Twin Turbo and the Ultimate Legacy

[Alex1]

Guys i need your brains and automotive knowledge!!

 

i read a post talking about swaping the turbo out of our car with a bigger one which got me thinking.. what is a twin turbo car? Can a car really have two turbos or is that just a diffrent stage? wats a stage of a turbo? all stock cars are stage one right??

 

anyways, please define Twin Turbo and tell me how much it would cost and what the benfits would be to do this, with another stock turbo or two aftermarket ones... Also these types of mods will they hurt the other mechanical parts of the car? IE clutch and transmission and stuff??

 

Thanks, Alex

[Drift Monkey]

Twin turbo - two turbos. Yes a car can have two turbos. There is no "stage" of a turbo, just sizes. This can vary between stock cars.

 

It really depends on the vehicle engine layout and design to understand if twin turbos could/should be implemented.

[Guest JessterCPA]

You know, I was thinking of this also. Wouldnt a flat 4 be a optimum setup for a twin turbo setup? You can blow more boost with smaller turbos and have less lag. Not sure where you would put two intercoolers. I am sure 1 turbo has its advantages also, and many people converted their RX7's and Supras to one large turbo instead of twins. Anyone else care to elaborate on this?

[red beast]

why not quad?

[Drift Monkey]

You know, I was thinking of this also. Wouldnt a flat 4 be a optimum setup for a twin turbo setup? You can blow more boost with smaller turbos and have less lag. Not sure where you would put two intercoolers. I am sure 1 turbo has its advantages also, and many people converted their RX7's and Supras to one large turbo instead of twins. Anyone else care to elaborate on this?

Actually, the older B4 Legacys DID utilize sequential twin turbo setups. We have more efficient technologies today (twin scroll turbo) that replace that of the old.

 

"The heavy, complex and oft misunderstood twin turbo is retired to make way for a new generation engine that takes advantage of variable valve timing on both inlet and exhaust sides (a first for Subaru) and a 4-2 exhaust manifold connecting cylinders across the engine feeding a twin scroll turbocharger."

 

-apexjapan.com

[akm3]

6 cylinder is more 'ideal' for twin-turbo in my opinion.

 

The theory is, as I understand it, you can have smaller turbos that spool up faster giving better response (But the same combined pressure) of a single larger turbo. This gets you a wide/flat torque curve without lots of peaks/valleys.

 

I view it as more EXPENSIVE parts to break.

 

Innovation with things like twin-scroll turbos give a lot of the benefits of twin-turbos with few sacrifices. Now that things like your Legacy GT's have wide/broad/flat torque/hp curves, twin turbos isn't really necessary.

 

We have the benefit of the 2.5l engine helping us out

 

=-Allen

[Drift Monkey]

6 cylinder is more 'ideal' for twin-turbo in my opinion.

 

The theory is, as I understand it, you can have smaller turbos that spool up faster giving better response (But the same combined pressure) of a single larger turbo. This gets you a wide/flat torque curve without lots of peaks/valleys.

 

I view it as more EXPENSIVE parts to break.

 

Innovation with things like twin-scroll turbos give a lot of the benefits of twin-turbos with few sacrifices. Now that things like your Legacy GT's have wide/broad/flat torque/hp curves, twin turbos isn't really necessary.

 

We have the benefit of the 2.5l engine helping us out

 

=-Allen

Depends on if it is a sequential setup or parallel setup. Sequentials build boost boost one after the other whilst parallels build boost at teh same time.

[05LegacyGT330Ci]

Check out the Bugatti Veyron or the Chrysler ME124RSTUVPQ whatever the things name is, both use Quad-Turbo setups to produce large horsepower and torque numbers. Twin Turbos were very common on some of the most well known sports cars of the 90's as has been said.

 

 

 

Edit: Damn you DM for posting as I did, sequential turbo setups are still used today on diesels often to create some very torquey engines fron 1000 to redline.

 

Song of Post- Sublime- Santeria

[fineout]

sublime rocks...and yes the optimum engine for a TT is a V6 or V8 where there is a lot of exhaust pourin out to the turbos so they spool quicker..im not sure if a TT can be used efficiently on a 4cyl such as the boxer, but the cyl config would work to add 2 turbos. price and maintenance would kill you though.

[John M]

Twin turbos on a v6 is quite rewarding. A 3000GT/Stealth with a pair of TD04-14b's (stock 90-94 Eclipse turbos) will do 11.0 @ 127 mph with just a fuel pump, exhaust, and fuel controller.

[rao]

If you don't factor in cost or added complexity then twin turbos (one for each bank of 2 cylinders) would be great. However, you can get the same, or close to the same results with a single for much less cost and with much less complexity.

