On the flip side of this, are people having issues with the car overheating? There seems to be such a raging debate about that plastic piece and how much heat comes out with it on, vs. how much water gets in with it off.

Similar to taking medications only when you're sick, why would people be adding extra cooling to a car unless they are having chronic issues with overheating engines?

I've never removed mine. I can see and understand how the low pressure (created as you drive faster and faster) above the vent works to suction air out of the vent, regardless of how small the hole is. Since my engine has never run particularly hot, I've never considered that this venting might not be enough.

Even if you were looking to cool your engine more than stock, wouldn't an upgrade to the coolant system have much more of an effect than slightly increasing the air flow over the engine bay?

Actually, all of the reports are that the press car have been punished on the race track all day and the engine temperature always stays in the middle. Even M cars have cooling issues after several hard laps. Goes to show how good the cooling system is from the factory.

I think you guys are right. I had my water tray out today and I looked closely at it and you can clearly see the air stabilization fins molded into the plastic. These fins clearly make the air flow more uniform through the small gap into the plastic tray and were probably a major consideration while designing the car in the wind tunnel.

Can't believe we're discussing possible air stabilizing fins on a freaking water drain.
Lexus: the pursuit of perfection.

Some of these comments are crazy.
It is designed to cool the 2URGSE. This engine, from day one, has been on the hot side of operation so Toyota/Lexus put a ton of work into keeping it cool. Hence the ISF side vents and the furthering ventilation on RCF and GSF. While this engine creates a lot of heat, it is properly cooled based off peoples reports of long track days. Why anyone would think Lexus would lie about it is beyond me. Heat rises, with a lot of heat and high pressure, yes, that little hole will still extract heat, not to mention more heat will radiate out of the less insulated plastic area than the insulated metal hood area. With it out it will extract much more heat. probably a good idea if you're going to put the 2UR through its paces on a hot day or track day.
The cover is designed to send water directly down in front of the engine. On a rainy day I have seen steam rising up out of the bay with it out which means some water splashed onto something hot enough to evaporate water but when inspecting under the hood it did not look like any water got on top of the engine and only on the intake tube.
It would be cool if someone created a 3d printed cover that was slightly more open but still diverted any water.

Not necessarily in every case. You can find some info online about how much Lexus put into the cooling of the 2UR. I would guess it is engineeringly maxed out seeing that the oil and transcoolers are forward mounted, side vents, and hood venting have been used. It's basically every trick in the book to manually (the vents) and internally (the coolers) cool an engine. Oh, ****, I forgot to mention the intake flap that is designed to reduce heat soak as well. It opens at a higher RPM than idle to keep cool air coming through the box and only opens when the car is moving knowing that there is now air flowing through the front of the car. They would not have designed and made them functional if they weren't needed and they had other means to cool the car.

On the flip side when people are talking about M cars overheating, they are talking about turbo cars and forced induction is a totally different story. Now you're talking about knock. Not "overheating" in the traditional sense of coolant boiling. Knock is intake temps so high from hot compressed air it causes pre-ignition detonation bang bangs. So some turbo cars may have a cool off safety to ensure you're keeping temps in a healthy zone because knock can severely damage an engine. Just to be clear though, knock can happen on NA cars as well but often related to gas or timing issues.

I also have seen steam rising after car wash drives and also small bubbles shooting out of the vent.

The side vents are functional both in the RCF and GSF. They are somewhat controversial on the ISF as ISF owners don't agree and are split as to whether they are functional or cosmetic.

Lexus put the hood extractor only in the RCF and not the GSF. Probably the same reason RCF has the 4-point shock tower chassis brace while the GSF does not.

Thanks for the correction. I was envisioning the GSF was cooler than in actually is 😄. But that also got me thinking, the new ISFSP doesn’t have any of the air cooling ducts. Have any reviewers had cooling issues with that, Lexus find other ways to cool the 2ur, or is the engine just reliable enough to withstand the abuse? Now Im curious to know.

I was of course joking about the fins. Of course maybe the aftermarket could come out with a carbon fiber water tray with bigger fins.

I took the damn thing out. I live in Phoenix desert hell and I’m all for additional cooling. I’m not worried about rain, which we hardly get. Even with rain I’m not worried at all. Had an evo 8 before with a much larger hood opening with the factory vent removed for years and never had any issues.

Since it is an F-Sport, it is really meant for the streets with that engine so it does not need that much cooling. It does not have the oil cooler either. There are many other things different with the IS500 such as, tires, wheels, brakes and suspension/chassis etc. as Lexus said it was for people who want an IS350 F-Sport with that engine from the RCF.

Is it not because Lexus just wanted to use up the remaining V8 engines since the GSF is out and the RCF is at end of life?

LOL Reminds of how I used to hear the same thing back when I got my Corolla XRS in 2004 with Celica GTS 2ZZ engine and 6 speed in it. Lexus does not build a boatload of these engine spares as these are not mass produced due to the price to manufacture and sale volume . The manufacturing of such engines is in planned quantities and also LC500 gets the same engine aa well. From what I know, RCF will be around till year 2023 because of the GT3 homologation requirement so 1 or 2 more model years left.

What Lexus officially said was, they got a lot of feedback from customers who wanted an IS350 F-Sport with the V8 from RCF and none of the other track oriented stuff plus Lexus really wanted to compete in the TLX Type S price range so instead of putting a more powerful V6 (like the one from LS500), they chose to put the RCF V8 in it.

Aerodynamicist for heavily aero dependent racecars such as LMP1, Formula1 have at times been infamous for deploying innocent looking features and calling them cooling ducts. They will purposely distract inquisitive minds from the main function which is essentially a device to reduce drag. The innocent looking aero devices are their secret weapons and how races are won.

Don't forget Toyota has successfully run LMP1 cars (which are heavily aero dependent) for years now and know a thing or two about aero.

Just because evo or subaru uses scoops to keep their turbo engines from frying has no paralles to Lexus's purpose with the opening on your RCF hood. Does one suppose a company like Lexus would do a half -**s job and give such a tiny hole to cool your RCF engine? That is where the joke is at. It has nothing to do with vanity. It's main purpose is aero, some heat extraction just being a small added bonus.

As for the argument the RCF will enjoy more cooling with that vent opened wider, it's not going to happen. The RCF will always let the temperature rise to its predesigned optimal temperature and maintain it there. Your temperature gauge will be smack dead center all day, no desert heat will throw this out of balance. If it has, then you have a more complex problem at hand then your environment dictates.

Why ruin something so well crafted right out of the factory.

Wonder why they bothered etching those grooves on there? Airplane/Jet wings, aero dependent race cars (utilizing all forms of aero fins and wings), ballistic projectiles, may feature this clever yet simple grooves on the leading edge or surface. The grooves do exactly as you stated (albeit tongue in cheek). They essentially provide a periodically corrugated surface which will dial out the vortices in the exiting air allowing it to smoothly travel over the front end of your car, as opposed to tumbling. Just exactly as Lexus advertises.

Lexus RCF Aerodynamics Tech Sheet
Notice emphasis on "air to exit smoothly" this is only made possible by the pre-meditated design of the Hood scoop seal (the so called "water tray", Lol).