Twin or Single Turbo

[91z24build]

This question is for all you turbo guys. What would be the better setup providing good power throughout a broader range, a single turbo setup, or a paralell (twin) turbo setup.

I know that the two smaller turbos would spool up faster, but would they still "choke" the engine at high RPM?

I am talking about the regular parallel setup, not sequential.

[Guest]

I really wish this myth of two smaller turbos spooling quicker would get dropped.

While there is a slight advantage to a lower moment of inertia, due to a lighter and smaller diameter compressor/turbine wheel(s), the difference in spool threshhold is minimal, usualy not noticble, given the same overall outcome.
Here's why:

With a single turbo set-up you will have all of the exhaust gases entering the turbine housing to be turned from heat and gas velocity into a kinetic energy. Let's us a 3L engine as an example. So you will have 3L of air going through the turbine per revolution of the engine.

Now in most twin turbo systems, each bank (assuming a V engine) will feed a single smaller turbo, so now that same 3L engine only has 1.5L going through each turbine housing, in addition to the less volume of exhaust gasess, there is usually a slight reduction in over all heat that will be introduced to each turbine, which will also effect spool time or rather turbine acceleration.

In the end, the spool time or boost threshold ends up being about the same, given same overall engine performance between proper matched single vs. proper matched twins.

I have built a few single turbo systems, and have layout twin systems, and will be converting my Jimmy from a single to a twin turbo, mostly because I've always wanted a twin turbo vehicle, and it will end up being less expensive for me to go this route at this time, since I can use some junk yard turbos that no one really seems to want because "they are too small".

In most vehicles a single turbo will work best overall, and usually easier to install, simply because of space, two small turbos take up more space than one large turbo in the same application, piping is also more complicated with two as opposed to the single.

[rickykline]

SINGLE.... i would hate to have two of these under my hood...

[Guest]

4 turbos is the way to go. shouldnt' be hard. DO IT!

[RacerX11]

4 turbos is the way to go. shouldnt' be hard. DO IT!

Stop being a jackass.

[timg]

I would recommend a single as well. Take a look at most high HP Supra guys. Rather than running a pair of GT30R's or GT35R's, instead they run a large GT42, GT45, or GT47. Some of the larger turbos seem to be so efficient that a pair of smaller twins just can't match up. It seems that a lot more development work has recently been put into large size turbos. A single is also easier to plumb, will require less space, one less wastegate, and fewer oil/water lines. There should be great advantages to weight, cost, complexity, and reliability as a result. To me, the main advantage of twins comes when you have a RWD V-X engine where it would be difficult to position a single turbo large enough, but easy to place a smaller turbo on each side of the engine.

Tim

[91z24build]

Thanks for the good answers. I'm trying to pick the best setup for low and high rpm, I realize the best I could probably get is low end, top end, or somewhere in the middle. I am working with very limited space so the single turbo setup would be easier. But on the other hand I am doing all the modifying myself and thought it would be easier to make two single header to turbo setups rather than trying to make everything come togather right for the single. I also prefer the sound of true dual exhaust. Which isnt available through the single turbo setup.

Does anyone have any suggestions for which turbos to use for each setup? As I am still undecided...

[Guest]

Thanks for the good answers. I'm trying to pick the best setup for low and high rpm, I realize the best I could probably get is low end, top end, or somewhere in the middle. I am working with very limited space so the single turbo setup would be easier. But on the other hand I am doing all the modifying myself and thought it would be easier to make two single header to turbo setups rather than trying to make everything come togather right for the single. I also prefer the sound of true dual exhaust. Which isnt available through the single turbo setup.

Does anyone have any suggestions for which turbos to use for each setup? As I am still undecided...

Once you stick a turbo in the exhaust that sound you love with the dual exhaust will be different anyway.

Think about it this way, the turbine itself acts like a muffler, and quite efficient at doing so as well.

[Identity Crisis]

Right now I have a T4 Garrett and I am considering Twinning. So does that mean I will have to install another T4?

I was thinking a T25 might be better on one bank and the T4 on the other. Someone clearify what they think about this set up and why it maybe BAD or GOOD. Thanks

[alainman15]

No i dont think u have 2 get another T4. u'll just have sequential twin turbo, i think... maybe get another opinion. but i dont see any problem.

[Identity Crisis]

Well I mya have the opportunity to obtain a T3/T4oe Turbo. This would most likely work better then I would say. Any comments on this?

[X11_STE]

whats the trim specs? Hows it work on your compressor maps?

[Guest]

Uhhh, If you are running one turbo off one bank and the other turbo off the other bank, they MUST be the SAME. You will get into all sorts of flow inconsitancies, and choking problems that will cause running issues and a whole slew of problems.

ALWAYS match SAME turbos in a set-up like that.

The only reason to use two different sized turbos is to build a sequntial set-up, which is at best an extremly difficult thing to pull off well.