Twin Turbo?

[ninja-philbo]

ive got a Z31 300ZX motor in my nissan 720 ute lol i don't like the look of the compound setup seems like abit of force on that lil turbo i can see that smaller turbo imploding throwing metal all threw his engine bye bye 10 second 2jz

[Felix]

ive got a Z31 300ZX motor in my nissan 720 ute lol i don't like the look of the compound setup seems like abit of force on that lil turbo i can see that smaller turbo imploding throwing metal all threw his engine bye bye 10 second 2jz

 

Why? When the big turbo kicks in it diverts exhaust away from the small turbos exhaust housing.... The small turbo would then effectively freewheel as it is no longer compressing air. It is obviously going to keep spinning, but doesn't have to spin anywhere near as fast if it is not boosting.

 

It isn't a true compound turbo setup.

[KeelzaMate]

So if you wonted good power down low and up top you would have to run a smaller turbo and when that is spolled the bigger one kicks in and takes over? Is it as simple as just making a twin turbo manifold and outing one small one bigger turbo on or do you have to set it up in a diffrent way?

 

thats the one :jamie:

[ninja-philbo]

this si the first time ive seen a compound turbo setup what is a true setup and i just think it looks restrictive

[KeelzaMate]

I'm trying to think how you could run it without running it first into the small to the big turbo, you couldnt run the small turbo off two cylinders and the big turbo off two cylinder cause that will throw out the cylinders, maybe have all four cylinder supplying both turbos and the small one will spool first and the bigger one will take over in the high end. maybe for a 4age, a t28 (small turbo) and gt30 or gt35 (big turbo).

[Hiro Protagonist]

going against hiro's logic though, the B4's were sequential twins.

 

And they were crap too, with a massive hole in the middle around the changeover point.

 

It looks like the GT2 Porsche is twin parallel, but they've got all sorts of fancy variable vane stuff on them anyway. Wonder what the older models had...

 

The 911 Turbo has been twin (ie parallel) turbo since the 993, and the GT2 has always been a variant of that (except for the 997 series 2, which retained the 3.6L whilst the Turbo went to the 3.8L)

[philbey]

Yeh my mate always used to complain about that turbo changeover lag in his B4.

 

993 GT2, always my favourite.....

[Jason]

I like to see a dyno plot of boost for that 'compound' setup, looks like a lot of losses. And basic turbomachine thoery is that your extracting enegery out of the stream, so the dumped gas has little left so little driving force of the large turbo.

I saw a similar setup up on a V6 and the guy was wondering why he couldnt spool is big turbo until 6000

[towe001]

this si the first time ive seen a compound turbo setup what is a true setup and i just think it looks restrictive

Have a google for "compound turbo diesel"

and you'll find

http://forums.dieselstation.com/index.php?showtopic=17291 for a write up

and here you'll find what some are getting from their compound setups

http://www.cumminsforum.com/forum/general-...und-turbos.html

 

But you'll never see those figures for a petrol, unless its a grenade.

[Trev]

Have always thought about a system where there is 2 turbo's (1 big, 1 small) where the small one is bolted to the head and the compressor outlet feeds into the big turbos turbine and the big turbo's compressor feeds the intake.

[iwontarolla]

Trev-So are you thinking use a small turbo to get tge bigger one going quicker?

Edited April 16, 2010 by iwontarolla

[Jason]

Sorry trev like I said there is a fundamental flaw in the way turbomachines works. For it to work in series you would need a high flow turbine which is allowing lots of heat to flow through (ie low efficiency). Which is what that cummins setup looks like its doing. What that setup up is doing is using that fact centrifugal pumps have large gains in pressure ratios in series. Also don't forget the large back pressure the primary turbo would see attributing for further losses.

Edited April 16, 2010 by Jason

[irokin]

I'm pretty sure trevs just trolling because thats a really really stupid idea.

 

Regarding sequential twins, you just need to look at how poorly manufacturers set these up to realise its a bad idea. A huge amount of factory sequential twin setups I know of suffer from flatspots or power choking. As such usually the first thing to do when modifying these is to turf the sequential twins. Do you really think you're going to be able to spend more on R&D than a major manufacturer? You might end up buying half a dozen turbos before you find something that works together almost properly.

 

 

For parallel twins the whole idea here on larger motors is to overcome the inertia of large single turbo thus providing more response. I think for a small capacity 4cyl motor you're going to see negligible to negative gains with a parallel setup. Because the motor is small you're already running a low inertia turbo. A smaller turbo isn't going to lose a whole lot of mass on its rotating assembly so no real gain in response. Further because you've now split the exhaust flow you're only getting an exhaust pulse to the turbo every 360 degrees of crank revolution. A 6cyl twin only has to wait 240 degrees for a pulse which is just 60 degrees away from a 4cyl feeding a single turbo.

 

Now you could propose to aggregate all 4 cylinders into one manifold then split the pressure off to two turbos. The problem I see with this is that unless you're some kind of fluid dynamics genius you are always going to be feeding one turbo with more flow than the other. You would need to take into account everything from manifold design to turbo placement (probably angle them at 45-90 degrees to each other) and very carefully manage downstream flow such as dump pipe and waste gate convergence. Packaging this system with something close to balanced the flow for each turbo is going to be almost impossible on a K motor and difficult on an A motor.

 

Basically what I'm trying to say is, forget it. Too much effort for little to no gains. You'd be far better off putting your efforts towards selecting the ideal single turbo for your application, getting a high quality manifold and doing all the other mods to the motor properly than doing a half arsed twin turbo setup.

[Trev]

I'm pretty sure trevs just trolling because thats a really really stupid idea.

 

Thanks for your input, Now I know why I never told anyone, I like how I am 'trolling' because I put my idea forward.

 

Oh and BTW Ben if I buy an S13 do I get to be a senior member like Bianca did?

[irokin]

Oh and BTW Ben if I buy an S13 do I get to be a senior member like Bianca did?

 

I think you'll find she made the new headers you see up the top.