Hood Vents and Under Hood Temps

[MRX330]

Look at the air intakes on funny cars - the intake hole points point the windshield b/c that's where the pressure is. The hot air rises from the pot b/c there's cooler air around to replace it, but gravity cooling goes to hell when there's more than just a bit of air movement.

On the FiST the natural low pressure zones are on either side hood of the towards the top where the crease is.

I know I was being an obliviot

 

[Mikey456]

Not sure if anyone's done this to their FiST yet, but here in Phx, I've seen a number of import cars with the hood lifted slightly at the back...just in front of the wipers. I'm talking all of 1". Might be some type of hinge modification in an attempt to let out some engine bay heat.

I cut a little of the rubber weather strip on the end of the cowl separating the engine. I did notice some hot air coming out that would otherwise stayed in the engine compartment.

 

[shouldbeasy]

Hood vents that work:
https://cmcomposites.co.uk/shop/fiesta-parts/fiesta-wrc-bonnet-vents

 

[jeffreylyon]

Hood vents that work:
https://cmcomposites.co.uk/shop/fiesta-parts/fiesta-wrc-bonnet-vents

I've almost bought these a couple of time. The problem I have with them is the lack of rain guards and, without them in hand, I'm not sure I can easily fab something. The Verus Engineering vents have optional rain guards and come with a wicker that might improve extraction, even though they're not in the idea location: https://whoosh-motorsports.myshopif...gineering-hood-louver-kit-fiesta-st-2014-2018

 

[shouldbeasy]

I'm really wondering WHY you think rain guards are necessary... I'm going to be ensuring that the electronics on the driver side are as water resistant as I can get it but I'm not concerned really. Then again I live in a dry climate...

Shit, I lightly pressure wash my engine bay... Water follows gravity and with some forethought and dielectric grease I'm sure I can get things sorted.

EDIT - I'm combining them with some low pressure zone funnels on my skid to remove the air from under the car and direct it up through the engine bay and out - hopefully it works well.

 

[MRX330]

You guys should seriously look into race coatings for your manifold, turbo hot side, dp and exhaust. That reduces under hood temps big time instead of hacking up your hood

 

[jeffreylyon]

You guys should seriously look into race coatings for your manifold, turbo hot side, dp and exhaust. That reduces under hood temps big time instead of hacking up your hood

I'm going to Cerakote my exhaust manifold if I stay with the log or Cerakote and wrap if I go tubular, blanket the turbine, and Cerakote and wrap when I go with a larger downpipe. I'm ok with a hot exhaust after the downpipe.

Hacking the hood is to get air out of the front of the car for better aero and less lift.

 

[MRX330]

I'm going to Cerakote my exhaust manifold if I stay with the log or Cerakote and wrap if I go tubular, blanket the turbine, and Cerakote and wrap when I go with a larger downpipe. I'm ok with a hot exhaust after the downpipe.

Hacking the hood is to get air out of the front of the car for better aero and less lift.

So this works in lieu of a rear wing?

 

[jeffreylyon]

So this works in lieu of a rear wing?

Not at all - this manages front lift. A splitter adds front downforce. A rear wing and diffuser add rear downforce.

 

[MRX330]

Not at all - this manages front lift. A splitter adds front downforce. A rear wing and diffuser add rear downforce.

Brain fart. Meant front splitter. I was just looking at rear wings.

 

[jeffreylyon]

Brain fart. Meant front splitter. I was just looking at rear wings.

If you look at the underside of the front of your car you'll see a 1.5" or so air dam. This creates a low pressure area behind it to pull the cooling air out of your car. When you install a splitter that eliminates this you have to entice the air to go someplace else. The best place on out the top of the car. Most street splitters do not extend that far back so you can leave the stock air dam and avoid hacking on your hood. Racey guys are trying to increase the speed of the air under the car to reduce drag and lift so the rules are written to control the size of the splitter in front of the car and how far it can extend back. Most rules say to the wheel arch opening or the front axel-line.

 

[MRX330]

If you look at the underside of the front of your car you'll see a 1.5" or so air damn. This creates a low pressure area behind it to pull the cooling air out of your car. When you install a splitter that eliminates this you have to entice the air to go someplace else. The best place on out the top of the car. Most street splitter do not extend that far back so you can leave the stock air dam and avoid hacking on your hood. Racey guys are trying to increase the speed of the air under the car to reduce drag and lift so the rules are written to control the size of the splitter in front of the car and how far it can extend back. Most rules say to the wheel arch opening or the front axel-line.

Would you put hood vents on a street car is the $10,000 question?

 

[maestromaestro]

Would you put hood vents on a street car is the $10,000 question?

I did. It's cool (hehe).

 

[jeffreylyon]

Would you put hood vents on a street car is the $10,000 question?

Yup

 

[shouldbeasy]

You guys should seriously look into race coatings for your manifold, turbo hot side, dp and exhaust. That reduces under hood temps big time instead of hacking up your hood

Some of us are rather skilled with a cut off wheel / reciprocating saw so it's hardly a hack job.

Shit, my hood already has a giant dent in the front from a rock.

 

[MRX330]

Some of us are rather skilled with a cut off wheel / reciprocating saw so it's hardly a hack job.

Shit, my hood already has a giant dent in the front from a rock.

Well now you can use those skills and just cut the dent out and add another vent

 

[shouldbeasy]

Well now you can use those skills and just cut the dent out and add another vent

Man, you really aren’t the sharpest tool in the shed eh?

I’m placing the hood vents where there is a natural low pressure zone which will pull under hood air out. This is documented. It’s not just some slap dash hood vents ‘because race car’.

Go understand the aerodynamics at play with our cars, then come and provide something beneficial to the conversation.

 

[MRX330]

Man, you really aren’t the sharpest tool in the shed eh?

I’m placing the hood vents where there is a natural low pressure zone which will pull under hood air out. This is documented. It’s not just some slap dash hood vents ‘because race car’.

Go understand the aerodynamics at play with our cars, then come and provide something beneficial to the conversation.

Come on one more vent won’t hurt anything

 

[TyphoonFiST]

Rally roof vent!

Sent from my SM-N950U1 using Tapatalk

 

[MRX330]

Rally roof vent!

Sent from my SM-N950U1 using Tapatalk

Also known as the Scalper