hp vs torque
03-13-2005, 09:46 PM
#17
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Did I not specifically say that an inertia dyno is a good indicator of peppiness on the street or track? Did I not say that an inertia 'dyno' is a relative device and can be used to make comparisons on the same truck? What an inertia dyno is NOT is an accurate horsepower measuring device which can accurately derive the rear wheel horsepower between two very different trucks... say one with 300 HP vs. one with 600 HP, or one with 35" tires and steel wheels and one with 32" tires and aluminum wheels....
Please let me clarify some more.... So you say that you are interested in rear wheel horsepower...great I agree. Now as you said the horsepower is 'measured' in an inertia dyno by accelerating a known mass (the rollers). great we still agree. Now since the RATE of RPM change is what is used to 'calculate' the HP then all factors which effect the RATE of RPM rise of the truck itself will effect the calculated HP. My point is that as the RATE of RPM rise becomes very very rapid on high HP trucks, the vehicles own inertia becomes a HIGHER PERCENTAGE of the total inertia and thus the measured HP is less than is actually on tap. Yes we want to take into account the friction in the drive train, but if you want to measure HP you don’t want the inertia of the drivetrain to come into play. Yes if you want to measure quickness on the street and on the track you do want to factor in the vehicles rotating inertia. This is why an inertia dyno is not a true indicator of developed HP at the rear wheels or anywhere else. It is a tuning device and a relative device and a great indicator of vehicle accleration. But for two guys with totally different drivetrains, wheels, tires etc. to compare 'dyno' sheets looking at torque and horsepower for braggin rights it is woefully inadequate. Steady state developed horsepower is not effected by the inertia of the drivetrain. To correct your statement, no it doesnt take more horsepower to drive 44" tires (well a bit more while you are goin down the road due to increased rolling resistance) it takes more horsepower to ACCELERATE those 44's and that HP is used up prior to the rollers so that guy gets a lower HP readout on an inertia dyno than he really makes steady state while pulling a grade lets say. And guys with large single turbos really get hosed on an inertia dyno because just as their turbo is starting to spool the run is almost over and since its a RATE device they get a painfully low number printed out. But if he could have sat steady state with the pedal on the floor of another second or two and really got the turbo hot and lit, he would have had a much better printout. That’s why guys who are 'good' on an inertia dyno mash the go pedal while dragging the brakes for a couple of seconds holding the same RPM to get the turbo lit then let go of the brake pedal and start the record of the pull. I said before, make a 30 ton roller inertia dyno and I would agree 100% that would work great. But the ones I have seen don’t have enough mass in them to give a reasonable RATE of RPM increase on high HP trucks.
As for all the drag racing stats and who will be behind on race day, that’s cool but 99% of us don’t drag race our trucks, we tow the drag race cars and their trailers, and sled pull and do truck type stuff and that’s steady state HP and not effected by the inertia of the driveline.
As for a real dyno, a water brake or eddy current dyno, the actual delivered torque is measured with a torque arm of a known radius and a load cell. You can check the cal on it in like 5 minutes by hanging known weights from the arm. Then after the torque is measured HP is calculated by the well known formula: HP = torque*RPM/5,252.
PS, a common ramp dyno pull on an engine dyno is at 125 RPM rise per second. I've seen a 450 HP truck ramp at 500 RPM a second on an inertia dyno.... that’s way too fast of a ramp rate to be accurate with varying driveline inertias.....
I think that a Dyno jet is a great dyno for a 200 to 300 HP vehicle and is certainly perfect for little 150 HP ricers who have very little driveline inertia. But I don’t think it is a fair device on a 500+ HP single turbocharged diesel 1 ton dually for instance. The rollers are not heavy enough to give a slow enough rate of rise to accurately measure horsepower in that case.
