TRUE OR FALSE ?? (Opinions Needed!)

[jb666]

Ok guys.. Help me out with something here...  TRUE OR FALSE (and why you feel the way you do).


A car will run cooler WITH a hood on (even if it's cut open for a blower), because the hood to radiator seal will direct air flow where it needs to go.

[Dmichels]

I would say false the hood  does not channel air anywhere. Without the hood there would be considerably greater airflow around the motor. Open your hood after a drive and the heat pores out.
Dave

[Indygenerallee]

I wouldnt think so, if you have a fan shroud your pulling plenty enough air through the radiator, plus the heat has nowhere to build up.

[jb666]

Without the hood the latent heat (block ,headers) will escape but the hood directs the air through the radiator cooling the block internally... No?

[Baldwinvette77]

new york taxi drivers swear leaving the hood popped up (about 1.5") helps cool the engine  have also seen a few "hotrod" videos and articles where people have taken there hoods off to cool the engine 

[ws23rt]

This sounds like something that would vary greatly from one vehicle to another. Going down the road or sitting still.
Ask the myth busters. Remember the guestion about fuel economy in a pick up with the tale gate down?
Sometimes what feels right is not.
My instinct tells me that the hot air from the radiator does little to slow the cooling of the coolant inside the engine. What we feel in our face as we raise the hood is not a good enough gauge to tell the story but it is what has raised the question.

[Indygenerallee]

If you have a fan shroud and a large enough radiator for your application it should not overheat regardless if the hood is off or on, with the hood OFF or with a HOLE cut in it you will have far less "heatsoak" as you are letting all that hot air escape the engine compartment.

[skip68]

This is a really good question Jeff.    I'd say the external engine and internal would both be cooler.   Air would pass through the radiator easier since it would have a more open exist flow.     This would be great for myth busters.  

[Indygenerallee]

I would say that with no hood there would be far less front end lift at high speed due to trapped air under the front of the car (I believe this is why the wing cars had fender scoops)

[Darkman]

My opinion is that with the hood on, the air will be directed better through the radiator allowing the internals to cool better.

When driving, the hot air will be "sucked" out of the bottom of the engine bay allowing the engine to cool externally.

With the hood off, you are not funnelling the air through the radiator as it will find an easier path. The air will cool the outside of the engine to a degree, but the difference is insignificant (remember most blocks are cast iron and take a helluva lot of cooling down). You will lose aerodynamics however, forcing the engine to work harder and therefore nullifying any benefit you would have. If driving a car with the hood off would help keeping the engines cooler, don't you think race cars would be doing it?

The hole in the hood for a blower would have little affect as it is mostly stuffed with the components sticking out of the hood (basically acts the same as if the is no hole).

[Ghoste]

Hmm, I think hood off will run cooler.  No scientific evidence just jumping off the fence.

[68X426]

I will take "IT DEPENDS" for $1000 Alex.

Here's why. Say you are a header. Just minding your own business. Then someone fires up the motor. You are going to run say 600 to 800 degrees, maybe 400 degrees at the collectors. What do you care if the hood is open or not?? You are a header and you are hot.

Same for a radiator. 180, 200, 220. You are hot, and hood or no hood, hot is hot.

I've seen open engine roadsters overheat all the time. Closed hood muscle cars with huge aluminum rads and electric fans overheat. Take a trip to Hot August Nights in Reno (typical 100 degree day and 5000 ft. elevation) and every car runs hot and large numbers overheat. So I don't think there is any universal truth, it just depends.

[JB400]

As stated before, I say sitting still or in stop and go traffic, it'd be cooler with the hood off.  Going down the road at a steady speed, cooler with the hood on.

Heat rises, so you'd want to let the heat go somewhere when you're sitting still.  If you're moving, so is the air and allows the heat to go somewhere as well; usually sucked out the bottom of the car, unless you have heat extractors in the hood.

[Cooter]

IMO, it is the job of the Radiator fan shroud to direct airflow THROUGH the radiator. However, if the hood isn't important, then why are many cars[Including these] equipped with cowl/hood seals to promote airflow through radiator?

[Dino]

When a closed hood seals in the engine bay air then yes leaving it off wil cool it better, but the Charger does not have that problem.  Heat can't get trapped in there.  Unless it's raining cats and dogs when that hood is off I say the engine will run at exactly the same temps as with the hood closed.

Some cars have the protective shield under the engine a little bit too tight and those engine bays will turn into ovens after a few minutes of idling.

[Tilar]

The hood wont make any difference at all to the cooling system. The air headed through the radiator isn't all of a sudden going to say "Hey the hoods open, lets go that way!"   

The only thing it will change is the ambient air temperature of the engine compartment which won't affect the engine operating temp.

[ws23rt]

The hood wont make any difference at all to the cooling system. The air headed through the radiator isn't all of a sudden going to say "Hey the hoods open, lets go that way!"   

The only thing it will change is the ambient air temperature of the engine compartment which won't affect the engine operating temp.

You and I think alike. What we feel as hot air is warm air and has very little affect on the engine. 

[Old Moparz]

Are you friends with any midgets?   

If so, get one to ride somewhere near the engine with a thermometer & have them take readings for you. A small kid would work, but you know how kids are, they'll do something dumb like get their fingers caught in the fan blades or touch the exhaust pipe. (Try explaining those injuries to their Mom) The ride with the hood off is easy, but when they take the ride with the hood is closed you'll have to make sure they can see the thermometer. Don't let them use a flashlight with a halogen bulb because they burn hotter & may alter the under hood temperature readings.   

[68X426]

You're killing me. 

[Dino]

That's hysterical.   

[bull]

Yes, it would be cooler but as stated by others you have to have a hood so the cooling systems are designed to work with one. It is obviously bad for an engine to run too hot but it's also bad for them to run too cool.

Besides, hoods keep the rain off your engine.

[moparstuart]

hoods     we dont need no stinken hoods 

   

[Dino]

hoods     we dont need no stinken hoods 

   

Or fenders, bumpers, head clearance... 

[Indygenerallee]

it is the job of the Radiator fan shroud to direct airflow THROUGH the radiator.

X2

[moparstuart]

hoods     we dont need no stinken hoods 

   

Or fenders, bumpers, head clearance... 

i got plenty of head room and i'm 6 foot 3 and fat