wow on the exhaust manifold? never heard of that. i bet that does heat up fastThat's how ICE cars used to produce cabin heat, but some such as my VW have a heat exchanger on the engine's exhaust manifold that can supply hot air practically as soon as the engine is running. It's something I have come to greatly appreciate when it's chilly.
I grew up with one of those in Minnesota. It never got warm all winter long.My 60s vintage air cooled VW's sole heat source was air blowing over the exhaust manifolds. It could get quite toasty, until the body rusted out enough that more heat was blown into the atmoshere than cabin.![]()