A friend of mine is using these vents from Renault Mégane 3 rs. Field tested to give -14 degrees under the bonnet.
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GR Yaris WRC bonnet vents to reduce heat issues?
- Thread starter 6mt
- Start date
great effort. you might consider adding a gurney flap to the upper leading edge to make it more efficient. I cant see from your prototype, but do you plan to add a clip or similar so they hold in place? have you considered where water will flow into the engine compartment?
many thanks, they look neat. no internal cutting needed?? do they have built in clips so they simply push into place when the hole is cut correctly?
Hi,
it is designed with a spoiler-lip, so the airflow will be bended upwarts, that will help not to reduce the exit-area with turbulences.
But no gurney or so on.
It is primary designed for my 99% road-car, so maybe for a track-tool or rally-car there are maybe a few % to make it better, but I have to fullfill the rules of TÜV and it should look good too.
So, I was at my TÜV-station and showed my TÜV-inspector the prototype before I order the final parts and cut the bonnet.
Pedestran-security is a big topic, but should work, he only checks, if I can use the position I chose, becouse of the structure on the underside of the bonnet.
From his perspectiv, it is ok to cut the "subframe" but the just to check it finally, before I cut the bonnet.
But looks good so far !
Pedestran-security is a big topic, but should work, he only checks, if I can use the position I chose, becouse of the structure on the underside of the bonnet.
From his perspectiv, it is ok to cut the "subframe" but the just to check it finally, before I cut the bonnet.
But looks good so far !
Istiban
Devoted member
- Mar 5, 2023
- 97
- 170
These look good, any pics from underneath the bonnet?
- Dec 21, 2021
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Hey guys, so I've made my own vents from scratch and thought I'd share.
I managed to get the 3d scan of the bonnet and I profiled the bonnet vent to match the shape of the bonnet and the underside and to miss the bonnet stay.
I created a slot in the vent to slide in a mesh grille as well and I have created the profile of the vent to pull air out of the vent.
Here's what the vents looked like after lots of sanding, painting and clear coat.
I had help cutting the holes but it worked out really well.
Here's the final result!
I've also printed some flexible plastic "plugs" that block them off for when it is parked up and it might rain etc.
The heat they throw out when you park up after a drive is significant, almost like putting your hand infront of a hairdryer set to heat!
I managed to get the 3d scan of the bonnet and I profiled the bonnet vent to match the shape of the bonnet and the underside and to miss the bonnet stay.
I created a slot in the vent to slide in a mesh grille as well and I have created the profile of the vent to pull air out of the vent.
Here's what the vents looked like after lots of sanding, painting and clear coat.
I had help cutting the holes but it worked out really well.
Here's the final result!
I've also printed some flexible plastic "plugs" that block them off for when it is parked up and it might rain etc.
The heat they throw out when you park up after a drive is significant, almost like putting your hand infront of a hairdryer set to heat!
Just wondering if spacers under the rear bonnet hinges might be a non destructive track day alternative as all the vents I have seen to date do not improve the look of the car. I am not criticizing their effectiveness and if you are ok with them that's fine but if you want an unmolested bonnet?
- Dec 21, 2021
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Strongly disagree, I think my bonnet vents look OEM grade and suit the car hehe
So there is room for tall rally struts. I've removed them as free bonnet vents. And put back the one in the picture as I was getting VOC smells from the engine bay into the cabin ventilation. Might try again this year...
- Dec 21, 2021
- 134
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They're there for homologation purposes. When you remove them they give more clearance for the suspension struts in rally cars that run a larger suspension assembly.
Well obviously if you made them you will like them. My point was that if you like them that is ok but if you do not wish to modify your bonnet there may be another way. You clearly expended effort to create a part that works to create the desired effect and well done, as for some that is job done. Beauty is in the eye of the beholder after all.
I have tried some meddling and measuring with decreasing under bonnet pressure but the scuttle panel area is high pressure so any changes in that region won’t make that much difference. It’s slightly less pressure than the front of the rad but only a few pascals. Ideally vents are placed in the low pressure zone so the delta between the rad pack is much higher. Look at most mid engined sports cars for the ideal placement.
As above not very effective on the move, BUT when making a pitstop, or red light/queue in traffic etc, it will act as a chimney and allow hot air to escape at the highest point, instead of creating massive heat soak with in principle an air tight hood aka 'blanket'...
That's interesting. How about using the gap from the top of the front wing (under the bonnet) to direct air out from the front wing in front of the door with a vent situated approx where the one in the GR Corolla is?
My best guess is that would work better, based on the fact the base of the windscreen is just about the worst (at speed). As onehp said though if very slow moving any vents will let some heat out.
