Cleaning the 'exterior' engine compartment.

[Ridgeman580]

According to the DIY site, this is a proper procedure:
Using plastic bags and rubberbands to enact a waterproof
seal, cover the alternator, distributor cap, fuse box, and
any exposed wiring harnesses. Tuck the edges of the bags
down securely. Disconnect the battery cables and since
the Elise's battery is in the trunk we will need to use a
hand-held spray bottle of water to wash off the paste-
solution of baking soda and water that we apply to the
terminals, using an absorbent rag to clean off any paste
residue. On the engine and accompanying parts on and
around it, we need to spray a foam engine cleaner made
specifically for the task and available at all auto stores.
Spray liberally and allow 15 minutes before using the
spray attachment on your garden hose, rinsing well so as
to make sure all of the solution is washed away. Once
you've finished, take the car for a 1/2 hour drive to allow
the heat from the engine to dry the remaining water. Also,
make sure to cover any painted areas surrounding the
engine compartment so that none of the foam cleaner gets
on the paint. P.S. - Need to find out if once we disconnect
the connectors to the battery terminals, will we have to do
some sort of electronic re-set or not? Also, make sure the
foam cleaner is safe for aluminum.

[Ridgeman580]

Did find a degreaser that should work:

Permatex Eliminator II Engine Degreaser.
Quickly dissolves and removes grease, oil
and dirt from all types of equipment. Cleans
iron, steel, ALUMINUM, magnesium and
copper. Not harmful to metal, rubber, plastic
or concrete. Rinses off easily with water.
Suggested Applications - Engines, garage
floors, tools, machinery.

Found it at www.midwayautosupply.com

Look under 'Chemicals & Additives'.