I'm thinking of making a custom vented hood for my civic. I wanted to take some thermal pictures to understand where it was hottest. Though some of you would like to see.

These pictures were taken on a night when it was about 25F outside after I got home and parked in my garage. Car was parked fully warmed up and had only been sitting a few minutes when I shot them.

The thermal pictures are "hybrid" of pure thermal, and a sort of silhouette of the shape. This makes it easier to see what you are looking at than straight thermal. I also have it set to take a regular picture as well as the thermal so it's even clearer if there is any question.

 

you have my curiosity. if you would, take the rubber trim off the firewall that sits under the windshield. Will that cool the engine?

 

Anything that allows the hot air to vent should reduce bay temperatures. I am not interested in removing the seal as these typically cause whistles or warm air from the engine to work its way into the cabin (reducing AC efficiency)

Mostly I want to learn how to do this and the hood on this car is perfect to learn on as it's not in perfect shape. Even if I totally scrapped the hood I could get a replacement relatively cheap. I re-built a vent like this on one of my previous cars (I had a Mitsubishi Evo 9) so I am very familiar with how Mitsubishi designed theirs and I'd like to somewhat replicate it for functional reasons.

 

Guys - I have come back to working on this project. I have done a bit of research and I have an idea of what I want to do. I want to replicate almost what I see on an old s2000 thread I found somewhere else. Here is what I want to do. I now have this material (perforated aluminum)




I was also thinking of adding a sort of ramp underneath like this guy did- and it will create a surface to slow down the momentum of high pressure water spray when I go through the car wash. I realize it is not possible to eliminate water entry- but I want to do what I can to make sure that the water that enters is NOT under high pressure.




I did some cardboard mock-up work- and there isn't enough room to make this ramp low enough and far enough forward to prevent water from really blasting the plug wires.




As far as water entry goes- the spark plug wells would be at risk if water flows up and around the lip of the well



Another thing I noticed - is that the casting of the intake manifold has a sort of "cup" to it where it will retain water. You can see there is some debris in mine here. I was thinking about buying a used manifold to see if I can drill through some of the webbing where it separates the runners and may be able to make a way for the water to run though.







I was previously thinking of adding these types of vents in the spots shown with yellow


My concerns - Water in 3 places

1) Near the oil cap. I have looked at the oil cap and it seems to have a hard seal on the bottom that seals by pressing against the valve cover. It is not an area where water would really pool because it can fall off easily.

2) Spark plug wires where they enter the valve cover. It does have an up-step here, and water does not usually flow uphill- however if it hits here at high pressure it could be a problem. The top of the valve cover is right in the middle of where the vents would be.


3) intake manifold aluminum casting - the center of the intake manifold sits and looks like it has a cup shaped pool area where water can fill up and not spill out.


Please understand - this is mostly being done because I want to learn how to do it. This is about modding my talent set- not so much modding the car. If need be I can replace the hood if something goes wrong- I can get a replacement hood and paint it myself.

 

so I have been busy on this but I have done a poor job updating the progress and what I've learned.

First - intake manifold. The intake has a shape which almost acts as a big cup that can hold water. I bought a spare manifold- and drilled some 3/16" holes in the webbing. I did NOT pass into the runner path. Just to be greedy- I actually went through my 3/16" holes with a 1/4" drill bit and still did not create a leak. There is plenty of metal. This will give me a place for the water to drain out and prevent it from flooding if this is a problem.





Next - water on the spark plug wires and other areas.

I researched this for some time, and it bothered me. I saw that many "premium" aftermarket hoods performance have some sort of way to mitigate water entry through a form of water management - so re-routing the water to a safe area. I decided to copy.

I first prototyped some trays with a sort of "chute" which will move the water in front of the engine where it is safe to fall.






Once I got a design that I liked I copied it into CAD, and re-printed and made them again with cardboard. I then had enough confidence I was on the right track and made these with 1mm aluminum.








I thought about tig-welding the 2 parts of the tray together but went with rivets instead. This is crazy thin aluminum- I did try some of this but I had inconsistent results and it does warp the aluminum bad. I did some welding with this same metal a few years ago when I used it to make an lightweight aluminum undertray for my Evo ix- and it does distort with heat quite easily.

I also checked to make sure there was enough gap between the trays and the engine/wires so that nothing would touch. To the best of my measurements with metrology clay- there is about 15-18mm of distance under nominal conditions.

I then removed the hood and cut the holes. I added holes for clips to hold the trays, and installed the clips.








I did some calculations on how much over-hang was needed and then drew out an offset hole. I traced this design onto transparent paper, and scanned it into CAD. I then added a radius which I measured from a piece of sheetmetal that would work with a seal that I had found to cover the cut. This would ensure that it does not buckle in the corners when bent.










Here I installed the trays just to see how things would look. The seal is just mocked up for an idea of how things would look.







