Need some guidance on n2o 928s
07-12-2005, 06:17 PM
#166
Rennlist Member
Originally Posted by m21sniper
Right now all i'm interested in is WHAT does the RPM in the formula relate to specifically(ie is it the rpm that peak torque occurs, rpm that redline occurs, etc)?
I want to know just because i want to know. It must be a specific measurement of something.
My question is.....what?
The part of the formula i'm talking about is the part in bold.
hp= torque*rpm/5252.
I want to know just because i want to know. It must be a specific measurement of something.
My question is.....what?
The part of the formula i'm talking about is the part in bold.
hp= torque*rpm/5252.
Sit down with a plot of torque vs RPM. Pick any point on that curve. For that point, read the RPM off the X-axis of the plot, and the torque off the Y-axis. Now multiply those numbers together and divide by 5250(or 5252, the difference won't be significant). The result will be the horsepower for that particular RPM. The formula will allow you to plot a single point on the horsepower curve. Repeat for all points on the torque curve, and you will obtain a horsepower curve.
That's it... the formula in no way assumes min or max ANYTHING.... all it does is allow you to plot a single point on the horsepower curve. Only after you have plotted all points using the formula can you then look at the HP curve and begin to evaluate min/max etc.
07-12-2005, 10:34 PM
#167
Rennlist Member
Yep. Didnt i say this on post #1!!!! ???
good way to look at it. Now, I hope EVERYONE understands!
mk
good way to look at it. Now, I hope EVERYONE understands!
mk
Originally Posted by SharkSkin
Here's another way to look at that:
Sit down with a plot of torque vs RPM. Pick any point on that curve. For that point, read the RPM off the X-axis of the plot, and the torque off the Y-axis. Now multiply those numbers together and divide by 5250(or 5252, the difference won't be significant). The result will be the horsepower for that particular RPM. The formula will allow you to plot a single point on the horsepower curve. Repeat for all points on the torque curve, and you will obtain a horsepower curve.
That's it... the formula in no way assumes min or max ANYTHING.... all it does is allow you to plot a single point on the horsepower curve. Only after you have plotted all points using the formula can you then look at the HP curve and begin to evaluate min/max etc.
Sit down with a plot of torque vs RPM. Pick any point on that curve. For that point, read the RPM off the X-axis of the plot, and the torque off the Y-axis. Now multiply those numbers together and divide by 5250(or 5252, the difference won't be significant). The result will be the horsepower for that particular RPM. The formula will allow you to plot a single point on the horsepower curve. Repeat for all points on the torque curve, and you will obtain a horsepower curve.
That's it... the formula in no way assumes min or max ANYTHING.... all it does is allow you to plot a single point on the horsepower curve. Only after you have plotted all points using the formula can you then look at the HP curve and begin to evaluate min/max etc.
07-12-2005, 10:39 PM
#168
Rennlist Member
Your a genius!
as ive always tried to say, its really all about the area under the HP curve used over the range of speeds. average HP works for our uses, but area under the curve is most accurate.
I would add that the engine "twists" the hardest , but the rear wheels will twist the hardest at max HP relative to any speed, due to gearing. this is where most folks get confused. again, 2nd gear at max hp has more "twist" than 3rd gear at max torque.
Mk
as ive always tried to say, its really all about the area under the HP curve used over the range of speeds. average HP works for our uses, but area under the curve is most accurate.
I would add that the engine "twists" the hardest , but the rear wheels will twist the hardest at max HP relative to any speed, due to gearing. this is where most folks get confused. again, 2nd gear at max hp has more "twist" than 3rd gear at max torque.
Mk
Originally Posted by James-man
Keep in mind that you are looking at torque CURVES and power CURVES.
You will have to come up with a better equation to match what is really happening for each unique engine - empirically, that is.
I am an idiot. That said....
If you look empirically, peak torque happens wherever in the RPM band that an engine happens to be able to twist the hardest. Peak HP RPM occurs much higher than peak torque. The two peaks essentially have nothing to do with each other.
Since Torque varies across the RPM band, you are forced to consider the torque CURVE in order to understand the Power curve mathematically. Torque needs to be represented as a function, not a constant. RPM is the variable.
I already said I am an idiot, but flame on dudes.
