Twin Turbo or Single Turbo?

[RazorGTR]

Turbo charging is an art form with smaller engines. IE 6 cyliners and 3 litres or less. There is a fine balance for a street car yet when going for all out performance and hp there are many directions to go. Here are some examples.

As mopie pointed out the Subaru Legacy GT uses a twin turbo setup factory. As does the Series 6 RX7 and Supra 2JZ motor. The only thing they have in comon is they are sequencial. A smaller turbo or primary to give good low rpm responce while the larger secondary turbo takes over once the engine rpm's reach the required amount. The main draw back and one that is so comon a problem is the primary over spools and they just don't last long.

The GTR uses a paralle turbo set up. That is three cylinders feed each turbo. There is no primary and secondary. Both turbos push and boost (according to theroy) the same.

Evo, WRX, Skyline GTS-t etc use a single larger turbo setup. While the Evo and WRX are 4 bangers the GTS-t uses the RB20DET I6 engine.

Sequential turboing does not require high rpm's to achieve decent performance, but they have that draw back of the primary still using up valuable exhaust gasses to power it.

The debate over a single huge turbo vs twin parralle turboing will rage on. Putting two smaller turbos say each that will flow 250hp each vs a single turbo that flows 500hp and there is a huge difference in drivability. The GTR factory turbos will flow about 225 hp each. Boost comes on at around 3,000 rpms. Yet a Trust GT30 Rspec will flow 500hp but lag is more due to the larger A/R rating of the exhaust housing to flow that much. Boot on a GTR comes on around the 4,200 mark.

Now taking things a bit further and more drastic levels out the playing field. A Trust T8834D turbo on a GTR that is properly set up run that turbo will begin to create boost at around 5,700 rpms. I comes on like a sledge hammer and is in full boost of say 1.8 bar (26.5psi) at 6,400 rpms. The power delivery is so hard that for daily driving or street use it is not pratical. It will flow around the 1,000hp mark. Moving to twin HKS 30-37 ball bearing turbos you will see around the same power output. Given the engine is setup and tuned properly to run theset turbos your boost threash hold will be around the 5,700 but the full 26.5 psi of boost will not be made until nearly 7,000 rpms.
As you can see the power deliever would not be as hard with the twin but also as you move into the higher power ranges the lag becomes more. The twin turbo setup will give you better drivability with the same power output given the right combinations and engine setup. In some cases such as the HKS 35-40's they will out flow and produce single turbo setups, but again it comes at a price of lag and streetability.

Going to the Extreme such as twin HKS 32-40's, 35-40's or the masive T51RSPL lag is even more, though the T51RSPL comes in two flavours. One ball bearing the other bushed bearing.

Running parralle twin setups on a 2.0 litre 4banner is a waste of time. Putting a nice decent single on there and using all the exhaust gases that the engine can provide to power it is the optimal way to go. We can learn a lot from the Japanese as they have been doing this very same thing for years. Many more years of profecting it with smaller engines then anyone else in the world.

On a side note I only used HKS turbos because I know a few using them and the HKS distributor in NZ. They also undrate their turbos.

[98gsr]

Originally posted by RazorGTR
Turbo charging is an art form with smaller engines. IE 6 cyliners and 3 litres or less. There is a fine balance for a street car yet when going for all out performance and hp there are many directions to go. Here are some examples.

As mopie pointed out the Subaru Legacy GT uses a twin turbo setup factory. As does the Series 6 RX7 and Supra 2JZ motor. The only thing they have in comon is they are sequencial. A smaller turbo or primary to give good low rpm responce while the larger secondary turbo takes over once the engine rpm's reach the required amount. The main draw back and one that is so comon a problem is the primary over spools and they just don't last long.

The GTR uses a paralle turbo set up. That is three cylinders feed each turbo. There is no primary and secondary. Both turbos push and boost (according to theroy) the same.

Evo, WRX, Skyline GTS-t etc use a single larger turbo setup. While the Evo and WRX are 4 bangers the GTS-t uses the RB20DET I6 engine.

Sequential turboing does not require high rpm's to achieve decent performance, but they have that draw back of the primary still using up valuable exhaust gasses to power it.

The debate over a single huge turbo vs twin parralle turboing will rage on. Putting two smaller turbos say each that will flow 250hp each vs a single turbo that flows 500hp and there is a huge difference in drivability. The GTR factory turbos will flow about 225 hp each. Boost comes on at around 3,000 rpms. Yet a Trust GT30 Rspec will flow 500hp but lag is more due to the larger A/R rating of the exhaust housing to flow that much. Boot on a GTR comes on around the 4,200 mark.

Now taking things a bit further and more drastic levels out the playing field. A Trust T8834D turbo on a GTR that is properly set up run that turbo will begin to create boost at around 5,700 rpms. I comes on like a sledge hammer and is in full boost of say 1.8 bar (26.5psi) at 6,400 rpms. The power delivery is so hard that for daily driving or street use it is not pratical. It will flow around the 1,000hp mark. Moving to twin HKS 30-37 ball bearing turbos you will see around the same power output. Given the engine is setup and tuned properly to run theset turbos your boost threash hold will be around the 5,700 but the full 26.5 psi of boost will not be made until nearly 7,000 rpms.
As you can see the power deliever would not be as hard with the twin but also as you move into the higher power ranges the lag becomes more. The twin turbo setup will give you better drivability with the same power output given the right combinations and engine setup. In some cases such as the HKS 35-40's they will out flow and produce single turbo setups, but again it comes at a price of lag and streetability.

Going to the Extreme such as twin HKS 32-40's, 35-40's or the masive T51RSPL lag is even more, though the T51RSPL comes in two flavours. One ball bearing the other bushed bearing.

Running parralle twin setups on a 2.0 litre 4banner is a waste of time. Putting a nice decent single on there and using all the exhaust gases that the engine can provide to power it is the optimal way to go. We can learn a lot from the Japanese as they have been doing this very same thing for years. Many more years of profecting it with smaller engines then anyone else in the world.

On a side note I only used HKS turbos because I know a few using them and the HKS distributor in NZ. They also undrate their turbos.

nicely done Got all the details there too..

[R32's Kick ass]

about the twin turbo 4's the mistubishi galant vr4(older models im not sure if the newer ones have a six cylinder engine now)

but ne ways they used to run twin turbo's and my neighbour who is a proud owner of a evo 3(rare bastered) nows another guy who also owns a evo 3
(realy pisses me off cause i wont get one theyll all be bought and wont be sold)
has put a vr4 engine in it but has removed the twin turbo set up

[RazorGTR]

I have never seen or heard of anyone putting a twin turbo on an I4 VR4. Now given that the cars you guys get in the states are different, in not only name but body then what the japs release to Australiasa and Asia I suppose it could have been the V6 variant that has an entire different body.

Here is a picture of an 89 Mitzi Lancer VR4 and also an EVO III courtesy of NZMMC.

Mitzi VR4

It is the Silver one in the most front and also another (first white car) in the back. They come factory with a 1.8L I4 DOHC turbo 4WD. The engine is transverse

Here is a pic of a fuggly green EVO III.

The EVO cam with a 2.0L I4 DOHC turbo 4WD factory.

The early model GSR's or EVO I was also a 2.0L though some first gen's supposedly have come with 1.8L motors but I get different story's from different people.