I then proceeded to take measurements on the height needed for the grate. I bent the metal into a C-shape and plan to rivet them together. I hand tweaked the gaps so there will be about 1mm margin between where the grate stops- and the seal starts. This will ensure a tight fit and good functionality








Here is how the trays install and look. I still have not riveted them together because I want to paint first.

 

Wow! Good work! Really interested in seeing the final product and results!

 

Thank you. It is embarrassing that it took me a while to get motivated and start working on this faster. I normally work on this car during the months when it is warmer and nicer out- since it is the "least nice" of my 4 cars and my first go-to if I have to drive it in the winter.

I have plans to do thermal imaging to monitor how effective this is, and I also have a go-pro camera that I would like to test in the engine bay during a car wash event, and during a rain storm event to see how good my aerodynamic calculations were to see if it keeps water off the intended areas. Hopefully I did not make a big mistake but that is what learning is.

If I call this a success- I will do the same style modification to my 2001 CRV. I have already started looking at the hood inner design and been daydreaming about how I would put the vents in and route the water. One thing I notice is the CRV has a TON more room above the engine.

 

I took everything apart and powder-coated the pieces. Before I did that I had to media blast them to make sure it had a rough surface where it would grip. I used glass-bead and I did this in my harbor freight sandblasting cabinet. I used a cheap powder-coating gun (it does not come out perfect I know) and I bake everything in a electric oven (same one I use to modify headlights with)






I used a 3m rubber seal adhesive and put everything back together.






Installing the hood by myself was tricky- I used my transmission jack with a foot pump to support the front. It fits just like it did before I removed it. I need to let the sealant fully cure for 48 hours before I go for a drive.

 

updated pictures showing thermal data...

Today it was pretty cool (about 50F) and I went for a drive and got the car full warmed up. You can see these pictures I took with the thermal camera.

One thing I like is the temperatures around the secondary ignition wires are about 20 degrees F cooler than last year, even with a warmer day that when I took the pictures last year.

 

Guys car wash testing worked great. The water runs forward in the trays. I actually see more water getting in from the sides of the hood where it has a gap to the fender than anywhere near the vents. Happy with my trays so far. I still want to see how this works during a really bad rainstorm at speed. This should cover all different fluid dynamics scenarios.

 

Very nice final results. I’ll bet that also brings down your IAT temperature, since you’re expelling so much heat from under the hood. I was noticing my IAT today was 91°, while the outside air temperature was only in the 70’s. That engine heat being trapped under the hood makes a big difference.

 

have you seen a difference in MPG?

 

Yes - but I have not checked or quantified how much. I am more interested in having my electronics wear less from thermal soak.

I don't really measure.

One thing I can say- it rained today pretty good for about 10 or so minutes I had to have the wipers on setting 2. I was moving about 65mph the entire time. The water seems to roll forward on the hood toward the glass- and when it hits the edge of where the seal is it tends to kind of pool up on the hood in front of the seal- almost like the flow out of the vents kind of keep it from entering or getting away. It seems to flow around the seal slowly and then continue back. It's hard to watch at speed and be safe really. When I got home I opened the hood and I didn't see water anywhere, only a slight bit (few drops) in the trays. I still want to do heavy downpour testing at high speed but it seems like the exhaust out of the hood keeps water away.

I think I have plenty of data now and am really willing to try this now on my RD1 CRV. It should go much faster since I know what to do. CRV has a lot more room to play with also.

 

Just an update - the car is now getting daily driven in rain snow and Chicago winters. No problems so far. It snowed about 3 inches the other day when I had it parked outside at work and I remote started it 10 minutes before walking out to leave. I have a cell phone remote starter so I can do it from long distance. I expected the snow to kind of melt and drain in the opening but it really did not (maybe it was too cold) I car was this literally every time I take the car out and when I park it I open the hood every night to put the battery tender on the battery itself- I think I get more water inside the hood area from the fender margins that through the vent itself. Everything seems to be holding up good so far.

 

I did this same project on my 2001 CRV. If you want to see it, click here: https://honda-tech.com/forums/honda-.../#post53028371

 

I installed a metal air hood louvre on my Del Sol, no before or after data. I can tell engine bay temps have lowered by touching the intake manifold after driving. Works fine because it is right over my turbo manifold and upper radiator hose.

 

I considered pre-made trim pieces like this that would fit in the cut but wanted to integrate it with the factory skeleton that supports the hood. The other thing was that I wanted a rain tray.

 

Update - I recently built myself a pressure sensing puck and bought a digital manometer. This measures differential pressures. I put one end under the hood and the other in several places on top. I am getting negative pressures on the line where the vents are installed so it is most certainly breathing heat out, and not in.

In the picture below, at 70mph I get about:
negative .6 inches of water at the front most tape spot
negative .15 inches of water in the mid spot- where the vents are
positive .15 inches of water at the spot closest to the glass (this is where you don't want to have a vent)

 

where did you get the rubber edge protectors? Could use some on the cut underside of mine.