• Registered: 2009-07-19
  • Posts: 1,585

Topic: Want upward air flow through engine compartment

I need air to flow upward through my engine compartment and out the hood.

I'm currently thinking that a louvered vent grill from Lowes, mounted so the louvers stick out above the line of the hood, should create a low pressure area above the grill when I'm driving and move air upward out of the engine bay. 

A few years ago when I cut a 6" hole in the roof of my Civic, at about 60 MPH I got to see the Bernoulli Principle in action and it seemed like it really moved a lot of air. I was thinking that some 4" rigid ducting sticking straight up out of the hood and cut parallel with the ground would be cool and effective, but a louvered grill over a hole in the hood seems like a more elegant solution.

How do you guys solve the problem of getting the hot air from your portable generator set out from under the hood of your car without having it flow down over the electric drive motor?

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  • From: Vermont
  • Registered: 2012-04-19
  • Posts: 301

Re: Want upward air flow through engine compartment

What about trying to go out the fenders rather than through the hood?

The transition area from the hood to windshield is a high pressure area that will tend to force air into the engine compartment rather than extract it (e.g. cowl induction).

On the hood, the area of low pressure is generally behind where the radiator (not applicable in your case) would reside. That's likely too far forward to be effective in removing heat from a gen set under the hood.

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  • From: Wilmington, NC
  • Registered: 2016-08-14
  • Posts: 46

Re: Want upward air flow through engine compartment

Since our portable generator set is in the form of an inline-6, we cut louvers on the exhaust side of the hood and cut out the corresponding foglamp to have forced airflow over the manifold. No need to cut a hole and add a vent- simply bend the metal of the hood into the required shape.

You can see ours at this point in the video: https://youtu.be/0CuYtvklSQ4?t=199

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  • From: Pembroke MA 02359
  • Registered: 2016-06-27
  • Posts: 151

Re: Want upward air flow through engine compartment

On the TT we cut the hood just behind the radiator and ran a small duck at a angle  it pulls a lot of air out.

  • From: Staunton, VA
  • Registered: 2012-05-16
  • Posts: 606

Re: Want upward air flow through engine compartment

Here’s our hood vent- very easy to do with a transversely mounted four cylinder gen set.
https://i.ibb.co/QYnRfDt/66-E01-E83-C4-D7-4-E56-8487-4727-E508-D159.jpg

  • Registered: 2009-07-19
  • Posts: 1,585

Re: Want upward air flow through engine compartment

Thanks all, but another team member has suggested maybe we don't want anything that would let rain get on the lots of high-voltage, high-power stuff under the hood. I'm thinking that rules out louvers.

Now I'm thinking some type of reverse hood scoop or venturi system.

Everybody grab your brooms, it's shenanigans!
  • From: Houston, TX
  • Registered: 2012-06-21
  • Posts: 1,608

Re: Want upward air flow through engine compartment

When I saw the picture of your T-shaped duct in the other thread, my thought was maybe curve the horizontal piece S-wise, downward in the front, so any rainwater would have to go uphill to get into the vertical portion. Kinda like

Front

\
--|      Up
   \

Rear

(I've had a few drinks, and I'm still not an aerodynamicist)

Escape Velocity Racing
  • Registered: 2009-07-19
  • Posts: 1,585

Re: Want upward air flow through engine compartment

I was thinking the same thing, and cut a notch in the back junction to open up the back a bit so it will draw more air up out of the engine bay.

Everybody grab your brooms, it's shenanigans!
  • Registered: 2016-02-18
  • Posts: 15

Re: Want upward air flow through engine compartment

rmcdaniels wrote:

Thanks all, but another team member has suggested maybe we don't want anything that would let rain get on the lots of high-voltage, high-power stuff under the hood. I'm thinking that rules out louvers.

How would this be materially different from all the rain that will come in the bottom?

  • From: Shippensburg, PA
  • Registered: 2010-11-18
  • Posts: 1,963

Re: Want upward air flow through engine compartment

Just so you know, this scoop forced air down into the intercooler whether it was faced forward or backwards.

https://fastfotos.zenfolio.com/img/s/v-2/p1181978671-4.jpg

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  • Registered: 2009-07-19
  • Posts: 1,585

Re: Want upward air flow through engine compartment

It looks like this is what I'll be trying, a venturi to draw air up out of the underhood area.

I tested it last night out my truck window while driving to Norfolk. It was drawing a pretty good amount of air out of the cabin. For a total investment of $5, this works pretty well for moving air with no electricity or moving parts. I'll put a half dozen or so (or maybe more just for looks, something this good-looking is bound to enhance the appeal of any vehicle) on the hood to evacuate the hot air off the generator, and maybe a couple on the roof for battery box ventilation. It would be interesting to run one to a small tube for silent reverse helmet ventilation. 

http://www.carolinahondas.com/members/roger-albums-pj-picture6810-vent1.jpg
http://www.carolinahondas.com/members/roger-albums-pj-picture6812-vent3.jpg
http://www.carolinahondas.com/members/roger-albums-pj-picture6811-vent2.jpg

Everybody grab your brooms, it's shenanigans!