Does Driver Weight Effect Dyno Output?
08-08-2009 | 02:54 PM
#62
Rennlist Member
charlie, charlie, charlie !!! 
we already mentioned headwind, for a ground speed or true air speed of 0. Ill buy that all day. He is specifically talking about indicated air sped. air flow over the wing. stall speed, is when the plane is NOT flying, so just above stall speed, will result in air moving over the wings. the pitot tubes may not be regestering correctly, due to a high angle of attack, but it is very well known that if the plane is flying, air is moving over the wing, regardless of its relation to the ground. He said he saw "0 indicated" speed. I contend, and so does EVERYONE else in the aviation world, that flight is not possible without air flow over the wing, unless you are a helecopter , or have enough power to act like one. He also mentioned air flow from the propeller, which doesnt really count unless he had a bunch more power than his plane has. (see vectored thrust). plus, its a very turbulent air flow over the inner part of the wings.
we already mentioned headwind, for a ground speed or true air speed of 0. Ill buy that all day. He is specifically talking about indicated air sped. air flow over the wing. stall speed, is when the plane is NOT flying, so just above stall speed, will result in air moving over the wings. the pitot tubes may not be regestering correctly, due to a high angle of attack, but it is very well known that if the plane is flying, air is moving over the wing, regardless of its relation to the ground. He said he saw "0 indicated" speed. I contend, and so does EVERYONE else in the aviation world, that flight is not possible without air flow over the wing, unless you are a helecopter , or have enough power to act like one. He also mentioned air flow from the propeller, which doesnt really count unless he had a bunch more power than his plane has. (see vectored thrust). plus, its a very turbulent air flow over the inner part of the wings.Last edited by mark kibort; 08-08-2009 at 03:36 PM.
08-08-2009 | 03:06 PM
#63
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> A head wind > than stall speed will allow a plane to fly for hour's without momentum.
Only if you can somehow tether/anchor to the ground so that you can have that "headwind" happen to you, as opposed to just blowing you backwards.
Only if you can somehow tether/anchor to the ground so that you can have that "headwind" happen to you, as opposed to just blowing you backwards.
08-08-2009 | 03:10 PM
#64
Rennlist Member
No argument here regarding correlating ETs with dyno hp, regardless of which dyno was used. I certainly have a fration of you experiece with dynos, but nothing you have produced with mark and joes car has surprised me, nor what others have posted. Ive even done the dynopack vs dyno jet comparison and all sorts of mods, and most all results were pretty expected.
I know when you get into the post 100% volumetric efficiency world, its rocket science there. however you can look at formula 1 engines with under 3 lters making 800hp out of NA engines. maybe some of these concepts are in effect with louie ott's intake mods. 640rwhp out of a NA 7 liter is pretty stout, but more than 2x the displacement of a F1 engine and near the same hp.
I think you might be talking about Dennis engine. However, seeing the car on the track in a DE day and seeing its power vs mine i can say that its probably correct. after all, its not making more than the torque my original S4 Holbert motor made, when I got it after 15 years of abuse (ie 335rwhp 335rwt for the first 3 years and then down to 312rwhp before it was retired) . The cam just seemed to light it up passed 5krpm, due to the cam. It still is a little amazing, and would love to see it on a dynoject to really compare.
As far as a dynojet is concerned. you either move the rollers at a rate or you dont. forget about correction factors, its not really possible to cheat, or inflate, unless you dig in to the software and make a goal to cheat. how it compares to other dynos or ETs, is another game all together, Ill agree.
mk
I know when you get into the post 100% volumetric efficiency world, its rocket science there. however you can look at formula 1 engines with under 3 lters making 800hp out of NA engines.
maybe some of these concepts are in effect with louie ott's intake mods. 640rwhp out of a NA 7 liter is pretty stout, but more than 2x the displacement of a F1 engine and near the same hp.I think you might be talking about Dennis engine. However, seeing the car on the track in a DE day and seeing its power vs mine i can say that its probably correct. after all, its not making more than the torque my original S4 Holbert motor made, when I got it after 15 years of abuse (ie 335rwhp 335rwt for the first 3 years and then down to 312rwhp before it was retired) . The cam just seemed to light it up passed 5krpm, due to the cam. It still is a little amazing, and would love to see it on a dynoject to really compare.
As far as a dynojet is concerned. you either move the rollers at a rate or you dont. forget about correction factors, its not really possible to cheat, or inflate, unless you dig in to the software and make a goal to cheat. how it compares to other dynos or ETs, is another game all together, Ill agree.
mk
Hmm....