Kevin
Please let me clarify some more.... So you say that you are interested in rear wheel horsepower...great I agree. Now as you said the horsepower is 'measured' in an inertia dyno by accelerating a known mass (the rollers). great we still agree. Now since the RATE of RPM change is what is used to 'calculate' the HP then all factors which effect the RATE of RPM rise of the truck itself will effect the calculated HP. My point is that as the RATE of RPM rise becomes very very rapid on high HP trucks, the vehicles own inertia becomes a HIGHER PERCENTAGE of the total inertia and thus the measured HP is less than is actually on tap. Yes we want to take into account the friction in the drive train, but if you want to measure HP you don’t want the inertia of the drivetrain to come into play. Yes if you want to measure quickness on the street and on the track you do want to factor in the vehicles rotating inertia. This is why an inertia dyno is not a true indicator of developed HP at the rear wheels or anywhere else. It is a tuning device and a relative device and a great indicator of vehicle accleration. But for two guys with totally different drivetrains, wheels, tires etc. to compare 'dyno' sheets looking at torque and horsepower for braggin rights it is woefully inadequate. Steady state developed horsepower is not effected by the inertia of the drivetrain. To correct your statement, no it doesnt take more horsepower to drive 44" tires (well a bit more while you are goin down the road due to increased rolling resistance) it takes more horsepower to ACCELERATE those 44's and that HP is used up prior to the rollers so that guy gets a lower HP readout on an inertia dyno than he really makes steady state while pulling a grade lets say. And guys with large single turbos really get hosed on an inertia dyno because just as their turbo is starting to spool the run is almost over and since its a RATE device they get a painfully low number printed out. But if he could have sat steady state with the pedal on the floor of another second or two and really got the turbo hot and lit, he would have had a much better printout. That’s why guys who are 'good' on an inertia dyno mash the go pedal while dragging the brakes for a couple of seconds holding the same RPM to get the turbo lit then let go of the brake pedal and start the record of the pull. I said before, make a 30 ton roller inertia dyno and I would agree 100% that would work great. But the ones I have seen don’t have enough mass in them to give a reasonable RATE of RPM increase on high HP trucks.
As for all the drag racing stats and who will be behind on race day, that’s cool but 99% of us don’t drag race our trucks, we tow the drag race cars and their trailers, and sled pull and do truck type stuff and that’s steady state HP and not effected by the inertia of the driveline.
As for a real dyno, a water brake or eddy current dyno, the actual delivered torque is measured with a torque arm of a known radius and a load cell. You can check the cal on it in like 5 minutes by hanging known weights from the arm. Then after the torque is measured HP is calculated by the well known formula: HP = torque*RPM/5,252.
PS, a common ramp dyno pull on an engine dyno is at 125 RPM rise per second. I've seen a 450 HP truck ramp at 500 RPM a second on an inertia dyno.... that’s way too fast of a ramp rate to be accurate with varying driveline inertias.....
I think that a Dyno jet is a great dyno for a 200 to 300 HP vehicle and is certainly perfect for little 150 HP ricers who have very little driveline inertia. But I don’t think it is a fair device on a 500+ HP single turbocharged diesel 1 ton dually for instance. The rollers are not heavy enough to give a slow enough rate of rise to accurately measure horsepower in that case.
Kevin
03-13-2005, 10:54 PM
#18
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Great info here, but I still have to say that 1000+lbs of torque is A LOT!
Just kidding. Actually I didnt realize that that much was a resonable thought. Might have to change my ways of thinking.
Just kidding. Actually I didnt realize that that much was a resonable thought. Might have to change my ways of thinking.
03-14-2005, 07:57 AM
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Originally posted by 600 Megawatts
Did I not specifically say that an inertia dyno is a good indicator of peppiness on the street or track? Did I not say that an inertia 'dyno' is a relative device and can be used to make comparisons on the same truck? What an inertia dyno is NOT is an accurate horsepower measuring device which can accurately derive the rear wheel horsepower between two very different trucks... say one with 300 HP vs. one with 600 HP, or one with 35" tires and steel wheels and one with 32" tires and aluminum wheels....
