Airflow vs. HP
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Joined: Oct 2002
Posts: 2,931
From: Upstate NY
Originally posted by racer7088
Oldstroker,
Maybe it's more accurate to measure the strain gauge than the ammeter?
Oh yes!
Also I know ANY number of dynos can measure sufficient tq at a shop like hendricks where they are only seeing 550 ft pounds of tq or so but they again are much more interested in power absorption because other wise they cannot do sustained testing. At Hendricks and most other NASCAR shops they have a water temp control system which is again POWER removal and absorption though heat. Again tq at a lower rpm is not the same as tq at a higher rpm. The higher hp version of tq heats the water much faster and there's a limit there.
Yep. Power is torque times rpm, right? No disagreement there. Measurement is our only basic difference here.
Even when a water brake is applying a TQ it is really absorbing power...
When you are quoting tq at the wheels at any rpm or mph you are quoting POWER though not tq. You are doing exactly what I said and are using the power to figure tq backwards. That's why power is all that matters. The TQ just determines what speed it's at depending on gearing.
Yep. An engine dyno is just a power absorber where torque and rpm can be measured accurately, and therefore power can be calculated.
The higher the rpm you can get that extra lb-ft, the more power you have. That's the Holy Grail: get more torque at the same rpm, or keep the torque from falling off faster than the rpm rises. The end result is more power.
How about I say I have one engine making 700 ft pounds or tq and one making 700 ft pounds of tq. Which one is faster with all else held equal? You should be able to answer that since tq is important. Are they the same since they produce the same tq output?
You like to fish? You seem to like baiting the hook.
If you meant which engine would produce quicker acceleration, you (or I) need to look at the torque curve vs. rpm (of course) over the rpm range the vehicle will use. IOW, area under the curve determines what will happen, not a specific maximum point.
How about engine A has 500 ft pounds of tq and engine B has 600 ft pounds of tq. Which one is faster? One has more tq than another so which one is faster? You should be able to answer that since tq is important correct. You can make acceleration and other work estimates easily knowing nothing but power and you can do or estimate absolutely nothing if you only know the tq an engine produces.
I guess they are biting today. Same answer: need the torque curve, or the power curve, for that matter. One can be derived from the other. However just one point on either torque or hp curve doesn't give enough information, does it? If A and B had those max torques occurring at the same rpm, B would probably be quicker. Maybe faster also. But that's another story.
I will be at the AETC if at all possible and at PRI here too so I'd love to meet you too. I know several guys at Hendricks. NO one here said you couldn't use a 901 to test within 1 per cent. Most people believe it is more accurate than that if you control the atmospheric variables and dyno variables.
Absolutely. To get 1/4% or even 1/8% accuracy requires unreal control of those factors. When we are looking for 10-20% gains in our modified street engines, 1% accuarcy isn't so bad, I guess.
We're about to get arrested for hijacking!
Oldstroker,
Maybe it's more accurate to measure the strain gauge than the ammeter?
Oh yes!
Also I know ANY number of dynos can measure sufficient tq at a shop like hendricks where they are only seeing 550 ft pounds of tq or so but they again are much more interested in power absorption because other wise they cannot do sustained testing. At Hendricks and most other NASCAR shops they have a water temp control system which is again POWER removal and absorption though heat. Again tq at a lower rpm is not the same as tq at a higher rpm. The higher hp version of tq heats the water much faster and there's a limit there.
Yep. Power is torque times rpm, right? No disagreement there. Measurement is our only basic difference here.
Even when a water brake is applying a TQ it is really absorbing power...
When you are quoting tq at the wheels at any rpm or mph you are quoting POWER though not tq. You are doing exactly what I said and are using the power to figure tq backwards. That's why power is all that matters. The TQ just determines what speed it's at depending on gearing.
Yep. An engine dyno is just a power absorber where torque and rpm can be measured accurately, and therefore power can be calculated.
The higher the rpm you can get that extra lb-ft, the more power you have. That's the Holy Grail: get more torque at the same rpm, or keep the torque from falling off faster than the rpm rises. The end result is more power.
