Originally Posted by euromodder
Keep in mind that most folks on here already have their grilles blocked, which means less air going in. And less heat being blown out.
Sure, there are still a great many leaks - and you actually need them to get rid of the heat from the engine.
Simply blocking part of those leaks already seems to help warm up times ...
The grill block is a vastly different mod, and a good target for temp management at speed. It doesn't do nearly as much at stand still though for retaining heat, but would be more effective than a negligible insulator to the hood.
The grill block, which is more for aereo, works on more of a curve. The engine is designed to shed heat to run in an optimal range. The block just helps you reach and maintain that range more so in the fuel efficiency realm - it doesn't increase temps by any significant margin, unless you overdue and then overheat. You have to seriously modify the coolant system because the car will try to shed any significant amount of excess heat built up by the block.
A possible solution, if you had an engine that could handle the heat soak, would be a rig that could significantly reduce the cooling system so you could build up a lot of heat right before you shut off the vehicle, with an overheat override. There would need to be a lot of testing though as the engine is designed to shed lots of heat; it may only be practical for short term stops. It is basically a prius like system, but soaking the whole engine rather than a small amount of coolant. I'm guessing engineers have tried it before with lackluster results.
Another aspect would be like my old big car has, where the engine and trans oil are routed through the radiator to cool them, but in lower temps the engine coolant heat also warms both. Most fuel efficient vehicles don't have such systems nowadays as the EPA doesn't do fuel ratings in 20 degree temps.
Still, grill block or not, any measure of hood insulation would still have a negligible effect.