[gargoyal]

Originally Posted by aponting389

does it make any difference?

Yes. Extras air flow and less heat will make a difference.

I like hood closed better, because the air circulation under the hood does matter. Unfortunately heat will build up because the fan alone does not represent real world conditions accurately (it is more conservative). Most parts vendors do dynos hood up and sometimes with real big @$$ fans. This will usually show better numbers.

The important thing is to stay consistent (same machine, shop and set up ) from Dyno to dyno so you know you are looking at your car changes not the set up changes.

FYI… don’t expect the same numbers that a parts vendor gives unless you are testing under identical conditions.