• Why "hood risers" are for ricers and actually hurt the performance of your car.

      This article was originally published in forum thread: Why "hood risers" are for ricers and actually hurt the performance of your car. started by View original post
      Comments 49 Comments
      1. C230K's Avatar
        C230K -
        Cant argue with facts, well said sir
      1. .blank cd's Avatar
        .blank cd -
        I was going to post something similar, but I think this pretty much covers it.
      1. Black R's Avatar
        Black R -
        Err, I've done actual before and after testing on my autox car as well as my 240.

        While what you posted is mostly true, you can't speak for all speeds - the way air moves over the car at 35mph vs 100mph is very different.

        I've found that cooling was better, and the intake charge was better (my itb's are at the cowl).

        If its for looks, then yeah that's dumb.
      1. .blank cd's Avatar
        .blank cd -
        Quote Originally Posted by Black R View Post
        Err, I've done actual before and after testing on my autox car as well as my 240.

        While what you posted is mostly true, you can't speak for all speeds - the way air moves over the car at 35mph vs 100mph is very different.

        I've found that cooling was better, and the intake charge was better (my itb's are at the cowl).

        If its for looks, then yeah that's dumb.
        Get your results peer-reviewed and published and you might have some actual science!
      1. Doppelgänger's Avatar
        Doppelgänger -
        Quote Originally Posted by Black R View Post
        Err, I've done actual before and after testing on my autox car as well as my 240.

        While what you posted is mostly true, you can't speak for all speeds - the way air moves over the car at 35mph vs 100mph is very different.

        I've found that cooling was better, and the intake charge was better (my itb's are at the cowl).

        If its for looks, then yeah that's dumb.

        Jerrel...what's been happenin'? Long time no see.
        I'm more than happy to hear what you tested and the conditions you were testing in. What cooling do you speak of? What all parts were involved/installed? How did you do your measuring? I'm really always open to learning, listening and a good level debate.
        I know there are benefits to sourcing air from the cowl (we're all pretty familiar with cowl induction), but any properly designed setup is going to source air from the cowl and be sealed off from the rest of the engine compartment. It really is a great way to get good, cool air to the intake- when done correctly. Why wouldn't you have a nice plenum or cowl induction box on the ITBs and source air for them without compromising airflow?




        General post for the thread:
        Yes, I know the world is not a race track, and we don't need race car setups to get around town. But if there was any benefit to it, would you not see it designed into cars in general? I know there are vented hoods out there, and that even some cars have them from the factory, but such parts are in completely different locations on the car and are designed into the car. Much like a lot of the old muscle cars with factory cowl induction- but a look at any of them will show a system where the air from the cowl being used for induction is isolated so its sole purpose is to go to the intake.

        As seen here-






      1. craaaazzy's Avatar
        craaaazzy -
        above u speak of hood vents, used as induction to intake. how about vents which are just opening on the hood to allow heat out? thanks.
      1. l Gizzy l's Avatar
        l Gizzy l -
        Quote Originally Posted by craaaazzy View Post
        above u speak of hood vents, used as induction to intake. how about vents which are just opening on the hood to allow heat out? thanks.
        uhm, what?
      1. Elbow's Avatar
        Elbow -
        Quote Originally Posted by craaaazzy View Post
        above u speak of hood vents, used as induction to intake. how about vents which are just opening on the hood to allow heat out? thanks.
        Like this?



        My understanding is those are to move air in and out, meaning air enters the front, goes through the coolers, and exits versus hanging around. I may be wrong, but I thought it was more of an aero thing than cooling especially since many rear mounted engine cars have some type of hood vent up front.

        I think they would go along with fender louvers, fender vents, etc.
      1. craaaazzy's Avatar
        craaaazzy -
        ^ that's what I'm asking about.
      1. quickdodge®'s Avatar
        quickdodge® -
        Quote Originally Posted by Doppelgänger View Post
        I know there are vented hoods out there, and that even some cars have them from the factory, but such parts are in completely different locations on the car and are designed into the car.
        Damn right, Mike!!!

        Look at those awesome vents!!!


        10212012-Old_School_Meet-507
      1. Doppelgänger's Avatar
        Doppelgänger -
        I dont know if I see what you're getting at. All I can see in that picture is the main vent for the HVAC. But I see that the center "vent" is indeed isolated from the engine compartment.

      1. quickdodge®'s Avatar
        quickdodge® -
        ^^^ I hope you don't feel like a heel, dude, because I was adding to your post, not condescending it. I'm not sure why you got so defensive so quickly, dude. Thought we were better than that.

