Internal Bypass Valve on Saab Intercooler? [Archive] - SaabCentral Forums

: Internal Bypass Valve on Saab Intercooler?

18th July 2002, 09:28 PM
I have read that the 900 Turbo's intercooler has a internal bypass valve on them.

Would this effect performance or would it assist in spool-up time?

Has anyone remove this Valve and found a performance increase? more piece of plastic junk to remove?

Janne Selinummi
19th July 2002, 04:39 AM
Is the by-pass valve really mounted on the intercooler in NG900? Sounds odd..
Anyway, if you are referring to a common by-pass valve that connects inlet and pressure sides of the turbo system, the function of that part is to reduce turbo lag between gear shifts, and also protect the turbocharger from pressure pulses that would take place if such a relief valve wouldn't be there to dump the boost pressure when throttle plate is closed.
So, if your valve works, it's an improvement over not having such a valve. However, these valves can fail in time, which will lead to boost loss. In that case, just replace the valve with a new one.

Johann F
19th July 2002, 04:56 AM
The very early 900T16 (1984/85) IC's were all alloy and incorporated a bypass valve. I have no idea what it was for though - perhaps to help if the core became blocked with oil? What I do know is that these units did not flow as well as the subsequent plastic ended ones as the alloy inlets were both narrow and contained very sharp bends.

<font size=-1>[ This Message was edited by: Johann F on Jul 19, 2002 9:58am ]</font>

Janne Selinummi
19th July 2002, 05:02 AM
Johann F, the valve you are referring to, is supposed to be operative in sub-zero temperatures - there's a risk for ice being formed in the IC that will further cool the humid winter air, and to prevent this, there's a valve to by-pass the IC in case of such low temperatures. But such a thing should not be fitted to a NG900 Turbo, or what?