nvm

 

I haven't taken pics yet but I stated earlier that I trimmed the plastic after removing the rubber from the firewall in an effort to cool the engine bay down some.

I drove about 100 miles today and I'll be here for a few days, so I brought car cleaning supplies in case I need to clean anything quick. (Bird droppings, milk shakes, etc.) I sprayed my windshield and began wiping it down to remove bugs and then I moved my wipers to clean the entire glass. WOW! The wipers were REALLY hot. The heat coming out the back of the hood had the bottom of my windshield and the wipers feeling nearly as hot as engine bay components. To me, with wind hitting these areas, this confirms that removing the rubber and cutting down the tabs at the firewall evacuates heat from the bay. These parts should have been cooled by wind from driving at 70 MPH for most of the trip. Theoretically, the air flowing over the hood could also pull the heat out from under the rear of the hood as it goes over the car, which is even better if that's the case.

This is a good alternative if you don't want a raised hood and would probably be complemented by a raised hood by allowing even more heat the escape. After I did this, I put a flashlight in the bay and shut the hood. I sat in the car and saw a good deal of light at the rear of the hood. (Already posted this but thought a total summary would be better than 2 posts)

 

In theory, that area is a high pressure zone in which air is not actually evacuating the engine bay... this however doesnt mean raised hood (or other methods of creating an opening) wont help; the airflow that draws over and into that high pressure area gets sucked into engine bay and will evacuate underneath - theoretically drawing hot air with it.

I too originally thought that having an opening there would allow engine heat to escape and even draw cold air from grille to wash across bay and out the hood opening - in reality the only time (a little) engine heat is escaping from there is at idle.

I had a talk with Tony at Motordyne about this when I used his hood spacers and later had a hood cowl molded in (to help dissipate excessive heat from headers)... he explained the principles of how the air actually enters that area but also "washes over the headers" and helps keep heat down.

It's pretty common knowledge as I came to find out (quite a while ago) that it is a high pressure zone - and in fact one modded 240Z used that area to place an intake chamber (with intake at the rear of engine)... seems odd - but apparently it works.

So theoretically, the heat you felt was either from ambient temps outside - or from heat escaping at idle, but not during your 70 mph driving.

 

in conclusion, is it better to have it modded?
Where do you need the opening in order to have the cool air wash across the engine bay?
i have a VS II hood with hood spacers.

 

Maybe I can get a big fan and about 20 smokers to help me run some wind tunnel tests on my car? But seriously, other than actual wind tunnel testing, how can we know what aero/hood changes are actually functional?

 

Everyone has theories but none of us has proof. Any ideas how we can test this out?

 

Check the engine bay temp. before and after

 

Is there any proof yet? :- )

It looks like maybe the raised portion of the plastic trim piece around the wipers may keep the air from the windshield from being drawn in. Maybe they would allow the heat to escape if the the hood was raised?

 

ummm....https://my350z.com/forum/8881364-post16.html




40 bucks at harbor freight..

-J

 

I know the temps can be tested but I was more concerned about where air was going at highway speeds. I guess a wind tunnel is the only option there. If anyone else wants to remove all the excess molding and plastic at the rear of the bay, test it first! I'm not reinstalling all that crap!

I did buy these Racetemp stickers that have the thermometers on them for the engine bay. I put them at various places. 1 on my intake bracket, 1 on the plenum spacer and until I wrapped the CAI with gold thermal, I had 1 on the CAI at the TB. These, on a 90+ degree day and after 30 minutes of mixed highway and city driving and an immediate check when I got home, were reading around 138 degrees. This info, however, is pretty useless without a comparison of what the temps were without all the "blockages" removed.

 

all the Hondas in VA have this done...in my opinion it looks bad as if the hood didn't fit right...if you want your engine bay to cool down quicker why not buy a hood with vents or go to a shop and get it done

 

I agree. But on the 350Z, you can remove the rubber at the rear of the engine bay and trim the plastic down some and it opens up the rear of the hood without changing the look of the car. Essentially, this is the same as raising the hood but without looking tacky.

 

Your wipers would be hot regardless of removing that plastic.

That's a dead area in the aerodynamics, the front of the car and hood push the air up onto the windscreen, you'd have hot wipers in the sun and from the heatsoak from the engine bay with or without the mod.

 

using a temp gun or heat strips to log those temps in the engine bay would be a pointless way to record the temps because once slow down to stop the car airflow stops and by the time you get out and open the hood the temps would have been increased due to the airflow being stopped.

To test it in motion you would need temp monitors during the drive and a logger would be the best.

I just removed the rubber seal to help with some venting on the hood. Won't reduce engine temps but the engine bay might be a little cooler which will slow down the eventual heat soak of the engine.

 

http://www.gtfactory.jp/cms/page.php?11

All the way at the bottom.

 

haha, "huge gains"

 

personally i cant believe this works unless its pushing air into the the engine bay and then out under the car. theres a reason they make cowl induction hoods, but hey prove me wrong then i can go smack my head against the wall for wasting the time i have working on hood vents lol. thats just a really high pressure area of stagnant air, even if it pushs the air into engine bay theoretically its not going to be good aerodynamically since that area which normally has stagnant unmoving high pressure air that helps air flow over the roof smother is now a lower pressure area of constant air loss and its going to make it harder for air to flow over the roof since it dosnt have a "air bubble" to ride on anymore.

i imagine its going to move the high pressure area higher up the windshield and cause an erratic merge of air in the rear of the car, somewhere up above the car vs directly behind it. personally imo and just thinking here so dont string me up for it, i would think hood vents will be far better, the hood is a low pressure area above it and high pressure below it so hood vents would not only allow heat to flow out better it would also provide less lift to the front of the car.

it might seem like a very small or insignificant part but those are the ones that usually provide the biggest hit, just take a look at gurny flaps on wings tiny piece that provides pretty big gains for downforce and changes to how the air flows around the vehicle.