Ford Focus RS Forum banner

1 - 20 of 22 Posts

·
Registered
Joined
·
30 Posts
Discussion Starter #1
Perhaps there's no practical need for vents in the bonnet, but aesthetically would make the car look better.
 

·
Registered
Joined
·
376 Posts
I think a vented hood / bonnet would be a really good thing to have as long as it's functional. Ford has already said they are close to the cooling limit on the car so and additional air flow would help.
 

·
Registered
Joined
·
171 Posts
I think a vented hood / bonnet would be a really good thing to have as long as it's functional. Ford has already said they are close to the cooling limit on the car so and additional air flow would help.
My clone loves its hood vents, you can see the heat signature bellowing out at stop lights.
 

·
Premium Member
Joined
·
3,287 Posts
Just need to make sure placement of vents are not counter productive (ie: placed just forward of windshield in very high pressure area and pushing that air back in to the engine bay and increasing bay pressure behind radiator and reducing air flow through radiator) Granted may work great at a stop, but under speed work against the goal.
 

·
Registered
Joined
·
376 Posts
It would be pretty interesting to see what the temp are like with and without. I wonder if Ford even considered adding a heat extractor?
 

·
Registered
Joined
·
851 Posts
Early prototypes had hood vents, but were removed because they were not effective during testing.
 

·
Registered
Joined
·
1,551 Posts
Just need to make sure placement of vents are not counter productive (ie: placed just forward of windshield in very high pressure area and pushing that air back in to the engine bay and increasing bay pressure behind radiator and reducing air flow through radiator) Granted may work great at a stop, but under speed work against the goal.
I'm not an expert in these things but it would seem to me that the pressure above the hood would always be lower than below the hood. Certainly there are better places than others to put it, but I don't think you would see a flow going into the engine bay from outside.

Air Velocity Model


Air Pressure Model


Non-relevant source for images: https://mathieuhorsky.wordpress.com/tag/star-ccm/

My understanding is that a faster moving fluid will have a lower pressure than a slower moving fluid (all else being equal). I would think that any vent on the hood would draw air out of the engine bay. I can see that Ford may have decided in the cost benefit analysis that it wasn't making a significant difference, but it would seem to me that it would help, even if only minutely so. Besides hood vents look bad ass.
 

·
Premium Member
Joined
·
2,032 Posts
Just need to make sure placement of vents are not counter productive (ie: placed just forward of windshield in very high pressure area and pushing that air back in to the engine bay and increasing bay pressure behind radiator and reducing air flow through radiator) Granted may work great at a stop, but under speed work against the goal.
The back half of the hood and the base of the windshield is actually a fairly neutral area and the airflow under the car and through the radiator would probably pressurize the engine compartment enough to make this work. It would be really messy in the winter or on dirt roads, passing all the road salt and sand onto the windshield and paint. It's why automaker don't do it!
 

·
Registered
Joined
·
45 Posts
I would like to see more after market vents on the RS. I've googled a couple and I think the car looks way cooler (no pun intended) with them. I'm still in love with how it looks now though. I just like the aesthetic of the vents more, not to mention their function.
 

·
Registered
Joined
·
282 Posts
I have seen some photos or computer photos of Hood Vents in 2016 RS,s they are the same as the 2010 Focus RS

Now the main reason for some would be for looks the way to solve problems in this case would be to block of the underside of the hood vent so no air comes through or very just have a holes for water to get out off otherwise you will have two ponds on your bonnet
 

·
Registered
Joined
·
98 Posts
The pressure maps were developed at 160km/h on a WRX per the source data. I needed to look up the speed! The model was a simplified one, but enough thought put it to give ballpark values for above the hood. I would expect that the focus would see similar results.

But the underhood pressure/velocity is much harder to model accurately, and the pressure distribution is going to be much more chaotic than the above-hood profile. I agree w/ you that generally the underhood pressure will be greater, but there may be hot spots where it is concentrated and weak spots where the air gets channelled and pressure actually drops below the above-hood pressure (rendering vents counter-productive). Furthermore, sometimes the locations of the "hotspots" are speed dependent so an ideally placed vent at 80km/h could be counter-productive at 120km/h!

You get the idea - make the aftermarket do their homework and show your their test data.

Awesome post BTW.

I'm not an expert in these things but it would seem to me that the pressure above the hood would always be lower than below the hood. Certainly there are better places than others to put it, but I don't think you would see a flow going into the engine bay from outside.

Air Velocity Model


Air Pressure Model


Non-relevant source for images: https://mathieuhorsky.wordpress.com/tag/star-ccm/

My understanding is that a faster moving fluid will have a lower pressure than a slower moving fluid (all else being equal). I would think that any vent on the hood would draw air out of the engine bay. I can see that Ford may have decided in the cost benefit analysis that it wasn't making a significant difference, but it would seem to me that it would help, even if only minutely so. Besides hood vents look bad ass.
 

·
Registered
Joined
·
1,551 Posts
The pressure maps were developed at 160km/h on a WRX per the source data. I needed to look up the speed! The model was a simplified one, but enough thought put it to give ballpark values for above the hood. I would expect that the focus would see similar results.

But the underhood pressure/velocity is much harder to model accurately, and the pressure distribution is going to be much more chaotic than the above-hood profile. I agree w/ you that generally the underhood pressure will be greater, but there may be hot spots where it is concentrated and weak spots where the air gets channelled and pressure actually drops below the above-hood pressure (rendering vents counter-productive). Furthermore, sometimes the locations of the "hotspots" are speed dependent so an ideally placed vent at 80km/h could be counter-productive at 120km/h!

You get the idea - make the aftermarket do their homework and show your their test data.

Awesome post BTW.
Thanks, I try to preface when I know I don't know enough to say something definitively. I totally agree that simply wiring up some thermocouples and logging data is the best way way to know for sure.

Sent from my XT1254 using Tapatalk
 

·
Registered
Joined
·
1,019 Posts
My Mk2 Focus RS had bonnet (hood) vents as OE and there was never an issue with the engine bay getting dirty. I believe that AutoSpecialists in the UK do Airtec carbon vents for the Mk3 RS.
 

·
Registered
Joined
·
286 Posts
Doesn't the GTR and a few other super cars run hood vents?
GT500 have the hood vents in forward 1/3 of hood. It vents quite a bit hot air.
 
1 - 20 of 22 Posts
Top