With all the talk of IM's and the potential power increase I am wondering what would be the ultimate IM design for a street driven VQ? If cost and fabrication skills were not an issue, what would you build and why?

I'm thinking a dual plenum setup with two throttle bodies where the LH 3 cylinders get fed by a plenum above the RH valve cover and vice versa, like the stock 300zx IM but w/shorter runners and larger plenums. I'd build it one piece to replace the lower IM because of it's fairly sharp turn right before the heads. That would allow a pretty straight shot from the plenum straight to the valves.

opinions?
allen

 

For N/A.. Here's a thread for you.

http://www.forums.maxima.org/showthread.php?t=373568

 

Thanks, forgot all about that thread.

No mention of redesigning the lower IM though, wonder if it's a significant restriction.



allen

 

If you plan all that radical ITB stuff, but don't want to touch th LIM, then hmm strange.

 

He isn't talking about ITB's. He was saying two TB's like on the 300ZX.

The shape of the LIM doesn't seem very restrictive. Maybe its a bit small for the correct flow but the angle of the injectors and the radius of the curve is nice and gradual. Maybe do some flowbench work and port it out. Then port out the intake ports to match. Just a thought.

 

I'd get a hold of a 350Z IM, or an aftermarket 350Z IM and make it work.

If you built an IM to replacing your lower IM altogether, that would require making ports for the injectors, and have a custom fuel rail setup. I don't think it's worth all of the trouble..

 

True, it's probably not worth the work for the HP increase but I like doing this kind of work and enjoy the process of designing and fabricating parts and having unique parts.

BTW, you can buy the injector bungs that epoxy on to your custom manifold, thread into holes you drill/tap or the kind that you weld on. I think the stock fuel rails could be reused. If not they really aren't that hard to make (no, I haven't made any yet but it looks pretty simple here: http://www.sdsefi.com/techrail.htm )


allen

 

Side feed fuel rails are pretty hard. The tolerances needed on the injector cup are fairly precise. So welding on it would throw those tolerances out of whack.

 

You would probably be better off converting to top feed if you redid the lower IM. If anything I would just maybe port it or just use the 5th gen one (00-01) since it already uses top feed and is supposed to be lighter and maybe flow somewhat better.

It would be nice if the pathfinder VQ35 IM would fit under the hood of a Maxima or your 240SX for that matter, but it is pretty big and I doubt it would fit. The VQ30DET IM would probably be nice but it would be pretty hard to source without buying a whole engine.

 

Has anyone looked at installing a Pathfinder/QX4 intake manifold ? I have a QX4 at work that I am working on and I think the manifold would fit- but it woud require some modifications to the air intake tubing as the throttle body would sit in bout the same spot as the VG30E 3rd gen TB. I been looking everywhere to find a used 01-03 intake manifold but no one wants to part it off the engine.

 

IIRC krismax was ....

redmax (3rd gen dude) was supposed to get back to me on dimensions and other details, but I'm still waiting.