Go Back   EcoModder Forum > EcoModding > Aerodynamics
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 06-01-2019, 05:22 PM   #41 (permalink)
Tyrant-at-large
 
Vman455's Avatar
 
Join Date: Feb 2012
Location: Champaign, IL
Posts: 1,340

Little Red - retired - '05 Honda Civic EX
90 day: 49.03 mpg (US)

Pope Pious the Prius - '13 Toyota Prius Two
Team Toyota
90 day: 54.18 mpg (US)
Thanks: 127
Thanked 1,117 Times in 577 Posts
I'll be curious to see what results you get; to my knowledge, no one on this forum has tried hood vents yet. I probably won't get around to them until later this summer if I do them at all.

__________________

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 06-05-2019, 10:39 AM   #42 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 9,989
Thanks: 14,987
Thanked 5,300 Times in 3,108 Posts
hood vents

Quote:
Originally Posted by Vman455 View Post
I'll be curious to see what results you get; to my knowledge, no one on this forum has tried hood vents yet. I probably won't get around to them until later this summer if I do them at all.
I did them for the last wind tunnel trip.After losing an igniter,I thought some additional engine bay ventilation might help,after 'looking around' in there with a pyrometer.
Money ran out,so I don't have an A-B-A result,just for the two hood extractors.Blocking the cooling system inlet and extractors off did register a Cd 0.027 difference.It wasn't feasible to alter the underside of the truck for testing,so it remains an unknown quantity.
I used the 1976 Pininfarina/Morelli, CNR 'banana' car as an inspiration for the extractors.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
The Following User Says Thank You to aerohead For This Useful Post:
Vman455 (06-05-2019)
Old 06-19-2019, 06:14 PM   #43 (permalink)
EcoModding Apprentice
 
Join Date: Aug 2018
Location: USA
Posts: 245

Jeep - '97 Jeep Cherokee Sport
90 day: 19.36 mpg (US)
Thanks: 58
Thanked 44 Times in 42 Posts
My vents are here! Now it is just a matter of when I'll have time to cut into my hood. Results should be here in the next few weeks or so.
  Reply With Quote
The Following User Says Thank You to Taylor95 For This Useful Post:
aerohead (06-22-2019)
Old 06-22-2019, 01:15 PM   #44 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 9,989
Thanks: 14,987
Thanked 5,300 Times in 3,108 Posts
cutting

Quote:
Originally Posted by Taylor95 View Post
My vents are here! Now it is just a matter of when I'll have time to cut into my hood. Results should be here in the next few weeks or so.
Be mindful of the bracing under there.I chose to make the penetrations only where there wasn't any ribbing,to maintain the stiffness of the panel.
Tufting will reveal areas of accelerated flow(typically near the A-Pillars,with tufts closer together),these represent lower pressure for scavenging.
Any placement will be at a lower pressure than the grilles inlet,so the air is gonna come out regardless.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Old 06-24-2019, 01:54 PM   #45 (permalink)
EcoModding Apprentice
 
Join Date: Aug 2018
Location: USA
Posts: 245

Jeep - '97 Jeep Cherokee Sport
90 day: 19.36 mpg (US)
Thanks: 58
Thanked 44 Times in 42 Posts
My vents are actually pretty large, so doing a tuft test won't benefit me much. I have a good idea where the low pressure spots are on my hood though.

The hood vents I got are made for my vehicle so they will fit nicely between the braces.
  Reply With Quote
The Following User Says Thank You to Taylor95 For This Useful Post:
aerohead (06-26-2019)
Old 07-02-2019, 05:41 PM   #46 (permalink)
EcoModding Lurker
 
Join Date: Jul 2015
Location: Louisiana
Posts: 60
Thanks: 6
Thanked 22 Times in 19 Posts
I've installed louvers on my Jeep TJ Wrangler with the 4.0L straight six engine. I did it to release extreme engine bay heat rather than for any aerodynamic benefits. At the speeds my Jeep travels, whether on-road or off, it needs the extra cooling benefits much more than any potential aerodynamic effects that might come from trying to improve on the shoe-box shape of the vehicle.

The hood louvers I installed are positioned to avoid having to cut any hood bracing, but are in places known to develop into relatively low pressure areas over the hood. This makes it more certain that the high-pressure hot air from the engine bay is easily pulled into the low-pressure air above the hood when at speed.

The louvers I installed are two rectangular-shaped Gen-Right louvers on both sides of the hood, and two somewhat-triangular-shaped Hyline louvers at the left/right center of the hood.

I've also installed a 12-inch electric radiator fan on top of the engine to blow hot engine bay air up-and-out of the louvers. This fan is used in slow-speed traveling/crawling while off-road, and I also run the fan on a timer for 10 or 15 minutes after the engine is shut down in hot weather to avoid heat-soaking everything under the bonnet. After engine shut-down in hot weather, it can get to around 300F just above the engine at the fuel rail and intake/exhaust manifold, according to the temperature gauge I installed above the engine to measure ambient engine bay temperatures.