How about I say I have one engine making 700 ft pounds or tq and one making 700 ft pounds of tq. Which one is faster with all else held equal? You should be able to answer that since tq is important. Are they the same since they produce the same tq output?
You like to fish? You seem to like baiting the hook.
If you meant which engine would produce quicker acceleration, you (or I) need to look at the torque curve vs. rpm (of course) over the rpm range the vehicle will use. IOW, area under the curve determines what will happen, not a specific maximum point.
How about engine A has 500 ft pounds of tq and engine B has 600 ft pounds of tq. Which one is faster? One has more tq than another so which one is faster? You should be able to answer that since tq is important correct. You can make acceleration and other work estimates easily knowing nothing but power and you can do or estimate absolutely nothing if you only know the tq an engine produces.
I guess they are biting today. Same answer: need the torque curve, or the power curve, for that matter. One can be derived from the other. However just one point on either torque or hp curve doesn't give enough information, does it? If A and B had those max torques occurring at the same rpm, B would probably be quicker. Maybe faster also. But that's another story.
I will be at the AETC if at all possible and at PRI here too so I'd love to meet you too. I know several guys at Hendricks. NO one here said you couldn't use a 901 to test within 1 per cent. Most people believe it is more accurate than that if you control the atmospheric variables and dyno variables.
Absolutely. To get 1/4% or even 1/8% accuracy requires unreal control of those factors. When we are looking for 10-20% gains in our modified street engines, 1% accuarcy isn't so bad, I guess.
We're about to get arrested for hijacking!
Last edited by OldSStroker; Oct 19, 2003 at 09:09 AM.
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Joined: Jan 2001
Posts: 293
From: houston, Tx
OldStroker,
""You like to fish? You seem to like baiting the hook.
If you meant which engine would produce quicker acceleration, you (or I) need to look at the torque curve vs. rpm (of course) over the rpm range the vehicle will use. IOW, area under the curve determines what will happen, not a specific maximum point. ""
You're talking about a POWER curve when you say tq at a certain rpm. Like I said tell me the acceleration of a car that weighs 3000 lb and has 300 ft lbs of tq. If you need to know the rpm it makes that tq at you're looking at a POWER curve again and not tq. If I know the power, I can calculate the tq I have at any particular wheel speed. Since gearing can manipulate the amount of tq I want the tq at the engine is not that important. If I want good tq at the wheels though at higher speed I need POWER again whether I have a little tq and a lot of rpm or a lot of tq and a little rpm.
Again the amount of power you can make tells you how fast you can accelerate not any tq you measured by itself. Power is force at a time based rate which is a useful thing to know. Back to my turbines or most any industrial engines. They don't even usually quote tq do they? They tell you the power they can make because they assume you will run a gearing package to make it work.
ZWILD,
You already have shown you don't know what you're talking about. The dyno jet measures power. There is no strain gauge of any kind on them. No force is measured.
""You like to fish? You seem to like baiting the hook.
If you meant which engine would produce quicker acceleration, you (or I) need to look at the torque curve vs. rpm (of course) over the rpm range the vehicle will use. IOW, area under the curve determines what will happen, not a specific maximum point. ""
You're talking about a POWER curve when you say tq at a certain rpm. Like I said tell me the acceleration of a car that weighs 3000 lb and has 300 ft lbs of tq. If you need to know the rpm it makes that tq at you're looking at a POWER curve again and not tq. If I know the power, I can calculate the tq I have at any particular wheel speed. Since gearing can manipulate the amount of tq I want the tq at the engine is not that important. If I want good tq at the wheels though at higher speed I need POWER again whether I have a little tq and a lot of rpm or a lot of tq and a little rpm.
Again the amount of power you can make tells you how fast you can accelerate not any tq you measured by itself. Power is force at a time based rate which is a useful thing to know. Back to my turbines or most any industrial engines. They don't even usually quote tq do they? They tell you the power they can make because they assume you will run a gearing package to make it work.
ZWILD,
You already have shown you don't know what you're talking about. The dyno jet measures power. There is no strain gauge of any kind on them. No force is measured.
