SpeedJunkie

I've been thinking about the Ram air2 hood and how it works. I quess it lets "rammed" cold dense air flow in through the vents and into the engine or the special air filter in front of the tb.
But what if you cut the back out and made it an open hood. Would the air just flow through the front and out the back that now looks like a cowl hood? Wouldn't it work as a ram air hood and a cowl hood when your say sitting in traffic? Best of both worlds. You guys tell me, its gotta be about pressure differences inside and outside the hood and car.

scauffiel

The only "ram air" that is worth a crap is "compressed" air; meaning supercharged via supercharger or turbocharger. You may get some benefit from a cooler intake charge via the ram air hood, but that's about it. I may cut out the back of my ram air II hood to allow air to flow through it at highway speeds, or I may add extracters somewhere to help move the air along instead of it getting trapped under hood. FWIW, I think it's worth a 1% horsepower increase for every ten degree drop in temp of the intake charge.

S.

SpeedJunkie

I understand that its not really"rammed air" i'm just wondering if the rammed effect will be lessen by doing this. I think it will work but i need to keep thinking about it.

scauffiel- Where will you put all your gauges then? Your setup now is so sweet!:hail:

scauffiel

If I went that route I'd have to open up the area off to the right of where the gauges are. I'd still like to put in those M3 vents along the sides... I've got another post somewhere about a "mod to my ram air hood" that has some pix in it... As far as lessening the effect - it would depend on if you had a tray that your open element filter sat in that kind of sealed it to the hood. It'd be open enough for air to flow around the filter as well as through it then out the back at speed. I'm not sure the effect would be measurable though.

S.

12 Sec GTA

The usbody source RAII hood is open in the back when you get it.

It works as both ram air, and a cowl hood when the front scoops are opened.

Sonar_un

DO NOT, I repeat.. DO NOT get US Body's ram air hood.

I wouldn't reccomend it to anyone, go for GT Auto's

Sonar_un

oh yeah, and it is not open in the back either.

12 Sec GTA

You saying the USB one isn't open?


Wow. Mine must have fallen out then



Why so against the USB hood? Mine is great.

SpeedJunkie

12 Sec GTA - No he said the the USbody one was open in the back.

scauffiel - Yeah I would really like to do something along those lines. Make a cowl around the filter that attaches to the the MAF or tb for SD. But you could also answer this- Is the bar in the back that is closed a structural piece? I know its all molded but I wonder if there is a design difference in the two hoods since one is open and one is closed.

scauffiel

Weird. I dunno because mine is a US Body hood and it wasn't cut out. Maybe they changed their mold or something. You'd probably need to check their site and see if they've changed the photos or give them a call to find out what the deal is. I think you could cut it out without any problem.

Steve

Matt427

The original cowl induction hood was found on the '69 Camaro. It was known as RPO ZL2, special ducted hood. In fact, at first it wasn't even called a cowl induction hood by GM. It was called the "Super Scoop" hood. I think the first official use of the term "cowl induction" was on the '70 Chevelle. Anyway, this hood allowed the low pressure air at the base of the windshield to be drawn into the engine when a throttle triggered solenoid opened a small door in the hood. When someone is talking about a cowl hood and whether one is functional or not, this is the process that I assume they are referring to. That being said, unless you have the air cleaner assembly sealed to a duct that is open at the cowl area of the hood, it can't be considered a functional cowl induction hood. Some guys will open the rear of the raised portion of a non-functional hood to allow the hot air to be drawn out. This process works according to Bernoulli's principle; air pressure decreases as velocity increases. When the car is moving forward, the higher pressure air under the hood will seek the lower pressure zone at the base of the windshield, thus moving the air out of the engine compartment and providing some cooling effect. Nevertheless, the original intention of this hood design was as an induction system, so if it does anything but that, I wouldn't call it a functional cowl induction hood.
Now to try and answer your original question. I suppose you could devise a duct system that draws air from both the front and rear of the hood, but I don't think there would be any advantage to doing so. As long as one or the other was sufficient to feed the engine with all the air it could possibly use, any additional intake areas in the hood would seem unnecessary. I'm not sure what you mean when you say it would work like a cowl hood when you're sitting in traffic since the car must be moving forward to create the low pressure zone at the base of the windshield, so I don't quite know how to address that part of the question. Maybe you can clarify that part and I'll take a stab at it later.

12 Sec GTA

Maybe this will help out some..

When stopped, with my car running and both fans on.. I can feel the air pouring out of the back "cowl" of my Ram Air II hood from US Body Source.



I asumme that is what you are referring to when saying"cowl like" when stopped.

SpeedJunkie

Yup thats exactly what I was talking about. I say"cowl induction" as the name of the hood and not in the verb form.

Matt427

That's cool, it's when someone says they have a "functional" cowl induction hood that it can get confusing.

redraif

WHY? When I was looking at buying a RAII hood I was going to go with US Body. What wrong with their hood. You can't say do not buy it and not say why!

Sonar_un

their quality is **** basically.

Unfinished edges, warps in the hood. The holes in the front are not cut open, so you have to modify that yourself. The shipping box was bad, in fact, I had cracks in my hood because of it. Its just not worth it. GT Auto makes the same hood, and I hear it is much better quality, plus they are a sponsor of the boards. You can't go wrong there.

scauffiel

Mine wasn't bad, a couple of little things but not like he's talking, so "your mileage may vary."

S.

devianb

Cutting the back out would let cool air in and hot air out, neither one will stay in the engine compartment. Hot air would be displaced by the cool air coming in, which forms into hot air on its way out. The effect is increased at greater speeds.

LT1guy

iTrader: (1)

I think everybody's fiberglass hood requires some extra work...I have tons of hours in Shannon's Suncoast RA 1, and it was pretty nice! Just the nature of fiberglass...

redraif

Yeah Joe and I wet sanded that thing for hours. Then the painter had to work on it as well.