Hey Guys,

Have done a search but haven't found exactly what I'm after.

I'm at the point of buying a bonnet for my street/track project.

I like the subtlety of the FEED bonnet for street use. The main reasoning for wanting a different bonnet is for cooling.

My question is - Is the Feed bonnet effective or should I be looking at something else? Those with experience having one, did it drop engine/engine bay temps? and by how much?

Please don't recommend a Scoot bonnet as I don't particularly like the OTT look of it. Especially for a street driven car.

Thanks in advance

 

It makes sense because the vents are over the heat source. I'll have to perform some tests to see if a vacuum effect takes place with the moving of the air over the vents and the windshield. Any vented hood should help with better airflow in the engine bay.

 

i believe this has been covered before,
i ran across it looking for info on scoot hoods

 

Any vent will be effective compared to none. However, it's the amount of effectiveness that may or may not make it worth it.

I like the Feed design, it is sleek. However, I imagine there is a middle ground of form & function. I would say a Mazdaspeed or Knightsport hood would be that area.

I run an RE vmount with no vented hood. I have ZERO cooling, IAT issues and my underhood temps are quite good. I think going single, proper wrapping, turbo blanket, and ceramic coating contributed to much of my success.

Just my .002

Logging these changes could be relatively hard. Identical loads, driving type, ambient temperature, and car would be needed to make any sort of practical comparison. It would be interesting to see though.

 

I think somebody tested the FEED, and determined that there was no venting at speed—like removing the weather strip on the stock hood, the high pressure area in front of the windshield pushes air in, not out.

It should help w/ heat soak on the street tho, when sitting, parked, etc.

 

I think over a long period of time the results should be clear or non-existent.

I'm under the belief that vented hoods do help. Whether or not it's the best bang for your buck depends on the state of your ride.

What else have you done to deal with heat, OP?

 

I agree they may not have much direct cooling effect, but I've noticed mine cools down a lot faster after it's parked. Less baking is a good thing unless you're making a cake.

 

We could rent time at aerodyn in NC and test multiple hoods, bumper and diffuser combination's. At some point I'd like to gather interest for something like that to test the aerodynamics of different kits. But we'd need to pool money together for the tests hahaha.

http://www.a2wt.com/

 

that's really cool, I had no idea there was something like that available to the public.

 

Yeah, there were a few threads on here discussing the effectiveness of the FEED hood. Crude methods of measuring airflow were used (small streamers I believe) but nonetheless adequate. I do not think the FEED hood pulls hot air from the engine bay while at speed, but like mentioned above it would be effective at removing heat from a car moving slowly, or parked reducing the effects of heat soak.

So really it would be good for a street car. As for a track car, if you are ducted correctly and take car of the sources for heat (exhaust and turbo mainly) then you should not really have any issues with heat. Sure it will be hot, but far from causing any issues. Not many vented hoods on the gran prix endurance racing cars... That is not to say there could not be great benefits from the right vented hood combined with a good VMount setup. MS, scoot, REA hood or a few others are better choices. For that and to take full advantage you need to create a seal between the hood and IC.

 

For cooling I have the following -

PWR ´Race´ Radiator (near on 100mm thick)
Wrapped dump pipe
Ceramic coated the exhaust manifold/turbo housings
Billion 72 degree C thermostat.

The information about it not dispelling heat during speed is exactly what I was after. On the street the car is lucky to see over 82 degrees C. Once on the track it warms up a bit but haven´t passed 98 degrees C yet. Seen as heat is the major killer for these engines I am trying to get my cooling system top notch.

So I´m going to take from this that the Re-Amemiya bonnet may be a better choice?

 

The vented hoods aren't designed to work by themselves. The stock cooling system is a bottom breather, you want to change it to be a top breather. That means sealing off the bottom so that air is forced out the top and not the bottom. Race cars get downforce from the bottom of the car, that means that there is some kind of scoops or aero work down there sucking air up into the engine bay. But the underbody coverings are always the best kept secrets. I've never seen any of the Japanese tuner companies give up their secret yet.

Christian v. Koenigsegg designed the cooling system of the Koenigsegg CCX as a thrust nozzle. He borrowed the method from WWII fighter planes. They had massively inefficient engines like ours and created tons of heat. Using thick, long radiators the cooling system uses high air pressure instead of high flow. The outlet is thinner than the inlet and as the pressure increases it eventually becomes thrust propelling the plane/whatever forward more quickly than it could go with engine power alone.
These methods are certainly used in racing today to create downforce. I'm sure you could make some duct work like other people have done with aluminum sheets, tin snips rivets, and weather stripping.

