Quote:
Originally Posted by manolo
They're not likely getting a good exhaust sample on the dyno at lower RPM's. The car wouldn't actually run if it was at 18:1. The probe is probably too short and getting reversion at lower RPM's. They could put the dyno O2 sensor directly in the exhaust if you have a spare bung in the headers or bypass tubes.
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Are you guessing or have you seen data to support this? 18:1 is not really that lean in terms of efficiency ratios. I run a large displacement flat four with a fuel and ignition system far less sophisticated than those in our Porsches at efficiency ratios approaching that level. Some of the new direct injection engines run at 60:1 or more under certain conditions.