I like this setup. 
As far as "how hot", I imagine him Akiba knows pretty well. They were testing that for a while on several vans. I would think somewhere around 150-175* ambient. Certainly localized hot spots would exist and items could be upwards of that to the touch, but there's pretty fair airflow back there. 

-craig

On Jun 28, 2013, at 11:39 PM, Loren Busch <starwagen@GMAIL.COM> wrote:

> RE: Fire Suppression System
> 
> Just got to thinking (always dangerous).  Just how hot does the engine
> compartment, especially the engine lid, get when running?  Like climbing a
> mountain pass?  I'd hate to spend $200+ for that setup, install, and have
> it trip on just the engine heat without any fire.