Originally posted by: Roger
Something makes me question the exhaust thing though. It seems possible that the retarded timing could increase emissions, even if ever so slightly? I don't know if that would effect say the catalytic converter's longevity, or perhaps even worsen the milage hit even more due to the ECU compensating? I dunno. Roger?
The ECM will compensate for the lower octane rating.
As for the exhaust system, temps in the exhaust would be slightly raised do to the retarded ignition timing but I doubt very much that it would shorten the life span of the exhaust.
Catalytic convertors require a stoichiometric air fuel ratio (14.7 parts air, 1 part gasoline) to operate efficiantly.
This ratio does not produce maximum horsepower, a ratio as low as 12 to 1 will produce more power but emissions increase exponentially as the air fuel ratio deviates from 14.7 to 1.
The ECM will slightly richen the fuel mixture along with retarded ignition timing when a lower octane fuel is used to combat preignition.(a richer mixture burns cooler)
The ECM will also alter EGR function to compensate for the altered mixture ratio thereby keeping emissions within desired parameters.
This will ofcourse lowers temps in the engine but raises temps in the exhaust system.
But, now here is the catch, most automibile manufactures design there engines and control systems to accomadate lower octane fuel.
So, what is the overall picture ?
You will do no harm when using a lower octane gasoline.
I'd say 80% of the ones I've seen listed are autos. So WHO will be driving the Maxima when you get one?
Facebook
Twitter