I don't think the hoodscoop will decrease the air through the radiator. They are getting air from two different areas...any air NOT going through the grill area will pass over the hood. I don't think it will create any negative air pressure in the engine compartment. If anything, IMO depending on the opening in the hood, will suck hot air out of the engine compartment when moving, either over the car or under it. I don't have a wind tunnel in my back yard, but I think basic logic will tell you this.
Again we, including myself, have taken this off topic....although it never really got back ON topic...LOL

 

The same thing holds true for the upper grill vs. the bumper openings. The comments made earlier in this thread about not having an open grill affecting the amount of air getting to the lower openings is bogus.

I'd be willing to bet the amount of air transferred from in front of the stock grill over the bumper and down into the bumper openings is slim to none. Air just doesn't travel that way. When a car is cutting through wind the wind acts just like water. Just like water seeks it's own level and follows the path of least resistance, so does the wind.

It is NOT going to double back on it's self and move the move down in front of the bumper. The air will get redirected along the face of the grill over the hood and across the headlights to the side of the vehicle. Adding a more open grill design is not going to decrease the amount of air seen by the lower bumper openings. It will affect the air that would have been hitting the stock grill. While some will still travel up over the hood and some will travel out the side, much will travel through the grill and get diffused behind it.

 

Let's try some of that "logic" you speak of. If you have a compartment ( like an engine compartment for example) that has one entrance and one exit, and then introduce another entrance, airflow at the original entrance will decrease, all other things being equal. Now , if our original entrance happens to contain the condenser and radiator and we reduce the airflow through them, how does that net us any additional cooling? Logical thought #2: Toyota engineers aren't stupid and the car was designed the way it was for good reasons and you would be hard pressed to truly improve on it. Class dismissed!

 

All I can say is put it in a wind tunnel. Or watch any video of a wind tunnel in action. The upper grill is further back than the lower bumper openings. Any air that hits the upper grill has already had any opportunity it would have had to get to the lower grills. You are not reducing the air seen by the lower grills. The air you are affecting is the air that usually travels up over the hood, or across the headlights out the side.

IF the lower bumper openings were on the same plane as the upper grill your argument could hold water. But they don't, so your argument doesn't.

Now, if you can prove to me with empirical data that the airflow across the front of an xB travels from the location of the upper grill down to the location of the lower bumper openings I will gladly rescind my statements. And I will publicly apologize to the forum and you for providing bad information. And yup, I'll even say I was wrong and you were right professor.

 

I don't think it really is going to make much of a difference on our little boxy cars if we open up that upper grill or not...but a friend of mine has a separate temperature gauge installed in his xb- and a couple of months later added an open air mesh upper grill, and a functional hood scoop, and found that his temps dropped a couple degrees on average...nothing to make all that fuss about.

 

I think what Scott is talking about is the effect this added wind would have in the engine compartment, not how it would affect the airflow into the grills.

As i see it, the air flows in the lower grills, thru the radiators and out the bottom of the engine compartment. The air flowing under the car will pull the engine compartment air with it which helps to pull air thru this path, of course the wind being pushed through it is the bigger help. As the wind follows the path of least resistance, if the upper grill is open and allows air to push thru it, it will draw more air in that opening and less may be drawn thru the radiator opening. I'm sure that would require a wind tunnel to verify too, but that's just how I see it.

But just for the bug factor alone I wouldn't recommend it.

 

Exactly! Gold star for you ! That's how it works. Running an open grill will decrease airflow through the radiator but luckily the cooling system has plenty of capacity so this will not result in much of an actual difference. Bugs are another problem altogether.......

 

What you guys are saying would be true if we were dealing with a pressurized compartment, or at least a compartment that had small inlets and outlets. It would be right if the exit were smaller or equal to the opening...creating a situation where it will only allow in as much or less than it can allow out. We are talking about a BIG opening on the underside of this car. There is no 'negative pressure' that we are dealing with.
Yes, gold stars for both of you, but like I said, without a wind tunnel, you have no way of proving I am wrong with my analogy, and on the same note, I have no way to prove you wrong either....other than MULTIPLE cars with hoodscoops, vents, openings, in the racing world and this is what I base my opinion on.
I do agree with the design of the xB and the way the top grill is closed...and I wouldn't open it up, but to say a hood scoop DECREASES air flowing through an opening that is 3 feet away is a little off.
What if the hood scoop were 'functional' and it was for the airbox...would it take away from the opening at the very front of the car a foot off the ground? I know, now I am talking about a closed circuit system pertaining to just the intake air, but is that air being 'borrowed' from the opening on the lower grill? No, it is being 'borrowed' from the excess air that didn't make it through the opening the first time.
In other words, the air hitting the top grill area or hood area already bypassed the opening at the bottom...so how is the bottom not getting as much air now?
Please don't flame or personally attack me. I'm here to learn too, and I will be the first (and usually am) to admit I'm wrong, but I don't see how you can back up the claims or prove what you say is right. Heck, maybe we're both right!
Show me your theories and if it makes sense, I'll admit I'm wrong, but as it is, I see no reason to believe I'm wrong...YET...LOL. I've been wrong before and have no problem saying it.

