Grill Block question?

[chipX]

I am planning on doing a grill block to my crx.
Mine has the later ( vtec ) front end.

Aswell as installing a lower front lip, i am thinking of blocking one or two of the grills.
I think ill go for the larger bottom one first.
However , as it is the vtec model, i don't want it to be noticeable ie : to detract from the sporty looks .

A lot of people put coroplast ( or similar blocking material ) infront of the grill , right? To me this seems like the easier and most likely more efficient way to do it obvious.... However it may spoil the looks ( in my eyes )

So i was wondering if it would be worthwhile to block it from behind? So from the outside it looks like it has a functional grill .... but in reality it no longer does.

Im trying to work out whether the mouth of the opening will act more like a parachute ( higher pressure zone ).
Like imagine the lid of an aerosol being pushed ( open end ) forwards through the air..... Its going to be acting like a parachute, as the air inside cannot flow out the back.

Opinions ?

[i_am_socket]

Either way will work. I'm guessing there will still be some aero drag if it's blocked behind the grill instead of in front, but significantly less than if left open. Try it both ways with some scrap cardboard first and decide which one works/looks better for you.

[PaleMelanesian]

I'd start from the top down for aerodynamics. If you're after faster warmups, any blocking will help, top / bottom / front / back.

[aerohead]

I would not be concerned about a parachute effect.The leading-edge radii away from the grille area will prevent any flow separation.You will have a bubble of stagnant air in front of the blocked area but it won't really compromise drag.-------------------- I would recommend that you do a temporary block and first make sure you don't overheat.I never blocked either the upper or lower openings but rather had a nose with internal ducting which limited the "grill" opening,but once past there,the air was free to enter the original grill openings behind the new nose,both upper and lower.------------------------ The only time she ran hot was at wide-open-throttle for six miles during one summer.

[winkosmosis]

Originally Posted by i_am_socket

Either way will work. I'm guessing there will still be some aero drag if it's blocked behind the grill instead of in front, but significantly less than if left open. Try it both ways with some scrap cardboard first and decide which one works/looks better for you.

The drag comes from the shape of the grill's effect on the airstream, not air going in, so I don't see the point in those rear blocks

The other thing I don't understand is when people block the lower grill but not the upper. Even if you get smooth flow from the bottom one, going up the air will hit the top grill like it's a parachute-- even more so because it's higher pressure and faster air.

[aerohead]

Originally Posted by winkosmosis

The drag comes from the shape of the grill's effect on the airstream, not air going in, so I don't see the point in those rear blocks

The other thing I don't understand is when people block the lower grill but not the upper. Even if you get smooth flow from the bottom one, going up the air will hit the top grill like it's a parachute-- even more so because it's higher pressure and faster air.

Actually the drag is caused by the air going through the cooling system and the tortuous path through the engine bay on its way out.

[winkosmosis]

Originally Posted by aerohead

Actually the drag is caused by the air going through the cooling system and the tortuous path through the engine bay on its way out.

The only drag that matters is the resistance the air encounters going in. It doesn't matter what the path is inside, except the effect on the resistance to inflow. A grill block has 100% resistance to inflow, but if it's angled the flow over the top of it will be much easier.

Do a thought experiment-- picture a powerful fan pulling air through the engine bay. Of course it's not going to increase drag, regardless of how much turbulence and resistance there is inside. All that matters is the force exerted on the airflow outside the car.


The difference between a rear block and the engine bay's aerodynamics are that one pushes 100% of the air back out, and the other pushes some fraction back out.

[MetroMPG]

Originally Posted by winkosmosis

The only drag that matters is the resistance the air encounters going in.

Since after passing through the radiator, cooling air generally exits in a turbulent fashion to the aerodynamically dirty underside of a vehicle, that should be taken into consideration too.

Which is why it makes sense that blocking grille openings above the stagnation point has the dual benefit of reducing cooling drag and diverting that airflow to the relatively smooth top & sides of the vehicle, vs. underneath.

[NeilBlanchard]

Hi,

I would try blocking the upper grill first -- this will help lower the stagnant point, which is a good thing. Also, the early indications are that I am getting slightly better cooling with only a lower opening; despite the smaller total open area. (I also have a large portion of the outer parts of the lower grill blocked.)

[Frank Lee]

Originally Posted by winkosmosis

The only drag that matters is the resistance the air encounters going in. It doesn't matter what the path is inside, except the effect on the resistance to inflow. A grill block has 100% resistance to inflow, but if it's angled the flow over the top of it will be much easier.

Do a thought experiment-- picture a powerful fan pulling air through the engine bay. Of course it's not going to increase drag, regardless of how much turbulence and resistance there is inside. All that matters is the force exerted on the airflow outside the car.


The difference between a rear block and the engine bay's aerodynamics are that one pushes 100% of the air back out, and the other pushes some fraction back out.

Credentials? Backing data?