Is a turbo always spinning?

[fjord]

Something I thought about on the way into work yesterday.

Is a turbo spinning 100% of the time? I know you get turbo lag, which is where the turbo takes time to spin up, but is it spinning up from a standstill or spinning from a slow rotation.

Assuming it only starts spinning at certain revs, what makes it spin? Does it just happen when the revs rise sufficently to generate enough gas/pressure to make the turbine move?

[Raize]

Pump efficiency diagrams and stuff. It's not linear. Engineering stuff. Someone else explain it.

[xRIEx]

Pretty sure it will always be spinning when the engine is on, maybe about 10K revs with the engine idling, up to 100K or 200K when it's producing full boost.

Edited by xRIEx on Saturday 2nd November 15:07

[kambites]

It will always spin while exhaust gas is flowing (which it always will be if the engine is running).

However, it wont be spinning very quickly at low throttle openings (regardless of engine RPM) so the pressure in the in-take manifold wont be very high. When you open the throttle, the exhaust gas velocity increases and the turbo starts to pressurise the intake manifold which in turn increases exhaust gas rate which pressurises the manifold more and so on. The engine has to go around this this feedback loop many times before the turbocharger is running at full boost - that's what turbo lag is.

[LukeR94]

kambites said:

It will always spin while exhaust gas is flowing (which it always will be if the engine is running).

However, it wont be spinning very quickly at low throttle openings (regardless of engine RPM) so the pressure in the in-take manifold wont be very high. When you open the throttle, the exhaust gas velocity increases and the turbo starts to pressurise the intake manifold which in turn increases exhaust gas rate which pressurises the manifold more and so on. The engine has to go around this this feedback loop many times before the turbocharger is running at full boost - that's what turbo lag is.

Sorry to hijack the thread, but you seem like a knowldgeable chap, how do Anti-Lag systems work?

[DaveCWK]

LukeR94 said:

Sorry to hijack the thread, but you seem like a knowldgeable chap, how do Anti-Lag systems work?

Inject air into the exhaust manifold between the turbo and engine, keep the fuel injectors on with the throttle shut, this mixture combusts in the manifold due to the heat and the energy from this acts on the exhaust turbine.

[LukeR94]

DaveCWK said:

LukeR94 said:

Sorry to hijack the thread, but you seem like a knowldgeable chap, how do Anti-Lag systems work?

Inject air into the exhaust manifold between the turbo and engine, keep the fuel injectors on with the throttle shut, this mixture combusts in the manifold due to the heat and the energy from this acts on the exhaust turbine.

Im guessing the insane popping is the igniting coming down the exhaust?

Thanks =

[DaveCWK]

LukeR94 said:

Im guessing the insane popping is the igniting coming down the exhaust?

Thanks =

Yep. As you can imagine it's not great for durability of either the manifold or turbo

[DanielSan]

DaveCWK said:

Yep. As you can imagine it's not great for durability of either the manifold or turbo

Sounds awesome though

[750turbo]

Pedant mode...

http://www.toyotagtturbo.com/forums/showwiki.php?t...

Actually on my bike, with a K & N fitted the "Chirrup" is quite accentuated!

Also, aren't Smart cars regularly making the same sound? (I worked with them in Germany years ago, and seem to remember this...)