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Just lifted this from another site as it was a good explanation of the difference of petrol turbos and diesel turbos. "diesel turbo's are similar to petrol but, petrol turbos can blow into the carb (or throttle bodies) then into the engine, or suck through the carb then force fuel and air into the engine, known as 'blow through', or 'suck through' respectively.diesels do not have a throttle plate, the inlet manifold is open all the way into the cylinders, ie no throttle (engine speed governed by the amount of diesel injected), so the turbo allways 'see's' no or nearly no vacuum from the engine, however a petrol turbo configured in the 'suck through' configuration is subject to high vacuum (when the engine is throttled back the throttle plate is nearly shut upstream from the turbo thus causing high vacuum in the turbo housing), in this application a diesel turbo is incompatible as the high vacuum sucks lubricating oil out of the turbo's compressor side and then ends up in the engine causing smoking.diesel turbo's in the blow through config will work ok on petrol, but petrol suck through turbo's have an extra oil seal in the compressor side to stop the oil being sucked out.long winded, but you know now."Dump valves and wastegates are different:Waste gate is on the exhaust side and opens at a predetermined boost pressure to bypass some of the exhaust gas and hence limit the boost pressure and turbine speed.Dump valve is fitted in the air side between the turbo and inlet manifold and opens when the throttle is shut to vent the air and stop the turbo stalling, as has been said.There is little point in having a dump valve on a diesel engine because you don't have a throttle and aren't therefore in danger of closing off the inlet manifold suddenly at high boost pressures, and stalling the turbo.

Rocks7032013-03-02 18:40:20
 
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