Quote:
Originally Posted by nize
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Sorry resurrect a seriously old thread but the problem with the turbos available from Borg Warner (aside from those on the 997) is stated clearly on their site:
"BorgWarner Turbo Systems currently offers various sizes of turbochargers with variable turbine geometries for
diesel engines in automobiles and
light commercial vehicles."
Though BW has created a great turbo for gasoline engines on the 997 the problem still remains that none of the turbos they offer would be correctly sized for application on a 944/951/968. However the BW variable turbos are still no more than a conventional turbo with a variable turbine housing. Though there is a noticeable performance difference (I have had the luxury of driving one after another, both cars with similar modifications) turbo lag is still an issue. This is due to the fact that the bearing design still remains the same as any other conventional turbo: bearing cavity in the center, flooded bearings, hot engine oil. All of which add up to friction, drag, reliability issues, and turbo lag still being an issue. Friction from heat prevents the shaft/wheels from spinning up as fast as they could. Flooded bearings means more drag, again preventing the wheels from spinning as fast as they could, causing turbo lag. Hot lubrication from the engine means that when you run your car hard you absolutely need to let it idle for a minute or two before shutting your car off the prevent the bearings and seals from cooking within the turbo.
That said I'd like to point out that a variable-vane turbo that is free from the aforementioned burdens has been in production for quite some time:
the Aerocharger.
We use these turbos on an extremely wide range of applications: automotive, small engines (snowmobiles, motorcycles, ATVs, etc.), aircraft, even military applications. The technology has been proven time and time again to truly eliminate turbo lag.
The ingredients are simple: The bearing assembly is placed in front of the compressor housing, at the coldest location on the turbo where air is constantly drawn past it. Lubrication is self-contained. A small oil cavity on the front of the compressor housing provides oil to the ceramic ball bearings via wicks which mist the oil onto the bearings. This is absolutely the lowest drag lubrication system of any turbo, allowing for the fastest spool-ups in the industry. This significantly controls heat within the turbo by less friction and no engine to heat the oil. Heat transfer is controlled by a specially designed heat shield within the turbo, separating the two housings effectively. Radiant heat is controlled by a form fitting turbine heat shield for the exterior of the turbo. Several layers of header wrap can be sandwiched between the heat shield and the turbine housing to further reduce radiant heat.
Again I apologize for bring back an old thread but it's unfortunate to see people needing our turbo but don't know that it exists. Anyone can see that the 951s don't exactly have the most efficient turbo system. However to adapt on of our turbos to these cars would not only provide an excuse to redesign the exhaust side, but the turbo itself would be a night and day difference. Even at stock boost levels. Driving one of these cars with no turbo-lag would be exhilarating to say the least.