Twin Turbos

[G35COUPE]

having switched from a single turbo car to a twin turbo car last year, I can now let you read the first indication that bi-turbo is better. It considerably reduces turbo lag.
Probably you may want to read also a test of a BMW 335i, which is a car that is more familiar to the country where you live.

First of all I said it all depends on how the intake system is designed relative to the engine. Some intake systems are designed poorly and thus incapapble of providing the sort of air volume required to make the sor tof horsepower the engine has the capacity to make.

So, the idea that a bi-turbo is better than a single turbo system, is relative to the car in question, and untrue. Some engines will fare better with single turbo systems than with bi-turbo systems. Maybe in BMWs, bi-turbo systems are better. I don't know. I don't own a BMW.

[henk4]

First of all I said it all depends on how the intake system is designed relative to the engine. Some intake systems are designed poorly and thus incapapble of providing the sort of air volume required to make the sor tof horsepower the engine has the capacity to make.

So, the idea that a bi-turbo is better than a single turbo system, is relative to the car in question, and untrue. Some engines will fare better with single turbo systems than with bi-turbo systems. Maybe in BMWs, bi-turbo systems are better. I don't know. I don't own a BMW.

I'll spell it out for you. My previous car had the same engine with one turbo, the latest one has two turbos. IT IS BETTER.
(and it is not a BMW).

[CapnBoost]

Sequential systems are often difficult to maintain. The only aftermarket sequential system I know of is the [ame="http://www.youtube.com/watch?v=JBn7hivnePU"]YouTube - Sound Performance Sequential Turbo[/ame], and that's $$$$$.

The plenum & throttle bodies will determine the number of inlets. You could in theory put a common plenum[ame="http://www.youtube.com/watch?v=3ZwM8P-G38I&feature=PlayList&p=7F03647F483F79E8&playnext= 1&playnext_from=PL&index=89"]YouTube - Lexus V8 supercharged SC 400[/ame] on a bunch of ITBs.

That being said, there are too many factors to say that single or twin turbo is better. Attempts at using a smaller turbo as a primary and a larger turbo as a secondary (while keeping the plumbing of a parallel system) usually fail.

[henk4]

Perhaps people should have a look at this

Jaguar XF 3.0 Diesel S (2010) CAR review | Road Testing Reviews | Car Magazine Online

and TBH I am not interested in any discussions which aftermarket options should be better.

[G35COUPE]

may I suggest an engineering book?
Just think about it, in an ideal world there are no loss and friction, and if with two turbos you can achieve a good response of the engine at low revs with a smaller one, and plenty of power at higher revs with a bigger turbo, what if we could have a dedicated turbo every, don't know, 1.000 revs?
Every turbo could be designed and dimensioned specifically for its range of revs, without bothering considering what's going on later or before of it.
It's basically what VVG is all about, changing the geometry so that it can be modified accordingly to all the conditions it has to face, so basically, in a single system, you try to have more of them.
A clever idea to gain space and efficiency in the real world.



Yes, thank you, it was both a mistranslation and a brain fart as it was late and I didn't even check, sorry.

First of all, i don't need an engineering book for this sort of stuff. Depending on the engine design relative to the intake system, a bi-turbo maybe relatively better than a single turbo system. Its all relative. Its not always true. check your engine design and see what fits that engine rather than throwing unnecessary stuff at your engine when it does not need it.

What you are in essence suggesting is the equivalent of saying that having double wheels on a rear axle of a vehicle is better than having single wheels in the same axle, while ignoring rear axle design, differential design, and gearing in the differential, and towing capacity. On some vehicles (trucks) double wheels do better than single wheel axles but not always.

In air flow design, what you want is the ability for the air to get to the combustion chamber as fast as possible without restrictions and as turbulent as possible by the time the air reaches the combustion chamber. A bi-turbo should ordinarily achieve this better than a single turbo system, thus its advantage. As the air flows away from the turbine through the intercooler and towards the combustion chamber, it changes behavior from turbulence to laminar flow, which reduces the air flows velocity and the power it will produce, especially at low RPMs for regular turbos. Also, the heat it will absorb does reduce the power the air will create as well.

What you want is to have turbulence or a vortex even at the point the air has reached the combustion chamber. Mostly for this reason does a bi-turbo or a VVT makes sense because they are able to create the vortex or turbulence up to that point because of increased air flow up to the combustion chamber. However, I suspect a VVT system will do this much much better than a bi-turbo, and do so efficiently.

