SonicRaT

iTrader: (6)

I figure the compressors should flow right around 620cfm @ 74% efficiency at ~14psi on a rotary.

Makenzie71

^lmao...right over my head...

RETed

250RWHP should be doable, but the stock turbo does that already.
Spool-up should be instantaneous, but I wonder if those turbos are going to choke the top end close to redline?
It should make for mucho low-end torque though.

Good luck!


-Ted

SonicRaT

iTrader: (6)

They do have different turbine sections for most of them, the 7cm has a .48, the 8 is like a .52 or so.

NZConvertible

I'm pretty sure that's the first time the word divorced has been used in connection with a turbo. Most people just call them parallel turbos.

Why not minimise restriction by keeping them seperate? True duals!

How? Any single you can find can be out-powered by twins of the right size.

FYI, here's an exceprt from an AutoSpeed article on the development of the VG30DETT.

"The engineers justified the use of twin turbos with some careful study. To avoid the response penalty of fitting a single large turbo with a commensurately large rotating inertia, the engineers used two hybrid turbos, each with a Garret T25 compressor and a Garret T2 turbine. Using these hybrids reduced rotating inertia by 20% over conventional T2 turbos. And then of course there was the use of two smaller turbos, rather than a single large one. Compared with a single turbo of equivalent flow performance, the use of twin turbos reduced the rotational inertia by 30%. However, the Nissan engineers suggested that the use of twin turbos only became advantageous at peak power outputs of over 250hp."

So now you know what the turbos are.

fcfdfan

A coupla' Sevenstocks ago, as I recall, at the K2RD booth(?) there was a 3rd gen with a divorced set up. My memory is a little vague on it, but I seem to remember the set-up was with no BOVs and the guy said "who needs 'em, modern turbos can handle it." No much to go on but you could Search it, maybe.

Good luck with the project. Read the Corky Bell Turbo book if you haven't already (Amazon Search).

Makenzie71

Yeah I kinda used the term "divorced" wrong...a divorced setup would 100% independant from intake to exhaust, which isn't really feasable.

The likely route I was thinking of something different with my exhaust when I came up with the merged idea before.

Of course they can out-power a single...it's just a matter of keeping it cost effective. If I scavenged and did a lot more research I'm sure I "might" be able to run a twin setup with more power than a single, but generally two big twins are going to be a bit more expensive than a bigger single...but, like anything, once the restrictions of money get involved everything becomes impossible.lol

Didn't the VG30DETT put down over 300hp? Either way, thanks for the text...

What do you think of slapping these two on the side of the motor?

RETed

Zenki Z32's were rated at 300.
Kouki Z32's were rated at 320.

I still think the reason the VG30 went twins was cause of the V-configuration of the engine - it just was more practical than running all the pipes into a single - ala Grand National plumbing nightmare!


-Ted

Makenzie71

Well yeah...but if you can figure out gains like how smaller twins spool faster than a larger single and such to go along with the added simplicity, why not brag about it? lol

RETed

Cause almost no one builds a 13BT with twin turbos for "just 250hp"...


-Ted

Makenzie71

meh...I've never been about big numbers. I like useable, on demand power all over the band and a light, well balanced car. Only thing big numbers are for is going fast and as much as going fast in a seven sounds cool, I have a 128rwhp maching that's likely faster than every other seven on this forum......everything else can be modest.

NZConvertible

Depends on your approach. For example a 400hp turbo set-up is not exactly cheap. Wiht a bit of scrounging two 200hp OEM-type turbos can probably be picked up much cheaper and won't need an external wastegate. If you can fab pipework, I think it could be done cheaper and should perform better on the street. There are lots of ways for this to be done; some cheap, some expensive. A twin-turbo set-up doesn't have to be expensive.

Me likey.

I wouldn't say twins made piping easier at all. Earlier versions of the VG30 were already available in single-turbo form (in the Z31 300ZX and various Japanese-market sedans) with the turbo tucked under the right bank in the same location as the TT. You're replacing one exhaust cross-over pipe with two of everything. Nissan ovbiously though the ugrade was worth all that extra pipework.

ultradef

The stock Z32 turbos (or "pea-shooters" as I like to call them) are really tiny. I've held them in my hand on several occasions...they are seriously one of the smallest turbos I've ever seen. Way too small for a rotary IMO. I'm sure they WOULD spool instantly, but I don't think they would offer much on the top end. If thats what you're looking for, then go for it...but I would look into a supercharger if I were you.

Also, are these stock turbos from a Z32? If so, I'm almost positive that they didn't come with TD04s stock...in the research that I did in the past (for a friend with a Z32TT) there was a lot of debate over the turbos. From what I remember, in the end, people just pretty much agreed they they were similar in size to a T22 I believe. As I said, they are really tiny.

Mason Rx7

I really really like the idea. I'm just curious how you will keep them seperate. I would want to run an intercooler obviously. Of course I think you adressed this.

I really like the idea of running two smaller turbos for faster spooling. IMO I don't think lowering the redline would be too big of a deal if you are going to have more power down low. Of course then again, a TII hits full boost at 3,200rpms right?

What size of turbo would be perferable for this set-up? RE twins? REW twins? Or do you think those are too big?

This is a curious idea (yeah, I know it has been discussed before) and would like to see some more thoughts/action. I might be intrested in trying this with a spare 6-port engine I have. If I can get my hands on a pair of turbos for cheap.

RETed

Separate "runners" from engine to each turbo.

Turbos discharge into two pipes - merge into one single.
If you got the money and the pipes, run em separated all the way back into two separate mufflers.

