Effectiveness of vented hoods/heat extractors

[meFiSTo]

Wasn't sure where to post this, but since I'm looking at this option for performance reasons in a track day setting, I'm plopping it here.

With he Seibon vented CF hood pre-production hood successfully test fitted and a commitment to build for our small community, I got to ruminating on whether I wanted this bit of bling for my car.

Most of the reason that I'd opt to get this would be justified by:

• Reduced weight on the nose of the car
• Apparent help in removing heat from under the hood

I poked around the web and found this interesting thread on a BMW forum: Effectiveness of Vented/Extractor Hoods

Some intriguing notes in there regarding tradeoffs in air flow and potential side-effects of diverting that air flow, aerodymamics, etc.

But wait, there's more: On page 2 of the thread there is a user by the name of raamaudio who chimes in about this topic (and his prior cars). Hah.

Anyway, left me still chewing on this mod. Not sure my application really warrants it, plus I'd have to paint it.

Have a look at the BMW thread. Comments welcome!

 

[Chuckable]

Was going to post a similar thread, so thanks for bringing up the topic! I'm no engineer, so can only add another source of information: http://www.motoiq.com/MagazineArticles/ID/3184/Project-S2000-DIY-Vented-Hood.aspx

I don't know if the Seibon vents are ideally placed or sized for heat extraction, nor how they handle the inevitable rain and snow. OEM vented hoods often have rain tray to divert water from underhood components.

 

[Harvick]

It would be interesting to see how much heat the Seibon vented hoods actually reduces in the engine compartment. This is a very cool topic.

 

[rodmoe]

It would be interesting to see how much heat the Seibon vented hoods actually reduces in the engine compartment. This is a very cool topic.

Haha I see what you did there ..

 

[Chuckable]

My friend's into Jeeps and a lot of them run these hood louvers: http://www.hoodlouvers.com/ The website has stories of how much heat they vent, for whatever it's worth.

 

[BlueBomber]

You know what I did for heat extraction? I removed the inner cowl panel thingie.

Hot air bleeds right out through there nicely.

 

[meFiSTo]

You know what I did for heat extraction? I removed the inner cowl panel thingie.

Hot air bleeds right out through there nicely.

Well, that is certainly more cost effective than some of the options! The thought of cutting up the hood to add those louvre things makes me a little queasy.

 

[OWfisting]

Curious how much these tiny hoods go for, if it would be worth it picking up one or two for experiments. There's gotta be some laying around scrapyards for dirt cheap.

 

[meFiSTo]

Curious how much these tiny hoods go for, if it would be worth it picking up one or two for experiments. There's gotta be some laying around scrapyards for dirt cheap.

If you are asking about the Seibon hood, ModBargains has them listed for $712: http://www.modbargains.com/seibon-carbon-fiber-vented-hood-Ford-Fiesta-ST.htm

However, BoostBumps has indicated that Seibon plans to offer forum members a discount (one way or another), once they have ramped up the capacity to build them or have accumulated inventory, or whatever their criterion is for triggering the group buy or discount or something.

I thought BoostBumps was connected to ModBargains, but am not sure now.

Anyway, I'm waiting to see what that forum group buy/discount/whatever looks like, but am still on the fence. I have a moon roof for @#$%#'s sake.

 

[BoostBumps]

^ Just to clarify, I have no affiliation to any vendors other than making contact with Seibon SoCal and inquiring if they intended to offer a CF hood for FiST and then announcing such on this forum...If and when they do plan on offering a group buy for the vented hood when its finally released it will probably be through a vendor they currently work with...

Back to OP topic...

 

[OWfisting]

If you are asking about the Seibon hood, ModBargains has them listed for $712: http://www.modbargains.com/seibon-carbon-fiber-vented-hood-Ford-Fiesta-ST.htm

Good info, but no. I was referring to picking up junk factory hoods for pennies on the dollar and hacking them up. Maybe take them to a hot rod shop and have louvers pressed in. Or even someone well-versed in composites take a crack at fitting some fiberglass or carbon fiber vents in the stock hood, kind of like the newer mustang gts, and include a template for people to ballsy enough to follow suit.

