I'd never really considered it, but I was thinking to myself today why so few people in the Z community run tubular turbo manifolds. Is it that they are prone to cracking, or does it have more to do with the cost and availability. From my reading, it seems like they can net substantial gains, so I'm curious why more people don't run them.

Which brings me to my next question. Why don't more people run twin-scroll turbos? Is it also a cost thing, or is there another reason?

 

Regarding tubular manifolds, longevity and cost would be my guess.

 

Twin scroll turbos work well for the 4cyl guys, as it's easy to design a manifold to divide up the cylinders, but for a v6 it would be difficult to plumb in such a way as to be useful.

 

Not sure I completely understand.

 

This may help



http://www.modified.com/tech/modp-09...ign/index.html

 

Would it be partly because our cars don't need really anything over 20psi for great numbers? So there is no benefit to having a twin scroll turbo.

 

The article that goes with the picture posted above:

http://opc.forumup.co.za/about3340-opc.html

Very good read.

 

True, but for people running GT35s, like XKR for instance, faster spooling turbos would be desirable.

 

the 350z/ g35 community has more of a "kit" mentality, and there really are only a few real race cars out there that are trying to push the limits within a rules sanctioning body.

for 99% of the FI crowd, one of the kits will provide more than enough power than needed, and as such people haven't needed to explore ways to make more power....so they have stuck with the cast log manifolds. For example, look at the GTM car that recently went 9s with cast logs! that's very fast, but that car isn't built to run in a specific class or organization. Turbos (and boost) can mask alot of other design shortcomings, and most people just look at the dynos numbers/timeslips, etc.

now, conversely, take a look at the Injected race car. They built that car to conform to the rules of a specific drag race sanctioning body. In short, there are alot of rules governing the size of turbos, etc in such classes. To maximize the engine, Injected need to get as much power as they possibly could from their GT47 (i think that's what it is). Part of that equation included maximizing the rpm band of the motor too. so in order to extend the rpm band and the utilize the their turbo of choice to its fullest, most efficient setup, a tubular ( and low back pressure) exhaust manifold was the right choice.

the cast log manifolds on the market work very well and they are really well suited for daily drivers, street/strip, and weekend warrior duty. they help make for a quick spooling turbo(s) and great street manners......and for most people, when you want more power, they just turn up the boost and aren't concerned with increased pressure in the exhaust manifold or losing overall efficency in the turbo system. as long as the power keeps increasing, that satisfies most.....even though you may have diminishing returns. an example of this is too look at the dyno graphs of almost every log manifold 350/g35..........they are all making peak power below 7000 rpm. many of them are peaking closer to 6000 rpm and then the power band continues on roughly flat ( with slight increases) beyond that. And, it is almost the same irregardless of the cams being used.

I think that pretty much covers the basics.

 

Cannot argue with this at all.

 

James.... I went with my setup because I wanted an all around car with big powa that could be driven on the street or on any track.... Drag or road race.... Tubular manifold would hurt me on a road course....

 

That's a great illustration, thanks for posting

 

mmm tubular

 

Ideally, you'd have it setup with a nice merge collector and tuned runners for optimal , which is not what is in the pic above. that pic looks like a set of NA (off the shelf) headers that were cutoff at the collector and had an extension welded onto them to mate up a turbo.

 

That is what I see as well, and If I was ever to go TT that is how I would go about it too.

 

Due to the way the V6 exhaust pulses a twin scroll would not work you would have one scroll that is only powered by one cylinder due to 3 cylinders on each side You need a inline engine to make a twin scroll work look again at the picture shown how twin scrolls work is they mate up the cylinders that pulse together on the V6 with 3 cylinders per side you would have one cylinder by itself.

 

True, but thats what SP and SFR manifolds look like for their standard kits.

 

I didn't realize the manifold piping was separated for the two different aspects of the turbo. I thought that the gas was only separated when it reached the exhaust intake flange on the turbocharger. I see why it wouldn't work now.

 

http://www.speedforceracing.com/inde...productID=1011
Actually it looks like SFR uses Burns collectors on their units. Not cheap and I'd be interested to see a head to head comparison between log-type and tubular manifolds.

 

^Having experience with both, SFR's standard kit is like SP's standard kit, in that they both appear to be ebay-like manifolds with the end cut off and an extension welded on for turbo flange (and wg mount). Both companies offer upgraded manifolds with better collectors and design, which would be my preference.

As for a head-to-head comparison of cast to tubular - tubular headers leave the cast headers in the dust when you seek great performance. It is easy to add a turbo and run 5-10psi which adds "some" power and "feels good". It is much more difficult to build an efficient setup to maximize power at higher levels.

Quadcam, nice comments regarding what most desire and why cast works for most currently. It is unfortunate, but true. Many have the mentality like *boose* above, "20psi is enough for great numbers", and that is the end. Yes, that is probably "great numbers" for most, but my question to those people... do you know what 30 or 40psi feels like (on an efficient setup)? Unfortunately the cast-header people will never know.

Twin scroll would best be utilized in a single-turbo configuration on the Z, but spacing constraints make it difficult to run two separate exhaust inlet pipes. Also the available single turbo kits are small enough that spool isn't much of a concern.