Please let me clarify some more.... So you say that you are interested in rear wheel horsepower...great I agree. Now as you said the horsepower is 'measured' in an inertia dyno by accelerating a known mass (the rollers). great we still agree. Now since the RATE of RPM change is what is used to 'calculate' the HP then all factors which effect the RATE of RPM rise of the truck itself will effect the calculated HP. My point is that as the RATE of RPM rise becomes very very rapid on high HP trucks, the vehicles own inertia becomes a HIGHER PERCENTAGE of the total inertia and thus the measured HP is less than is actually on tap. Yes we want to take into account the friction in the drive train, but if you want to measure HP you don’t want the inertia of the drivetrain to come into play. Yes if you want to measure quickness on the street and on the track you do want to factor in the vehicles rotating inertia. This is why an inertia dyno is not a true indicator of developed HP at the rear wheels or anywhere else. It is a tuning device and a relative device and a great indicator of vehicle accleration. But for two guys with totally different drivetrains, wheels, tires etc. to compare 'dyno' sheets looking at torque and horsepower for braggin rights it is woefully inadequate. Steady state developed horsepower is not effected by the inertia of the drivetrain. To correct your statement, no it doesnt take more horsepower to drive 44" tires (well a bit more while you are goin down the road due to increased rolling resistance) it takes more horsepower to ACCELERATE those 44's and that HP is used up prior to the rollers so that guy gets a lower HP readout on an inertia dyno than he really makes steady state while pulling a grade lets say. And guys with large single turbos really get hosed on an inertia dyno because just as their turbo is starting to spool the run is almost over and since its a RATE device they get a painfully low number printed out. But if he could have sat steady state with the pedal on the floor of another second or two and really got the turbo hot and lit, he would have had a much better printout. That’s why guys who are 'good' on an inertia dyno mash the go pedal while dragging the brakes for a couple of seconds holding the same RPM to get the turbo lit then let go of the brake pedal and start the record of the pull. I said before, make a 30 ton roller inertia dyno and I would agree 100% that would work great. But the ones I have seen don’t have enough mass in them to give a reasonable RATE of RPM increase on high HP trucks.
As for all the drag racing stats and who will be behind on race day, that’s cool but 99% of us don’t drag race our trucks, we tow the drag race cars and their trailers, and sled pull and do truck type stuff and that’s steady state HP and not effected by the inertia of the driveline.
As for a real dyno, a water brake or eddy current dyno, the actual delivered torque is measured with a torque arm of a known radius and a load cell. You can check the cal on it in like 5 minutes by hanging known weights from the arm. Then after the torque is measured HP is calculated by the well known formula: HP = torque*RPM/5,252.
PS, a common ramp dyno pull on an engine dyno is at 125 RPM rise per second. I've seen a 450 HP truck ramp at 500 RPM a second on an inertia dyno.... that’s way too fast of a ramp rate to be accurate with varying driveline inertias.....
I think that a Dyno jet is a great dyno for a 200 to 300 HP vehicle and is certainly perfect for little 150 HP ricers who have very little driveline inertia. But I don’t think it is a fair device on a 500+ HP single turbocharged diesel 1 ton dually for instance. The rollers are not heavy enough to give a slow enough rate of rise to accurately measure horsepower in that case.
Kevin
Did I not specifically say that an inertia dyno is a good indicator of peppiness on the street or track? Did I not say that an inertia 'dyno' is a relative device and can be used to make comparisons on the same truck? What an inertia dyno is NOT is an accurate horsepower measuring device which can accurately derive the rear wheel horsepower between two very different trucks... say one with 300 HP vs. one with 600 HP, or one with 35" tires and steel wheels and one with 32" tires and aluminum wheels....
Please let me clarify some more.... So you say that you are interested in rear wheel horsepower...great I agree. Now as you said the horsepower is 'measured' in an inertia dyno by accelerating a known mass (the rollers). great we still agree. Now since the RATE of RPM change is what is used to 'calculate' the HP then all factors which effect the RATE of RPM rise of the truck itself will effect the calculated HP. My point is that as the RATE of RPM rise becomes very very rapid on high HP trucks, the vehicles own inertia becomes a HIGHER PERCENTAGE of the total inertia and thus the measured HP is less than is actually on tap. Yes we want to take into account the friction in the drive train, but if you want to measure HP you don’t want the inertia of the drivetrain to come into play. Yes if you want to measure quickness on the street and on the track you do want to factor in the vehicles rotating inertia. This is why an inertia dyno is not a true indicator of developed HP at the rear wheels or anywhere else. It is a tuning device and a relative device and a great indicator of vehicle accleration. But for two guys with totally different drivetrains, wheels, tires etc. to compare 'dyno' sheets looking at torque and horsepower for braggin rights it is woefully inadequate. Steady state developed horsepower is not effected by the inertia of the drivetrain. To correct your statement, no it doesnt take more horsepower to drive 44" tires (well a bit more while you are goin down the road due to increased rolling resistance) it takes more horsepower to ACCELERATE those 44's and that HP is used up prior to the rollers so that guy gets a lower HP readout on an inertia dyno than he really makes steady state while pulling a grade lets say. And guys with large single turbos really get hosed on an inertia dyno because just as their turbo is starting to spool the run is almost over and since its a RATE device they get a painfully low number printed out. But if he could have sat steady state with the pedal on the floor of another second or two and really got the turbo hot and lit, he would have had a much better printout. That’s why guys who are 'good' on an inertia dyno mash the go pedal while dragging the brakes for a couple of seconds holding the same RPM to get the turbo lit then let go of the brake pedal and start the record of the pull. I said before, make a 30 ton roller inertia dyno and I would agree 100% that would work great. But the ones I have seen don’t have enough mass in them to give a reasonable RATE of RPM increase on high HP trucks.