Turbo compressor outlet into two pipes - merge into single - one pipe into the IC.
If you wanna get fancy, keep the path separate until after the IC - IC outlet endtank marges into one - into TB, cause you only got one inlet into TB.
The IC is actually two cores in one unit - i.e. one turbo onto one half, and the other turbo in the bottom half - but the IC's outlet will merge all the airflow into one exit pipe.

Pipe work is the key to make everything work.
Either you get a good welder (someone who can weld) to take care of the piping, or expect to pay big bucks to get a shop to take care the pipes!


-Ted

FCguy

One turbo I think alot about is the stock T28 BB off an S15 Silvia. I hear they can be had for a decent price from the japanese tuners (used) after S15 guys go to bigger turbos. I dont know how well the sizing would work but being ball bearing these turbos would probably spool pretty good. I often used to daydream about a twin T28 BB setup on an S5 TII and TRUE DUALS (with an X pipe so it balences and doesnt sound weird)

Mason Rx7

Alright. That's kinda what I figured would have to be done. It is a really interesting idea. I can't wait to see how your project turns out.

Makenzie71

Yeah at the moment the idea is to power the turbos individually by the rotars. One runner off either exhaust port into either turbine. After that I like the idea of true-duals off the turbos.

On the intake side, for this rather mild setup, a lot of the stock intake will be kept. I'm going to attempt to design this so that it'll fit under the stock 6-port intake assembly so that I might be able to sell the manifold to the N/A-T guys too. I'll fab up a y-pipe that will merge the AFM with both turbos, then another that'll merge the turbos into a single tube to the intercooler.

After I get some design-time into this project, I'll look at making the system fully "divorced". At the moment I'm in the middle of an independant TB project for andrewruiz, and I might mi the ideas a bit. Everything will be 100% independant...exhaust side of things will be the same, but the intake side will be seperated: twin intakes, two 5X24X3 intercoolers stacked, and twin throttle bodies...or twin splitters to adapt the two intakes into quad TB's. Of course, aftermarket ems would have to be used...

SonicRaT

iTrader: (6)

Yikes, a T22 flows what, like 14lbs/min?

Makenzie71

These aren't T22's...go back and read the excert NZ posted at the end of page two, I think.

NZConvertible

In stock form at a mild boost level they made 300+hp on a bigger engine, so can you explain why they won't make much top-end? And not much compared to what?

I just posted what they were.

Turbos have no effect on redline. If you meant top-end power, see above.

Personally I wouldn't bother with the dual intercoolers or TB's, there's just no advantage to it. A 2-in/1-out intercooler like Ted said is more practical and more effective. Dual intercoolers make sense in a symmetrical layout like the 300ZX but not on a rotary where everything has to pass from one side of the engine bay to the other. As much as I like twin-turbos, the obvious disadvantage is the extra piping. No sense making that even worse for no gain.

Just as an idea, you might want to consider relocating the AFM to the intercooler return pipe. This isn't for better performance, but to simplify the intakes to the turbos. I think you'll find two turbos, a Y-pipe, an AFM and a pod filter very difficult to fit in such a small space, plus you have to add the turbos' discharge pipes too. You'll need a fuel controller because doing this throws off the AFM's reading, but you'll probably need one of those anyway.

I really hope you get this off the ground, even if it ultimately isn't successful. I seem to have participated in many of these twin-turbo discussions but none have gotten anywhere.

Makenzie71

My only reason for wanting to do something like that is for the people who look for independant TB setups. Just trying to think of something creative that could be added to the ITB manifold I'm building for andrewruiz...but it'd be mostly **** factor, reguardless. My setup will likely be merged right off the turbos into a single 2.25 or 2.5 section of tubing into a front mount. Wish i liked my top-mount a little more...now THAT would be the ultimate in simple plumbing.

I thought about relocating the AFM and maybe using a slightly stiffer spring on the flapper...or maybe just adapting an S5 AFM to the S4 setup (I think it would be better suited for a blow-through application)...but I wasn't sure how it would effect the ECU readings. I will be getting an SAFC so I suppose the only thing the AFM is going to be there for anyway is to keep the ECU happy. Ultimately, ANYTHING that frees up things in front of the turbos I'm all for.

The turbos are already enroute, I already have rough cut exhaust flanges, I already have the tubing (not that I'll need much for the manifold), I have a plasma cutter and lots or 3/8" mild and time enough to sit around and think about this all the time...if I don't get it built, I'll let one of you guys come kick me in the nuts.

Mason Rx7

Well they were talking about maxing out the turbo due to too much flow at higher rpms so I figured that a lower redline *BEFORE* the turbos got into danger.


Hmmmm... I've been thinking about the place ment of turbos and such. I'm not sure how big these turbos are without having a pair. If you set the rear turbo higher than the front turbo that would give more room for making a true duel exhaust. Manifolds are gonne be custom anyways.

In the front the IC piping would merge, go to the IC, then hit the AFM (S5 does seem to be the way to go, but standalone would work even better, hell might even be required for a project like this), then hit the TB.

NZConvertible

Post-turbo pressurised air is denser than pre-turbo atmospheric air, so the effect is that the AFM will underead the mass airflow and you'll run lean. You need to keep a very careful eye on mixtures when you set this up, as you start lean and need to enrichen to suit.

The AFM's purpose and importance are exactly the same with a fuel controller added. All the fuel controller's doing is tweaking the AFM's output signal a bit.

Makenzie71

Wouldn't the air on the pressure side, being denser and moving faster, cause the AFM door to read higher? It'd force the door open faster, I thought.