remove underhood rubber lip?

the one on bottom of windshield closest to wiper blades?

If so, its a 3 piece assembly that needs to be removed when trying to get to the top strut bolts. I had to do it when installing the Cusco Front Strut Bar and removing wiper assembly as well.
Here's an old pic I found when I did it:

 

I think he's just talking about the rubber strip. I know it's easily removed in the area around the brake fluid reservoir, but I think maybe it's glued to the rest of the assembly. I'm not sure.

The disadvantage to removing it would be dust entry. The easier way would be to remove the useless plastic cover over the engine.

 

Heat soak of what, exactly ?

NO not a good idea. That strip prevents heat and fumes from the engine from being drawn into the HVAC air input which is right behind that strip at the base of the windshield.

Removing that strip will make your A/C work harder and could be hazardous to your health if an exhaust leak should develop in the engine compartment.

When you STOP the car, the engine stops producing heat. What is already is in there moves around a bit but overall it does NOT get any hotter.

 

BUT......that actually recirculates only about 70% of the air. The other 30% still comes from the outside via the inlet at the base of the windshield.
It is done that way in an attempt to keep a slight positive pressure in the cabin to help keep exhaust gasses from entering.
Removing that rubber seal strip pretty much negates that safety feature.......or it can in some circumstances.

 

What does that mean?

Never mind. I googled it, and unless your talking a small greek boy, I'm going with Believe it or not.

 

If that last statement is true, that is not a good idea either........as in certain weather your windshield will fog up and having it in recirc will cause the defrost to work at about a 25% efficiency and you might not be able to SEE.

AND......if your modification really does just permanently invoke the normal recirc mode........you STILL get about 30% outside air.

BUT it looks like you are going to have an "answer" to everything and don't really CARE what the facts are........so do whatever you want.
Good luck.

 

Starcaller, be careful of carbon monoxide. You cannot smell it. It will make you drowsy while driving and eventually one passes out. Your re-circulating idea is what scares us all. You are re-circulating carbon monoxide and don't know it because it is odorless. All it does is slowly make you tired and then you pass out. Please be careful about this idea you are doing.

 

Thank you for casting your vote.
This is ESPECIALLY true since the perceived benefit of doing that in the first place is mostly an illusion.
"Heat soak" is not a problem and therefore does not require a "solution".

 

Few things:
1) What "heat soak"? Why are you trying to fight it? Have you measured an increase in temperature after the car is stationary? When the car is warmed up and in Ready, the engine shuts off when the car isn't moving anyway, and who cares if it stays warm after you're done driving it?
2) Heat is not necessarily a bad thing; armchair engineers like to talk about cold air intakes and engines "working easier" and whatnot (which we like to think is true but isn't); the reality is hotter, less dense air will allow an engine to run more efficiently by requiring a wider throttle plate opening to make the same power.
3) The area at the back of the hood/base of the windshield is in a high pressure zone; removing the rubber strip will allow air to migrate down into the engine bay when the car is moving. The pressure differential isn't as high on the Prius as other cars with flatter hoods and more upright windshields, and the "scallop" cutout in the hood is deliberately placed to lower the pressure in that area, but there will still be a differential. Results: slight increase in drag/decrease in mileage.