As for all the drag racing stats and who will be behind on race day, that’s cool but 99% of us don’t drag race our trucks, we tow the drag race cars and their trailers, and sled pull and do truck type stuff and that’s steady state HP and not effected by the inertia of the driveline.
As for a real dyno, a water brake or eddy current dyno, the actual delivered torque is measured with a torque arm of a known radius and a load cell. You can check the cal on it in like 5 minutes by hanging known weights from the arm. Then after the torque is measured HP is calculated by the well known formula: HP = torque*RPM/5,252.
PS, a common ramp dyno pull on an engine dyno is at 125 RPM rise per second. I've seen a 450 HP truck ramp at 500 RPM a second on an inertia dyno.... that’s way too fast of a ramp rate to be accurate with varying driveline inertias.....
I think that a Dyno jet is a great dyno for a 200 to 300 HP vehicle and is certainly perfect for little 150 HP ricers who have very little driveline inertia. But I don’t think it is a fair device on a 500+ HP single turbocharged diesel 1 ton dually for instance. The rollers are not heavy enough to give a slow enough rate of rise to accurately measure horsepower in that case.
Kevin
You said "My point is that as the RATE of RPM rise becomes very very rapid on high HP trucks, the vehicles own inertia becomes a HIGHER PERCENTAGE of the total inertia and thus the measured HP is less than is actually on tap. Yes we want to take into account the friction in the drive train, but if you want to measure HP you don’t want the inertia of the drivetrain to come into play. Yes if you want to measure quickness on the street and on the track you do want to factor in the vehicles rotating inertia. This is why an inertia dyno is not a true indicator of developed HP at the rear wheels or anywhere else. "
HP is HP. You say we don't want to factor in drivetrain inertia for a true wheel hp number, yet you say you do want to factor it in when looking at street/strip time. Factoring in EVERYTHING between power made at the flywheel and power developed to the contact patch of the tire IS RWHP. So we agree then, the dyno jet is accurate for rear wheel hp.
You said "But for two guys with totally different drivetrains, wheels, tires etc. to compare 'dyno' sheets looking at torque and horsepower for braggin rights it is woefully inadequate. " Not sure what you are saying here. The higher rotating mass will result in less rwhp.
And you said "Yes if you want to measure quickness on the street and on the track you do want to factor in the vehicles rotating inertia. This is why an inertia dyno is not a true indicator of developed HP at the rear wheels or anywhere else. It is a tuning device and a relative device and a great indicator of vehicle accleration." Is acceleration not directly related to HP? How can factoring in the rotating inertia not be a part of rwhp?
A dyno jet doesn't use Rate of RPM rise to measure HP.
The bottom line I test a truck, I then calculate it's trap speed. At the track, it is always within a reasonable mph to what was expected. I calculate out with 200hp trucks, and 750hp trucks. You expect me to believe that we are ramping too fast to get accurate results. But the math from the track says we are not.
I'm not trying to change your mind about inertia dyno's. What I am trying to do is stop the post like you made where you make statements that are simply not true. You said there was no way a truck made 1100tq because of the inertia dyno that is a joke. Yet in our conversation you say that an inertia dyno will tell you less HP than is actually on tap. If you prefer a loading unit that is fine. I actually see benefit in one, but would always crosscheck with mine for driveability. And I also can provide numerous trucks that have been on mine machine then on load cell type machines of all HP levels that compare very well. Very well. I can also though show you some load cell numbers that make more STOCK power or TQ than rated at the factory flywheel. Never has happened with mine on any of the stock trucks I have tested. I quess the load cell dyno needed calibrating... something I never have to worry about.
