Group,

  Interesting information from a site about the construction of a 400+ hp turbo Harley Davidson

built for Bonneville speed trials...........A very extensive site but what was very interesting  to me

and perhaps others of our group flying or planning to fly with a turbo was the info below stating

that wideband oxygen sensors are not suitable for turbo engines...........This is just a small part

of the turbo portion of this site and more interesting info is at the link below..........FWIW

 

   http://www.rbracing-rsr.com/bonneville2.htm#turbo

 

 

Why EGT and Narrowband.... Not Wideband for Turbos

As you can see from the chart a Bosch LSU 4 wideband sensor has a 15% error if subjected to 2 Bar exhaust pressure. On turbos you have to mount a wideband sensor after the turbo which is a big problem because turbos, at least in race applications, use short dump tubes and this is way too close to oxygen-rich atmospheric air. On our race bikes we use our RSR Air Fuel Ratio Gauge which is not affected by exhaust pressure. On our Bonneville Bullett we run two single wire high temperature Bosch O2 sensors in addition to the dual egt ORCA Turbo Dash. Wideband LSU 4 sensors can be damaged with egts greater than 1500 Deg F. We run above this.

A second reason you use egt on turbos is that, if you are running leaded race gas, any O2 sensor, narrow or wideband, will become contaminated, resulting in false readings. This can happen very quickly or maybe 10 hours later depending on the fuel used. When fouled, they render false lean readings. It is better to watch and record high egt temperatures which are completely unaffected by either pressure or racing fuels.