Radiator hood vent?? Aero, cooling, WAI, all in one??

[gumby79]

This article

Undertrays, Spoiler & Bonnet Vents, Part 3

Designing, siting, installing and testing bonnet vents
by Julian Edgar

Sorce: AutoSpeed - Technology, Efficiency, Performance
Details how to find the ideal spot to place your vent. How to determine if you are getting the desired effect. As stated its all about the pressure Vs lack there of.
This graph shows the pressure differential ( fore and aft of the intercooler) results of several of the mods that you are trying to design.

Your goal is to find the purple spot in the next pic. For your exit. And the red on tbe front for the intake.


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The magic of a "good" ecm tuner/ carb. tuner is the ability to adjust for today's up to the minute environmental conditions. This magical skill is able to be simplified when you eliminate some of the variables. The variable I am referring to is the IAT just pulling fresh air or just under "sealed" hood require a wide tuning map . Pulling both through a mixing valve will allow the smallest tuning window. AKA the most efficient.
OilPan has shown that a gen set non-intercooled is supposed to pull intake air from inside the enclosure below 20°f . As this is outside the tuning parameters. Aka a significant loss of efficiency is seen below this pre turbo IAT caused by a change in air density.
Gumby Stay Flexible

[ECONORAM]

Wish I'd found this thread sooner. Like 2 years sooner.

@chillsworld
I have encountered a couple of the issues highlighted in this thread. My quest began when I traded a 2004 Ford Taurus on a 2007 Dodge Ram 1500. I started with a partial radiator/grill block, and a partial belly panel. I then put fairings in front of the front wheels, and added wheel covers. Later came weather stripping to fill the gap between the hood and the fenders. About then I increased the area of the engine belly panel to 90% or so (had a couple gaps), and extended the belly panel about 6 feet down the length of the truck. Last, I modified the Ford Taurus radiator shroud I was using with my Taurus e-fan, so it stretched across the entire radiator. I thought that’d be even better. Not so, I soon learned.

At this time, i was living in San Antonio, and noticed that coolant temps stayed about 200*F. The T-stat opens at 193, but I didn’t like seeing it sit so high. My electric fan was running more frequently than I thought it should. And, highway mileage wasn’t as good as I thought it should be, given the aerodynamics work I’d completed.

It didn’t help either, that I added a crankshaft under drive pulley (25% reduction, the only one available). It did increase the fun factor though.

At my next oil change, I pulled the belly panels off that were past the engine bay. In this instance, I delayed reinstalling the panels a couple weeks. Oddly enough, that seemed to help highway mpg a bit. Which made me think (to your point, I think) I had sealed the engine bay up such that I was actually preventing or restricting airflow through the radiator. It also occurred to me that mpgs (and temps) were better prior to me stretching the radiator shroud. I also checked my logbook and confirmed this. Nothing enormous, but enough to bother me.

So, I cut out the radiator shroud extensions and put it back to covering only 2/3s of the radiator. I also changed how the second belly panel mounted. Specifically, I left a one-inch height gap between it and the trailing edge of the engine bay panel, with the engine bay panel being the lower of the two. They also overlap about 2 inches in length. Why the change? So I could use the passing airstream to pull hotter engine bay air out of the engine bay, like aircraft engine cowl flaps do. I did the same thing where the second and third panels meet; added a one-inch height gap, with the second panel being the lower of the two.

I also modified (and based on what I read here about pressures on/near the hood, need to do more of) the weather stripping between the hood and fender. I added a couple venting gaps close to the hinged part of the hood. Now, I think I will put these about every 4-6 inches, to help vent the engine bay more. I’m not planning to cut vents in the hood, but if I can tweak a few more things I think I’ll rest easier. Engine temps are better now; hovering at 195-197*F in the summer. And the fan runs less.

