Ram Air VS. Upper grill block
 

I got the idea from this article on a Honda Insight.

I had been considering an upper grill block, but then I saw the above link in another thread on this forum and that got me thinking. I could maybe block the passenger half of my upper grill and then use snorkel system as seen in the link to use some of that air to "force" or channel it into my air box on the driver side.

http://i.imgur.com/3ve0P.jpg

What are your thoughts on this?

My average driving in the car is hwy. My average speed is 55-60 mph.

I'd go for the full grille block myself. Reading the article it seems as though he didn't find any measurable gains with his system, whereas an upper grille block should give you an immediate and demonstrable aero (and therefore FE) improvement.

Hi Dunkler,
Ram intake can only improve efficiency at full throttle. How much increase in fe can you get from ram air? Very small. How much decrease in drag from full grill block vs partial block, well some anyway, but also small. So consider the amount of time you run full throttle vs the amount of time that you are forcing cooling air through the radiator that you don't need. If you get on the freeway at full throttle for 10 seconds, then cruise for 20 minutes at part throttle, that's 120 times longer. I don't see how ram air can be better for that kind of driving.

-mort

Mort, so what you are saying is that I would likely see an increase in FE from blocking the whole upper grill before I would see any benefit from using "forced" induction for part of it.

I would agree with Mort on this one, there have been plenty of proven gains from partial and full grill block, but I have yet to see anybody prove any gain from ram air at other than WOT(Wide Open Throttle), and even then the benefit was negligible.

@Mort, also take into account that most full load (100%) acceleration isn't done anywhere near full throttle and you effectively make any possible gains from ram air null and void. On my Ultragauge I accelerate at ~30% TPS, Idle is 14.1% TPS and pedal to the floor shows 76% TPS. I rarely get to even 50% TPS and therefore don't ever get to WOT which makes ram air useless

Thanks a lot guys for the knowledgeable responses! That is why I ask things here when my google search results are a bit ambiguous.

I came across this thread after reading an article on the new generation Honda Insight. If you look at this picture: 2010 Chrysler Daewoo Dodge Ferrari Ford Hyundai Acura Honda Photo Gallery it seems as though Honda has placed some value in getting some cooler air with a velocity into the intake. The path comes through the upper grill then is directed by the vents through the rad support cowl towards the intake horn (which is quite large & pronounced).

There are some conclusions that I can draw from this:

1) The designers/engineers feel that colder than engine bay air is beneficial. Otherwise they would have easily put the intake end on top of the rad or directly behind it (like they did in the linked AutoSpeed article) to get a warm air intake.

2) The designers/engineer feel that taking advantage of some of the velocity of the air that is coming through the upper grill to be beneficial. Otherwise they would have routed the horn off to the side between the drivers side headlamp and battery somewhere, and not gone through the trouble of designing the radiator cowl vents etc.

They have designed the upper grill on the new Insight to be fairly aero with the wide bars so they do seem to be taking advantage of the concept, but not entirely as it isn't 100% blocked...which it could be because its a 'mild hybrid' and that area isn't designated for inverter cooling like it is on the Prius. 2010 Chrysler Daewoo Dodge Ferrari Ford Hyundai Acura Honda Photo Gallery

Unless you stuffed a diesel in there, ram air won't do much for fuel ecomomy.
I think you would be better off with a grill block.

Is it possible that a properly sized slot used as an air intake has an actual aerodynamic advantage over a block? A block means pushing the air aside, which is drag. An intake that is sucking air in at something close to the car's speed, should be pretty clean, aerodynamically s[peaking, I would think.

As for the ram air effect, the only way I see it possibly helping is during pulse and glide operation and I'm not sure if it is helpful there. I could certainly see where it is a hinderance. Remember, a CAI means less air is needed for a given power output. And less air means more pumping loss.

Mine is a Turbo Diesel and when I did the Ram Air setup I got an improvement engine response, power & economy, that is because delivering a higher pressure to the turbo, means the turbo is using less power to suck the air in.
On a gas engine ram air and CAI can help, but not as much & depending on your stock setup & tune maybe not at all. On most gas engines I have looked up they are all inclined to draw in cooler air, even those with intake in the engine bay, if you look carefully you will see they will be positioned to draw air that is slipping past the radiator, or some other holes in the front panels. Hot air is good to get the car warmed up, but cooler air is better once up to temp. I know a lot of people claim better FE with a Hot AI, can't say anything on that, but being so easy to do, I would think that all cars would just be set up in stock form for Hot AI from the factory if it was better.