Turbochargers - Gap or Clearance between turbine wheel and housing

[scutarius]

I need help with authority or proof that the gap between the turbine wheel and its housing on a turbocharger is important to the engine's performance.

I need to show that if the gap is out of tolerance then this will result in lower than specified boost pressure which will result in lower rpms, lower horsepower, and increased exhaust gas temperatures.

This is for a diesel engine on a boat.

Thank you in advance

[PinkertonD]

Hi and welcome,

Is this for some kind of Litigation or Warranty complaint? Turbochargers operate through and outrageous temperature range and "gaps" are critically designed to allow operation throughout that temperature range and beyond.

There is an awful lot of information to be worked through in order to establish the correct "gap" for a given Turbocharger and engine combination.

If you have simply measured the "gap" and decided it could be smaller and thus improve operation, then you must take into account thermal expansion, rotational distortion and a myriad of other conditions before deciding to arbitrarily reduce or increase that "gap."

[jboggs]

"I need to show that if the gap is out of tolerance then this will result in lower than specified boost pressure which will result in lower rpms, lower horsepower, and increased exhaust gas temperatures."

You've answered your own question. Think about it:
Who established the tolerance? The manufacturer.
Why did they pick some certain range of tolerance and not another? Because their analysis and testing showed that anything outside that tolerance caused a problem, probably degraded performance if not catastrophic failure. It wasn't just an arbitrary decision. They would want the largest possible tolerance that would work just for ease of manufacturing.

[dalecyr]

scutarius:

How far out of the manufacturer's specified tolerance is it?
Is the answer you are looking for a specific amount (x% per .001 inch)?
Or is the answer you are looking for a graph of gap vs performance?