Effectiveness of vented hoods/heat extractors

[Dustys318]

Running through the mountains in Cloud Croft, New Mexico I would never be able to get under 20 degrees over ambient (I have DHM race intercooler too). Now I'm single digits! (8-9ish)...

 

[Dustys318]

The average area of the factory grill opening is 120 inches. The two vents area combined are 62 inches (31 each). [college class fluid dynamics blah blah] reminded me of 50% exit flow from intake flow for maximum velocity and other blah blah whatevers. Look at a jet engine intake and exhaust and you'll get the picture...

 

[jayrod1980]

You should write a tutorial! How did you cut it and where did you buy the ducts? I just don't want to move a bunch of stuff around. I wonder if I could make some kind of umbrella for the fuse box... Not that it rains much in Vegas.

 

[Dustys318]

The only reason I'm moving stuff around is to minimize flow obstruction between grill and vents. I can hold my hand out the window by the mirror and I can feel the hot air so I know it still doing its job as is.. I'm just trying to add a little more...

 

[RAAMaudio]

Very clean install by the way

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Are those the real rally vents or the other ones available?

They look great either way, I can look but if you have a link you can post as to where they were sourced I might just order as set for my CF hood I am installing soon.

It has the RS style vents which might look funny with two sets of vents so I might sell the hood instead if I somebody is interested, great price as well

Going back a few pages to see if the info on the vents is on this thread.

Rick

 

[Dustys318]

I had done a write up on my magnehelic gauge/string testing last summer-ish time. The highest negative pressure was in this area. All across the hood was high positive pressure. The RS vents worked on the older body style because of the curve at front of hood.

I don't have a link to whom I purchased the vents but it is a Sico product so I'm sure you can find it easily (I think someone posted it here already)..

It does look good, thanks, but I should have gone a hair lighter grey primer, it has a slight mismatch from the hood

 

[meFiSTo]

I don't have a link to whom I purchased the vents but it is a Sico product so I'm sure you can find it easily (I think someone posted it here already)..

I traded a bit of email with a fellow named Simon today at Sico. They can sell direct. Price shipped to U.S. customers (with a discount VAT zeroed, and shipping included) was quoted as £259.95 shipped to my location in WA state. Google converter today makes that $369.90.

Link: http://www.sico-developments.co.uk/...zetec-s-and-st-180-acr-wrc-style-bonnet-vents

Seriously considering this adjustment to my stock hood.

Regarding color: Practically impossible to get a perfect match, although we have a couple of VERY good shops around here.

 

[Dustys318]

Yes, that's about what I paid for them..

 

[Siestarider]

I cannot remember what air dam/undertray Dusty is running. My yarn and pressure tests also showed his vent locations are at the lowest pressure area on hood, low pressure wraps around edge of hood also. There is a thread on here somewhere about it.

Now that the theory is proved (thanks Dusty) I may go this route plus lower air dam. My undertray experiments have not produced the heat extraction needed for stock cooling system. When undertray is mounted and you look from behind up toward nose, there is not a lot of ducting area available at rear. Hence cut away sides of undertray helped cooling more as I opened it up more. But this approach is also opening up into wheel well aero, which I flat cannot understand well enough to have a clue.

Plenty of evidence that lower air dam improves both aero and cooling. Maybe hood vents are the ideal compliment. I am thinking of a little different approach, maybe first try venting rear sides of hood, see how much that helps. Mainly for stealth first.

 

[Siestarider]

Forgot this thread was up, posted my hood vents and air dam extension under aero mods and cooling. Data collection next.

 

[meFiSTo]

Forgot this thread was up, posted my hood vents and air dam extension under aero mods and cooling. Data collection next.

I saw that. Linked here for reference.

I've also pondered the question of getting a hood to cut up, but also figured that if I really needed to go back to stock, one can be had locally for $285 plus tax. I've seen them for $280 shipped, no tax (I think) oh EBay. Then painting (and for me installation, which be comparatively nominal). In the scheme of things (considering what I've shelled out to my local shop), not a deal breaker. A bridge I'll cross if needed. I've ordered the Sico bits and am waiting on them to move into production. There's a queue.

 

[RAAMaudio]

I will be in the Phoenix area another 9 days or so and have a silver hood for free though it has two holes for hood pins in it, after that if not before it might go to recycling.

I really do not have the time to pack and ship it as did not get the box with the CF hood as picked it up in person and did not need a box.

If somebody wants it and not local perhaps a local member could get it and ship it. I might be able to take it to SoCal as heading back that way most likely, depends on if the car is driven back or stowed in the trailer.

Let me know, anybody that is interested that is

Rick

 

[LT Berzerker]

For those of us that may want to do this and not spend as much money on the vent itself this might be an option, posted this in the aero & cooling thread.... Snowmobile vents lol!
Since it's hard to find a similar shape to the WRC/functional vents...

Sent from my Nexus 6 using Tapatalk

 

[meFiSTo]

As a follow-up to this thread, I did wind up getting the Sico vents.

Here's a view of the vents installed:

I include some installation notes and a few more images in my build thread.

As an aside, I did get out for a couple of track days last month just before these went on, but after the Mishimoto cooling bits were added, and the car ran well with no apparent overheating issues. They were both cool days, so I hope to learn more when the car is out for a warmer day late this month. I did not have my AP mounted, but the stock in-dash "gauge" did not budge from the "warmed up" indication (midpoint bar). I'll connect the AP next time to get a better sense of water temps. No oil gauge in place.

 

[wspec]

Here is what I did for vents.

 

[Siestarider]

I have not found any measurable cooling difference post-hood vent vs pre-vent on track. Sebring two days, had to run heater on Hi to keep coolant temps under 235F. PBIR in June, same thing. Need to get back to air dam experiments, but need ride height set first. Ordered, hopefully coils come soon.

 

[meFiSTo]

Here is what I did for vents.


View attachment 10784

One thing I did do is remove the sound insulation lining the inside of the hood. I also figure to remove the little plastic neatness covering over the ugly intake mess at the track. I figure plastic shields and blanket-like covers act as insulation when the car is hot (keeping more heat in). The steel hood is a better heat sync and taking that material away frees up a little air flow through the top of the engine bay.

But: It's all relative. Not sure how many actual deg F are actually trimmed by doing any of that (including the vents).

YMMV.

 

[Siestarider]

I also removed the sound blanket. Taped up every crack I could find that might let cool air bypass radiator. Running coolant temps of 235F with the stock 1.3 bar cap is actually about 35 degrees below boiling point of my 30/70 antifreeze/water blend, so its not like there is some coolant loss likely. Oil hits 260F, but again, good oil can take it for tracking.

What I would really like to do is remove the hokey flap stack adjacent to right side of fan shroud and replace it with a vertical oil cooler on back side of radiator, but the clearance is really tight. If I could get this arrangement to work, in theory it offers the most fluid cooling for least weight while still being daily friendly.

In meantime, heater works enough, just need to plumb the outlet that burns my right foot out the window with some flex hose.