Alternative forced induction? Trans-Am racing series tricks?

[Hearsesrock427]

I swear I saw this on a documentary on the Trans-Am racing series.

Toward the end of the '60s, Ford and GM wanted to extract more power from their small displacement Trans-Am racing motors. Engine size was limited to something like 305 cubic inches by the racing series' rules. So the only other option was a power adder- such as a supercharger. But the rules prohibited forced induction systems. You coudn't just throw on a Paxton and run with it.

But the rules never said you couldn't create a sort of "natural" supercharging. In other words, forcing more air into the engine without a belt-driven supercharger. So one of them (I think it was Ford?) came up with their own forced induction system. It involved creating an area of high (air?) pressure inside the engine bay. And since pressure flows from low to high, this would in effect, force more air into the engine. Bada-bing. Supercharger effect without the supercharger. How cool is that?

Can anyone chime on about this? I'd love to try this on Ebyt. I remember seeing lots of ducts and shrounds and stuff in the documentary. They lead to the carb IIRC. But since I've got the EFI Windsor.... it'll be a bit different.

[turbo2256b]

Think they allowed hooking the air cleaner to an hole (usally retangular) in the cowel were the heater and cooling vents pulled air from. Some I THINK had inlets in the grill or head light pockets.

[Midnight Drifter]

NASCAR uses cowl induction "natural supercharging". It's worth about 35 hp@200mph/25hp@190 mph (restrictor plate)

[Bobcat]

What I was thinking of doing with my box, I was going to get an old dual snorkel air cleaner and run down snorkel tubes into the front bumper, thereby as the bumper pushes air forwards, its directly pushing air into my air cleaner. Though it's a carb setup, similar is easily done with EFI. Alternatively you could cut holes in your hood and fab up something along the lines of:


Now the downside to running natural aspiration on our cars is that. You really only get good gains from it if you're traveling at high speed. More air forced into engine - more power.
That's problematic for boxes because at I'd say 90 MPH the front end starts to lift and they become flying couches. Boxes weren't designed to go fast.

But theoretically it's a cool idea and I was going to do it for the cool factor but it's not really a super gain. Now if you want gains, turbo all the way.

[cld783]

That's problematic for boxes because at I'd say 90 MPH the front end starts to lift and they become flying couches. Boxes weren't designed to go fast.

i've never experienced it. my ho converted box has been pegged quite a few times at 100+

[sly]

if the ass is lower than the nose, it'll catch more air under it. get the car level or a little rake and it'll handle higher speeds easier (as long as the wheels/tires/ and other rotating parts are balanced).

[turbo2256b]

If you drop the front end a 1" ... 1 1/2" or so and or the rear raised a 1" or so combo it reduces front end lift helps with fuel economy to once the angle is dialed in.
What gave me the most trouble is the luggage rack on the trunk lid. Because of the angle of the cross piece speeds around 100 would cause the rear end to lift. Got a bit loose feeling mostly cornering at that speed or above. Wind in certian directions effected its handling at speed also. Removed the cross bar and speeds up around 160 no lift. Certian direction winds have to be realy strong to affect it now.
The front air dam added later was a real improvement at almost any speed.

[merc91]

a decently healthy v8 pulls air in at speeds of 200mph on up to 300mph at wot through the intake tract... until you can match those speeds you are building no pressure at all and creating only turbulance that hurts flow. Cool concepts but unfortunatly their performance gains are only cold air on sub-200mph cars

[Hearsesrock427]

Ah, I see. I kinda figured something like this was only suitable for race cars. I like the idea of cowl induction, but I can just see water pocket issues rearing their ugly head in the future. That plus the fact that any gains from alternative forced induction happen at such high speeds really kills it for me. A cool concept yes, but not a practical one.

if the ass is lower than the nose, it'll catch more air under it. get the car level or a little rake and it'll handle higher speeds easier (as long as the wheels/tires/ and other rotating parts are balanced).

I actually plan on having the nose and tail at the exact same height. If I get around to suspension and brake upgrades this summer (may very well need them, seeing as how Ebyt will be rocking long tubes and true duals!), that'll be one of the first things I tend to- after the rear disc brake conversion.

[88Vic]

How much are you spending to have longtubes made, or modified to fit?

[sly]

a decently healthy v8 pulls air in at speeds of 200mph on up to 300mph at wot through the intake tract... until you can match those speeds you are building no pressure at all and creating only turbulance that hurts flow. Cool concepts but unfortunatly their performance gains are only cold air on sub-200mph cars

somehow the redneck ram-air on my 88 works good enough to reduce the speed needed to crap out the vacuum to the AC if the check valve is hosed from 65 to 55... so YMMV.

[Hearsesrock427]

How much are you spending to have longtubes made, or modified to fit?

Burning $550 on these: http://www.latemodelrestoration.com/...-Header-Automa

Making them fit will likely set me back a couple hundred bucks. Won't know how much exactly until I see The Little Speed Shop on the 13th.

[merc91]

not sure what you are describing with your ac but at wot in any car your ac checkvalve will be closed because any street motor setup will be at no vaccume (14.8psi)... to overpower that checkvalve held vaccume you would need to generate over 8psi of boost. Even nascar guys at 200mph generate about 1/2psi of "boost" over atmospheres 14.8 for the 25hp gain.
Ya stick your hand out the window at only 70mph and you'd swear all that force would net you some air pressure via ram air but it's incredible the amount of air an engine pulls with each cylinder firing 40x/sec at 5000rpm which generates the 200mph+ runner air speeds... the reason such small visual porting changes net such large gains in comparassion.

On a side note I agree with the above, at 90mph+ the car in stock form started to float and is pretty scarry if you have even the slightest bend to negotiate... now the front end sits 1"higher than stock, and the rear sits 3.5" higher for a current 2" rake and the car "handles" much better up to the 130mph it's seen. The big addco swaybars, 6" wider tire stance, and stiffer ballenced rear suspension hellped allot aswell. Still wouldn't want to do any manouver that would be described as cornering though lol

[sly]

I'm describing the check valve being broken and just passing both ways... IE: no check. The engine looses enough vacuum to maintain that at 55 instead of 65 without the snorkel or 70 with the original intake. This is at cruise though, not WOT.

[merc91]

ahh gotcha. At part throttle, your throttle body still applies the same amount of resistance (vaccume) to the engine side regardless of the pressure being built up by a turbo/supercharger on the intake tubing side... it's the only control over the engine that directly correlates to the load to move the vehicle... a stock lopo will be at say 9in/hg vac cruising at 70mph, add 20lbs of boost aginst the tb and you will still be at 9in/hg of vac on the motor cruising at 70mph... you must have a vaccume leak or more resistance to moving causing you to have to open the throttle more and reduce vaccume, increasing engine load.