falcor75
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| posted on 14/6/23 at 05:32 AM |
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Rear engine bay/scuttle hot air evac?
I'm closing in on my first 500 km driven now and one thing I have noticed especially in the latest two weeks summer weather is that the hood just
infront of the scuttle seems to become the hottest area due to the hot air being trapped there with no way out. I would like to see some examples of
hot air evacuation and what you feel have done a difference on your car.
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nick205
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| posted on 14/6/23 at 08:37 AM |
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Any chance of adding some louvres across the top rear of the bonnet/scuttle area so the heat can escape?
Appreciate it looks to be Alloy bodywork. Might be a case of cutting some apetures and fitting ready made louvres.
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adampage
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| posted on 14/6/23 at 09:09 AM |
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Cool looking car!
And a volvo engine too?!
I think we need to see some photos of the engine bay.... Then I'd agree with either louvres or nicely swaged holes in the aluminium could look
pretty smart, either along the top back edge of the hood/bonnet, or maybe some at the side if you don't want them so visible on top?
Looks great though.....
Good luck!
Ad
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falcor75
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| posted on 14/6/23 at 10:12 AM |
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There is a build thread in that section of the forum
Louvres would have to be drained somehow as I have a few fuseboxes below that section of the hood. My first choice would be some vents just ahead of
the side repeaters but I dont know how effective that would be since its not the hottest part of the engine bay but I guess getting some circulation
would be better than none.
(edit, the side repeaters ar ethe small dots below/infront of the mirrors)
[Edited on 1 by falcor75]
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adampage
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| posted on 14/6/23 at 10:29 AM |
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Lovely work
Oh yeah, i thought it looked familiar, looks great!
Maybe on the side is your answer then, as you say about electrics up high that you want to keep dry.
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falcor75
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| posted on 14/6/23 at 10:58 AM |
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Here is a photo of the engine bay. My idea would place the vents between the expansion tank and black ECU box on the righthand side and just rear of
the airfilter on the lefthand side. Aslong as I can confirm I have good airflow over the sidepanels in that area it should be effective to draw hot
air out and get some circulation going in the rear area of the engine bay.
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adithorp
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| posted on 14/6/23 at 11:01 AM |
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When you say "due to the hot air being trapped there with no way out." does that mean you have a full floor? If not most air will be exiting
that way; though heat rising will cause the bonnet to trap it when stationary or going slow.
If you have a floor you need to make some provision for air to escape at the rear.
What appear to be side vents (?) might be ineffective if they're in dirty air near the wheels. Moving or extending them backwards might help.
Other than that, top vents...
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pigeondave
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| posted on 14/6/23 at 12:23 PM |
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From the pic it doesn't look like you have a full floor.
I'd try adding a floor using correx sheets as a quick temporary measure.
I'd try covering from the nose to in front of the engine and then maybe cut it shorter and shorter. To see if it sucks out the air.
What you're looking to do is get a (big as possible) pressure differential between the engine bay and the underside of the floor.
If you leave a gap its like blowing across the top of a bottle.
Check out some if the Julian Edgar stuff on youtube and the net
https://youtu.be/LglaWRbM3dQ
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Schrodinger
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| posted on 14/6/23 at 02:05 PM |
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Stylus_bonnet
I had a vent added to my Stylus( see above pic) to get rid of excess heat and it works very well at keeping temps down.
Keith
Aviemore
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SteveWalker
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| posted on 14/6/23 at 07:12 PM |
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From the photo of the engine bay, it looks like you could add a vent to the top rear of the bonnet, add a small lip around the top of the pedal box to
catch water that comes through it and a drain pipe to under the car.
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falcor75
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| posted on 15/6/23 at 04:16 AM |
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I dont think venting downwards will do much since the indicated area is a box with the only open side towards the front of the car. After a drive the
metal above the engine (apart from the exhaust) is noticably cooler than the area further back.
Its either out the top or out the sides to get som circulation in that area. Since I am in the process of adding a short windscreen I guess the top
will become a higher pressure zone which in that case really only leaves the sides.
I will steal som yarn from the Mrs and do some testing this weekend.
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JAG
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| posted on 15/6/23 at 11:59 AM |
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quote:
I will steal some yarn from the Mrs and do some testing this weekend
I would be very interested to see some pictures of this testing - please
I'm going to add a bonnet bulge to my car soon (I raised my engine a little) and I'm thinking of opening up the rearward edge to provide a
vent. However it will be within 30-40cm of the bottom of my windscreen sooooo 
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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nick205
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| posted on 15/6/23 at 03:07 PM |
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Another thought - have you got the exhaust manifold in the engine bay covered in heat wrap?
That may help reduce engine bay temperatures even before you add any venting.
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falcor75
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| posted on 16/6/23 at 04:47 AM |
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quote:
Originally posted by nick205
Another thought - have you got the exhaust manifold in the engine bay covered in heat wrap?
That may help reduce engine bay temperatures even before you add any venting.
I havnt, so thats a good idea. Might do that during the summer vacation.
We went out last night to get some video of the air flow. The topside of the hood is pretty good as expected but the side is a bit more erratic,
probably turbulence from the front wheel.
https://www.youtube.com/watch?v=slXdUBA9g2s&t=1s
[Edited on 1 by falcor75]
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JAG
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| posted on 16/6/23 at 01:21 PM |
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I noticed, in the video, that the rear of your bonnet bulge isn't sealed to the bonnet.
Could you open that a little more and use that to remove hot air?
So allow the hot air out and thereby prevent the hot air from travelling to the rear of the engine bay and accumulating ahead of the bulkhead?
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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falcor75
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| posted on 19/6/23 at 04:40 AM |
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Well the plan is to eventually close the end of the bulge up but as the car is new and the hood comes on and off alot its proven to be a usefull grab
handle for the time being.
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40inches
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| posted on 19/6/23 at 09:53 AM |
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I vented the back of the bonnet, it makes a huge difference to under bonnet temperature. I block them off in the winter and it keeps my feet warm
 
Description
 
Description
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JAG
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| posted on 20/6/23 at 08:21 AM |
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40inches - your vents are very close to the base of the windscreen.
Can you give us an idea of how close? It looks like 250-300mm?
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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