03-14-2005, 08:55 AM
#20
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David, Sell your DynoJet before its too late! 
The world is gonna figure out yer DynoJet is a joke and its not gonna be worth nuthin'.
I will call Nascar and give them the same advice. Since just every team out there uses a DynoJet it may take a few weeks. With the higher funded teams having up to 6 DynoJets in one shop.
I have decided to forget the DynoJet and buy a Dyno Dynamics brand. Its made in Australia. You know, the country where they have never even built their own make of car. Lets forget the automobile, the Diesel engine and even the defination of HP were all original products of the US. The nice thing about the Dyno Dynamics is I can input all kinds of complex variables that will change my HP number when it suits me
Or there is always the Superflow. They even have a software package that will allow their dyno to graph much like a DynoJet when folks begin to complain the numbers are weird in comparison to the DynoJets that the overwhelming majority of the country is used to seeing.
Down with DynoJet. Down with DynoJet
Don~
The world is gonna figure out yer DynoJet is a joke and its not gonna be worth nuthin'.I will call Nascar and give them the same advice. Since just every team out there uses a DynoJet it may take a few weeks. With the higher funded teams having up to 6 DynoJets in one shop.
I have decided to forget the DynoJet and buy a Dyno Dynamics brand. Its made in Australia. You know, the country where they have never even built their own make of car. Lets forget the automobile, the Diesel engine and even the defination of HP were all original products of the US. The nice thing about the Dyno Dynamics is I can input all kinds of complex variables that will change my HP number when it suits me
Or there is always the Superflow. They even have a software package that will allow their dyno to graph much like a DynoJet when folks begin to complain the numbers are weird in comparison to the DynoJets that the overwhelming majority of the country is used to seeing.
Down with DynoJet. Down with DynoJet
Don~
03-14-2005, 09:00 AM
#21
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Originally posted by Don M
Lets forget .... even the defination of HP were all original products of the US.
Lets forget .... even the defination of HP were all original products of the US.
Rusty
Thanks for the correction.
03-14-2005, 09:06 AM
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I am in massive disagreement with you on this matter. That's ok, lets just agree to disagree. But let me try once more to explain this....
Higher drivetrain rotating mass will NOT effect steady rear wheel horsepower unless the rotating assembly is in a state of acceleration. This is my whole point. For a truck pulling a grade on the highway at 60 MPH steady state he is interested in steady state rear wheel horsepower. For holding a speed on a grade, the drivetrain rotating mass has nothing at all to do with it because the rotating mass is not accelerating. Yet on an inertia 'dyno' you are in a very rapid state of drivetrain acceleration, thus the rotating mass of the drivetrain being accelerated IS consuming HP which does not show up on the dyno ticket. Yes this is a great indicator of vehicle quickness, as I have said a thousand times. BUT IT IS NOT THE ACTUAL DEVELOPED HORSEPOWER AT THE REAR WHEELS FOR A STEADY STATE CONDITION LIKE PULLING A GRADE ON THE HIGHWAY. As the rate of RPM rise decreases then it becomes a more accurate number.
You need to think about the simple fact, that rotating mass has no effect on HP unless that mass is in a state of acceleration or deceleration. The higher the rate of accel the more HP that the mass will consume. Thus as the rate of accel of the rollers gets quicker the HP consumed by the trucks own drivetrain gets larger and so the dyno ticket gets smaller.
It all boils down to whether you want to measure the true delivered steady state horsepower at the rear wheels or the horsepower that's left over at the rear wheels while the vehicle is in a rapid state of acceleration. The former is more indicative of the real world use of our trucks, the latter is a GREAT indicator of how fast a truck feels and its drag strip time.
So if you want to compare trucks quickness in accelerating than an inertia dyno is the perfect tool, but if you want a true printout of delivered STEADY STATE horsepower than a loading dyno is the only thing to give you that.