However, a VVT single turbo should be just as efficient as a regular bi-turbo system because it will ordinarily cause a vortex of airflow, which is very desirable in creating power with less energy. Under this system, more air gets to the combustion chamber at a faster rate. This means at low speeds, enough air is being generated enough to eliminate lag. In fact, at low speeds, a VVT turbo system should generate a lot more more torque than with a regular turbo system. For example, Infiniti and Nissan are able to use the creation of a severe Vortex in the NA engines to develop the sort of power their cars are generating. They call it Swirl technology.

One reason why i am always skeptical about bi-turbo systems is the additional heat the extra turbo will create relative to the increased and desirable vortex or turbulence it will produce. A bi-turbo system should generate more heat in its turbines than a single turbo system. And if the turbulent air becomes too hot as it nears the combustion chamber, power is lost, and then again, it is fruitless to have a bi-turbo system if there isn't a significant venting or cooling system to go with that.

Once again, the VVT system wins. It is the best of both worlds. You get a single turbo system that produces less heat than a twin-turbo system and yet is able to create the sort of vortex or turbulence of a twin turbo system, at an efficient pace, as required, by the time the air reaches the combustion chamber.

However, i suspect the manufacture of the variable vanes may require a little bit of expertise to create, especially with special materials. Why would special materials be required in a VVT system? You will probably need special materials because the stressess placed on the system due to the centrifugal and counter-acting force on the smaller and thinner vanes relative to the larger and thicker vanes, may cause some vanes to fail prematurely, unlike a regular equal vane system.

[G35COUPE]

Sequential systems are often difficult to maintain. The only aftermarket sequential system I know of is the YouTube - Sound Performance Sequential Turbo, and that's $$$$$.

The plenum & throttle bodies will determine the number of inlets. You could in theory put a common plenumYouTube - Lexus V8 supercharged SC 400 on a bunch of ITBs.

That being said, there are too many factors to say that single or twin turbo is better. Attempts at using a smaller turbo as a primary and a larger turbo as a secondary (while keeping the plumbing of a parallel system) usually fail.

I agree completely.

[G35COUPE]

I'll spell it out for you. My previous car had the same engine with one turbo, the latest one has two turbos. IT IS BETTER.
(and it is not a BMW).

How do you define "better"? Are you suggesting more power at higher rpms or more torque at lower rpms or a smooth power or torque band across all rpms?

[henk4]

How do you define "better"? Are you suggesting more power at higher rpms or more torque at lower rpms or a smooth power or torque band across all rpms?

I already gave you the answer. It considerably reduces turbolag and if you have ever driven a turbo car you know hwat that means.

[G35COUPE]

I already gave you the answer. It considerably reduces turbolag and if you have ever driven a turbo car you know hwat that means.

I don't disagree with you at all. I explained why twin turbos would have less lag than single turbos.

[henk4]

I don't disagree with you at all. I explained why twin turbos would have less lag than single turbos.

Good, then we can agree that twin turbos are better.....isn't it? I am not interested in how it technically works, but how it works for me (playing the ordinary consumer) and it works greatly better.

[G35COUPE]

Good, then we can agree that twin turbos are better.....isn't it? I am not interested in how it technically works, but how it works for me (playing the ordinary consumer) and it works greatly better.

Twin turbos are "relatively" better and not "actually" better when one considers the final output---turbo lag. However, to do so ignores the extra heat generated by bi-turbos and the additional maintenance cost of having such a system.

One thing I have learnt from auto modifications, and I suspect auto manufacturers grapple with the same as well, is that when you do one thing to your car, you better expect a change somewhere else in the system, while considering other unintended factors and consequences. Surprisingly, something as simple as making a car lighter, can actually be expensive--the lighter the car is, the less power you need to do the same amount of work.

[Wouter Melissen]

Twin turbos are "relatively" better and not "actually" better when one considers the final output---turbo lag. However, to do so ignores the extra heat generated by bi-turbos and the additional maintenance cost of having such a system.

No in this case the twin-turbo setup is relatively and actually better; there is less lag. You were wrong and posting very long rants does not that change or hide that.

[CapnBoost]

Parallel twins often perform worse than a larger single in every respect. Only an oem or highly over-engineered aftermarket (see the SP Supra in my post above) sequential system will be better.

[henk4]

Parallel twins often perform worse than a larger single in every respect. Only an oem or highly over-engineered aftermarket (see the SP Supra in my post above) sequential system will be better.

My car has an OEM system.....so that answers the question.

[henk4]

Twin turbos are "relatively" better and not "actually" better when one considers the final output---turbo lag. However, to do so ignores the extra heat generated by bi-turbos and the additional maintenance cost of having such a system.

The Veyron engine is probably a very poor piece of engineering in your book