You will have to come up with a better equation to match what is really happening for each unique engine - empirically, that is.
I am an idiot. That said....
If you look empirically, peak torque happens wherever in the RPM band that an engine happens to be able to twist the hardest. Peak HP RPM occurs much higher than peak torque. The two peaks essentially have nothing to do with each other.
Since Torque varies across the RPM band, you are forced to consider the torque CURVE in order to understand the Power curve mathematically. Torque needs to be represented as a function, not a constant. RPM is the variable.
I already said I am an idiot, but flame on dudes.
07-12-2005, 10:53 PM
#169
Rennlist Member
I may not really understand your question's roots, as I know you are looking to get a clear picture of everything. (i hope this discussion has done some of that)
The RPM element of the equation is just that, RPM. speed of the engine. or any point of the in the driveline. Take the rpms of that part of the driveline, engine, or at the wheels, and multiply times torque and divide it by 5250 (the factor that puts ft/lb units into the form of HP . As we were talking about, it doesnt have any other significance, and doesnt point to anything other than a mathamatical cross over point.
the answer to the last RPM queston is also anywhere on the speed curve. idle, max torque, max hp , etc. you measure the torque anywhere and measure the speed at that point, and you get HP by your equation.
MK
The RPM element of the equation is just that, RPM. speed of the engine. or any point of the in the driveline. Take the rpms of that part of the driveline, engine, or at the wheels, and multiply times torque and divide it by 5250 (the factor that puts ft/lb units into the form of HP . As we were talking about, it doesnt have any other significance, and doesnt point to anything other than a mathamatical cross over point.
the answer to the last RPM queston is also anywhere on the speed curve. idle, max torque, max hp , etc. you measure the torque anywhere and measure the speed at that point, and you get HP by your equation.
MK
Originally Posted by m21sniper
"Torque is not a measure of "Work". It is a measure of applied force."
HP(or watts) is the measure of torque applied over time. IOW, work.
This is from your link:
" Torque and power are inescapably linked by the fact that horsepower equals torque (in ft-pounds) times RPM divided by 5250,"
RPM measured where is the question....
Is it RPM at torque peak, rpm at redline, or what?
HP(or watts) is the measure of torque applied over time. IOW, work.
This is from your link:
" Torque and power are inescapably linked by the fact that horsepower equals torque (in ft-pounds) times RPM divided by 5250,"
RPM measured where is the question....
Is it RPM at torque peak, rpm at redline, or what?
07-12-2005, 10:53 PM
#170
Banned
Thread Starter
Thanx shark skin, that's been driving me nuts.
"the answer to the last RPM queston is also anywhere on the speed curve. idle, max torque, max hp , etc. you measure the torque anywhere and measure the speed at that point, and you get HP by your equation."
I was shooting for the info sharkskin just shared.
At no point was i confused about the crossover point or the 5252 constant. It was the RPM that was bedevilling me all along.
I do not like to be bedeviled.
"the answer to the last RPM queston is also anywhere on the speed curve. idle, max torque, max hp , etc. you measure the torque anywhere and measure the speed at that point, and you get HP by your equation."
I was shooting for the info sharkskin just shared.
At no point was i confused about the crossover point or the 5252 constant. It was the RPM that was bedevilling me all along.
I do not like to be bedeviled.
07-13-2005, 04:59 AM
#171
Rennlist Member
So now, seeing how the math works, you can see WHY HP & Torque always cross at 5250... mathematically, they have to!
Anyway, glad I could help.
Oh, and... er... uh... did someone mention Nitrous?
Anyway, glad I could help.
Oh, and... er... uh... did someone mention Nitrous?
07-13-2005, 01:05 PM
#172
Rennlist Member
I spend hours explaining it up and down, forward and backward and you only thank sharkskin????? gezzzz, Im not feeling appreciated,and a little hurt! Ha ha!
(by the way the quote below was from my post too!)
MK
(by the way the quote below was from my post too!)
MK
Originally Posted by m21sniper
Thanx shark skin, that's been driving me nuts.
"the answer to the last RPM queston is also anywhere on the speed curve. idle, max torque, max hp , etc. you measure the torque anywhere and measure the speed at that point, and you get HP by your equation."
I was shooting for the info sharkskin just shared.
