turbo question

[auggystyle]

just wondering, does an exhaust leak affect the opperation of a turbo? thanks-

[Subarian]

If it's before the turbo, it could. If it's after it, it shouldn't.

[Saltty]

Before or after is bad......a leak before will affect how much boost the turbo will make and a leak after can allow the turbo to overspeed due to reduced back pressure. I've seen them blow and launch pieces though the hood:-\

[nkx]

if you have a pre-turbo exhaust leak, youre being robbed of power. post turbo exhaust leaks arent going to hurt the car, but you might not pass inspection. back pressure on a turbo car is the devil.

 

saltty, that turbo that exploded must have had some other factors involved. a turbo shouldnt fail "due to reduced back pressure".

[BoostedBalls]

A 'minor' exhaust leak before or after the turbo is not going to show up on the butt dyno. It will not damage the engine or turbocharger either.

 

The stock wastegate is sort of a 'controlled leak' and almost never seals up perfectly anyway. I good sized leak before the turbo will increase turbo lag but probably have no effect on wide open top end power as the wastegate is surely open at that time anyway.

 

Yes- back pressure IS the devil! Your turbo will actually run better with no down pipe attached at all and the 'turbo lag' will disapear. I run mine with an open down pipe.

[jeffast]

boosted balls is right a leak after is no big deal

[NorthWet]

Turbo failure can occur with an after-turbo leak... if the turbo has no wastegate and was "sized" to be controlled by back pressure (e.g. - Corvair).

 

A pre-turbo leak can make a HUGE difference... one of mine has the typical cracked flange at the turbo and will not build positive pressure until 3K+ and never developes significant boost. (Would be fixed except for "frozen" turbo mounting bolts... ARGG!!)

 

And some tail piece should be fitted to the turbo outlet to avoid/control turbulence and chaotic flow (and its attendant back pressure). Turbos operate with supersonic and transonic flows, and "normal" concepts of air flow do not apply very well.

[4WDFrenzy]

Pre-turbo leak, the car will rev fine, but the turbo will feel as if it is lagging. Post- turbo leak is no biggie unless it is before the muffler. It shouldn't hurt anything except your pocketbook if Johnny Law comes a knockin' with his Db meter.

Patrick

[Phizinza]

don't forget; if its before turbo, and O2 sensor, you will also be running rich. So you might be getting even bigger drop in power.

[BoostedBalls]

The Corvair turbos can hardly be compared to our modern IHI units. The corvair turbo was a caveman in the evolution of turbochargers. Those turbos had seals that dragged heavily on the shaft that caused some pretty severe spooling delays. Modern turbocharger systems are not controlled by downstream back pressure. That is what the wastegate is for. Apples and oranges...

 

 

 

Turbo failure can occur with an after-turbo leak... if the turbo has no wastegate and was "sized" to be controlled by back pressure (e.g. - Corvair).

 

A pre-turbo leak can make a HUGE difference... one of mine has the typical cracked flange at the turbo and will not build positive pressure until 3K+ and never developes significant boost. (Would be fixed except for "frozen" turbo mounting bolts... ARGG!!)

 

And some tail piece should be fitted to the turbo outlet to avoid/control turbulence and chaotic flow (and its attendant back pressure). Turbos operate with supersonic and transonic flows, and "normal" concepts of air flow do not apply very well.

[BoostedBalls]

There's almost always a positive pressure in the exhaust manifold on a turbo system. This means that the oxygen content of the exhaust flowing past the 02 sensor is constant. The 02 sensor can only measure oxygen content and not flow or pressure.

 

don't forget; if its before turbo, and O2 sensor, you will also be running rich. So you might be getting even bigger drop in power.