so i have a question

[dallasb84]

if you were to use a smaller turbo to spool a big one.... how does it get plumbed up and how does the exhaust go

for instance....

exhaust leaves head and manifold flows to small turbo..... wastegate gets routed to downpipe.... downpipe feeds big turbo... to which another wastegate feeds its downpipe....


intake enters small turbo compresses and feeds big turbo...


or does air enter big turbo compresses air entering small turbo...


how does this kind of setup work...... diesels use a setup like this right???

[blown_ss]

they share the same manifold in mose cases besides a v6/v8. in a i4 or i6 you split the manifold in half which in a lot cases is not the best bang for the buck. i could be wrong but the smaller turbo will spool faster causing more exhaust sooner so that the larger turbo will spool faster. as far as the charge pipe goes, they end up becoming one rather its before the intercooler or at it. (ex.) 2 charge pipes go into the intercooler on the hot side and one pipe comes out of the cold side.

[Formally...]

You have the exhaust side ride Dallas but not the intake side. Yes, you would have exhaust go through the small turbo first and a wastegate to bypass it. All the exhaust coming out of that wastegate and small turbo would then go into the exhaust housing of the big turbo. You have to remember though that if you are doing this to make big power (say 600+whp on a 4cyl) all that exhaust (there is alot of exhaust gases with that power) has to go through or around the small turbo. This means that you would have to have some very large wastegates or you will overspin the small turbo.

As for intake side, I think you would just want to have the charge pipes of each turbo going into the intercooler pipe. If you go from one turbo to the other then that means all the air will have to go through the small turbo at some time and this will cause a restriction.

As for the diesels, they do have one turbo's charge pipe going into the inlet of the next turbo. BUT they use the same size turbos for both. This is because a turbo will increase the inlet pressure buy x amount. For example if your turbo is running 10psi of pressure out then it took the atmosphere pressure and increased it by 10psi. So if one turbo is running 20psi and feeds the second turbo running 20psi the outlet pressure of the second turbo will be 40psi. Hope this makes some sense. And the diesels do this because they make there power on crazy high boost pressures (60psi and above) and one turbo has a hard time doing that.

[blown_ss]

You have the exhaust side ride Dallas but not the intake side. Yes, you would have exhaust go through the small turbo first and a wastegate to bypass it. All the exhaust coming out of that wastegate and small turbo would then go into the exhaust housing of the big turbo. You have to remember though that if you are doing this to make big power (say 600+whp on a 4cyl) all that exhaust (there is alot of exhaust gases with that power) has to go through or around the small turbo. This means that you would have to have some very large wastegates or you will overspin the small turbo.

As for intake side, I think you would just want to have the charge pipes of each turbo going into the intercooler pipe. If you go from one turbo to the other then that means all the air will have to go through the small turbo at some time and this will cause a restriction.

As for the diesels, they do have one turbo's charge pipe going into the inlet of the next turbo. BUT they use the same size turbos for both. This is because a turbo will increase the inlet pressure buy x amount. For example if your turbo is running 10psi of pressure out then it took the atmosphere pressure and increased it by 10psi. So if one turbo is running 20psi and feeds the second turbo running 20psi the outlet pressure of the second turbo will be 40psi. Hope this makes some sense. And the diesels do this because they make there power on crazy high boost pressures (60psi and above) and one turbo has a hard time doing that.

thanks for the info. i didnt think i was right on all of that but i figured i would give it a shot.

[all-mota]

thanks for the info. i didnt think i was right on all of that but i figured i would give it a shot.

charles is right the outlet of the compressor on the small turbo feeds the air intake inlet of the larger turbo and then they go throught the intercooler in one pipe from the bigger turbo. they also use a smaller turbo because when you can only acheive 2000rpm while trying to brake boost it takes the smaller turbo just to spool up the larger one. that why if you watch a diesel race they take so long to stage up

[dallasb84]

am i correct that on the sequential turbo supras they have a bypass valve to divert air from the small to the big.... sorta like a swing valve..... i think the rx7 has it too.

mind you on a sequential setup. i guess it would be like a wastegate in operation

[Formally...]

am i correct that on the sequential turbo supras they have a bypass valve to divert air from the small to the big.... sorta like a swing valve..... i think the rx7 has it too.

mind you on a sequential setup. i guess it would be like a wastegate in operation

Twin turbo supras use two of the same size turbos. They have a valve that makes all the air go through one turbo first to get it spooled and then the valve opens and both turbos get exhaust. We normally just disconnect this and wire it open all the time. Very little difference in spool time.