custom plenum(idea and discussion)

[ramper]

Ok I know this has been cover several times but this isnt a where to find thread. I have been working on my own design for making a plenum. Now Im stumped on a few things.1. should I be concerned about equal lengths?2. is there anything else I should think about?3.

now what brought this on is I don`t like the idea of lowering my cross member, or cutting my hood. So it seems the only option is to do something with the intake I mean the thing is huge and spidery and just seems that it can be much much smaller in profile.

So I started drawing up some ideas on paper and sadly I don`t have a scanner to show u so I guess the next best thing is to describe what I want to accomplish.

my idea is to run a 4inch plenum as low and far back in the valley as I can get it. With 4 runners on one side and the other 4 on the other side. Now at this time im not planning on the runners being equal length. I don`t know if that will make a difference or not. Im hoping not. but I dont see it being to hard to fab up either way.

Now the reason I want to discuss this with everyone is once I complete a working prototype and have all the issues worked out I want to offer them up to you guys.

what notes I have for now are as followed keep in mind this is very basic1. custom flange with injector bungs for bosch(sp) injectors.2. fab a q45 tb mounting plate3. 2.25 head side stretched to 2.50 plenum side runners4. plenum is going to be 4in half round alum. pipe 14inchs long5. custom top feed fuel rails.

The fabrication work of this isnt my concern im more concerned if I left anything out. or forgot anything in my plans to account for. or if the idea is even worth my time. anyways time to let the ideas fly. lmk

[npez]

If you're doing forced induction changing the runner length or the plenum volume won't really impact as much. If you're planning on staying atmo, then you really need to look at it a bit more. The length of the runners, etc. affect your powerband. My understanding is that the VH induction system is "tuned" (that's why the runners look like spaghetti under the upper plennum) so the powerband everyone is raving about on all the threads partially hinges on that.

My Z32 plenum was the same way - the runners were like 19-20" long forming a very large "spider". From what I read the Z's plenum at least was a multi-million dollar design - I'm almost certain than the VH is no different.

I'm not saying that what you're proposing will not work, it just will be less optimal than what the Nissan engineers designed. So it boils down to trade-offs between getting it to fit .vs. powerband impact. I'm sure you'll be able to find a happy medium.

Good luck with your project.

Thanks,Nick.

[Chrispy300]

Yep, huge dollars went into the development of the VG intake. Can't say the same for the RB26 suprisingly, they just wacked on 6 throttles and a plennum that fit

[ramper]

thats a really good point. This is why I posted. Right now i dont have any plans of boosting the vh(altho it is a dream) and from what I can u want a long runner. Im doing alot of research on this so Ill update my findings but anymore advice would be awesome.

[hannibal]

I wish there was a way to lower the spider manifold easily. Like cutting the lower runners (or the legs on the spider), rewelding the flange, and just bolting on. I havent held a VH intake so I dont know how practical this idea would be.

I know this would detract from the engineering of the stock manifold, but should be better than building a new mani from scratch.

[ultrapulse]

Yep, huge dollars went into the development of the VG intake. Can't say the same for the RB26 suprisingly, they just wacked on 6 throttles and a plennum that fit

The z32 has more torque and lower down from memory than the gtr. But what a dog to work on!! I have a couple of zeds:)Also whether atmo or forced still does affect torque and tuning in my opinion, as the manifold and heads don't care whether its 15 or 30psi gauge pressure outside:) I don't mean to start an argument, but this is from my research and own ideas. I guess the zed inlet tuning may be answered with nissans approach to this design, when trying to take on other sports cars at that time. Considering the TT was their pinnacle zed sportscar model suggests they did all they could to get the best performance.I made my best 'allrounder' which JUST fits under the std zed bonnet. Everything is all good, but unfortunately the tuning is a bit higher due to shorter than std runner length. I have all this info somewhere but designed and built this mani around 18 months ago, and I believe this link from the original nissan v8 site has gone. heres some pics I have just uploaded:I have used some 3/4" square for the fuel rails and when its all fitted up looks awesome too, yet extremely easy to reach everything around the top of the engine. It sounds like what you have in mind may look something like this.

Modified by ultrapulse at 2:30 PM 8/23/2008
Modified by ultrapulse at 2:35 PM 8/23/2008

[Chrispy300]

Do you want to make another one?

[ultrapulse]

To be honest i'd be keen on casting it if I knew how, how much and where...But building it was a mish, and 2nd time would prob be 'only' half the time as I know what took time unnecessarily. I may actually be making another one later out of steel, but I have a 3bay garage to build first:)So short answer for now is no sorry.If someone could dig up my original post that would be good, because I cant find it.

[hannibal]

^ your manifold rocks!

Here's the original thread...zerothread?id=211041

[craigztoyz]

Why the aibv? I dont have any hooked up, just the throttle plate set for idle. No issues at all, only takes a minute to warm up, and its no issue, hot is great too.

past that, SWEET JOB!!!!!!!!!!!!!!!!!!!!!

I have thought about a design similar lately, only with a Roots in there too. The way this thing pulls, it would be awsome with a roots.

[darinz]

What I've been thinking about is a manifold with a Laminova I/C built into it. Surely it could be done and kept pretty low as well. I would think we'd need 4 or 5 cores but the saving in intake length etc and the increased efficientcy of the Laminova over normal water to air would have to be an advantage.

[ultrapulse]

I did think about plonking a twin screw blower on top for roots style torque but have the top end efficiency as well. However intercooling, fitament and cost made me steer away. Though if a positive blower could be used with a mint intercooler arrangement then that would be awesome with the exception of the inlet runner length being way too short to assist low end torque. Mind you the blower would take car of that:). I had already built my manifold too, so am staying with the procharger D1 and treadstone icooler. I will just dial in some more advance lower down at low rpm before the blower is on song:) I was alos going to slightly overdrive it, and blow off air at the top end...but this idea will be all trial and error and may not even work.

[npez]

The manifold looks fantastic!

Nick.