[alvah]

Interesting(ish) tangent - the UK fuel economy specs used to be published at a constant 56mph & 75mph. When the Mk3 Vauxhall Cavalier was launched in the late 1980s, it had great (theoretical) fuel economy, much better than its rivals, but a couple of noticeable flat spots under acceleration. Turned out Vauxhall had leaned the fuel maps at the exact engine revs that corresponded to 56mph and 75mph in top gear...

[mywittyname]

My old (14) Mustang had exactly the same thing: there was a very noticeable reduction in power at ~2000 RPMs. I always suspected that it was to improve highway fuel economy, as that's exactly where the engine was spinning at 74mph in sixth.

[londons_explore]

Defeat device...? Cheating...? Multi-billion pound fine?

[mft_]

Totally different, isn't it?

Presumably the Vauxhall mentioned would provide exactly the measured MPG when driven at the correct speed by any owner in the real world - hence the 'flat spot' noticed.

The defeat concept you're referring to (presumably VW's) was set to only function during a test, and not in the real world (AIUI).

[londons_explore]

VW's defeat concept was set to function only at the exact RPM's used during the test. If a real-world customer were to use those RPM's and conditions, it would activate too. In fact a CCC talk showed that 5% of regular driving activated it.

Perhaps about 5% of regular vauxhall driving was in those flat spots...

Seems the same to me.