Quote:
Originally Posted by Old Mechanic
A block heater would definitely help.
Increasing cat heat retention (insulation) would help.
Grille block would help.
Warmer intake air temp would help.
All potential uses of normally wasted heat energy would mean higher cat temperatures and better function.
It certainly is a goal worth pursuing and an admirable sense of ecological responsibility.
A tip of the hat to a man who is dedicated to both goals.
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All true. But I wonder how much it would help. I think keeping the cat above "light off" temperature (~500F) with engine off would help emission efforts. However, when the cat reaches this temp, it then relies on chemical conversion to get to up to its operating temp of >1000F. So under normal operating conditions, inlet temp is [let's say] 600F and outlet temp is 1100F. The heat increase is mainly the result of adding O molecules to H and C molecules (to get CO2 and H2O). The cat needs to be >500F for this to start happening, keeping it >500F with heat wrap would make the reaction occur sooner.
BUT....by shutting down the engine, the cat will always drop to ~500F and have to restart the chemical reaction reheat to 1000F over again, so I am wondering if raised emissions is unavoidable no matter how much heat we try to retain. I wonder if an HC doser (aka extra fuel injector) and metered aftertreatment combustion air injected into the manifold when the engine is off would work. Diesel engines have a doser after the turbo to get the catalyst over 1000F for DPF regeneration.