The great "dyno" debate, again. I love this stuff! Hell, I'm old enough to have/remember V-8 engines from Detroit that barely made one horsepower per cubic inch that would snap your head off. Now, things have evolved to the point if you can't make 1.5 horsepower per cubic inch (to the rear tires, naturally aspirated) you shouldn't be allowed to own tools. However, these engines don't seem to be much faster than the "old school" engines. Something got inflated or deflated, over the years. I suspect that it is the "dyno".
I've had a real interesting dyno experiment, over the past couple of months. Not going to go into details...the information has been very time consuming/expensive to gather...but I've learned a whole bunch about dynos and automatic 928's in the past couple of months.
I'm going to go with Danglerb, here...dyno results are worthless, when compared to ET's. My dyno results are always very low...hell, there's people doing minor changes to stock engines that claim they make more horsepower than my strokers do. This confuses me. The supercharger guys all seem to make over 500hp...some 150 horspower than most of my strokers. Funny that these guys can never seem to cross the finish line before we do.....this confuses me, even more.
I'm even more confused by the really "big" horsepower 928 engines. It's always been my understanding that on naturally apsirated engines, the only way to increase horsepower was to either make the engine bigger, increase the volumetric efficiency, or move the power range up in the rpm range (assuming that combustion is close to optimium efficiency.) For a given rpm range and a given displacement, it is pretty easy to come up with how volumetric efficient an engine is, once you know the horsepower....this is not rocket science. So, if I'm working on engines that make "X" horsepower and are close to 90% volumetrically efficient, what's the volumetric efficiency of an engine that makes "1.5X" horsepower? And more importantly than that, how the hell do you make a naturally aspirated engine that is 135% volumetric efficient? There's a whole bunch of really smart automotive engineers that would love to know how to do this....and, of course, so would I.
Of course, I'm easy to confuse. It's the age thing.
The great "dyno" debate, again. I love this stuff! Hell, I'm old enough to have/remember V-8 engines from Detroit that barely made one horsepower per cubic inch that would snap your head off. Now, things have evolved to the point if you can't make 1.5 horsepower per cubic inch (to the rear tires, naturally aspirated) you shouldn't be allowed to own tools. However, these engines don't seem to be much faster than the "old school" engines. Something got inflated or deflated, over the years. I suspect that it is the "dyno".
I've had a real interesting dyno experiment, over the past couple of months. Not going to go into details...the information has been very time consuming/expensive to gather...but I've learned a whole bunch about dynos and automatic 928's in the past couple of months.
I'm going to go with Danglerb, here...dyno results are worthless, when compared to ET's. My dyno results are always very low...hell, there's people doing minor changes to stock engines that claim they make more horsepower than my strokers do. This confuses me. The supercharger guys all seem to make over 500hp...some 150 horspower than most of my strokers. Funny that these guys can never seem to cross the finish line before we do.....this confuses me, even more.
I'm even more confused by the really "big" horsepower 928 engines. It's always been my understanding that on naturally apsirated engines, the only way to increase horsepower was to either make the engine bigger, increase the volumetric efficiency, or move the power range up in the rpm range (assuming that combustion is close to optimium efficiency.) For a given rpm range and a given displacement, it is pretty easy to come up with how volumetric efficient an engine is, once you know the horsepower....this is not rocket science. So, if I'm working on engines that make "X" horsepower and are close to 90% volumetrically efficient, what's the volumetric efficiency of an engine that makes "1.5X" horsepower? And more importantly than that, how the hell do you make a naturally aspirated engine that is 135% volumetric efficient? There's a whole bunch of really smart automotive engineers that would love to know how to do this....and, of course, so would I.
Of course, I'm easy to confuse. It's the age thing.
08-08-2009 | 03:14 PM
#65
Rennlist Member
I already mentioned head wind. we are talking indicated air speed, not ground speed. big difference. Its all relative.
Here is the snip of the post if you missed it:
4. your true air speed might have been 0, but that means you were flying in a pretty stiff headwind. This could have been why you looked out the window and didnt see the ground moving. But, for a plane to fly, you need air moving over the wings to the requirements of just above full power, full flaps stall speed.
Its all relative. Here is the snip of the post if you missed it:
4. your true air speed might have been 0, but that means you were flying in a pretty stiff headwind. This could have been why you looked out the window and didnt see the ground moving. But, for a plane to fly, you need air moving over the wings to the requirements of just above full power, full flaps stall speed.
