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Dean, from what I've seen & read, the Volvo V40 boost management setup is very similar to Saab 9-3 & 9-5 with a couple of notable exceptions. Unfortunately, there are no sites as informed as Saabnet for Volvos -- and I'm not just saying that to flatter!
The Volvo's Mitsu turbo has an integral dump / bypass valve which cycles boost pressure back into the intake side of the turbo when the throttle's shut. This is controlled by a vac line from the inlet manifold, downstream of the throttle plate -- when the plate's shut, the manifold vacuum "sucks" the dump / bypass valve open.
The wastegate actuator is a separate bolt-on unit with the usual threaded, adjustable linkage to the wastegate arm itself. As per most Saabs, there's an ECU-controlled boost control solenoid which takes air from the output side of the turbo and routes it either to the wastegate actuator, or back into the intake just after the air mass meter. In this way, the engine only gets the air that the AMM is telling it -- there's no venting to atmosphere. There's a large intercooler (front mounted).
Now here's the difference between the Volvo and many other turbo cars. It has an air mass meter, a charge temp sensor and two exhaust gas temp sensors (one before and one after the cat) but no boost pressure sensor. Apparently the ECU works out the mixture, boost pressure etc from the air mass, charge temp, exhaust gas temp, RPM and so on, and simply follows a 3D map of these. So, for example, if it's hot and on the verge of knocking or pinging, the exhaust gas temp will show this and rather than richening the mixture the ECU will slightly reduce boost pressure.
In other words, the ECU is not aiming for a set boost pressure, but instead aiming for a range of ideal exhaust gas temps for all conditions. The car uses a Siemens EMS2000 ECU which is apparently unique to the Volvo S/V40. As far as I can tell, there's no boost limitation in 1st or 2nd gear -- it's easy to spin wheels in either gear.
TME (IPD in the US) do upgrades for the ECU, but at £1000 UK it's a little expensive. Anyway, hope this helps ...
posted by 195.102.2...
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