 

Yes they are.


Ducting is always recommended, but the sides are more of a problem than the bottom, given the stock undertray/radiator alignment.


Untrue.

 

I didn't design the stuff so don't shoot the messenger. This is just what Fujita Engineering (FEED) designed.

 

OP - the REA hood would provide better cooling (heat venting) characteristics than the FEED. BUT they also significantly change the looks of the car. Personally, I have an REA hood on order and I like the look. But some don't and the FEED hood keeps a very oem, clean look while providing a way for some heat to escape. Honestly if you are only seeing 98C at the track that is pretty good and nothing to worry about. Do you run AI (water/meth) injection? If not, that would be more of a wise investment of $$ over a vented hood.

Race cars get downforce from both the top, and bottom of their cars. From front canards, splitters, under plates (reduce lift), rear diffusers, front bumper cover design, and wings on the hatch. Think about formula cars, Rolex (gran prix) cars, or even Lamborghini, Ferrari's and the new GTR.

 

Barban,

Scoops are not required to create down-force. Bernoulli's Principal states that as velocity increases, pressure decreases. This principal is much more effective than a direct scoop. It is the same principal that is used to calculate lift from an airfoil.

 

I love my Feed hood.....it vents tons of heat at a standstill/parked....

 

Have you contacted them for ballpark pricing? Maybe I'm just lazy, blind, stupid, or some combination thereof, but the site didn't offer much in the way of cost.

If you ever get this pool started, contact me.

Thanks.
ryan

 

It used to have the prices listed. If it's your first time at the tunnel they gave a discount and the first few hours were like $350 then it went up to like $450 an hour. Looks like they removed the pricing information though. It does say "New lower pricing" call for information.

They have a staging area just outside the tunnel. So technically you could probably have two cars and while one is being tested make changes to the other.

 

I was a bit hasty in my response, If you take scoops out of that last quote then it is true. I've never seen a scoop on the underside of any racecar, but those bevels or ducts on the sides are prevalent in many rx7 under panel designs.

It would be more apt to say that radiator and intercooler design take advantage of vented hoods than to say vented hoods are intended to be used with top draft setups.

I'm not sure how I incited this or how to reply. I'm moderately familiar with aerodynamic principles, wing, and diffuser design. Underbody Aero is obviously very important in racing applications. My assertion was simply that cooling air is not, in my experience, sourced from under FR cars. Mid/rear engined cars may have to do so, I don't know.

 

Those are simple diffusers to help create lower pressure areas in the wheel wells. That appears to also have no splitter lip, so its only an under tray. So its more efficient aero wise than a regular(flat) under tray, but would be better if it had ~2-3" more material on the front protruding from the nose. You're very correct in that real ducting of the I/C and radiator out a vented hood would be by far the best solution. Thats a lot more work than most people would want to do though. Hence RE, scoot, KS style hoods popularity.

Scrub's idea would be great, however I doubt enough people would pony up the $$$ for that... A simple string test could tell you if the FEEDs vents are too close to the windshield or not, much cheaper than renting tunnel time. But if by any chance some people got together to rent tunnel time in the future, count me in, I've got all sorts of stuff I want to test!

 

That is quite a trick. Sounds like perpetual motion to me - just get rid of the engine and run on all that thrust automatically generated by the duct?

It sounds to me like that ducting with higher intake area than exit area (I assume that is what you mean?) is designed to generate higher air density for better cooling efficiency and thus smaller radiators, and would generate drag, not thrust. If true, the trade-off would be thrust for weight - maybe especially worth making for an aircraft at high altitude?

 

It's a lost technology called the "Meredith Effect". There isn't much information about it that I can find, but the Koenigsegg CCX uses it.

http://contrails.free.fr/refroid_meredith_en.php
http://www.aviationkb.com/Uwe/Forum....eredith-Effect

The pilots of the P-51 Mustangs reported that the airplane was capable of greater speeds than the engine could produce, it was the Meredith effect.

It's all way above my head. But I kind of get the concept. Don't ask me to engineer something like this though.

But yes it did say that the effect increased with speed and altitude.

 

Thanks for the info guys! Most helpful.

I have a WI kit but it hasn't been installed as yet. On my to do list.

Wind tunnel time would be amazing! but highly unlikely here in Australia I think, atleast for a reasonable price anyway.