Thank you for posting at TSN!
The B204R SAAB 9-3 SE should already employ the T04HL-15T turbocharger which is very common to the VIGGEN or SE models, and MITUBISHI manufactured.
All turbocharger compressor wheels will have a manufacturer flow "Map" which details the ability of this wheel to delivery efficient(Cool) air when at a specific engine horsepower target, and more. Most automobile manufacturers, such as SAAB, would select the best compressor wheel trim which allows for the most efficient charge, but also factor the wheel's ability to climb to full boost(Spool). SAAB selected the 15T wheel due to it's ability to deliver a cool charge at the 210 to 260 horsepower targets, as this wheel will be found at the 210 horsepower 9-3, with B204R engine, as well as the 9-5 Aero.
Typically, the larger the compressor wheel, the greater it's efficiency at higher horsepower target, but this also generates additional rotating mass due to the increase in diameter.
The same 15T compressor wheel trim has typically been very capable of reaching higher engine horsepower targets, and you will find many customers in excess of 300 horsepower with these same assemblies, even though this is not the most efficient charge, at this level, but the efficiency changes are negligible, for short charging durations(Most Daily Driven/Modified SAAB).
The trend in 19T wheels are a substantial increase in compressor wheel size, as compared to 15T, and will always require additional time to reach full charging pressures, which is also referred to as "Lag". Aftermarket turbocharger replacements are also very common for this TD04 assembly which always results with a greatly reduced service longevity due to sheared turbine shafts, when integrated with a 19T compressor wheel trim.
Another common problem has been the slower rotation of a large(19T) rotating assembly when at engine idling conditions. Slower rotating turbocharger speeds, at engine idle, will always reduce the 19T rotating assemblies engine oil consumption, which could always create turbocharger oil seal bypassing, at nearly all idle conditions. We had experience when offering our hybrid T3/T4 turbochargers and employed an overlapping turbine oil seal to resolve any oil bypassing conditions.
Good luck with this project, and regards!,
Gary K. at SWEDISH DYNAMICS, INC.
->Posting last edited on Thu, 31 May 2018 20:53:18.
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