by induction1, April 26, 2004
i looked under the hood of a 2004 corolla and saw a plastic cover bolted to the engine and what looks like plastic covers over the exhaust ports, too. i just read that keeping the exhaust gas hot will send it out faster and increase performance (true?), but won't these just add heat and weight to the engine in general? what about the fabric sheet attatched to the bottom of the hood? doesn't that just insulate the heat, also???
thanks
True - keeping exhaust gases hot will help them move faster and help with higher RPM horsepower. The cover you saw - just covers the valve cover and the Associated wiring and plumbing around it - it extends a little around it as well. Just for looks though - I doubt it will trap a significant amount of excess heat. Weight is almost negligible - just a few ounces. That sheeting under the hood is for mostly sound deadening and to insulate your hood from too much engine heat. There again, negligible amount of heat trapped - remember there is a fair amount of air circulating around the engine compartment.
