Jump to content
SAU Community

Twin Turbo vs Bi Turbo ?

ferni

By ferni,
in Engines & Forced Induction

 Share

Recommended Posts

ferni Grand Master

ferni

Posted
Posted

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
ferni Grand Master

ferni

Posted
  • Author
Posted

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

Roy Grand Master

Roy

Posted
Posted

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...

Laurence Mentor

Laurence

Posted
Posted

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
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • sunsetR33
      Blue/grey smoke after idle

      By sunsetR33 · Posted

      I get that taking off the head is best but that's a bit much for "just" valve seals. I was just under the impression that one would be able to rotate to TDC and be able to temporarily drop the valve without losing it and effectively having to remove the head to then recover it. I never knew people actually pushed rope into the cylinder to do valve seals hahaha So just to confirm, just going to TDC will not work? In that case I know when I do valve seals I'll maybe just remove the head and do some other things while I'm there, or just wait until I do an engine build.
    • GTSBoy
      Blue/grey smoke after idle

      By GTSBoy · Posted

      The old approach was to fill the cylinder/chamber with a length of rope pushed in through the sparkplug hole. The new approach is to connect compressed air to the sparkplug hole and fill it with enough pressure to push the valves up. Doing either of these things with the head on and the engine in the car is a lot less pleasant than doing it properly.
    • sunsetR33
      Blue/grey smoke after idle

      By sunsetR33 · Posted

      Can't you put the pistons to TDC and then do the valve seals? Or will the drop down too far to pull them back up?
    • sunsetR33
      Replacing turbo water line - any recommendations or advice?

      By sunsetR33 · Posted

      One thing I can tell you is, do it properly the first time. If you encounter unexpected problems just let the car sit for a week or two if you have to get some other parts or figure stuff out.  I'd have said go and use as many OEM parts as possible but since you want to change the turbo later on a custom kit is probably the better choice. Since I have no experience with RB25 just compare parts diagrams and images before buying a line kit and it should be easy to see if it has everything you need. Amayama has very good parts diagrams and part number lists, that is what I used a bunch to figure out what I might need. And don't forget to plan ahead and possibly renew other stuff that's easy to get to while you're in there doing the turbo lines. Happy wrenching
    • sunsetR33
      Unpeeling the Orange

      By sunsetR33 · Posted

      Update 4:   Hi all, good news. Engine is running and all the gaskets and seals seem to be working as intended. No leaks so far, even the JB Weld seems to hold. I flushed out the old coolant a few times and put in fresh coolant, not Nissan stuff, I decided to try the Ravenol Protect FL22, they claim it works for a wide variety of JDM cars and the opinions on it by some people were pretty good. And it has the nice poison green color! And man am I glad I bought a coolant system tester earlier this year, vacuum filling works wonders on this engine. I can definitely recommend this to anyone still doing it the old school way. All you need is compressed air supply. Will have to do a small test drive as soon as I can, I removed the gauge cluster again as the tacho needle was still bouncing around a bit but it was much better than before already.  I also found some cracks on all 4 tires inner and outer sidewalls. Apparently these tires should 't be parked on for extended periods or be kept under 0 degrees during storage, which I did not know. Clearly the previous owner didn't look into those details either, he probably bought them just cause they are cool semi-slicks. I'm just wondering how tf I am supposed to reach 30-80 degree tire temperatures on the public road consistenly, these tires were never going to work for my use case. I'll probably order Continental SportContact7 ones as these are the best allround summer tire available right now and I don't think I'll need anything crazier for now. Do let me know if you have experience with various tires and which ones you recommend.
×
×
  • Create New...