I've searched all the posts and nobody seems to have addressed this topic.

I noticed that the stock grille just below the hood on my Scion XB does not allow any airflow into the engine compartment. I was thinking about increasing the airflow to the engine by replacing the stock grille with a billet grille that would allow air to flow through it. Af first, I though this would be better for the engine, but then I realized that at freeway speeds the incoming airflow through the opening below the hood might build up air pressure in the engine compartment and make the electric fan have to work harder to pull air in through the radiator.

Some questions:

Does the grille just below the hood on the bB in Japan allow airflow or is it solid like the stock US domestic grille?

Is the grille made without airflow because Toyota wanted to direct the airflow to the engine in a specific way or did they just want to save a few bucks by not making holes in the stock grille?

Does anyone have any thoughts on this?

 

I don't think it was a money decision on the closed top grill. I think it was probably a flow related decision. If it is open though, as my JDM grill was for a while, bugs get everywhere. I closed it off, and like it much better, but I didn't overheat or have any problems while it was open.

 

that grille needs no airflow. it's the part below that, that gets the air. it was made like that on purpose. you should not allow air thru the top grille for the proper airflow

 

Absolute genius I tells ya... Must be one of them there Toyota engineers posting in the forums.

So why is it that the RS1.0 was equipped with a billet grill? And the RS2.0 with a "speed" grill? There will be no ill affects to installing a billet grill.

The only possibility of a drawback is in very cold weather climates during the winter. But then, it wouldn't be any different than most 99% of other cars on the road with fairly open grills.

 

I really don't think installing a billet or open grill up top will cause you any problems at all. Just might get your engine a little dirtier quicker.......

 

[quote="RTon20s"]The RS 2.0 has a solid panel behind that speed grill so no airflow there. The RS 3.0
also has a solid grill. It's not needed. I live in Atlanta and I didn't overheat this summer.
I think that the back of the engine compartment allows plenty of airflow down and under
the car. Any extra air is not needed but I don't think is does any harm. As noted above,
cold climates might want to restrict the air flow during the coldest months.

 

From an aerodynamic stand point, you want as much air as possible to flow over the car, the least amout under the car. If you open the grille up the only place the air has to go is under. If anyone is a nascar fan you know how much difference 1 small piece of tape can make.

 

^^^LOL...but we aren't running 190 MPH around a track either. I understand your point, just thought it was funny to use that example....

 

When I was in high school my father was the pilot for an IMSA GTP race team. He also
helped on the crew during races. I spent a lot of time at the garage watching them build
962s. The ground effects on that car didn't even really do much until the car was well over
100 mph. The NASCAR aerodynamics you refer to also increase logarithmically the
faster you go. At the speeds our cars are traveling on a daily basis, the air under the
car has little effect. Heck a strong side gust could do us in. If you push a box much over
100 mph, the overall aerodynamics of the entire car will cause all kinds of unpredictable
instabilities. So keep it under 100.

My two cents

 

He is exactly right Mr. Genius, the RS grills all have backing plates to direct airflow where it's SUPPOSED to go- through the condenser and radiator which are below the "grill" at the top. The car was designed that way for a reason and opening the top grill will reduce airflow through the condenser and radiator somewhat. I would keep it blocked for best performance.

 

well first of all keeping yoru engine at a standered temp is fine, in fact your radiator fan is usally off while ont he highway cuase if the rapid air cooling the raditor so more air flow is better. the fan isn't to suck air though the raditor it to cool the engine. it goes on and off it never works harder it just turns on and off when the cts (coolant temp senso) senor reads a higher than normal coolant temp. and billets grills disort easy from the heat of the engine and the rapid cold air going though it. and toyota most likely made the grill like that cuase it doesn' tmake much of a differnce. so if yoru engine isn't over heating dont worry about makeing more air flow. but you wan to make holes or diffent girlles go for it it wont make much of a differnce

 

^^^ The fan IS to such air through the radiator...not to blow over the motor to cool it...Thats why there is NO OTHER way for the fan to get air except by drawing it through the radiator. Look at the shroud from the engine side and you will see what I mean. If it were as you stated, then why suck HOT air from the radiator (the air is ambient till it passed through the radiator) to a hot motor?
As far as opening up the upper part of the grill, I don't think it'll hurt much unless you do a lot of stop and go in heavy traffic, but I wouldn't do it.

 

Could always buy a hood with funcional hood scoop. i did.

 

our cars being a box we really cant gain much from aerodynamics anyway i would guess...not that we would notice anyway...

except maybe low-end aero, im thinking the more airflow we can get over the car instead of under would help possibly

i know that i sure as hell feel that boxyness when its windy lol i feel like im in an 18 wheeler!

 

i figure if you're worried about incresing the air flow w/o the bug problems, then take a dremel and dremel the undersides of each of the ridges on the grille

my friend w/the turbo xB did that to keep it a bit cooler in there - and it looks stock w/no bug issues

 

you sure you didn't mix something up here?

 

Perhaps that should read "very much over 100" meaning slightly above 100 or
a small amount over 100. The down force generated by a ground effects car
at 100 mph is very little but the as your speed increases, the down force increases
at a higher rate. At 200 mph a 962 could drive upside-down on an inverted highway.
Does that make sense??

 

It seems to me as though the only reason the R.S grill would have a backing plate is so that you don't see into the engine bay through the grill which would be sort of unsightly for some. Im sure the "Engineers", who have degrees in this sort of thing, would know their reasoning for not needing slits in the grill. The radiator is down below as it wouldn't be in most cars. Maybe they figured they would design that way because they knew people would be replacing it.

 

Ummmm, OK.......

 

Actually, our aerodynamics aren't that bad..Especially when lowered, its about the same as any other wagon.