supercar cowl induction tid bit..

[markjohnson]

I think the most important aspect of '68-'69 L-88 Corvettes being dominant in Pure Stock is the massive amount of engine setback which is a major factor in a class with such tire limitations. It's obvious that a 12.5 Compression, massive solid lifter camshaft, factory 850 double pumper on an aluminum headed 427 CID might be a small factor also! Superior exhaust manifolds also compared to Camaros, Chevelles, etc. Chevrolet started the Cowl Induction theory with the '63 Z-11 Impala and even Smokey Yunick said that during testing, a Cowl Plenum air cleaner was good for approximately 1.00 PSI at speed. When this Pure Stock way of racing took off several years ago, it was obvious that as soon as someone properly prepared an L-88 Corvette, that it would be over for everything else.

[StealthBird]

Yes, but Smokey's "at speed" was NASCAR speed, as in 150+ mph. On a street car, even a fast drag car, there is virtually no ram effect, and certainly not through a plenum or cowl setup.

Holding your arm out the window and cupping your hand, you feel tremendous pressure. But getting that air to the carb, through a series of hoses, elbows, or ducting, you lose a lot of pressure. When that pressurized air does get to the carb, it has to overcome a wide open throttle condition, a carb that's gulping in huge amounts of air on every stroke, to the tune of around 800 cubic feet per minute, and then you need to build up even MORE pressure to force air into the cylinders, under a wide open throttle condition, revving at maybe 6,000 rpm. Air needs to fill the cylinders and carb plenum, refreshing it constantly while the engine sucking down air. A forward traveling car does not produce this much pressure, unless it's traveling at a VERY high speed and a VERY good air intake setup. On a street car, add in the restriction of air filter, and there's no chance of getting a ram effect at all.

Pro Stock cars use a huge air scoop, taller than it is wide. They discovered the optimum scoop height and inlet opening via wind tunnel testing in the 1990's. The older scoops used in the 70's and 80's were sort of guess work, but they did know they had to get the scoop high, very high, much higher than even the A12 style scoop, to be effective.

The whole Ram Air thing was a great marketing ploy by Pontiac. It brought in cold air, but there was no ram effect. By attaching a name to the setup, and marketing it as something unique to Pontiacs, was a stroke of genius. To this day, more people use the term "ram air" than any other term when referring to an cold air intake setup or hood scoop.

I've built a lot of ram air setups, some using a mix of Pontiac and Chevy parts, some using the hose-fed idea (I did a lot of those), and I've tried headlight entry, parking light entry, separate bumper scoops, etc. In every case, the car runs BETTER. No doubt about that. It's also much quieter from the interior under full throttle.

But I have to chuckle when I see ads selling ram air kits claiming 20% hp improvements. That sounds great for yer ego, but lousy for your bank account. [img]<<GRAEMLIN_URL>>/wink.gif[/img]

[GreenLS6]

Being a Pure stock racer, Long time car guy . I truly believe the biggest Plus to Cowl induction- or Ram air, is the bonus of a cooler air charge entering the engine rather than a forced effect. At least in a drag racing sence 11-12 second sub 120 mph. I'm sure that would be different case in much faster drag cars.

[GreenLS6]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: markjohnson</div><div class="ubbcode-body">I think the most important aspect of '68-'69 L-88 Corvettes being dominant in Pure Stock is the massive amount of engine setback which is a major factor in a class with such tire limitations. It's obvious that a 12.5 Compression, massive solid lifter camshaft, factory 850 double pumper on an aluminum headed 427 CID might be a small factor also! Superior exhaust manifolds also compared to Camaros, Chevelles, etc. Chevrolet started the Cowl Induction theory with the '63 Z-11 Impala and even Smokey Yunick said that during testing, a Cowl Plenum air cleaner was good for approximately 1.00 PSI at speed. When this Pure Stock way of racing took off several years ago, it was obvious that as soon as someone properly prepared an L-88 Corvette, that it would be over for everything else. </div></div>

You mean the biggest carb GM ever used, highest compression ratio, Best intake, Biggest solid cam ,best GM ex. manifolds, a 50-50 weight bias, best aero package, big tires. Might be an advantage over other cars ??? [img]<<GRAEMLIN_URL>>/dunno.gif[/img] Hahaha

[StealthBird]

Yes, it's the cool air that makes ram air setups effective, not any sort of ramming effect. But marketing is a great thing, and when you see the words &quot;ram air&quot;, people assume it's ramming air, but they don't.

Sort of like when people go to cruise nights, but everyone parks. [img]<<GRAEMLIN_URL>>/hmmm.gif[/img]

For NASCAR or other forms of racing with sustained high speeds, a ram effect can actually be achieved, and additional power can be had. But not with a street car, or with any of the factory setups.

[Fast67VelleN2O]

My personal favorite ram air setup of all time has to be the Ford Thunderbolt.