I can't say the louvers or scavenger fan improve my fuel mileage, because they don't, but they sure as heck reduce heat-soaking everything under the hood. This especially benefits such things as the battery, alternator, sensors, and rubber hoses, belts and gaskets. etc subject to the heat. It also helps prevent vapor-lock in the fuel rail, which can result in hard starts.

By the way, I also installed a couple of the triangular-shaped Hyline louvers in the hood of my Mazda3 to keep things cooler under there. I did this after losing a battery prematurely, which I think was due to the heat. I even installed a six-inch radiator fan to blow the hot engine bay air out of the louvers while in stop-and-go traffic and after engine shutdown in hot weather. Again, it didn't do anything for or against my fuel mileage, but the engine bay sure runs cooler, according to the ambient temperature gauge I've got to keep tract of things there.
__________________

Last edited by MeteorGray; 07-02-2019 at 05:52 PM..
  Reply With Quote
The Following User Says Thank You to MeteorGray For This Useful Post:
aerohead (07-03-2019)
Old 07-02-2019, 05:57 PM   #47 (permalink)
EcoModding Apprentice
 
Join Date: Aug 2018
Location: USA
Posts: 245

Jeep - '97 Jeep Cherokee Sport
90 day: 19.36 mpg (US)
Thanks: 58
Thanked 44 Times in 42 Posts
Keeping the engine bay cooler is the primary reason I am doing this. In theory having vents should improve aerodynamics, but I will know for sure if there is a measurable difference because I will be testing this with a scangauge at 60 mph and 70 mph. I will finally be installing the vents this Saturday, so my results should be expected soon after.
  Reply With Quote
The Following User Says Thank You to Taylor95 For This Useful Post:
aerohead (07-03-2019)
Old 07-03-2019, 06:26 AM   #48 (permalink)
EcoModding Lurker
 
Join Date: Jul 2015
Location: Louisiana
Posts: 60
Thanks: 6
Thanked 22 Times in 19 Posts
Yeah Taylor95, I installed the louvers to take mercy on all the stuff being baked in the engine bay. In the case of my Mazda, I'm convinced its battery died an early death due to the heat effects of living in an oven. Heat just ain't good news for the chemistry going on in a battery.

Regarding aerodynamics, I "believe" venting the hood and giving the heated air a natural escape route overhead does aid vehicle handling by keeping the front end from rising at speed due to the engine bay air trying to escape underneath. However, at the speed and methodology with which I drive, I can't quantify that. It probably would take before-and-after track time differentials to do that.

But I can say that in the case of my Jeep with a big, heavy hood and a quaint, rubber-band hold-down device on both sides of the hood designed to keep it from flying off, the hood used to shake-and-shimmy when on the highway in high headwinds or when being passed by big trucks. With the louvers, the hood no longer does that, presumably due to the fact that the engine bay air has an easy path upward and outward via the louvers, which eliminates the violent turbulence of backed-up air hammering at the hood for a way to escape. Also, after a hot run, I can now lift the hood without burning my fingers off, because the heat was allowed to escape before heat-soaking all the metal down below.
__________________
  Reply With Quote
Old 07-03-2019, 07:06 AM   #49 (permalink)
Master EcoModder
 
Join Date: Oct 2009
Location: Fort Worth, Texas
Posts: 2,240

2004 CTD - '04 DODGE RAM 2500 SLT
Team Cummins
90 day: 19.36 mpg (US)
Thanks: 1,241
Thanked 635 Times in 484 Posts
On a couple of our JEEP XJ Cherokee’s I simply shimmed the rear of the hood a little and removed a small portion of the hood/firewall gasket away from the HVAC air intake.

OEM Under hood was so hot one had to use gloves.

This was too effective as winter warm-up took longer. Reinstalled gasket portion for winter.

But no more cooked components or burnt fingers.
__________________
2004.0 DODGE Ram QC/LB 2500 2WD/NV-5600 305/555 ISB. 7,940-lb. Stock. 200,000 miles/5000-hrs @ 40-mph average.
1990 35' Silver Streak TT 7,900-lb.
11-cpm solo & 19-cpm towing; 21-mpg average past 54k-miles
Sold: 1983 Silver Streak 3411
  Reply With Quote
Old 07-03-2019, 08:20 AM   #50 (permalink)
EcoModding Apprentice
 
Join Date: Aug 2018
Location: USA
Posts: 245

Jeep - '97 Jeep Cherokee Sport
90 day: 19.36 mpg (US)
Thanks: 58
Thanked 44 Times in 42 Posts
I wonder why your engine bay gets so hot for the both of you. I shouldn't have a problem placing my hand directly on the hottest part of my hood after a run.

What you said about the hood shaking before you installed the louvers confirms my thoughts. I'm just hoping it's a significant difference because 90% of my driving is on the highway. A 1 mpg increase at 60 mph would be very good. The payoff from gas savings though would take about 15 months.

I did think about putting in hood spacers which would be similar to removing that rubber piece. I don't think that would be as effective though, and maybe dangerous in a front end collision.

  Reply With Quote
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com