Which Better Single or twin Turbo?

Most Turbo cars make big HP and TQ by replacing the Twin with a BIG SINGLE
but Aren't 2 BIG TWINS Better ?


On Twin turbo does both turbos run at the same time ?

 

Problem with a single turbo is the lack of low-end torque AKA turbo-lag. Single turbos simply require higher rpms to build boost as fast as twin turbos.

Otherwise, with a single turbo, there is lower friction and heat levels so the power output can be a lot higher in the the high rpm range. Which is good for race cars, since they spend most of the time in high rpm range.

 

Twin turbos in factory trim are small and don't make much out of the cars power potential it is cheaper to replace the fatory twins with one large aftermarket turbo that can put down almost twice as much power. You can get more power out of an aftermarket twin turbo set up like the HKS twins for a Supra but it's much more expensive! and the turbo lag is much greater. With a set up like that it's better to have a NOS kit to help spool up the large turbos faster.

 

On Twin turbo does both turbos run at the same time ?
It's seems people always make big power off a BIG Single turbo

Why not use 2 BIG Twins, each the same size as the Single ?

 

not enough exhaust power to turn them, and lag would be massive. also space is a problem and heat is a problem. basicly the limiting factor in a single or twin turbo is not the lack of PSI, they can produce way more PSI than any engine can handle. its all a matter of efficiency.

 

Twin turbo has les lag, for drag racing. Single turbo can be better for on track racing, where you will keep rpms high.

 

When talking about twin turbos on V6's, is it bad to have uneven backpressure for the left vs right bank of cylinders? If so, can a balance typically be found by adjusting the wastegates that bypass each turbo?

To me it seems that there are potentially serious issues when doing twin turbos that aren't of the same size because the smaller turbo will have greater resistance to air flow than the larger turbo.

--
Jeff

 

If the two turbos aren't running at the same time then the problem would seem to be even worse (if it is a problem).

One bank of three cylinders is blowing exhaust into a turbo that is producing resistance to the flow of exhaust. The other bank of three cylinders is blowing exaust right around its turbo via its wastegate. So it would seem that the first bank of cylinders is more "stressed" than the other side.

Are you sure they don't run together at the same time? It would seem that you would want to "blend" the boost from the two when you're transitioning from one to the other.

BTW, I'm talking about turbos that are parallel to each other and not in series.

--
Jeff

 

Apparently all this plumbing is needed just to control the two turbos on an RX7:







The RX7's turbos appear to be in series (I don't know for sure):




--
Jeff

 

On all of the twin turbo cars that I have heard of (including the one that I own), both the turbos are the same size, spool at the same time, etc. Each turbo runs one bank of the V. A bigger turbo does create more power, but has more "turbo lag." (Lack of power at low rpm speeds).

 

cotmfk is right. I think where getting conffused on the term twin turbo. Most twin turbo applications on V6 engines such as the 300ZX TT and Supra TT have two equal sized turbos that run at the same time on both banks of the V6. The faster spooling turbos give better low end torque, less time to spool up blah blah blah.

The system that porschekiller is refering to I think is more commonly known as a two stage turbo system rather then a twin turbo system where by one uses a smaller faster spooling turbo to help spool up the larger beast. I think modern day ball bearing turbos as well as two stage nitrous systems have curbed demand for these setups. After all using nitrous to help spool the turbo quickly has the same effect and takes up almost no space and weight.

The reason most people switch to single large turbo when they want big power is because it's easier to tune, if you add an intercooler system there is less plumbing to worry about and it usually drops weight.

 

Oh, ok. Makes sense. So the "two stage" turbo I guess is two turbos in series? I imagine the first small one runs for a bit then gets bypassed for the large one to take over?

--
Jeff

 

I Thought Supra had 3.0L Inline 6 Turbo
The Supra TT and 300zx TT are totally different because of engine
design

 

OK

 

Some TT are sequential, some are parallel.

RX-7 93-98 is Sequential
Supra 93-98 is Sequential
Z32 is Parallel

Most important, on a Z33 a TT would most likely be parallel.

The size of the turbo is dependent on the specific application, as Victor alluded earlier.

The sequential setup can use different size turbos. A small one for low boost, quick spool at low rpms, with a larger one that boosts higher and in the upper rpm range. IIRC

In parallel, the turbos should be the same size. The will be running at the same time. The size should be chosen based on the requirements of the application (i.e. low, medium, or high horsepower)

JD

 

the supra TT has a sequential twin turbo setup.

 

Also regarding sequential TT setups. I was under the impression that once the 2nd turbo spools up, that they will be both providing boost (obviously the 2nd one generating more). I believe this is true. VQ, can you provide any confirmation on this?