 

[RAAMaudio]

I have been involved in venting hoods for a very long time up to a full race Vette, nuts built BMW, etc....lots of research invested and time building one off parts, unfortunately I lost nearly all my pics from a system failure that ate my backup system as well......

1) removing the cowl trim to open up the area between the hood, firewall and base of windshield has long been known as the wrong approach as it is a low pressure area and does not allow engine bay heat out. It was used for cowl induction back in the muscle car days for this reason and sometimes still is on various race cars.

Note: With the shape of the hood, highly slopped windshield, etc, there may be much less low pressure in the cowl area on our cars than cars in the past but I would not take it for granted it is a proper way to vent heat from the engine bay. Simple test like the yarn method would help, sensor testing for heat flow and even further thermal imaging would be required to really see what is going on.

2) I like Siebon products and hoped they made a hood with bigger vents, The vented one is not going to help a great deal as just to small and possibly not optimally placed. I am considering a none vented version and add my own much larger vents, painting it body color, my interests are purely performance oriented, not cosmetic.

3) Thread on hood lovers, I have considered a set but only want the two longer ones or possibly a different set made by them.

http://www.fiestastforum.com/forum/threads/3563-Interesting-hood-lovers-I-might-order-a-set-%29

4) Ultimately sealing the outlet of the radiator and cleaning directing it out of the hood is the best way to do this. Cool to see it on the new Vettes though it does not seem big enough to flow it all out perhaps it is a split system but still a great improvement over the older cars, which I have had both C5 and C6 cars, C5 full race. There simply is not enough room in our engine bays for anything worth attempting unless some incredibly serious mods are done, like leaning the engine way back, etc....

Hope this helps, been there, done that, studied in depth including aerodynamics of it and spoken with an F1 aerodynamics engineer about it and other aspects of real aero work.

Sincerely,
Rick

 

[meFiSTo]

^ Just to clarify, I have no affiliation to any vendors other than making contact with Seibon SoCal and inquiring if they intended to offer a CF hood for FiST and then announcing such on this forum...If and when they do plan on offering a group buy for the vented hood when its finally released it will probably be through a vendor they currently work with...

Back to OP topic...

You know what, I think I got you confused with BlueBomber. Hah. Sorry for the confusiion.

 

[BoostBumps]

ha...no worries

 

[meFiSTo]

I'm tilting a bit toward the non-vented CF hood at the moment. There is venting at the very back of the engine bay in front of the windshield. I'm a little concerned that extracting air flow out the front (while useful I'm sure w/r/t to the radiator) might slow airflow to the remainder of the engine bay. I just am not sure if it is really more efficient to pull air from that spot. I like the weight savings, just wary of introducing a part that I think benefits performance when in fact it is potentially having an unintended (and uncertain) side effect.

Hey BoostBumps, any chance that Seibon might do a discount/group buy on the OEM style CF hood?

 

[RAAMaudio]

I asked them if they would make a lower cost one made to paint or pre paint them for us, they said no.

I would like to mold in my own design and paint the hood stock color, it gets a bit pricy to pay for a fully finished hood then do that to it.

 

[BoostBumps]

Hey BoostBumps, any chance that Seibon might do a discount/group buy on the OEM style CF hood?

I'll ask Ryan..never hurts to ask!

 

[D1JL]

Although I like the strength and lightness of CF, I have never been real fond of the plane CF look.
That being said I think a CF hood would look very good on a car the color of mine.
I however would keep the graphics I currently have and just reverse the color scheme on the hood.
That is instead of the orange hood with a black center and orange stripes.
I would have the CF hood with an orange center and black stripes.

In addition if I had one of these hoods, I would do some real world string tests sense a wind tunnel is not available.


Just some random thoughts.



Dave

 

[re-rx7]

plenty of fiesta part outs in my neck of the woods. Salvage yards probally sell a hood for 100 or so. Vented hoods only work as well as the ducting that allows them to.

 

[D1JL]

Vented hoods only work as well as the ducting that allows them to.

That is a very profound statement. LOL




Dave