Watch this and see if you can guess what McLaren's P1 supercar is powered by

A few nights ago, our own Michael Harley visited the McLaren P1 at an event in Beverly Hills, California. A recording of the engine note was played, and that led to speculation that the P1 will get a hi-po version of the 3.8-litre V8 employed by the MP4-12C, rocking something like 800 horsepower.

McLaren has been testing the P1, getting it showroom ready for its 500-unit run, and part of that involves full-throttle test-track duty with its tail held high. After checking out the official development prototype "spy shots," you can hear that engine note for yourself and guess how much flame spitting horsepower The Woking Wonder is pushing by watching the video below.