350z Manifolds - Hold on to your shorts, this is going to be looooong...

Some of you may know about the single turbo system I had built for my car a few years ago. To be honest, I had originally built it half-assed, more to prove a theory of turbo placement and the complications of its location as well as the long tube length and pulse mis-match. The old system I had built with off the shelf ebay manifolds and left over roll cage tubing I had laying around, again, just to prove a theory on the low-buck. That system, on a GT4094R made 673hp and 6xx torque and performed fairly well at 24psi on a road course. Well the time had come that I do it correctly with the proper length of tubing, calculating the long side to match pulses and ultimately a system that didn't generate a 3-1 (yes, 3-1) pre-post turbo pressure ratio. (scary isn't it?) I had heard about the 350z manifolds and how well they match up. They kinda do, kinda. This is by no means an afternoon project, 4 months in fact, is what it took to make it work. I have loads of pictures and will do my best to give everyone that wants to take on this challenging endeavor upon themselves a bit of insight as to what it takes. A few things will be left to your own interpretation, not to give the farm away, as to why some of these lengths and sizes are the the way they are. Over the next few days I'll post up a number of pics and how it all turned out but I'm rather excited to share my findings. I fired up the car for the first time over the weekend and the initial results are good. My tuner had to make a tremendous amount of changes as the volumetric efficiency has significantly changed. Enough, pics..

This is what I started with, old vs. new in the attached pics.
Also, a pic of a crack I found on the old system. I know, it's fairly thin walled. It's light, and will crack over time. No worries, I have a welder and typically do inspections before races days in advance.
A nice pic of some of the 304L stainless I'll be using too.

So how well do they match to a stock head. In short, they don't. I didn't want to fill it weld, plus in this pic I have it on a stock spare head, not the ported monsters I'll ultimately be attaching them to. So, cut off the old flange, spend hours die grinding out the old pipes and get to work. The next pic is them tacked to the flange and mounted on the car. The step between these two pics took days. Hours and hours of heating with a torch to glowing red, expanding the tubes to match the port and contouring the "mouth" to a proper taper. You can see the discoloration in the pic from the torch work on the mounted flange. Notice as well, the 350 flange was not cut directly across, part of the length matching I mentioned earlier. (gotta do some math on your own for that one) :excitement:

Moving on, these aren't level. There's a bit of an angle to them which was intentional. There's also an additional step down in the collector to go from the stock 350z 2.5" down to the 2". (reason: match) LOL It's internal and that part we'll just file under the secret folder. Not to mention the huge amount of internal work it took on the crappy collector, I think a little kid may have assembled that part, get out the grinder fellas, it's nasty in there. The turn down, mandrel 304L, with V-band for easy removal. There's tons more to come but figured I'd start here for now...

Looking good. Excited to see where this goes.

I always thought these fit rather well from the get-go... never seen anyone do a real writeup on them! I've also never looked for one, so...

However, I'm surprised your holding any cards close to your chest on this. I'll never understand the point... especially in such a small community and forum. But to each their own. Good job at doing the R&D to get these as nice as you are!

Well done Erron,

I always thought a single turbo setup would work from the standard manifolds, even if it isn't optimal. Well done for the write up on the 370z manifolds, are these what you have installed for your Facebook video? What sort of increase in power have you seen going to the new manifolds?

Cheers,
Ewan

Sent from my SM-J500FN using Tapatalk

Still have it routed down to the bumper?

Don't really know if that's that's a great idea to have it there tbh. Sure alot of cold air but also alot more sand and dirt passing by down there.

But, if you havn't seen any ill-effects in your intake or cylinderwalls by it I guess it's fine..

Yes, the turbo is still down low, same spot. Two reasons for being down there. It's out of the engine bay making more room and also for better weight distribution. We're light on the tranny side of the car. It also really helps with heat as the deflector that is directly behind it pushes the hot air out to the side rather than through the hood.

Keeping a few things to myself really as it's just theory still. I can do the math all day long but until it's done in practice it's just numbers on a page. Plus, a couple of the folks that assisted me in the design asked that I not disclose exact details to the general public.

Continued...

The rear manifold was a bit of a different story. I needed to do two things here. Match the pulse with length and timing to the front manifold as well as raise it up a number of inches so it would clear the rear mount and move it into the position I wanted it in. Had to get away from the brake lines, clear the dry sump oil tank, and still make the forward turn. I added a number of inches to each runner to accomplish this.

After test fitting, tac-ing it all into place and loosely fitting every was good, but at this point I needed it all welded up properly. Although I have a Tig and Mig, I opted to have my buddy weld all of this at this point as he is considerably better at tigging than I am, plus he's setup for back purge welding. To get a proper weld on all stainless you must back purge the weld with an inert gas. We used 100% Argon for this purpose keeping the sugaring to a minimum and ultimately creating a stronger weld and hopefully keeping cracking to a minimum. You can also see the flanges at this point have been planed as well as the additional runner length that was added to the rear manifold. The flanges were welded on the outside as well as on the inside then ported. Again, in hopes of keeping cracking to a minimum. Some basic port grinding took care of the excess.

On to the turbo mount. This is where the tubes go under and mate up with the turbo flange. This is another long process that requires a lot of heating and manipulation of the tubes to get them to fit properly. (round tube, oblong holes) Keeping the length and bends that I wanted and needed wasn't exactly easy. Looking the pics makes it seem simple in hind site. What you don't see is the numerous cuts, test fitting, re-routing, that took place to make this work. The tubes go inside the flange to ensure an air tight fit once welded. Even though it was welded both inside and out when finished, two welds is always better than one.