Ram Air

[KMcCullah]

I'm working on ram air ducting for the F100 right now. This is something that I've read quite a bit on but never tried. Most guys report it's worth a few tenths in the quarter mile.  Hoping for some advice from the braintrust.

 The opening of the duct will pass approx. 6800 cfm at 120 mph. Ducted from the cowl. This air will be funneled down to a 1050 Dominator. One of my questions is, is it possible to have too much air? Also..... What happens to A/F ratio with ram air? Before I get too carried away with hours of TIG welding, I figured I should ask. I might be overkilling it again. Lol thanks guys.

[jayb]

It's not possible to have too much air as far as I know.  As far as A/F, the big change will be from a lower inlet air temperature, as compared to the truck without a fresh air induction package.  If you are adding the fresh air package, you may need to jet up a step, but I think I'd try it back to back at the track to see.  It may not be necessary, depending on how hot it was under the hood without the ram air.

[BattlestarGalactic]

I've seen a tenth or so difference in a few cars using ram air.  I tried it one day, 20 yrs ago with my car and saw no big change but I didn't change the tune up to see what it actually needed.   I've contemplated trying again since I still have the tubes, but need to build a bonnet for the carbs.

I know they used the cowl on many cars, but is it better then in the front?  Worse?   I've only see it used up front.

[cjshaker]

Even though the cowl area is a somewhat higher pressure area, I'd bet the ram effect would be much greater in the front. Still, any outside air is going to be better than under hood air.

[Falcon67]

I've noted .2~.3 in the 1/8 in back-to-back testing of a tear drop open to the engine compartment vs air cleaner sealed to the scoop.  So yea, IMHO it's worth the effort and no, you can't get too much air in there.

[Stangman]

I agree on th 2 or 3 tenths. In my case I got almost three tenths( front hood scoop with tray and foam seal on bottom of hood. But I know that at the time the tune was alittle on the fat side, maybe if it was leaner i might not have gotten as much.

[Drew Pojedinec]

All these results are cars tho.

My 76 pickup had a huge frontal area and a good bit of flow through.
Sure it’ll help, sure it’s a good idea. But I dunno if you’ll have the drastic results like you would from a car.

[mbrunson427]

Our '64 went from a 11.40 to an 11.20 by just hooking up the headlight snorkels. We didn't re-jet, may have been closer to 3 tenths off with a re-jet.

[KMcCullah]

Thanks for the input fellers.

One of my reasons for trying this is the fact that my local air is so thin. Typically 8k+ DA.  So...maybe if I can stuff more of this crappy air down the carb, I can shave a tenth or two. We'll see how it goes. I'm planning on welding in a bung to hook a manometer up to. Maybe we'll see a 1/4lb of boost. Lol Kidding aside, what I do know is, at 120 mph, there's one hell of a breeze coming out of the factory vents. I figure it must be something to do with the angle of the windshield. It sits up pretty good.

[cjshaker]

The cowl is just a natural high pressure area on all vehicles. Nascar teams did it clear back to the '50s I think, and Chevy had their cowl scoop, which is actually much better than Fords "ram air", although I'm not sure about the hood leading 427 Fairlane/Comet scoop, so it's a good place to grab that outside air.

[Cyclone03]

The cool/cold air may be the biggest benefit .

My car,Mustang, is FI so I can monitor inlet air temp.

180-200 v. Ambient plus 10deg or so.

[wowens]

Consider wrapping the bonnet and duck with a heat barrier. It should get you a few more degrees drop in air temp.
Thermo-tech 13575 works well on bends. Summit carries it.
It ain't pretty exposed under the hood, but it works .

[67428GT500]

What the hell is a "Bonnet"!? Do you mean a hood?     Damn Limies! 

                                                        -Keith

[shady]

Everything's better with a blue bonnet on it.

[KMcCullah]

It turned out to be a silver bonnet. I tacked some 1/16 aluminum together last weekend. It came out looking like a gigantic vacuum cleaner attachment. Dad figures "we're gonna suck our way into the 10's with this baby!" Lol He's always the optimist.