Registered User
Joined: Jan 2001
Posts: 293
From: houston, Tx
OldStroker,
I absolutely concede the measurement arguments that at least more dynos measure tq as a function of power than don't and measure power directly although they can do both. Also to measure power you MUST make power with the engine being tested by doing actual work vs a time increment such as shearing water or generating electricity or increasing rotational energy of a drum. You cannot even measure tq unless the engine is loaded at speed which means it is making power. Tq in the absense of time is meaningless to us all. Tq with the time element such as power is all important.
"" guess they are biting today. Same answer: need the torque curve, or the power curve, for that matter. One can be derived from the other.""
I see you concede that you need to know the POWER curve and not just the tq so I rest my case. Unless the tq curve is plotted against engine speed it would tell you nothing since again it wouldn't tell you the power you were making.
I don't see that you challenged the fact that power can be measure as well without any tq element or engine speed element that can be back figured to give us tq or rpm as well so you also concede this by default or agree with me anyway.
Case in point the dyno jet or a generator being used to power other devices. Since you cannot create free power you must be making it and you can measure the power coming out of the generator requardless of what rpm of tq the engine creating the power is doing. A large recipricating engine or a smaller turbine can both make 25 MW even though they have different tq and engine speeds so tq as an independent variable alone is not important. Put it with rpm in the case of rotating equipment and then you can make useful sense of what you have since you now know hp.
I absolutely concede the measurement arguments that at least more dynos measure tq as a function of power than don't and measure power directly although they can do both. Also to measure power you MUST make power with the engine being tested by doing actual work vs a time increment such as shearing water or generating electricity or increasing rotational energy of a drum. You cannot even measure tq unless the engine is loaded at speed which means it is making power. Tq in the absense of time is meaningless to us all. Tq with the time element such as power is all important.
"" guess they are biting today. Same answer: need the torque curve, or the power curve, for that matter. One can be derived from the other.""
I see you concede that you need to know the POWER curve and not just the tq so I rest my case. Unless the tq curve is plotted against engine speed it would tell you nothing since again it wouldn't tell you the power you were making.
I don't see that you challenged the fact that power can be measure as well without any tq element or engine speed element that can be back figured to give us tq or rpm as well so you also concede this by default or agree with me anyway.
Case in point the dyno jet or a generator being used to power other devices. Since you cannot create free power you must be making it and you can measure the power coming out of the generator requardless of what rpm of tq the engine creating the power is doing. A large recipricating engine or a smaller turbine can both make 25 MW even though they have different tq and engine speeds so tq as an independent variable alone is not important. Put it with rpm in the case of rotating equipment and then you can make useful sense of what you have since you now know hp.
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Joined: Jan 2001
Posts: 293
From: houston, Tx
ZWILD,
""Torque is the expression of an applied rotational or twisting FORCE. And I believe the definition holds whether you are using lbs/ft or newtons( 1 kg*m/s^2) to record that force.
Power on the other hand, is the time rate at which work is done or energy emitted or transferred.""
No one's arguing about that. I think we all know what tq is. Newtons are NOT tq however so you are wrong again. "Newton-Meters" could be a tq measurement but not just Newtons. That would be the same as saying that pounds is tq. It's just force.
""Torque - the rotaional or twisting force - can and most certainly does exist without horsepower and it can and must be measured. Horsepower on the other hand does not exist, and cannot even be calculated unless you first measure the twisting force which is applied and determine how long it was applied.""
We already know that power can be measured without any tq being known at all. We don't need to have a tq sensor to find hp. Also I can apply tq all day long and do NO work and make NO power no matter how long it was applied. Application of tq without movement does nothing to accelerate anything.
""Without torque, your car for darn sure is not moving away from a rest, and it doubly-darn-sure ain't going to accelerate, even if you find the mythical frictionless surface.""
A mag lev train moves along fine with no tq. You don't need tq to accelerate things you just need some force acting though time that does work on the object in question. A cannonball or jet accelerates with no tq present. You can even have inertia engines like a rocket that is using inertial thrust but all have POWER ratings based on their abilities to do work over a certain amout of time on an object.