At no point was i confused about the crossover point or the 5252 constant. It was the RPM that was bedevilling me all along.
I do not like to be bedeviled.
"the answer to the last RPM queston is also anywhere on the speed curve. idle, max torque, max hp , etc. you measure the torque anywhere and measure the speed at that point, and you get HP by your equation."
I was shooting for the info sharkskin just shared.
At no point was i confused about the crossover point or the 5252 constant. It was the RPM that was bedevilling me all along.
I do not like to be bedeviled.
07-13-2005, 01:33 PM
#173
Rennlist Member
Originally Posted by mark kibort
I spend hours explaining it up and down, forward and backward and you only thank sharkskin????? gezzzz, Im not feeling appreciated,and a little hurt! Ha ha!
(by the way the quote below was from my post too!)
MK
(by the way the quote below was from my post too!)
MK
07-13-2005, 05:11 PM
#174
Banned
Thread Starter
I know it was from your post Mark. 
You spent so much time 'answering' my question because you were answering a question i was never asking.
You kept thinking i was talking about the cross-over, when in fact, i never was.
Sharkskin immediately identified and answered what i was asking, hence it only taking him one post.
Of course there are still some things that are irking me a bit, namely this....
If the rpm measurement in torque*rpm/5252= hp is a measurement that is taken at numerous equally spaced increments along the curve(which makes perfect sense), then by applying the formula the point at which the torque peak occurs is also the point where the max hp occurs.........according to the formula.
Since we all know that's not the case, there's still some unexplained ambiguity here. I'm getting the feeling that there's more going on with that formula than meets the eye.
You spent so much time 'answering' my question because you were answering a question i was never asking.
You kept thinking i was talking about the cross-over, when in fact, i never was.
Sharkskin immediately identified and answered what i was asking, hence it only taking him one post.
Of course there are still some things that are irking me a bit, namely this....
If the rpm measurement in torque*rpm/5252= hp is a measurement that is taken at numerous equally spaced increments along the curve(which makes perfect sense), then by applying the formula the point at which the torque peak occurs is also the point where the max hp occurs.........according to the formula.
Since we all know that's not the case, there's still some unexplained ambiguity here. I'm getting the feeling that there's more going on with that formula than meets the eye.
07-13-2005, 05:19 PM
#175
Banned
Thread Starter
"Now that Sniper and racer boy are talking civilized-like (does Kibort have a nickname yet?) a NOS installation should be forthcoming?????"
Yep, one will be coming once the guy that bought my t-type finishes making his payments to me(I have a complete repaint penciled in before the n2o mod).
Mark actually answered my n2o questions in just a couple posts, and i did some other research that confirmed what he said.
Apparently any 'wet' universal Nitrous system will work fine for me since no timing retard is required because the system automatically supplies the extra fuel neccesary to maintain a proper AFR, and because the n2o itself will significantly cool the air intake charge.
I'm in business once i get the extra 600 bucks.
I plan on getting a tunable 50-100hp system, and starting out with the 50hp jets, then will probably up it to 75hp once i'm convinced all is well under the hood.
I'll let you lads know how it works out.
Yep, one will be coming once the guy that bought my t-type finishes making his payments to me(I have a complete repaint penciled in before the n2o mod).
Mark actually answered my n2o questions in just a couple posts, and i did some other research that confirmed what he said.
Apparently any 'wet' universal Nitrous system will work fine for me since no timing retard is required because the system automatically supplies the extra fuel neccesary to maintain a proper AFR, and because the n2o itself will significantly cool the air intake charge.
I'm in business once i get the extra 600 bucks.
I plan on getting a tunable 50-100hp system, and starting out with the 50hp jets, then will probably up it to 75hp once i'm convinced all is well under the hood.
I'll let you lads know how it works out.
