Turbo classification...?

Major Asstyrd

Active member
Old thread. When switching turbos around it's best to find someone with experience doing it on these engines. Ideally ask around and locate a truck with an engine/turbo combination that works really good and try to copy it. Learn what part number the turbo is off its data plate. I can tell you if BorgWarner or whoever still makes it. Or find a used one. One problem is if someone changed it around so maybe it has a different compressor wheel and housing or a machined housing. Reference materials showing wheel diameters for turbo PNs are sometimes still available.

Get to know your local fuel injection service dealers for possible pump tweaking. Look for the technician with the most gray hair.

One thing to remember about turbos is each end housing has an A/R ratio. This is usually cast into them. Like ".97" or "1.4". Small number is small volume, large number is large volume. This is the air-gulping ability. It makes the most difference on the turbine side. Assuming the rest of the turbo is a constant, a small A/R allows a given amount of exhaust gas to get the turbine wheel spinning quicker than if a big A/R. So the compressor wheel does the same and it makes boost early. Less smoke usually, and more power early. But it could over-spin the wheels at high rpms. And too much pressure. This is why wastegates were invented. At a certain compressor PSI an actuator pushes a rod that is connected to a valve in the turbine that opens and bleeds off pressure in there. This allows a smaller, better performing turbine work well without overspeeding the wheels.

A high power engine usually has a turbo with a large A/R turbine housing, all else being equal. This builds boost slow and engine can smoke, but there is room for a lot of exhaust gas before the wheels overspeed. A wastegate may not be necessary in this case but usually it is good to have one if needed.

Diesel trucks since the Ford 6.0L in 2003 have moving parts in the turbine that vary the amount of gas directed into the turbine wheel blades according to what pressure the ECM wants at what rpm and pedal setting. These act like a small then large turbine as engine goes from idle to max rpm.

Diesels are mostly about fuel. Generally, more of it makes more power. Then enough air (oxygen) needs to be added to make the big molecules burn more completely. Unleash their power. That lowers smoke and exhaust temperature. So the opposite of a gas engine, which is mostly about getting more air in, turning more rpm, and adding gas. This is why a hot rodder has to spend many thousands of dollars to get 500 hp out of his 300 hp Chevy 350. Cam, valves, high compression pistons, big carb or FI. His buddy with a 300 hp 2003+ diesel pickup just buys an ECM programmer for $700 to get 500 hp. Yes going that high probably means upsizing the turbo but it's still cheap thrills. But I digress....
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