Twin Turbo vs Bi Turbo ?

[ferni]

From what I know a twin turbo is generally setup sequentially - ie one smaller turbo that kicks in sooner, and a bigger turbo that kicks in a bit later... much like the Subaru B4...

a Bi turbo is 2 same size turbos kicking in same time etc.. etc...

Whats better for which application?

The GTR is setup as a Bi-turbo (2 same size turbos kicking in same time)...

Has anyone set it up as a twin-turbo (say a HKS 2530 and a HKS 2540)... is it possible?

Anyone know how it would go?

[Steve]

call it what you want. a twin turbo is a twin turbo, be they sequential or not.

why do you say you have bi-turbo setup? all you have to do is lift your bonnet and read?

anyway, sequential turbos are alot more screwing around, perhaps have a look on the supra forums.

[666DAN]

Bi means 2...it's just whatever wanky name a company calls it.....lucky no-one called it a bi-cam haha

[Steve]

yep it does, but have you ever noticed it says TWIN TURBO on under the GTR bonnet, not bi turbo, I would love to know where ferni got his bi-turbo theory from?

[ferni]

I know it says Twin Turbo under my bonnet....

Ok i may be wrong, just what i read somewhere about the definitions, can't remmeber where...

Was just interested to know if anyone ran a sequential setup... what the pros/cons are

[Amir]

with the sequential setup like in supras, the first turbo comes on boost at lower RPM, giving less lag down low. Then the 2nd comes on later.

The GTR and soarers are not sequential and the gases get split in half so you loose torque down low, so feels a bit laggy.

[ferni]

So whats the advantage of running non sequential like GTR's then?

[Roy]

Maserati are about the only ppl i know of that refer to twin turbos as Bi-turbos. Sequential turbo setups usually have common exhaust housing, and depending on the rpm/load etc a valve switches the flow of exhaust gases between the wheels, or variatons of.

I wouldnt go running a 2530 and a 2540 on an RB26, each fed by 3 cylinders. Have you seen how some aftermarket manifolds using balancing pipes, on a equal size twin setup may not be so critical, on a setup using different turbos it would be critical.

The back pressure would vary between the front 3 to rear 3 cylinders, meaning you would need an ECU like a Motec that could tweak MAPS for individual cylinders, as the scavenging effects of the sets of cylinders would likely vary.

What you are better doing is doing what tractor pulling competitors do and use series turbocharging...which is where the the first smaller compressor pressurises the air into the inlet of the 2nd larger turbo, whilst the exhaust gases are similarily plumbed into one another

Think of turbines on a jet, where they are multi stage compressors... this approach tries to copy that. But again on paper it works better then in practice due to the plumbing requirements, inlet temps etc etc, unless you are using trick fuels, and a tractor engine that due to its low rpm can run massive boost... you get the idea

The advantage of using twins is that you can still have high levels of flow (cfm) from smallish twin turbos, and as the wheels sizes are smaller, lower inertia etc etc can still be responsive despite each only beign fed half the exhaust gases. Then you look at the larger turbo with similar cfm capability as the wheels of the bigger turbo have higher inertia, meaning they need more cfm to spin the buggers... but this is also influenced not just by the size/weight of the wheels but the pitch of the blades/wheel design etc etc.

Basically like all engineering, its a matter of compromises, and seeing which best suits the requirements, withoug impinging on the negatives too much. Just thoughts...

[[WLDCRD]]

Audi use bi-turbo as well.....for example, the RS6 - 4.2L Bi-Turbo V8 pushing out 331kW (450bhp)

[ferni]

Thanks for that Roy, very informative

[Bass Junky]

Audi also say Bi Turbo.

I know, I've driven one!

Audi RS4.

Nicest car I've ever driven!

[R33NT]

read the latest zoom magazine (no 78), they have a twin turbo special where they discuss the pros and cons of these systems.

[JimX]

So a bi turbo is one that swings both ways?

[EnricoPalazzo]

Twin Turbo = More air at same time, MORE POWER eg. GTR

Sequential Turbo = 1 smaller turbo goes, runs out of puff, bigger turbo kicks in, LINEAR POWER BAND, eg FD rx7.

Which is better is up to what the driver wants, max power or a smooth power band?

[Laurence]

The term Bi-turbo is just a bit of Euro-English...

It is like AWD vs 4WD, they really don't mean anything different. Really.

It is all just marketing. As I recall Mazda called their sequential setup

a Twin-turbo...

The Porsche 959 has an interesting take on the twin-turbo setup.

It had two equal sized turbos but it would only use one of them

(spooled up by the exhaust of all six cylinders) then it would

switch to both of them... Apparently it worked quite well.

I suspect setups such as on the Audi, Maserati and even the GT-R are

more to do with packaging than anything else. On a Vee engine a

turbo on each side just makes sense. Also a long engine like a 6-cyl

ends up with a big mess of pipes as a manifold.

[EnricoPalazzo]

Yeh its all marketing bull shit!

[Gav]

sex with TWINS or BI sexual - I know which I'd rather!

[Laurence]

Personally I prefer my sex sequential... Gives me time to rest.

Though one time after a bit of a lag I went with a BIG single... oh boy. That was a mistake!

[Gav]

I'm not even gonna start on my experiences with wastegates!

[Steve]

Rofl