""I stand by my original assertion:
To the best of my knowledge, no-one has yet measured a single horsepower""
I guess you lose on all your arguments then since we do measure horsepower everyday. If I lifted 550 pounds a foot in one second against gravity I would have made one horsepower now wouldn't I? You measure things by doing something with measurable results. You saw me do it in the appropriate time increment and the appropriate distance with the appropriate weight so I made the 1 hp. Who knows what some tq was? I know I did that amount of work in that amount of time therefore I made 1 horsepower. You're wrong.
""Torque is the expression of an applied rotational or twisting FORCE. And I believe the definition holds whether you are using lbs/ft or newtons( 1 kg*m/s^2) to record that force.
Power on the other hand, is the time rate at which work is done or energy emitted or transferred.""
No one's arguing about that. I think we all know what tq is. Newtons are NOT tq however so you are wrong again. "Newton-Meters" could be a tq measurement but not just Newtons. That would be the same as saying that pounds is tq. It's just force.
""Torque - the rotaional or twisting force - can and most certainly does exist without horsepower and it can and must be measured. Horsepower on the other hand does not exist, and cannot even be calculated unless you first measure the twisting force which is applied and determine how long it was applied.""
We already know that power can be measured without any tq being known at all. We don't need to have a tq sensor to find hp. Also I can apply tq all day long and do NO work and make NO power no matter how long it was applied. Application of tq without movement does nothing to accelerate anything.
""Without torque, your car for darn sure is not moving away from a rest, and it doubly-darn-sure ain't going to accelerate, even if you find the mythical frictionless surface.""
A mag lev train moves along fine with no tq. You don't need tq to accelerate things you just need some force acting though time that does work on the object in question. A cannonball or jet accelerates with no tq present. You can even have inertia engines like a rocket that is using inertial thrust but all have POWER ratings based on their abilities to do work over a certain amout of time on an object.
""I stand by my original assertion:
To the best of my knowledge, no-one has yet measured a single horsepower""
I guess you lose on all your arguments then since we do measure horsepower everyday. If I lifted 550 pounds a foot in one second against gravity I would have made one horsepower now wouldn't I? You measure things by doing something with measurable results. You saw me do it in the appropriate time increment and the appropriate distance with the appropriate weight so I made the 1 hp. Who knows what some tq was? I know I did that amount of work in that amount of time therefore I made 1 horsepower. You're wrong.
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Joined: Dec 1969
Posts: 1,431
From: Pacific North West
WOW LOTS of good info!
I missed most of this while out in my shop swaping motors on my ElCamino.
I DO have some race info concerning my MAF readings. I do seem to peak with 370 or so GPS right where I make peak HP(6,800RPM). The number drops to about 340 where I shift at 7,000 RPM.
THis has got to be one of the best threads here in a while!
I need to get with the "strokers" on some component choosing for my 18* motor
I missed most of this while out in my shop swaping motors on my ElCamino.
I DO have some race info concerning my MAF readings. I do seem to peak with 370 or so GPS right where I make peak HP(6,800RPM). The number drops to about 340 where I shift at 7,000 RPM.
THis has got to be one of the best threads here in a while!
I need to get with the "strokers" on some component choosing for my 18* motor
Last edited by OneFlyn95z28; Oct 19, 2003 at 01:07 PM.
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Joined: Feb 2000
Posts: 1,009
From: Cincinnati, OH, USA
I agree it's turned into an interesting thread. But do you think one of the mods could split it into its own thread when the HP vs. torque discussion began? 
I might post some more questions/comments about airflow, and I know it'll get lost. It seems it'd be better to have these two subjects split, if the mods can do that.
EDIT: Oh and Ellis, could you find out what your HP and airflow was at 5600? I'd like to compare it to my data. Also, your engine specs if you wouldn't mind.
I might post some more questions/comments about airflow, and I know it'll get lost. It seems it'd be better to have these two subjects split, if the mods can do that.
EDIT: Oh and Ellis, could you find out what your HP and airflow was at 5600? I'd like to compare it to my data. Also, your engine specs if you wouldn't mind.
Last edited by JSK333; Oct 19, 2003 at 03:35 PM.
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