And with regards the original post, I never said that there is no way that his truck never made 1,100 Ft*Lbs. The numbers could be perfectly accurate, and we don't really know since no RPM's were given in the original post. If we had RPM'S at the HP peak and the TQ peak given we would know spot on for sure. What I did say is that goofy HP/torque numbers can easily be the result of testing performed on an inertia dyno. The reasons for this I have enumerated above.
Kevin
Higher drivetrain rotating mass will NOT effect steady rear wheel horsepower unless the rotating assembly is in a state of acceleration. This is my whole point. For a truck pulling a grade on the highway at 60 MPH steady state he is interested in steady state rear wheel horsepower. For holding a speed on a grade, the drivetrain rotating mass has nothing at all to do with it because the rotating mass is not accelerating. Yet on an inertia 'dyno' you are in a very rapid state of drivetrain acceleration, thus the rotating mass of the drivetrain being accelerated IS consuming HP which does not show up on the dyno ticket. Yes this is a great indicator of vehicle quickness, as I have said a thousand times. BUT IT IS NOT THE ACTUAL DEVELOPED HORSEPOWER AT THE REAR WHEELS FOR A STEADY STATE CONDITION LIKE PULLING A GRADE ON THE HIGHWAY. As the rate of RPM rise decreases then it becomes a more accurate number.
You need to think about the simple fact, that rotating mass has no effect on HP unless that mass is in a state of acceleration or deceleration. The higher the rate of accel the more HP that the mass will consume. Thus as the rate of accel of the rollers gets quicker the HP consumed by the trucks own drivetrain gets larger and so the dyno ticket gets smaller.
It all boils down to whether you want to measure the true delivered steady state horsepower at the rear wheels or the horsepower that's left over at the rear wheels while the vehicle is in a rapid state of acceleration. The former is more indicative of the real world use of our trucks, the latter is a GREAT indicator of how fast a truck feels and its drag strip time.
So if you want to compare trucks quickness in accelerating than an inertia dyno is the perfect tool, but if you want a true printout of delivered STEADY STATE horsepower than a loading dyno is the only thing to give you that.
And with regards the original post, I never said that there is no way that his truck never made 1,100 Ft*Lbs. The numbers could be perfectly accurate, and we don't really know since no RPM's were given in the original post. If we had RPM'S at the HP peak and the TQ peak given we would know spot on for sure. What I did say is that goofy HP/torque numbers can easily be the result of testing performed on an inertia dyno. The reasons for this I have enumerated above.
Kevin
03-14-2005, 09:13 AM
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Hey Don, for crying out loud, we are not driving drag vehicles or NASCAR vehicles here. We are driving diesel trucks. Diesel trucks pull things at steady state.
For the record, I test my NHRA Superstock GT/FA drag car on a DYNOJET ... YES I do !!!! Because it gives me an outstanding indication of the ACCELERATION of my race car. I use it as an indication of modifications to my car and what my ET ticket will look like. I dont however take the HP/Torque numbers literally because they are not real numbers for a steady state condition. My drag car is never in a steady state condition, so a DynoJet is perfect. My diesel truck is however in a steady state condition while I am pulling the drag car and trailer up that 6% grade on the turnpike and for that a loading dyno is the tool to use.
Kevin
For the record, I test my NHRA Superstock GT/FA drag car on a DYNOJET ... YES I do !!!! Because it gives me an outstanding indication of the ACCELERATION of my race car. I use it as an indication of modifications to my car and what my ET ticket will look like. I dont however take the HP/Torque numbers literally because they are not real numbers for a steady state condition. My drag car is never in a steady state condition, so a DynoJet is perfect. My diesel truck is however in a steady state condition while I am pulling the drag car and trailer up that 6% grade on the turnpike and for that a loading dyno is the tool to use.
Kevin
03-14-2005, 09:26 AM
#25
DTR Advertiser
Kevin is correct above.
But for us, the name of the game is showing what we have at the rear wheels. After all the drivetrain loss. Steady state dyno testing has a minor roll in motorsports.
Load dynos certainly have their place and really shine in development of products for many companies, but it is not in drag racing or tuning for faster 1/4 mile times.
Don~
But for us, the name of the game is showing what we have at the rear wheels. After all the drivetrain loss. Steady state dyno testing has a minor roll in motorsports.
Load dynos certainly have their place and really shine in development of products for many companies, but it is not in drag racing or tuning for faster 1/4 mile times.
