No decrease in temps noted on my gauges, but you can certainly see the heak dissipate through the vents while at a stoplight.

Also, as mentioned previously, the engine noise (while outside the car) is increased.

 

I think the vented hoods are great especially for cars with smaller/cramped engine bays. I feel it should help dissipate and avoid heat soak...plus some of them make the Z look more aggresive. I will definately get one when the time comes...just have to decide which one.

 

At the track with the stock hood I've hit a peak temp of 244 degrees (coolant temp). With the Seibon JS hood on a similar day I only got up to 233. Not a scientific test so take it for what it's worth.

Also as far as heat soak goes, at the drag strip with the stock hood I'd see intake temps at the starting line peak as high as 170 degrees. With the vented hood only 156.

With the car idling you can feel considerable amounts of heat coming out of the vents.

 

best hood... from seibon but got discontinued...





you cant imagine how the heat exit the engine bay by this hole.. when waiting at a red light, you clearly see the fumes and the heat going out..

 

That's a nice hood, but it is a Top Secret copy. You can get the authentic version or the Vis knockoff still.

It looks good but I'd probably prefer some mesh covering those holes.

 

+1 no actual figers but its noticable by driving and temp. differ

 

^ BTW, car looks very nice. That body kit looks so much better with an FMIC and in DB. Good work.

 

Im going to have nismo style louvers cut into my stock hood.

 

Here is an overhead shot of the VIS carbon fiber hood, which is made for both the G and the Z. Note the deflection of the flow of the hot air towards the A pillars from the "gill slits". When you hang your elbow out the window, you REALLY feel the hot air flow. Obviously at a standstill you can see the heat convection rising, but the real benefit is when in motion.



Here is a picture going into Cotton Corners at Buttonwillow, that shows the nose scoop that helps put air into the compartment from the high pressure area and create the air flow to express out the heat.



The measured water temp before and after the hood replacement is 4% centigrade. I have not measured the under hood ambient air temps, but suspect they are much more than that if the water temp is down that much

Here is a shot at apex through Bus Stop at Buttonwillow, showing the side view relative location of the exhaust slits over the motor.

 

I have the seibon carbon fiber hood and I'm running a Vortech S/C. I have not tested the under hood temps, but you can see the heat waves coming out from the vents. I can say it does work, but I do not know how much.

One down side is when it gets wet, the water does soak into the engine bay. With the supercharger the vent is right where the belts are and usually it will cause my belts to squeek. This only seems to happen when I wash my car. At start up the car will run very ruff like I got water on the plugs or something. And the belt will squeek for maybe a minute or two. If you can keep the water out, then they seem to work well.