Temp related low boost

Tom Ellis tom at tomellisphoto.com
Mon Sep 19 11:23:08 EDT 2005

Alright folks, here is one that I hope you can help me with.  For the past
month or so I've noticed that my boost is limited to 1.4 bar once the engine
temperature (as shown by the coolant temp gauge) gets above a certain point.
On the temp gauge this seems to be at the thin line halfway to the first
thick line, where that thick line is normal operating temperature.  At
coolant temps below the "thin line" I get full boost to 1.8 bar.

This does not seem to correlate to oil temperature.  Driving on the freeway
on a cool evening with the coolant gauge showing a temp at or below the
"thin line" and oil temps somewhere between 60 C and the next mark on the
oil temp gauge, I get full 1.8 bar no problem.  But once the coolant temp
rises above that magic line (regardless of oil temp) maximum boost drops off
immediately to 1.4 bar.

I've looked in the archives and found a reference to a possible problem with
the MFTS that might cause these symptoms.  So I disconnected the MTFS and
drove the car - same results.

Any ideas?  Is there some other coolant temp sensor that I don't know about
that could be the culprit?

Thanks for any suggestions!

Tom Ellis

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