how much shaft play is too much shaft play?

**BlitZ** · 08-04-2008 11:49 PM

how much shaft play is considered too much?

will shaft play dramatically effect power? or will just burn oil when it gets bad enough?

thanks guys

**Limbo** · 09-04-2008 11:13 AM

It will affect boosting and can damage depending on how much play there is.
It can move up and down which is normal, but it should NOT move side to side much at all, if it even touches the housing at all its no good.

If there is too much movement the fins will get stripped on the housing and byby turbo

**TODA AU** · 09-04-2008 12:05 PM

Originally Posted by Limbo

It will affect boosting and can damage depending on how much play there is.
It can move up and down which is normal, but it should NOT move side to side much at all, if it even touches the housing at all its no good.

If there is too much movement the fins will get stripped on the housing and byby turbo

Don't you mean in & out?
Side to side is same as up & down...

**[ricer]** · 09-04-2008 12:12 PM

Originally Posted by TODA AU

Don't you mean in & out?
Side to side is same as up & down...

lol thats what i was thinking...

not only byebye turbo but it could possibly go thru and mess up all ur pipes and front mount

**BlitZ** · 09-04-2008 02:29 PM

another dumb question..

If 2 turbos both produce 13 psi and on the same engine... and peak power is made at the same RPM... should the power output be identical?

Cause the turbo Im looking at has shaft play and will proabably need a rebuild, but i blades are scrapping the housing or anything like that, but the play is quiet a bit.. Could this hinder the power output provided that it is still producing the target PSI?

**TODA AU** · 09-04-2008 02:58 PM

Take it to GCG or John @ Presission...
They'll be able to tell you if it needs to be rebuilt.
Some turbo's, Garret BB units in particular do have a bit of play which is normal.
Best if an expert has a look at it.

Re power @ 13psi...
If the turbo's are identical, the power should be the same.
If one is bigger than the other,
The larger one will generally out power the smaller unit with increased flow at the same boost.

**Limbo** · 09-04-2008 03:23 PM

Originally Posted by TODA AU

Don't you mean in & out?
Side to side is same as up & down...

Good point i never thought about it but i'm sure you guys know what i mean.

The middle pin goes in & out slightly a mm or so, but should not move in any direction towards the housing

**BlitZ** · 09-04-2008 03:30 PM

Originally Posted by TODA AU

Take it to GCG or John @ Presission...
They'll be able to tell you if it needs to be rebuilt.
Some turbo's, Garret BB units in particular do have a bit of play which is normal.
Best if an expert has a look at it.

Re power @ 13psi...
If the turbo's are identical, the power should be the same.
If one is bigger than the other,
The larger one will generally out power the smaller unit with increased flow at the same boost.

thanks for that..

but how does the flow increase... isn't the flow governed by the PSI.. ?

**Limbo** · 09-04-2008 03:46 PM

No PSI is how much pressure not how much air
In a larger area you need more air to get to the same pressure in a smaller area.

Think of blowing through a straw. If the straw is bigger you need more blowing to get the same amount of pressure than you would a small straw.

Thus in a smaller turbo at specific PSI there is less air than a large turbo at same PSI

**BlitZ** · 09-04-2008 05:12 PM

but say u if an external wastegate... independent to turbo..

u upgrade the turbo and run the same PSI...

Wouldnt the external wastegate open and the same air pressure and flow?

**Aiight** · 09-04-2008 06:56 PM

the external gate will still open at the same point, but thats irrelevant to how much air the turbo will have compressed to reach that point in PSI...

a smaller turbo has a smaller amount of space to compress air into.

a twice as larger turbo, would say, compress twice as much air to the same psi

so both turbos are producing the same PSI but the larger one is pushing alot more air.

more air = more power

**Limbo** · 09-04-2008 10:07 PM

Originally Posted by Aiight

the external gate will still open at the same point, but thats irrelevant to how much air the turbo will have compressed to reach that point in PSI...

a smaller turbo has a smaller amount of space to compress air into.

a twice as larger turbo, would say, compress twice as much air to the same psi

so both turbos are producing the same PSI but the larger one is pushing alot more air.

more air = more power

yep that's exactly right