Basic Turbocharger question

notched86 · Apr 15, 2004

Ok so obviously boost pressure is positive pressure in the intake manifold. But my question is, since exhaust gas is always flowing through the exhaust manifold and turbine side of the turbo, (which in turn turns the compressor side of the turbo) does that mean the compressor wheel is spinning even in Vacuume? (just not spinning fast enough to build positive boost pressure?) And since the turbine side of the turbo is on the exhaust manifold, I assume the turbine wheel is spinning constantly? (even when the turbo is not spooled up)

I thought if the turbocharger is not spinning at all in Vac, I could make it last longer by staying out of boost when I don't need it.

Thanks, for helpin me out.

89lx2.3 · Apr 15, 2004

Interesting question, never really thought about it myself... but i would suspect that the turbo does indeed spin all the time, but doesnt create boost until it reaches it's "spool up" speed. It would almost have to, if it did not spin at all that would be a major restriction in both the intake and exhaust systems. I dont think that getting it to stop spinning would be beneficial because:
1) The aforementioned restriction
2) It would take longer for it to spool and reduce performance
3) Spinning at low speeds helps with lubrication and heat dissapation in the bearings
4) how could it even be accomplished?

also a BOV or bypass valve helps extend turbo life by keeping it spinning and avoiding having pressure hit the compressor wheel which could casue it to stop spinning. That would probably be a better way to go to get rid of some of that heat (especially after youve been on it for a while)... but i dont even know if it does or doesnt spin in vac, but in any case a good question never the less.

Lx89Stang05 · Apr 15, 2004

(just not spinning fast enough to build positive boost pressure)
thats correct,once it reaches a certian RPM it starts to make boost, but the turbine and compressor wheel are always spinning at idle. and the turbine and compressor wheel are connected by a shaft which means they spin at the same RPM all the time.

Stinger · Apr 15, 2004

They spin (at a pretty good speed) at idle...

G-90 · Apr 15, 2004

Lx89Stang05 said:
(just not spinning fast enough to build positive boost pressure)
thats correct,once it reaches a certian RPM it starts to make boost,.

This could be could be misleading to someone that does not fully understand turbo's. I know it was for me.

Although RPM is a factor, it has more to do with engine load than engine speed.
You could have that same given RPM and have no boost if the engine is not under a load, ie flooring it up a hill or taking off.

So; Boost is being created the instant you load the engine but, the max boost will be achieved at a certain rpm.

silver pony · Apr 16, 2004

turbo specs, engine size, Throttle position and Rpm are the key factors in boost.

G-90 · Apr 16, 2004

Print that on turboford and see what kind of responce you get.

mr_woodster · Apr 16, 2004

G-90 said:
Print that on turboford and see what kind of responce you get.

I can guess.... something along hte lines of !

and then finally a ...which generally leads to a few of the spectators ... *pat on back*

Basic Turbocharger question

notched86

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Stinger

G-90

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silver pony

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