Does minimum emissions = maximum efficiency?

[tandemsandy]

Been thinking about this one, possibly too much!
At his MoT Vinnie ( 1.9 DG) had to have his mixture tweaked to bring the emissions down within limits. If I cast my mind back to uni, nasty emissions like CO are a result of incomplete combustion, so if the emissions are lower, then the combustion of the air/fuel mixture must be more efficient in converting its calorific value to mechanical power and not leaving uncombusted waste by-products.
If that was the case, then Vinnie would now be running better than ever as he's extracting more energy from the fuel, but he seems down on torque on hills, and the MoT guy mentioned the mixture may need tweaked back because he was struggling to blow the skin off a rice pudding. My calculated mpg has also dropped a little, so clearly efficient does not equal power, so what am I missing?

Rob

[kevtherev]

So you have set the mixture at idle speed.
the idle jet is set in stone all you adjust is the air mixing with the fuel (14:1 being optimal)
After 1500 rpm your on main jet and the air passing down the venturi

If you're not getting power up hills it suggests extra air entering the inlet manifold.
Or poor advance timing.
Misfire
Poor compression
weak/intermittent spark

[tandemsandy]

Ok, so the emissions test is purely relative to the setting of the engine at idle? Once the revs rise and the main jet is in use we're into a different set of parameters being involved?
That I can understand.
Will check the points you mentioned. Most I've replaced recently but doesn't mean they still work properly!
Thanks,
Rob

[kevtherev]

Ok, so the emissions test is purely relative to the setting of the engine at idle? Once the revs rise and the main jet is in use we're into a different set of parameters being involved?
That I can understand.
Will check the points you mentioned. Most I've replaced recently but doesn't mean they still work properly!
Thanks,
Rob

Yes and yes
Furthermore
If the secondary butterfly throttle valve operated by vacuum is not functioning properly then power loss will be inevitable.