 

Didn't notice any change in engine temps with my "open" grill. It does hawever allow rain and especially carwashes on your engine and particularly the MAF.

 

Wouldn't a forward-facing scoop cram more air into the engine compartment, causing positive pressure in the engine bay, and subsequently less flow through the grilles?

Again, thats just a forward-facing scoop. I rear-facing scoop would, I believe, help suck air out, as the escaping air tries to catch up to the air flowing over the car, it is 'pulled' out.

 

rear facing scoop is also known as cowl induction look at the chevy chevelle they use that set up

 

found this on another site copy and paste baby
______________________________________________

The cowl induction hood is not a new idea and it actually works. That's why NASCAR uses them in their Winston Cup Cars. As the air passes over the opening, it creates a vacuum of cold air over the windshield. This allows the hot air from inside the engine compartment to escape letting the engine breathe cooler air and therefore running stronger and longer

a picture to help make all that sound simplerererer



Air glides over the cowl induction hood.
It then hits the base of the windsheild, creating a low pressure area, allowing the hot air to escape from the engine compartment.

 

A "functional" airbox inlet would have no effect on airflow through the radiator. I guess I might be thinking more of the XB hood with the large rectangular opening That is recessed like a reverse NACA scoop in it. The opening is quite large, about the size of the upper grill opening we are talking about. If you are referring to a smaller raised hoodscoop, then it would have little effect. The engine compartment (or more correctly the lower plastic pieces under the car or air dams on some other cars)is actually designed to draw air out the bottom of the engine compartment, and the front of the car with its large frontal area builds a high pressure area at the radiator inlet. If you open the area above the radiator, the airflow will definately take the path of least resistance and the airlow through the radiator will definately be reduced. Will it be reduced enough to cause a problem? Obviously not. The fan is thermostatically controlled and when the temperature reaches the limit the fan will turn on, drawing air through the radiator. I don't think you would notice it one way or another, but on a 100 degree day running the AC on max, it would probably make sense to get all the airflow through the condenser and radiator as possible and that would be by blocking the top section, just like the engineers designed the car in the first place. And no, I do not have the time or resources to physically prove my theories, but I do have a little experience in the automotive business as a Toyota MDT and about the same amount of experience in the aircraft business with Delta Airlines as an A&P mechanic. I may not learn anything and you may not learn anything from this discussion, but someone might and that can't be all bad.....

 

The cowl induction theory is a whole 'nother bag of potatoes. In your example, the air can flow that way, but in the instance of a more upright windshield angle, combined with a flatter hood line like older cars had, there is a pressurized boundary layer of air at base of the windshield that makes a great source of dense, low turbulence air for an intake source. A great example is back in the early 80s, the Regals, Monte Carlos, Cutlasses, and Grand Nationals started removing the rear cowl to hood seal to make more HP, until they got caught. The Chevelle cowl induction hood is another good example of using this for an intake.

 

Of course a functional airbox wouldn't have any effect.

My comment was directed to everyone without that functional hood scoop and airbox, which is, I'd wager, real close to all of them.

To put it simply, air coming in through the stock grilles is going to flow in easier as the pressure inside the engine compartment decreases. Adding a forward-facing scoop will increase that pressure.

Now it the difference going to be enough to worry about? I doubt it, I am just correcting a comment made earlier.

 

I agree with you Scott for the most part. WOOHOO DOUBLE gold stars and I'll even give you a smiley face!
I think I also stated back on page 1 that by removing the top grill or at least opening it up, it will not have ill effects on the motor, but I wouldn't do it especially if you sit still in traffic a lot on hot days.
Like the guy said earlier...we aren't running NASCAR here.
As far as the cowl hood...it was not done to help cooling but to get cooler, less turbulent air to the carb. Same with ram air...it usually had hoses hooked to the air cleaner and didn't affect engine cooling or the radiator.

 

vacuum hoses that opened up the air scoops when you mashed down on the gas