[Avishar]

The single turbo is rewarding in that it is much larger and therefore offers a much more powerful and higher boost. The tradeoff is a higher lag however. The parallel twin setup is usually more effective at eliminating lag and spooling quickly at the expense of more power and higher boost. The parallel twin has been very effective in cars like the B5 S4 however and is more useful for track setups where you need to quickly blast out of a bend with a blast of boost. Still unknown is the Sequential Twin setup which was used on the old Legacies. The idea behind these was that one wanted to use a smaller turbo to spool up the big turbo. This was ditched because of the complicated plumbing and even more complicated technology and lack of enough power to make up for these complications.

[05LegacyGT330Ci]

Check out the BMW 535 diesels engine, it uses a Variable Twin Turbo system and is said by many to be the best diesel engine produced today. Even better I'll provide you with an article about it http://www.topgear.com/jsp/individualRoadTest.jsp?carType=new&mCode=A4&rCode=E3&mDesc=BMW&rDesc=5%20Series&roadTestNumber=26.html

 

 

 

 

 

 

 

Song of Post- Led Zeppelin- In the Evening

[Th3Franz]

Twin turbos can yield amazing engine response since parallel twin turbo setups usually use two smaller turbos. The downside is added cost and complexity, and a single larger turbo usually yields greater peak power.

[Deer Killer]

It seems to me that it might be less complicated, IF you can tuck the turbos under the exhaust ports.. Making some very short manifolds, for even faster spoolup..

[SUBE555]

That's my thinking Deerkiller, at least for an H6.

[speeding_gaijin]

My 99 B4 RSK is twin turbo.

Smaller one kicks in at about 3000 RPM, large one - at about 5500-6000

Works very nice. In Japan they were installing it on all Legacy until new ones came out.

[Th3Franz]

My 99 B4 RSK is twin turbo.

Smaller one kicks in at about 3000 RPM, large one - at about 5500-6000

Works very nice. In Japan they were installing it on all Legacy until new ones came out.

Do you have any dyno plots of the sequential turbo setup?

[2005garnetGT]

Twin turbos can yield amazing engine response since parallel twin turbo setups usually use two smaller turbos. The downside is added cost and complexity, and a single larger turbo usually yields greater peak power.

 

not really, because on a larger displacement engine getting a large single turbo isnt economical, while getting two smaller OEM junkyard turbos is

[gfxdave99]

Previous generation Audi S4's had Bi-Turbos it had two turbos for different rpm ranges that reduces turbo lag.

[Deer Killer]

had two turbos for different rpm ranges that reduces turbo lag.

No it didn't.

[apexjapan2]

C'mon - who says the old twin isn't quick? Can't produce power?

 

I've got a car I drive everyday that says you can have a sequential twin turbo set up that is already in positive boost territory circa 1800rpm, pulling hard @ 2200, and screaming around 3000. It has BIG pull up top too. After mods I've no VoD - and sadly, since my car hasn't made it to a dyno yet, no idea what its "guesstimated by a machine" #s are.

 

All I know is that it pulls much harder than std, does low 5s 0-100km/h, and does very bad things to the egos of many drivers of modded STis, Evos and the odd GT-R on hill climbs. On a track it is fun to see the faces of frivers of some very expensive metal as they get passed, on the outside:D

 

Would I suggest a TT set up for the new BL/BP cars - absolutely not. It is heavier (you can read the numbers in the aritcles;) ), more complex, and more likely to go wrong if you don't have good technical support (although it's not as bad as certain computer programs;) ).

 

But for those who like punch loooow down (on a 2.5 it would be positively ridiculously low - like 1500rpm for turbo wake-up I bet) there is little that can beat the older twins. Personally, I think the new twin scroll is great, the 2.5 turbo too. Barring unforseen accidents, I'll keep my old, compromised, fuel drinking BE5 for a bit longer tho - it is just too much fun

 

Cheers:)

 

PS my ideal would be a 2.5 w/ball bearing turbo (possibly twinscroll, but that is a really tough mod! - just thinking about the sequencing makes my head hurt), decent breathing and exhaust mods (w/good cats please). Makes for tasty dreaming IMHO.

[John M]

The Stealth's 3 liter has two TD04-9b's that make 315 torque at 2500 rpm. I'd call that plenty of low end power, and after mods you can still trap almost 110 on the same snails. After boost is raised that number is more like 425+ by 3500 rpm.

 

However, a properly sized single turbo could provide exactly the same response. The key is properly sized. People usually get carried away with giant single turbos and thus the lag myth is born.

[brio11]

Twin turbos on a v6 is quite rewarding. A 3000GT/Stealth with a pair of TD04-14b's (stock 90-94 Eclipse turbos) will do 11.0 @ 127 mph with just a fuel pump, exhaust, and fuel controller.

 

Oh really, i plan to ship my GVR4 back with me to the states within a year. This mod is relatively sane for me. Currently my turbos start kicking ass after 2500, they are non-sequential.

[Prod]

V6s and larger tend to take well to parallel twins. Sequential turbos are cool and a great idea, but they're prone to problems because the systems are so complicated.