Question about turbos

[Sammy D]

I have a question about turbos. I've never turboed a car, but have explored and driven some. I've read about twin(sequential) turbos, and compound turbos, but am having trouble understanding the concepts, even with searching. My question is in regards to (I think) compund turbos.

Is there a way to set up a 2 turbo system where one of the turbos gives you a nice boost on the low end (say 1,500-4,000rpm) and the second will kick in for the high end (4,000-6,500[or whatever])? I'm not sure if that's what a compound turbo is, or if that's impossible. Just a question though, I don't plan on going forced induction anytime soon since I'm broke as h*ll... haha

Thanks guys

 

[mymmeryloss]

Yes its possible

 

[Wreckless Hype]

The MKIV Supra came with a sequential twin turbo setup. You can find some information on it pretty easily and it will give you a run down on how everything works. It's pretty complex compared to your basic single turbo setup. You'll need a decent EM to set that up and run it with consistency.

 

[xxBLOOD88SHOTxx]

It is possible, but impractical on a small 4 cylinder setup such as ours.

Sequential= Two turbos, one down low and the other activated up high and are independent from each other

Compound= Two turbos-the compressed air from the larger turbo is usually compressed again by a smaller turbo, packing more air into a smaller space. Common among diesel applications.

 

[Failsafe88]

Everything the said above

 

[Sammy D]

Great, thanks!

Now that being said, is there a way, in a sequential setup, to have the low end turbo disengage as soon as the high end turbo kicks in? It seems as though it would extend the life of the low end turbo, because then instead of working the whole time, it would only work until the high end one kicks in. If possible, has it ever been done, and if it hasn't why not? And if it's not possible, well alright then. I just figure with all the electronics of today, there ought to be a way to program an ECU/ECM to disengage a turbo the same way it engages one, at a certain rpm.

 

[Wreckless Hype]

A lot of the reading I did seem to point out normal scenarios where the exhaust from turbo #1 is used partly to spool turbo #2 because if you do not have the correct RPMs during the change over, you're going to have a bad stutter and the system will not function correctly. In most turbo setups, the turbo is consistently spooling anyway.

My old WRX had just a stock TD04 and the turbo had no issues, no leaks, cracks, no shaft plays after 160k miles. My boost gauge was almost always positive pressure unless I was low on fuel

 

[mc360]

im almost positive there is no way to completely stop the first turbo from spinning while the engine is running, what usually happens is you have two wastegates one is for the first turbo and one for the other turbo, say you have a small turbo for low rpm and one for high rpm the low rpm turbo will have a smaller wastegate spring to release most the exhaust (at say 8psi) then usually that wastegate is fed into the exhaust turbine of the other turbo to help spool and it takes over all the work from 8psi up. you can also just run the wastegate into the exhaust and have the first turbo compress the air and push it into the second turbos air intake and run the exhaust from the first turbo to the second turbos exhaust turbine, this keeps the turbo spooling beyond the 8psi when the wastegate opens on the first turbo which reduces how much air the turbo is compressing into the second turbos intake.