07-13-2005, 05:43 PM
#176
Rennlist Member
I know, i have a problem with doing that!!!! call me the jonny apple seed of the HP torque answers. 
as far as the equation, there is a problem in what you put down below. Yes, at any point in the torque curve, you can figure out HP. Think about this for a second , on any point on the torque curve, it is really hp anyway. there is always speed associated with it, due to the torque happening at a range of rpms. think of the torque curve as really a HP curve with the rpms stripped off. (ha ha)
no where will you find that at peak torque, that peak hp occures. the significance of PEAK hp is potentially at a rate of doing work that provides the greatest acceleration through the gears. peak hp is a point on the torque curve where torque x speed is the greatest. with HP, both torque and speed are equal factors , equally important to the measure of max HP
mk
as far as the equation, there is a problem in what you put down below. Yes, at any point in the torque curve, you can figure out HP. Think about this for a second , on any point on the torque curve, it is really hp anyway. there is always speed associated with it, due to the torque happening at a range of rpms. think of the torque curve as really a HP curve with the rpms stripped off. (ha ha)
no where will you find that at peak torque, that peak hp occures. the significance of PEAK hp is potentially at a rate of doing work that provides the greatest acceleration through the gears. peak hp is a point on the torque curve where torque x speed is the greatest. with HP, both torque and speed are equal factors , equally important to the measure of max HP
mk
Originally Posted by m21sniper
I know it was from your post Mark.
You spent so much time 'answering' my question because you were answering a question i was never asking.
You kept thinking i was talking about the cross-over, when in fact, i never was.
Sharkskin immediately identified and answered what i was asking, hence it only taking him one post.
Of course there are still some things that are irking me a bit, namely this....
If the rpm measurement in torque*rpm/5252= hp is a measurement that is taken at numerous equally spaced increments along the curve(which makes perfect sense), then by applying the formula the point at which the torque peak occurs is also the point where the max hp occurs.........according to the formula.
Since we all know that's not the case, there's still some unexplained ambiguity here. I'm getting the feeling that there's more going on with that formula than meets the eye.
You spent so much time 'answering' my question because you were answering a question i was never asking.
You kept thinking i was talking about the cross-over, when in fact, i never was.
Sharkskin immediately identified and answered what i was asking, hence it only taking him one post.
Of course there are still some things that are irking me a bit, namely this....
If the rpm measurement in torque*rpm/5252= hp is a measurement that is taken at numerous equally spaced increments along the curve(which makes perfect sense), then by applying the formula the point at which the torque peak occurs is also the point where the max hp occurs.........according to the formula.
Since we all know that's not the case, there's still some unexplained ambiguity here. I'm getting the feeling that there's more going on with that formula than meets the eye.
07-13-2005, 05:48 PM
#177
Rennlist Member
;Hey, ask andrew to look at the jet sizes that were used for 50hp. (both fuel and NOS jets) Nitrous Express gave me the 50hp through 100hp with all the jets that worked well for mixture and HP . 50hp was 50hp and 50ftlbs of torque.
mk
mk
Originally Posted by m21sniper
"Now that Sniper and racer boy are talking civilized-like (does Kibort have a nickname yet?) a NOS installation should be forthcoming?????"
Yep, one will be coming once the guy that bought my t-type finishes making his payments to me(I have a complete repaint penciled in before the n2o mod).
Mark actually answered my n2o questions in just a couple posts, and i did some other research that confirmed what he said.
Apparently any 'wet' universal Nitrous system will work fine for me since no timing retard is required because the system automatically supplies the extra fuel neccesary to maintain a proper AFR, and because the n2o itself will significantly cool the air intake charge.
I'm in business once i get the extra 600 bucks.
I plan on getting a tunable 50-100hp system, and starting out with the 50hp jets, then will probably up it to 75hp once i'm convinced all is well under the hood.
I'll let you lads know how it works out.
Yep, one will be coming once the guy that bought my t-type finishes making his payments to me(I have a complete repaint penciled in before the n2o mod).
Mark actually answered my n2o questions in just a couple posts, and i did some other research that confirmed what he said.
Apparently any 'wet' universal Nitrous system will work fine for me since no timing retard is required because the system automatically supplies the extra fuel neccesary to maintain a proper AFR, and because the n2o itself will significantly cool the air intake charge.
I'm in business once i get the extra 600 bucks.
I plan on getting a tunable 50-100hp system, and starting out with the 50hp jets, then will probably up it to 75hp once i'm convinced all is well under the hood.
I'll let you lads know how it works out.