Don~
03-14-2005, 09:37 AM
#26
DTR Advertiser
Looks like we agree in part Kevin.
A steady state load dyno would need to be in a wind tunnel to simulate the same CFM of air across the intercooler and radiator. Most dont have this. Most are in a shop with a fan in front of the engine. LOL. Now thats a Joke. Except the dyno centers with large cooling towers and massive airflow in the range tens of thousands of CFM. Without these things a loading dyno might as well simulate the vehicle driving in reverse.
The DynoJet in comparison gets the run over with before a large amount of heat soak begins to change engine outputs.
Don~
A steady state load dyno would need to be in a wind tunnel to simulate the same CFM of air across the intercooler and radiator. Most dont have this. Most are in a shop with a fan in front of the engine. LOL. Now thats a Joke. Except the dyno centers with large cooling towers and massive airflow in the range tens of thousands of CFM. Without these things a loading dyno might as well simulate the vehicle driving in reverse.
The DynoJet in comparison gets the run over with before a large amount of heat soak begins to change engine outputs.
Don~
03-14-2005, 09:53 AM
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Now that was fun wasnt it???
Nothing like a heated debate early Monday AM to get the blood goin...
Yes, this is true about airflow through the IC... An inertia pull definately is over before heat soak set in, thats for sure....
Kevin
03-14-2005, 10:22 AM
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Don beat me to it. I agree with steady state, etc. etc. I also agree with loading without proper air flow or cooling that simulates a 60 mph road speed.
And again, all I am saying is that the original poster was asking about over 1000tq with 450hp. The replies were, not with a stock turbo, and your reply was to explain the goofy dno numbers it must have been an inertia dyno. In other words, you implied that a Dyno Jet numbers would have been inaccurate resulting in this guys bogus numbers.
I simply pointed out that based on what you believe an inertia dyno doesn't do well would have made his numbers lower, not higher. I also believe steady state hp for pulling a load (what our trucks do) is a result of the torque level obtained at the given hp level. Hence why diesels are good pullers.
And again, all I am saying is that the original poster was asking about over 1000tq with 450hp. The replies were, not with a stock turbo, and your reply was to explain the goofy dno numbers it must have been an inertia dyno. In other words, you implied that a Dyno Jet numbers would have been inaccurate resulting in this guys bogus numbers.
I simply pointed out that based on what you believe an inertia dyno doesn't do well would have made his numbers lower, not higher. I also believe steady state hp for pulling a load (what our trucks do) is a result of the torque level obtained at the given hp level. Hence why diesels are good pullers.
03-14-2005, 11:56 AM
#29
Registered User
Not to be a wet blanket here but due to the fact that horsepower, rpm, and torque are mathematically connected, proportional, the only way to get higher torque (1000) at a lower horsepower rating is that the horsepower measurement must come in at a lower rpm... Regardless of how it is tested. I think the term is "inversely proportional."
A 3300 rpm engine will have higher horsepower than a 2600 rpm engine that will pull the same weight, just in a narrower power band. A perfect example that I am experienced with are the commercial engines with low horsepower ratings but 50% higher torque as opposed to the pickup truck engines with the higher rpm limits.
As Don knows, a lot of this has to do with cam timing. Retarded cam timing raises the rpm of the power band and sees higher horsepower ratings with lower torque on the low end. Great for racing, not so hot for pulling heavy loads.
A 3300 rpm engine will have higher horsepower than a 2600 rpm engine that will pull the same weight, just in a narrower power band. A perfect example that I am experienced with are the commercial engines with low horsepower ratings but 50% higher torque as opposed to the pickup truck engines with the higher rpm limits.
As Don knows, a lot of this has to do with cam timing. Retarded cam timing raises the rpm of the power band and sees higher horsepower ratings with lower torque on the low end. Great for racing, not so hot for pulling heavy loads.
03-14-2005, 12:06 PM
#30
Chapter President
Uh oh.....here we go again with the torque and hp debate!!
......it can make for some interesting reading, I suppose! ........HID, haven't you learned you can't win at one of these threads? A glutton for punishment aren't ya?
.....yeah, me too!
......it can make for some interesting reading, I suppose! ........HID, haven't you learned you can't win at one of these threads? A glutton for punishment aren't ya? .....yeah, me too!