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ArjayS(at)AOL.COM
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 Posted: Mon Jul 19, 2010 6:05 am Post subject: Cowl (Nose Bowl) Performance |
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Hi Cliff
You bet!
I'll try to make my explainations understandable to technical and non-technical alike.
1. First, where does the 200 RPM come from? (For reference the AA5B)
The 200 RPM increase is due to a number of things. The cowling mods no longer uses the stock induction air system. The stock induction system was fed off of the engine upper cooling plenum. (routed over the delightfully warm cylinders, essentially preheating the air. The NACA induction air scoop which is part of the cowl mod takes ambient temperature air from out side of the cowling which reduces the temperature considerably. The NACA lowers the induction air temp by about 20 degrees. The net result is that the engine ingests cooler, denser air and breathes better. (More RPM)
2. The reduced inlet and planform drag of the cowling also contributes and allows the aircraft to use that extra 200 rpm. Most measurable under the following conditions: Wide open throttle leaned to 100 degrees on the rich side of peak at 1000 feet. Under these conditions the butterfly valve in the carburetor is completely open. (Max efficiency). If you are flying at a condition where the butterfly valve is not open the airspeed increase is not as easily apparent. Under these condition the true airspeed is 3 to 4 knots higher than stock.
That's the basic physics and I hope that's understandable. If not....just say we use fairy dust.
From: "flyv35b" <flyv35b(at)minetfiber.com>
200 RPM is a hugh increase in horsepower and/or a reduction in cooling drag
with a fixed pitch prop. And are you talking about the AA-5B or AG-5B
induction system as a reference? The PF exhaust on a Tiger only results in
about an 80 rpm increase in full throttle RPM. And from the AA-5B POH a 200
rpm increase (from 2500 to 2700 rpm) at 7000 ft PA results in a 15 mph
increase in cruise speed. Care to explain how the 200 rpm increase relates
to the 3-5 kts you mentioned?
Cliff [quote][b]
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flyv35b(at)minetfiber.com
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| Posted: Mon Jul 19, 2010 10:21 am Post subject: Cowl (Nose Bowl) Performance |
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Hi Cliff
You bet!
I'll try to make my explainations understandable to technical and non-technical alike.
1. First, where does the 200 RPM come from? (For reference the AA5B)
The 200 RPM increase is due to a number of things. The cowling mods no longer uses the stock induction air system. The stock induction system was fed off of the engine upper cooling plenum. (routed over the delightfully warm cylinders, essentially preheating the air. The NACA induction air scoop which is part of the cowl mod takes ambient temperature air from out side of the cowling which reduces the temperature considerably. The NACA lowers the induction air temp by about 20 degrees. The net result is that the engine ingests cooler, denser air and breathes better. (More RPM)
2. The reduced inlet and planform drag of the cowling also contributes and allows the aircraft to use that extra 200 rpm. Most measurable under the following conditions: Wide open throttle leaned to 100 degrees on the rich side of peak at 1000 feet. Under these conditions the butterfly valve in the carburetor is completely open. (Max efficiency). If you are flying at a condition where the butterfly valve is not open the airspeed increase is not as easily apparent. Under these condition the true airspeed is 3 to 4 knots higher than stock.
That's the basic physics and I hope that's understandable. If not....just say we use fairy dust.
Hi Rj,
You explanation above does not really explain any further what you said previously AND you didn't explain the relationship of 200 rpm increase to the 3-5 kts.
1. Let me see if I understand what you are tryping to say. Your "NEW" nosebowl is different that the one you are currently selling? How is it that much different?
2. The induction air temperature rise across the top of cylinders #1/#3 in the AA-5B is nowhere near 20F that you claim from testing that I am aware of. That airflow is moving across the top of the cylinders and along the top of the cowling and then flowing downward across the cylinders where it picks up heat. How is that fast moving air going to pick up heat when it is flow down across the cylinders away from the air flowing in to the inlet duct behind cylinder #3.
3. You are cliaming a 200 rpm increase due mostly to the cooler induction air. So what you are saying is that a stock AA-5B that will turn 2700 rpm at full throttle now will be able to turn 2900 rpm at full throttle with your "NEW" nosebowl? This would take an increase of nearly 25 hp to achieve. Even a PF exhaust only increases full throttle rpm by 80 as I mentioned. Incredible if it's true! And if so, why only 3-4 kts. I would think you would see much more speed increase than that. Take a look at the AA-5B POH and see what kind of speed increase occurs with 200 rpm more engine speed.
Sorry, but I don't see anything more than fairy dust here!
Cliff A&P/IA
[quote][b]
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ArjayS(at)AOL.COM
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| Posted: Mon Jul 19, 2010 10:34 am Post subject: Cowl (Nose Bowl) Performance |
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Hi Cliff!
Well that's easily solved. How about coming down as my guest to our facility. I can walk you through our process, you can do the measurements yourself and see what we do. We'll videotape everything for everyone and put it online. It would be a great opportunity to see inside our operation.
By the way, not to be argumentative, but if every 200 rpm equals 15 knots, that would kinda amazing. And we're talking about apples and oranges here as to where the power is measured, but I assume you know that.
PLEASE, take me up on the offer. At the least, we get to wine and dine you and you get to show how unaffected you are by that!
Cheers!
Rj Siegel CEO/LoPresti Aviation Engineering [quote][b]
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n2_narcosis(at)YAHOO.COM
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| Posted: Mon Jul 19, 2010 3:52 pm Post subject: Cowl (Nose Bowl) Performance |
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RJ
Ok, I am still new to this, but if you convince Cliff off your claims I'll buy one. In the meantime, are there any solid specs and performance increases on the Jaguar cowl?
--- On Mon, 7/19/10, ArjayS(at)aol.com <ArjayS(at)aol.com> wrote:
| Quote: |
From: ArjayS(at)aol.com <ArjayS(at)aol.com>
Subject: Re: Cowl (Nose Bowl) Performance
To: teamgrumman-list(at)matronics.com
Date: Monday, July 19, 2010, 1:33 PM
Hi Cliff!
Well that's easily solved. How about coming down as my guest to our facility. I can walk you through our process, you can do the measurements yourself and see what we do. We'll videotape everything for everyone and put it online. It would be a great opportunity to see inside our operation.
By the way, not to be argumentative, but if every 200 rpm equals 15 knots, that would kinda amazing. And we're talking about apples and oranges here as to where the power is measured, but I assume you know that.
PLEASE, take me up on the offer. At the least, we get to wine and dine you and you get to show how unaffected you are by that!
Cheers!
Rj Siegel CEO/LoPresti Aviation Engineering | Quote: |
st" rel=nofollow target=_blank>http://www.matronics.com/Navigator?TeamGrumman-List
et=_blank>http://forums.matronics.com
llow target=_blank>http://www.matronics.com/contribution
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[quote][b]
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