Scoop = Boost ?

1. Scoop = Boost ?

How much boost could a scoop actually creat at 85mph ? I know it kind-of sounds off the wall but I know it has to do something. Has anyone ever messured with a boost guage ? Do certain scoops cause a lean condition on the top end(High RPM) ?

2.

3. Simple math bro, surface area(sq. inches) X velocity (easier in fpm) - cfm into carb, the difference is avail. air pressure in excess velocity, this can be converted to "w.c. (gotta go look for the formula for that)

I would be willing to bet it's negligable...Probably in the neighborhood of 1.5" w.c.

IMO the idea is to eliminate the negative pressure created by the air going into the carb...It wont be measurable in PSI...

GT

4. Yes, there is a pressure measurable. I really don't know about your scoop, but I know of drag racers that have put a pressure gauge in the base of a scoop on an injected engine, and they saw right at about 2.5 psi at full speed. And just under 2 psi at half track. Half track speed on this car was about 180. And that was with a 65 square inch opening. The amazing thing was the map on the pressure. It stayed very stable. I thought with intakes opening the pressure would fluctuate more.
So, just guessing, a good scoop at 85 may be pushing as much as .5 - .7 psi.

I have spoken with certain boat racers that have fattened up their jets to run with a scoop at speed and picked up MPH. But I don't know the specifics of how much, etc. And this was a 121 mph boat.

5.

6. Originally Posted by GT Jets
I would be willing to bet it's negligable...Probably in the neighborhood of 1.5" w.c.

IMO the idea is to eliminate the negative pressure created by the air going into the carb...It wont be measurable in PSI...

GT
You are probably correct. Many years ago I read somewhere that F-1 cars picked up about 20 hp by ram effect of their scoops at 180-200 mph those are the most engineered race cars in the world. An off the shelf boat scoop at 85 mph is probably worth zero.

Last year when I made 4 back to back passes off the Nos between 99.2 and 99.8 ( gps and radar) I wish I had thought of spinning the scoop around to see if there would have been a change with it run backwards for a 5th pass. There is always this Summer to do that I guess, or this weekend at the Tom Papp run.

Jim take a GPS for a ride and make some back to back passes, also once the air stacks up in the scoop it could work against you believe it or not. The F-1 engineers found out they got the most benefit by bleeding air out the back of the scoop with a long slit to relieve the excess pressure.

Hope that helps.

Sleeper CP

7. Originally Posted by Wannabe
Yes, there is a pressure measurable. I really don't know about your scoop, but I know of drag racers that have put a pressure gauge in the base of a scoop on an injected engine, and they saw right at about 2.5 psi at full speed. And just under 2 psi at half track. Half track speed on this car was about 180. And that was with a 65 square inch opening. The amazing thing was the map on the pressure. It stayed very stable. I thought with intakes opening the pressure would fluctuate more.
So, just guessing, a good scoop at 85 may be pushing as much as .5 - .7 psi.

I have spoken with certain boat racers that have fattened up their jets to run with a scoop at speed and picked up MPH. But I don't know the specifics of how much, etc. And this was a 121 mph boat.
There are so many variables here that it's almost impossible to say yes or no. A car is using the hood and front end (if designed right) to help feed that scoop where a boat scoop is behind a driver and the front of a boat...not the most aerodynamic thing. Bonneville cars traveling at 300mph with scoops designed to catch the air just right are seeing -maybe- 2# of boost. A boat at 80-85 with who-knows-what-kind of aerodynamics going on in the inlet will most likely have little positive effect on inlet pressure, and at best, feed the carbs some "clean" air. There are some scoops that IMO, just by looking at them, couldn't be helping things...
JMO...

8. Originally Posted by Wannabe
Yes, there is a pressure measurable. I really don't know about your scoop, but I know of drag racers that have put a pressure gauge in the base of a scoop on an injected engine, and they saw right at about 2.5 psi at full speed. And just under 2 psi at half track. Half track speed on this car was about 180. And that was with a 65 square inch opening. The amazing thing was the map on the pressure. It stayed very stable. I thought with intakes opening the pressure would fluctuate more.
So, just guessing, a good scoop at 85 may be pushing as much as .5 - .7 psi.

I have spoken with certain boat racers that have fattened up their jets to run with a scoop at speed and picked up MPH. But I don't know the specifics of how much, etc. And this was a 121 mph boat.
Seems suprising to me, I could definately see it at over 100 MPH, but would really question that much pressure at 85, if that's the case it would definately pose a huge gain in overall performance.

The circle racers would be better off leaving the scoop off and running a snorkle type deal, they almost always run them backwards...

GT

9. Hmm......

A properly designed divergent duct makes positive pressure at 160 MPH. And this is a wide open at both ends duct.

Divergent being the opposite of convergent. A convergent duct is a venturi.

But a scoop on a racing machine is directing air to the air metering device. So the point that the air feeding into the scoop exceeds what the engine is taking in, will be when you get a positive effect from it. So you can imagine every single application will be a little different.

10. Turbine engines are all a series of convergent and divergent ducts. The compressor section does not actually compress air like a piston does in a sealed chamber.

A turbocharger is the same way. It does so centrifugally.

If you look close at the impeller of a turbocharger, the space between the segments increases in area from where the air enters in the center to where it exits the outside diameter. This is really a bunch of divergent ducts arranged radially around the impeller wheel.

The hot section of the turbo is exactly the opposite. It is a series of convergent ducts arranged radially.

Crap not you got me started lol I can splain exactly how convergent ducts and divergent ducts do what they do if anyone is interested.

11. Originally Posted by GT Jets

The circle racers would be better off leaving the scoop off and running a snorkle type deal, they almost always run them backwards...

GT
That's a pretty blanket statement. I would guess most of the N/A circle boats are running with the scoop foward. K boats run them about 50/50, the GN's almost all run them backwards. For two reason, you are NEVER going to get the boat going fast enough to create pressure in the scoop of a blown circle boat, and there is way to much water flying in the GN class, and in 20 lapse you are bound to find some in the scoop. Take it to Long Beach with the salt spray, and the problem gets even worse.

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12. Oh, the car that did the pressure testing was a dragster. Scoop behind the driver in semi turbulant air. Rather similar to a boat, I figured.

13. So my thinking is telling me that equal pressure is better than negative pressure. But if I were to get it to go a little faster I may see a little possitive pressure. That will be a bit of possible free HP right ?

14. Think back to the glory days of the Chevelles with the air induction at the base of the windshield. It may have caused turbulence that "stopped" the air behind the deflector and made it easy for the engine to pull in.

Also, take a look at the winglets we often see on airplane wingtips. A pilot explained to me they had found that air moving off the bottom of the wing near the tip, was wrapping up, over, and on top which effectively reduced the usable control surface. If that logic could be applied to a rearward mounted scoop, the air leaving the trailing edges of the scoop may wrap back around into the scoop, not only due to the suction from the engine, but also from the natural path of the airflow...

15. [QUOTE=VDRIVERACING;493490]Think back to the glory days of the Chevelles with the air induction at the base of the windshield. It may have caused turbulence that "stopped" the air behind the deflector and made it easy for the engine to pull in.

QUOTE]

that wasn't the principle behind 'cowl induction' The base of the windshield is a high pressure area. The idea is still used today in Nascar

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Mount a very large forward facing funnel to your carb. A tuba for an example. @ 85 mph you will create pressure out of the mouthpeice BUT the drag created will FAR undo any power gained by "supercharging" the air.

HEY I GOT AN IDEA.... how bout 6 or 7 bilge blowers hooked up to a sealed scoop,,, j?k

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