08-08-2009 | 03:51 PM
#66
Rest in Peace
Rennlist Member
Rennlist Member
Trust me, BTDT, you do not want to do that.
08-08-2009 | 05:44 PM
#67
Rennlist Member
Mark, Mark, Mark; I was only objecting to your statement that flying must include momentum. If you define momentum as including velosity (p=mv) than the plane in my example does not require momentum. I agree with the rest of you statements, well, at least the ones that aren't way over my head.
08-08-2009 | 06:27 PM
#68
Nordschleife Master
So despite me being there and doing it, your argument is that it doesn't match theory as you know it, so it isn't technically flying? Do I get to add 3 seconds of riding a metal rock to my log book? 
I'm not done with dyno, but want to think about it more before I continue in a nice new thread.
I'm not done with dyno, but want to think about it more before I continue in a nice new thread.
08-08-2009 | 09:54 PM
#69
Rennlist Member
yep, you are right on charlie.
sorry, about the momentum comment. yes, the plane doesnt have the momentum if it is not moving forward relative to the ground. the air mass moving over the wing imparting a force on the wing keeping the plane aloft would have the momentum.
sorry, about the momentum comment. yes, the plane doesnt have the momentum if it is not moving forward relative to the ground. the air mass moving over the wing imparting a force on the wing keeping the plane aloft would have the momentum.
There's no need for a tether or a negative ground speed. As long as there is sufficient air speed over the wing the plane is flying. With a strong enuf headwind, the planes engine can hold you at 0 ground speed, or even allow you to move backwards in relation to the ground, and continue flying as long as you have fuel.
Mark, Mark, Mark; I was only objecting to your statement that flying must include momentum. If you define momentum as including velosity (p=mv) than the plane in my example does not require momentum. I agree with the rest of you statements, well, at least the ones that aren't way over my head.
Mark, Mark, Mark; I was only objecting to your statement that flying must include momentum. If you define momentum as including velosity (p=mv) than the plane in my example does not require momentum. I agree with the rest of you statements, well, at least the ones that aren't way over my head.
08-08-2009 | 10:01 PM
#70
Rennlist Member
Im just trying to undersand what you actually saw.
Do we agree that :
1. a wing must have air flowing over its surface to have force enough to fly?
2. a wings pitot tube , normallly located at the wing tips can get an inaccurate reading after stall if the angle of attack is high, even though air might still be flowing over the wing?
3. you might have had a quick moment of stall and 0 ground speed, but there might have been enough head wind to keep the plane aloft for a second or two?
4. there might have been a slight headwind?
5. flying is defined by lift greater or equal to gravity, and not resting on the ground
Do we agree that :
1. a wing must have air flowing over its surface to have force enough to fly?
2. a wings pitot tube , normallly located at the wing tips can get an inaccurate reading after stall if the angle of attack is high, even though air might still be flowing over the wing?
3. you might have had a quick moment of stall and 0 ground speed, but there might have been enough head wind to keep the plane aloft for a second or two?
4. there might have been a slight headwind?
5. flying is defined by lift greater or equal to gravity, and not resting on the ground
So despite me being there and doing it, your argument is that it doesn't match theory as you know it, so it isn't technically flying? Do I get to add 3 seconds of riding a metal rock to my log book?
I'm not done with dyno, but want to think about it more before I continue in a nice new thread.
I'm not done with dyno, but want to think about it more before I continue in a nice new thread.
08-08-2009 | 10:23 PM
#71
Rest in Peace
Rennlist Member
Rennlist Member
Just a guess, but you are not a pilot are you Mark?
Im just trying to undersand what you actually saw.
Do we agree that :
1. a wing must have air flowing over its surface to have force enough to fly?
2. a wings pitot tube , normallly located at the wing tips can get an inaccurate reading after stall if the angle of attack is high, even though air might still be flowing over the wing?
3. you might have had a quick moment of stall and 0 ground speed, but there might have been enough head wind to keep the plane aloft for a second or two?
4. there might have been a slight headwind?
5. flying is defined by lift greater or equal to gravity, and not resting on the ground
Do we agree that :
1. a wing must have air flowing over its surface to have force enough to fly?
2. a wings pitot tube , normallly located at the wing tips can get an inaccurate reading after stall if the angle of attack is high, even though air might still be flowing over the wing?
3. you might have had a quick moment of stall and 0 ground speed, but there might have been enough head wind to keep the plane aloft for a second or two?
4. there might have been a slight headwind?
