Anyone know if it's safe to spray your engine with high pressure water at the car wash ?

A safe bet might be to contact several "detail" places for their opinion. I say several just to get a consensus. I would also ask the dealers maintenance manager or, if you have a trusted maintenance advisor, ask him/her. At least they might be able to give you a good explanation why you can, or why you can't. Let us know what you find out.

All the electrical connections are water resistant. Cover the alternator and other things you don't want to get wet with aluminum foil. I would go with a garden hose spray before a car wash spray though. What is your end goal?

I like to keep my car clean inside and out.

It's just annoying how dirty my engine is.

Fore engine bay cleaning I prefer some degreaser on any oily spots then use a garden hose and brush to finish the job. I usually try to be a minimalist on spraying things down but most things under there are designed to handle water just avoid the fuse boxes and alternator. A high pressure blast might be a different story though.

It's NEVER a good idea to spray any kind of high pressure liquid on your engine. Too many electrical components to mess with. I just washed mine quick the other day using a soft brush and low pressure garden hose..came out good and no problems afterwards.

I would not use a high pressure spray (Gurney or similar) on any part of the car. It will damage paint work.

But high pressure fom the garden hose is a different story. (Unless you are an unfortunate who owns an old British car with Lucas electrics. They can only accept a damp cloth and compressed air).