Twin Turbo (different sizes)

SeattleSy#1255

SeattleSy#1255

Category 5 Conservative
I'm trying to understand turbo's so this may seem like a stupid question but can you do this...

Twin turbo a syty out with different sizes turbos. From what i know bigger turbo's for the most part are weaker at the low end but make up for it after they spool up. Smaller turbo's quicker spool, but crappy top end...with this logic (not sure if i'm right) why can't you use a two differing sizes on a twin turbo set up...the smaller aiding in the launch bottom end and the bigger sorta "taking over" at the top end when the smaller sorta "craps out"? Just wondering?
 
SY756

SY756

New member
In theory you could do it with the twin header setup But the 1 problem I see with that is one side of your engine will be breathing through a smaller exhaust housing on the small turbo making that side much less effecient. So your engine power would be mismatched side to side.
Im not much of car guy, truck guy hell yes, but someone might correct me if I wrong . On the twin turboed supras, they have the smaller turbo kick in at lower rpms to compensate for lag, then it "switches" over to the larger turbo once the engine gets in its power band. I think they have all 6 cylinders exhaust piped to both turbos in series.
I don't think there would be enough room in our trucks to have that sort of exhaust work and turbo placement. but I guess anything is possible
 
ParTyBoy

ParTyBoy

New member
SeattleSy#1255 said:
So on the TT Surpra's the smaller one literally stops functioning?
Click to expand...

There's staged or sequenced setups... green, mike, or sean could talk about in line setups I'm sure... personally I don't know much about TT's..
 
N

NSANY(ATL)

New member
Supras are a I-six so they have a twin sequential setup, the 300TT's have a true twin setup with 2 of the same sized turbos. If you were to twin turbo a SYTY you would have to run the same sized turbos on each bank. Otherwise you create unequal pressures to each bank, both intake and exhaust.

As far as turbo size, larger turbos = more lag and more top end, smaller turbos spool quicker. You can eleiminate alot of the lag problems by getting different cams.

Read the book Maximum Boost by Corkey Bell, it should answer all your questions.

Hope this helps
Chad
 
S

smeagol

Active member
Well a cam isn't really a solution to a turbo size issue. You should really decide what your hp/et goals are, build a motor that is capable of moving that amount of air, then size the turbo accordingly. Don't build around a turbo or pair of turbos.

You are right on the twin setup though. The sequential setups are more complex, but when done correctly work out great. It can be done on a V6 however. I know of a big company doing testing on a diesel V6 meant for mass production that has lots of R&D with a sequential twin turbo setup. The sizing is crucial, as the 2 turbos have to complement each other.. response is great once you have them properly sized, and exotic technology isn't needed (ball bearings/variable geometry etc). Let's just say I've been following this project closely ;)

The RX7's used a sequential turbo setup, as well as the Supras. It can create a mess of vacuum lines/actuators needed for control.
 
TurboManiacal

TurboManiacal

Donating Member
I finally broke down and bought the "bible" of turbocharging. Now, of course some will say it's more of a guide book than a bible but I like what's being said here about turbocharging. It's the Corkey Bell book titled Maximum Boost. He goes into twin turbo charging and what your goals would have to be to make the transition...essentially he expounds upon what Green just summarized in one paragraph. I try to read about 7 pages a day before my head explodes. Hopefully I'll slug through it...read it again and then understand enough to slug through the next holy grail: The chip burning thesis.

speaking of which...Green: Do you have the links to those handy? I know I'm rambling....
 
SyTyJedi

SyTyJedi

Jedi Council
SY756 said:
In theory you could do it with the twin header setup But the 1 problem I see with that is one side of your engine will be breathing through a smaller exhaust housing on the small turbo making that side much less effecient. So your engine power would be mismatched side to side.
Im not much of car guy, truck guy hell yes, but someone might correct me if I wrong . On the twin turboed supras, they have the smaller turbo kick in at lower rpms to compensate for lag, then it "switches" over to the larger turbo once the engine gets in its power band. I think they have all 6 cylinders exhaust piped to both turbos in series.
I don't think there would be enough room in our trucks to have that sort of exhaust work and turbo placement. but I guess anything is possible
Click to expand...

This is incorrect. Supra TT's turbos are the same size. One small and one large turbo would be an airflow nightmare.
 
Christian Dionne

Christian Dionne

Member
The new Saab 3.0L V6 has a turbo running off of one side of the engine. I'm sure the engineers designed the ports and cam lobes differently as well.

On the TT setup with different turbine A/R ratios, you probably could link the two collectors together to equalize backpressure in the exhaust. Nowadays, with these awesome torque converters and quick spooling turbos, WTF would you even bother?
 
N

nomoty

Still Boosted
Yes they are the best thing for a supra is a bigger single setup from what I have heard. I have seen a couple that went with a single t-72. Now that thing has got to be horrible for take off but they still run 11's easily!
 
L

Lynn D. Brown

New member
Twin Turbos

Twin Turbos

Yes, anything can be done w enuf $$$, and alot of GN's have done it. However, the cost is very high and probably only justified if U R going all the way - 1000 HP +. Now stock block, crank, heads no good, etc., etc. U would have to butcher the car significantly also.
 
tyndago

tyndago

New member
The theory is sound....... getting it to work is not.....


The best thing is just to accept the issues you will have and work around them....


The Supras setup is weird to say the least..... I tried to hook up a boost controller to a MK IV Supra one day----- what I thought would work was all wrong... you only control one of the wastegates.....WTF..got it right in the end.... but the amount of solenoids , vacuum lines , and acutuators made me happy to go back to the RB26.... Inline 6 - One turbo on these 3 cylinders . One turbo on these 3 cylinders....

If you go with one big turbo that is going to spool slower..... size the wheels correctly - go with a ball bearing center section.....looser converter....all that and it will make so much power in boost - you wont care how it is off boost.....

There are other theories about how to get a car to spool faster...some stuff works some doesn't. We had a GT-R with a ton of cam 280 duration intake/exhaust - small upgrade turbos - and that thing had crazy response.... Nitrous will do some interesting things too.... 4500 rpms 200 rwhp.....activate nitrous 5000rpms 600 rwhp.... 600 hp from 5000-8000 rpms....

People get so hung up on "lag" ...... I just think the torque that a motor makes on boost - give the perception of the car not making power when "off" boost. When actually the car would make decent power as is normally aspirated - but when it comes "on" boost....that rush of power makes the "off" boost time seem......slow..
 
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