5. flying is defined by lift greater or equal to gravity, and not resting on the ground
08-09-2009 | 04:19 AM
#72
Thread Starter
Not the sharpest tool in the shed
Rennlist Member
Rennlist Member
Whether Mark K. is or is not a pilot is irrelevant if what he posts is true and factual. In this case his comments are.
An anecdotal experience. Flying north from Ft Carson bombing range (Colo Springs). Encountered severe downdraft in our O-2 (military version of the Cessna Skymaster). Under full power we we still losing altitude at 200 ft/sec. Basically we were flying backwards in terms of ground position but in terms of airspeed we were screaming. Everything relative to aircraft is specific to speed of air over the wings.
BTW - we then encountered heavy hail, severe turbulance and ended up puking inside our flight suits instead of in the cabin or on the instruments. We landed at Buckley ANG base blind and damn near unable to read instruments. Both the command pilot and I purposely went to the O-Club and drank until everything seemed like a blur.
Having enjoyed two commercial airline "mishaps, one military hard dead stick landing and another private aircraft power loss hard bump landing, I know a little about airspeed and what it feels like when things go horribly wrong. Kibbort is dead on in his comments.
FWIW I am not a pilot, but I have spent a ton of hours as aircrew right seat / GIB guy in back on many aircraft types. Still get into the cockpits of aircraft that few have ever seen. I am not expert but knowledgable about basic concepts of flight.
An anecdotal experience. Flying north from Ft Carson bombing range (Colo Springs). Encountered severe downdraft in our O-2 (military version of the Cessna Skymaster). Under full power we we still losing altitude at 200 ft/sec. Basically we were flying backwards in terms of ground position but in terms of airspeed we were screaming. Everything relative to aircraft is specific to speed of air over the wings.
BTW - we then encountered heavy hail, severe turbulance and ended up puking inside our flight suits instead of in the cabin or on the instruments. We landed at Buckley ANG base blind and damn near unable to read instruments. Both the command pilot and I purposely went to the O-Club and drank until everything seemed like a blur.
Having enjoyed two commercial airline "mishaps, one military hard dead stick landing and another private aircraft power loss hard bump landing, I know a little about airspeed and what it feels like when things go horribly wrong. Kibbort is dead on in his comments.
FWIW I am not a pilot, but I have spent a ton of hours as aircrew right seat / GIB guy in back on many aircraft types. Still get into the cockpits of aircraft that few have ever seen. I am not expert but knowledgable about basic concepts of flight.
Last edited by S4ordie; 08-09-2009 at 05:59 AM. Reason: too many typos
08-09-2009 | 05:48 AM
#73
Nordschleife Master
Im just trying to undersand what you actually saw.
Do we agree that :
1. a wing must have air flowing over its surface to have force enough to fly?
2. a wings pitot tube , normallly located at the wing tips can get an inaccurate reading after stall if the angle of attack is high, even though air might still be flowing over the wing?
3. you might have had a quick moment of stall and 0 ground speed, but there might have been enough head wind to keep the plane aloft for a second or two?
4. there might have been a slight headwind?
5. flying is defined by lift greater or equal to gravity, and not resting on the ground
Do we agree that :
1. a wing must have air flowing over its surface to have force enough to fly?
2. a wings pitot tube , normallly located at the wing tips can get an inaccurate reading after stall if the angle of attack is high, even though air might still be flowing over the wing?
3. you might have had a quick moment of stall and 0 ground speed, but there might have been enough head wind to keep the plane aloft for a second or two?
4. there might have been a slight headwind?
5. flying is defined by lift greater or equal to gravity, and not resting on the ground
1. A wing needs differential pressure, air flowing over it is the conventional way that it happens.
2. I suppose, orientation of the plane was not static.
3. I don't recall any significant wind, but other effects may have been occurring, like warm air rising off the runway.
4. I still don't recall any significant wind.
5. Disagree, off the ground and I am flying. Maybe you are thinking of flying "well"?
Last edited by danglerb; 08-09-2009 at 06:05 AM.
08-09-2009 | 06:24 AM
#74
Rennlist Member
I was in the plane with an excellent view of the ground not moving out the side window, and airspeed needle resting on zero, yet here I am typing this message so it did fly ........................................................................ ...........................
A Cessna 150 will fly at zero indicated air speed with full power and full flaps, a very entertaining moment in my flight training.
A Cessna 150 will fly at zero indicated air speed with full power and full flaps, a very entertaining moment in my flight training.
A 928 will float at about 3000rpm in 5th gear.
It was a very entertaining moment in my drivers training.
(Mike, that's how silly your comment's sound to anyone that has any knowledge of the element's of flight.)
