Jump to content
SAU Community

Recommended Posts

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?

Link to comment
https://www.sau.com.au/forums/topic/41930-twin-turbo-vs-bi-turbo/
Share on other sites

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

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...

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.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Very decent bit of kit. Definitely black it out I reckon.  
    • Because people who want that are buying euros. The people with the money to buy the aftermarket heads and blocks aren’t interested in efficiency or making -7 power, they’re making well over 1,000hp and pretty much only drive them at full throttle  best way to way make money is know your customer base and what they want and don’t spend money making things they don’t want. 
    • It's not, but it does feel like a bit of a missed opportunity regardless. For example, what if the cylinder head was redesigned to fit a GDI fuel system? It's worth like two full points of compression ratio when looking at modern GDI turbo vs PFI turbo. I'm pretty reliably surprised at how much less turbo it takes to make similar power out of a modern engine vs something like an RB26. Something with roughly the same dimensions as a -7 on an S55 is making absolutely silly power numbers compared to an RB26. I know there's a ton of power loss from things like high tension rings, high viscosity oil, clutch fan, AWD standby loss, etc but it's something like 700 whp in an F80 M3 vs 400 whp in an R33 GTR. The stock TF035HL4W turbos in an F80 M3 are really rather dinky little things and that's enough to get 400 whp at 18 psi. This just seems unwise no? I thought the general approach is if you aren't knock limited the MFB50 should be held constant through the RPM range. So more timing with RPM, but less timing with more cylinder filling. A VE-based table should accordingly inverse the VE curve of the engine.
    • I've seen tunes from big name workshops with cars making in excess of 700kW and one thing that stood out to me, is that noone is bothering with torque management. Everyone is throwing in as much timing as the motor can take for a pull. Sure that yields pretty numbers on a dyno, but it's not keeping these motors together for more than a few squirts down the straight without blowing coolant or head gaskets. If tuners, paid a bit more attention and took timing out in the mid range, managed boost a bit better, you'll probably see less motors grenading. Not to name names, or anything like that, but I've seen a tune, from a pretty wild GT-R from a big name tuner and I was but perplexed on the amount of timing jammed into it. You would have expected a quite a bit less timing at peak torque versus near the limiter, but there was literally 3 degrees of difference. Sure you want to make as much as possible throughout the RPM range, but why? At the expense of blowing motors? Anyhow I think we've gone off topic enough once again lol.
    • Because that’s not what any of them are building these heads or blocks for. It’s to hold over over 1000hp at the wheels without breaking and none of that stuff is required to make power 
×
×
  • Create New...