger).

 

Q45 is pessimistic because he is right. There is a lot more to porting/polishing than just making the holes bigger and shiny. You really have to know what you are doing to do it manually. A far better option is to send in the whole upper and lower plenum to extrude hone and do the abrasive flow machining. It will be perfectly flow matched and all the rough turbulence inducing surfaces will be reduced or eliminated. If you want to get really crazy, do the heads too. But not really worth it unless you are doing cams at the same time.

http://www.gethoned.com/auto.php

 

Being right and being pessimistic don't necessarily go together (and I never said he was wrong). And where is the cost-effectiveness in what you suggest? lol. Talk about overkill for 5 hp.

It doesn't have to be "perfectly flow matched" - that's not the goal. It just has to flow better, not "flow perfect". The 1st and 2nd runner flow issue is clearly a design compromise inherited from the 350z strut bar and is easily addressed by enthusiasts.

chill

 

You dun polish plenum for gain, you make it rough ... since flowbench suggests that rough intake media increases flow and efficiency in general.

Moreover, if you really wnana do porting, do on your engine head; it is far more effective (provided that you do it right)

 

Go to the MY350Z's DIY section for almost 20 pages of fun. Rough surfaces cause turbulence (eddies). At low pressures to double the output you need to increase the input by 4 times. Smooth surfaces where no ED's are you only need to double it. But that being said I'm experimenting with this (or at least when I have time) to prove one way or the other. As for porting you need to match the two mating surfaces so there is no "step" . It should feel like one surface at the change of the two. I have a bunch of lower plenum's in my basement and can say that no two are identical. I don't think I've ever read Tony say that his MREV2 was ported. I've spoken to Tony about this and he said that he got about a 4 hp blip in his dynoing but he only did the runner section of the lower plenum. Rick on this forum had several polishings done and no real gains......................... but I'm out to try to prove you wrong Rick. But all I know is that we need to get the air in there quick as possible, meaning better flow to get more pony power. It's hard for me to think that Nissan's mass produced engine and parts are at peak performance. Oh well I have to see for myself.

 

1. Chill? This is an open discussion and who are you anyway? The forum police?

2. Cylinder to cylinder flow matching is absolutely the goal. If not, then WTF is the reason for having tuned intakes and equal length headers then? Anti-reversion maybe?

3. The 5HP gain you may be refering to was on a 110HP GA16DE 4-banger. That's 4.5%. If repeatable on the VQ35, that's 12.6HP and would be at the top of the heap for N/A VQ mods. Extrusion honing has proven itself long ago in the racing world and should not be news to anyone.

4. The alleged front cylinder air starvation "discovery" described on the Crawford site as a "sharp upper RPM power drop" was nothing more than the ECU closing the throttle body as redline approaches. TS figured this out while the Crawford boys got out the saws and torches when they started fooling around with their flow bench. Unfortunately, an engine does not draw flow that way in operation. Valves snap shut and open creating complex waves and reflections. That wedge helps direct the amplitude of the reflected wave to assist cylinder stuffing, not to clear a strut bar. The strut bar could have easily been formed to clear a flat plenum if that was the best plenum design. But obviously it's not since the '07 plenum is also angled down in the front and there is no strut bar to clear. See pix.

5. Anyway, I have yet to see any functional evidence of over rich front cylinders on a stock motor. Has anyone taken a multichannel exhaust gas analyzer and tapped into each exhaust port to measure A/F ratio? If the front 2 cylinders are as "air starved" as everyone says, they would be running rich wouldn't they? Not likely in this age of fuel mileage and emission regulations that the Nissan engineers would allow 33% of the engine to be running pig rich. The plenums and spacers are increasing overall volume and available flow, they're not "balancing" jack. If anything, the flat style plenums are altering the designed balance whereas the MD approach increases overall volume and flow while retaining the wedge effect.

 

Best f-ing post I've read in months on this site. I couldn't agree more.

It never ceases to amaze me the myths that abound the internet concerning "restriction" and "flow". As I've always contended, just because it's ugly and looks restrictive, doesn't necessarily mean it is. These shadetree aftermarket companies often do not employee powertrain engineers, use super-computers, or flowbench their work. They simply go with a more flow is better and bigger is better attitude, with little regard to what the intended purpose of said part really was. These aftermarket companies are also often guilty of taking advantage of their customer's automotive ignorance.

 

Thanks DaveB. I too cringe when I see products released that are a complete waste of time and money. People have the right to do whatever they want to their cars, but when I feel complete nonsense is being spewed, I also have the right to say so.

 

And we have the right to actually do the modification, actually test the modification and then talk about the results.