One to-do item is adding a small (8-10 inch diameter) fan somewhere between the frame rails, to pull air from the engine bay and out the back. Just need to keep it clear of the driveshaft. This may mean adding a duct in order to get the airflow I am looking for. Or I may need to mount it at the end of the tranny, so I can seal off the passage and vent the engine bay that way…

@gumby79, that is an interesting thought to vent the engine bay out behind the front wheels. In the purple area. Maybe a small fan ducted/mounted behind the front wheels?

Almost forgot. A benefit most may not realize with belly panels. In my truck, they reduce road noise on the highway. And keep the underbelly cleaner. Not to mention reducing fuel burn.

[eagle]

I am interested in this since I have mounted my cai in the cowl section since I figured that it would be a high pressure zone and would ingest clean cold air and as little as engine bay heat as possible

I copied 2JR intake (thats what its called) and I am now thinking of installing "wrc style" vents in the back sides of the hood since all wrc/s2000 fiestas have them, that point should be the best for hot air extraction

but after reading a lot of posts here I am worried, especially for my intake :/ anyone?

[JulianEdgar]

Originally Posted by eagle

I am interested in this since I have mounted my cai in the cowl section since I figured that it would be a high pressure zone and would ingest clean cold air and as little as engine bay heat as possible

I copied 2JR intake (thats what its called) and I am now thinking of installing "wrc style" vents in the back sides of the hood since all wrc/s2000 fiestas have them, that point should be the best for hot air extraction

but after reading a lot of posts here I am worried, especially for my intake :/ anyone?

I haven't read the whole thread, but you will gain much better pressure for the engine intake by picking up air from an appropriate place at the front of the car, not the base of the windscreen.

[Yippeekyaa]

Originally Posted by JulianEdgar

I haven't read the whole thread, but you will gain much better pressure for the engine intake by picking up air from an appropriate place at the front of the car, not the base of the windscreen.

Interesting! NASCAR uses the cowl Just beneath the windshield as the location for the air intake and have done so for many years. Do not know if that is an actual rule or for aerodynamic advantages. That being said, i assumed that considering the millions NASCAR spend on aerodynamics, that the cowl would be the best place to locate the air intake. Side note, a high school class mate of mine later when on to earn a phd in aerodynamics and was the first aerodynamic engineer hired by a NASCAR team way back in the 1990’s. He is a wee bit proud of his degree and insists on being referred to as “Doctor”, (His last name), even when in informal or casual situations.

[JulianEdgar]

Originally Posted by Yippeekyaa

Interesting! NASCAR uses the cowl Just beneath the windshield as the location for the air intake and have done so for many years. Do not know if that is an actual rule or for aerodynamic advantages. That being said, i assumed that considering the millions NASCAR spend on aerodynamics, that the cowl would be the best place to locate the air intake.

Easy enough to measure for yourself. The pressure at the base of the windscreen varies depending on the shape of the car, but it is typically 40 - 65 per cent the stagnation pressure (ie the max pressure at front of car).

[gumby79]

Cowl induction intercooler seems like a great idea, provided there is adequate pressure differential crossed the core.

Julian you missed the intercooler is mounted in the cowl ,not the air intake.
Subaru has been using top mount intercoolers for decades.

[JulianEdgar]

Originally Posted by eagle

I am interested in this since I have mounted my cai in the cowl section since I figured that it would be a high pressure zone and would ingest clean cold air and as little as engine bay heat as possible

I copied 2JR intake (thats what its called) and I am now thinking of installing "wrc style" vents in the back sides of the hood since all wrc/s2000 fiestas have them, that point should be the best for hot air extraction

but after reading a lot of posts here I am worried, especially for my intake :/ anyone?

This is the post I was replying to. Engine intake in cowl area. And this is the kit that was referenced:

[gumby79]

I stand corrected.

[eagle]

the stock and most aftermarket locations for the intake seem to route the piping above the exhaust manifold, around the cylinder head and place the filter near the oem front air scoop

like



the cowl intake (for this car at least) is shorter, places the filter in a kind of "sealed" compartment from the rest of the engine and supposedly benefits from the high pressure at the cowl area as well



*not my car, but same design*


so you could say the cowl intake benefits more because the most part is away from any heat sources