my undertray has broken so i took it off is this a problem apart for the engine getting dirty

 

i think the undertray helps with the cooling of the engine, sounds odd but when driving along it causes a vaccum under the car which sucks the hot air down and also aids the flow through the intercooler.

Dont think it will do anyharm with it not being there to be honest. i left mine off for a while while checking for leaks with the oil filter sandwich plate.