thalwr1

Ok so heres a dilema im having. . i was speaking with someone and it came up that he wants to do twin turbos instead of a larger single turbo(a v-8) because instead of running 20lbs on a big turbo he can run two smaller turbos at 10psi each(all exteranly wastegated) and get 20psi. . if im not correct please inform me but i was always under the impression that if you run a turbo at say 10 lbs of boost and you get 10lbs . .if you run two turbos at 10lbs you just get a more efficiant 10lbs of boost not 20lbs. . any enlightenment???!??!?

dpetro1

pretty sure the boost gauge would still read 10psi but since he has two turbos he is pushing double the cfm, essentially making the same power as 1 turbo at 20psi. of course thats a generalization but for your argument he still only reads 10psi.

someone correct me if im wrong

DaveF

i dont think it would be " more efficiant " to run 2 turbo's.. you would be losing energy spooling both of them, when you could be using all the exhaust energy to spool a single. ..

Boostage

This is just a basic summary and im just using these numbers just for arguments sake. if the goal is 800hp thats more or less 80 lbs a min of airflow needed a single 76mm turbo would flow enough to make that power.

with twins you would run two smaller turbos with a combined flow of 80 lbs a min. like two t04e 50 trims. The twins would respond quicker and make more TQ everywhere over the single at the same Horsepower level.

Now just to entertain your line of thinking. if the single made the boost gauge read 20psi to make the 800hp. and the twins only made the boost gauge register 10psi. the flow to the motor is the exact same.

Truth of the matter is, in the real world the twins would probably register maybe 2 less psi on the gauge less at the same horsepower level over the single. but make like 50 ft lbs of TQ more.

Boostage

This is the first time ever that I think you are wrong.

a V motor will always be more efficient with twins over single.There is a whole chapter in maximum boost talking about this. Especially on Fbody's where they have a crossover pipe running from one bank of cylinders help spool the turbo. Manifold designs for those motors for singles are horrible from a technical standpoint. Properly paired twins on a V motor will create a stronger exhaust pulses. and will make more tq at the same power level.

This is what 99% of Lt1 single setups look like



These are the typical style of manifolds used on TT Fbody setups..




Singles are cheaper, lighter and much easier to deal with on those motors, but not more efficient. The response is faster, and the tq is higher throughout the whole powerband. find any two stock Ls1 motors making power in the same ballpark range, but one twin and the other single. and 100% guaranteed the curve is much nicer and tq is alot higher on the TT setup

Turbo92cx

Dave I know you are a very wise man and you know your stuff but i will have to disagree with you on this!! On a V8 engine it is actually more efficient to run twin turbos of a smaller size then it is to run one big turbo. With the current manifold designs for these twin turbo V8 applications there is no real noticeable loss in spooling energy. For example a friend of mine picked up 4 tenths when he made the switch from a single 106 to twin 101 (I know its not a big turbo size difference but you get the point.)

grndcont

^ that twin setup is damn sexy. O.P. you are correct. if both wastegates are plumed from the same intake manifold, and both turbo's feed from ambient air, they will produce a total of whatever your target boost is (either the spring pressure or the boost controller target). what you friend might be thinking of is a "compound turbo" setup that some diesel engines use. where one turbo feeds another turbo.

quote: . .if you run two turbos at 10lbs you just get a more efficient 10lbs of boost not 20lbs. . any enlightenment???!??!?

yes...if both turbos are selected to flow the divided cfm requirement of the engine @10psi, this could be more efficient than one big turbo running @10 psi. but like the twin picture above, the result of a 10PSI setpoint would be 10PSI.

think of it like this. i have a v8 that needs 1000 cfm to make x hp. what would get me there with less lag? a big 1200 cfm turbo plumed from both exhaust banks with a crossover pipe? or a dual bank setup like above with both banks flowing directly into 2 600 cfm turbo's?

DaveF

what makes it more efficiant though ? less restriction on the exhuast with 2 turbo's as opposed to one ?

MidShipCivic

The banks will run uneven power due to pipe lengths and you'll have less rotational mass. It's best to split the two sides up .

blinx9900

If it has not already been said, boost is measured at the manifold, not at the turbo's, 10psi is 10psi 1 turbo or 2 does not matter.

MadScientistMatt

Compound turbo systems are sort of an exception, but they don't really make sense unless you are trying to run over 40 psi of boost. Usually a V8 will run twin turbos in parallel so each turbo moves half the volume but all the pressure.

blinx9900

true but you know nobody on this board would ever do that.