        And to add more, here is another shot of the other vents on top of the car:


        10212012-Old_School_Meet-132
      1. DarKStaR's Avatar
        DarKStaR -
        But what if you HAVE to use risers
      1. Doppelgänger's Avatar
        Doppelgänger -
        Eh, I guess I was being a bit of a smartass. My apologies, Mike.
        With that said, I couldn't really see the vents on the side of the hood you referring to. Do you have pics of the underside of the hood where they are located? What I was getting at about some cars having vents like that, is that things like that are generally placed in areas when airflow is smooth and will create a Venturi effect to help extract air from the engine compartment.

        As or vents like what Simon posted, placement of extractor vents is very critical to get just right. I really don't know how much R&D goes into hoods intended for the general street car market. While I doubt they hurt anything, how optimal they are is questionable. Vents like that act similar to what the undertray does to airflow under the car.
      1. Sinfix_15's Avatar
        Sinfix_15 -
        Lot of genius on display in the picture of that old CVCCs engine bay. With anything car related, you can usually put yourself on the right path by simply asking the question "what would honda do?" Theyre the world's leading engine manufacturer for a reason. Do you honestly think that some dip shit kid thought of something that honda didnt?? do you really believe that? do you think Honda engineers are reading this thread right now and saying " OMG!!!! an opening in the back of the hood! why we no think of this?!?!?!"

        The only thing that matters when it comes to cooling your engine is water and oil.... most specifically, water. Your engine is not air cooled. Reducing your under hood temps to cool your intake charge is about as effective as filling up a swimming pool by pissing in it. The only place you need air to flow is through your radiator. If you want to do more to cool your engine.... get a better radiator or better fan for your radiator. If you want to do even more to cool your engine? better or bigger oil pan or oil cooler. Your engine cools from the inside out....... do you really think some air blowing on the outside of your engine has that great of an effect on it's operating temperature?




        On an air cooled engine the push rods are located outside of the engine and the surface area of the head is increased with fins. The emphasis in the design is placed on oil cooling..... from the inside out.................... reducing the surface temperature of your engine has little effect on the inside of it. How cool would the air hitting the outside of your block have to be to have a significant impact on the temperature of your cylinder walls? think about it.






        If something so simple to accomplish needed to be done. Honda would do it. Honda is smarter than you.
      1. Elbow's Avatar
        Elbow -
        LOL....
      1. ash7's Avatar
        ash7 -
        ...what if your engine doesn't fit?

        Take a K swapped EF for example. If you don't have the skills or equipment to modify a hood to properly fit, it makes much more sense to cowl the hood than to cut half of it away.

        But if we're gonna talk about morons and rag on their cowled hoods; shouldn't we be more focused on the domestic crowd?

        -jonathan asher
      1. Sinfix_15's Avatar
        Sinfix_15 -
        Quote Originally Posted by ash7 View Post
        ...what if your engine doesn't fit?

        Take a K swapped EF for example. If you don't have the skills or equipment to modify a hood to properly fit, it makes much more sense to cowl the hood than to cut half of it away.

        But if we're gonna talk about morons and rag on their cowled hoods; shouldn't we be more focused on the domestic crowd?

        -jonathan asher
        There's engineering behind the shape and design of cowl hoods and vents. They create a vortex of air. Simply allowing air to escape serves little or no purpose other than disrupting the vortex that the factory intended when they spent millions of dollars designing the vehicle.

        If you have to tilt your hood to fit an engine, you did what you had to do, but i would hope that you acknowledge there is a better way.


        Here's an example from the domestic crowd

      1. Elbow's Avatar
        Elbow -
        Quote Originally Posted by Sinfix_15 View Post
        There's engineering behind the shape and design of cowl hoods and vents. They create a vortex of air. Simply allowing air to escape serves little or no purpose other than disrupting the vortex that the factory intended when they spent millions of dollars designing the vehicle.

        If you have to tilt your hood to fit an engine, you did what you had to do, but i would hope that you acknowledge there is a better way.


        Here's an example from the domestic crowd

        That's a poor "domestic" example since it's a Le Mans GT car. The radiator on those is also mounted in the rear, or is now, or was. Not sure what else is up front or if they're just controlling the air. Escaping air = using it. Of course just allowing it to run free would not serve any real aerodynamic purpose.

        A cowl hood on a muscle car can serve the purpose of getting air into the carbeurator, that's what I always thought they were for anyway and mentioned above.
      1. Doppelgänger's Avatar
        Doppelgänger -
        Correct Simon, but also notice that even back then, designers knew that the air used from the cowl for induction had to be separated from the engine compartment.
        It seems to me, the diagram Sin posted with the 'Vette, the airflow is used to help with reducing lift by putting more are over the top of the car rather than it going out under the car. But now we are getting on a slippery slope of functional, race car aerodynamics- not the original topic of OE designed air flow to keep a street car's cooling system working efficently and how a dumb ricer mod negates what engineers have designed into the car.
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