07-13-2005, 05:49 PM
#178
Banned
Thread Starter
"no where will you find that at peak torque, that peak hp occures. the significance of PEAK hp is potentially at a rate of doing work that provides the greatest acceleration through the gears. peak hp is a point on the torque curve where torque x speed is the greatest. with HP, both torque and speed are equal factors , equally important to the measure of max HP"
I know, which is why the formula doesn't seem to make much sense.
I know, which is why the formula doesn't seem to make much sense.
07-13-2005, 05:53 PM
#179
Rennlist Member
what part of the formula doesnt make sense? where does it seem to not make sense?
There are lot of these types of formulas that are counter intuitive, and its not until you ask the right question, do you get the answer that seems to clear it all up. trust me, ive been there many times, especially in areas of air flow!
MK
There are lot of these types of formulas that are counter intuitive, and its not until you ask the right question, do you get the answer that seems to clear it all up. trust me, ive been there many times, especially in areas of air flow!
MK
Originally Posted by m21sniper
"no where will you find that at peak torque, that peak hp occures. the significance of PEAK hp is potentially at a rate of doing work that provides the greatest acceleration through the gears. peak hp is a point on the torque curve where torque x speed is the greatest. with HP, both torque and speed are equal factors , equally important to the measure of max HP"
I know, which is why the formula doesn't seem to make much sense.
I know, which is why the formula doesn't seem to make much sense.
07-13-2005, 06:40 PM
#180
Banned
Thread Starter
Never mind, i just figured it out on my own with the below problem applying sharkskins earlier answer.
It all makes perfect sense now...and i think i've figured out the easiest way to explain it to someone next time this comes up!
Example problem using made up observed torque readings for a hypothetical engine in 1000rpm engine speed increments:
1000rpm = 200lb-ft observed
2000rpm = 300lb-ft observed
3000rpm = 350lb-ft observed (peak torque rating)
4000rpm = 325lb-ft observed
5000rpm = 300lb-ft observed
6000rpm = 225lb-ft observed
7000rpm = 200lb-ft observed
8000rpm = 125lb-ft observed
Answers:
200lb-ft*1000rpm/5252 = 38 hp
300lb-ft*2000rpm/5252 = 114 hp
350lb-ft*3000rpm/5252= 200 hp
325lb-ft*4000rpm/5252= 248hp
300lb-ft*5000rpm/5252= 286hp (peak HP rating)
225lb-ft*6000rpm/5252= 257 hp
175lb-ft*7000rpm/5252= 233hp
125lb-ft*8000rpm/5252= 190hp
This way of explaining it clearly shows the Torque applied over time to yield the rpm range at which the most work can be done.
For the above engine the HP peak is 286hp @5000rpm and the torque peak is 325lb-ft @ 4000rpm.
The engines broadest useful power band is from 3000-8000rpm, but it's most useful peak power band occurs from 4000-6000rpm.
Setting up a race car, we'd want to gear it so that we spent as much time between 4000-6000rpm as possible.
All makes perfect sense now.
Yay me!
It all makes perfect sense now...and i think i've figured out the easiest way to explain it to someone next time this comes up!
Example problem using made up observed torque readings for a hypothetical engine in 1000rpm engine speed increments:
1000rpm = 200lb-ft observed
2000rpm = 300lb-ft observed
3000rpm = 350lb-ft observed (peak torque rating)
4000rpm = 325lb-ft observed
5000rpm = 300lb-ft observed
6000rpm = 225lb-ft observed
7000rpm = 200lb-ft observed
8000rpm = 125lb-ft observed
Answers:
200lb-ft*1000rpm/5252 = 38 hp
300lb-ft*2000rpm/5252 = 114 hp
350lb-ft*3000rpm/5252= 200 hp
325lb-ft*4000rpm/5252= 248hp
300lb-ft*5000rpm/5252= 286hp (peak HP rating)
225lb-ft*6000rpm/5252= 257 hp
175lb-ft*7000rpm/5252= 233hp
125lb-ft*8000rpm/5252= 190hp
This way of explaining it clearly shows the Torque applied over time to yield the rpm range at which the most work can be done.
For the above engine the HP peak is 286hp @5000rpm and the torque peak is 325lb-ft @ 4000rpm.
The engines broadest useful power band is from 3000-8000rpm, but it's most useful peak power band occurs from 4000-6000rpm.
Setting up a race car, we'd want to gear it so that we spent as much time between 4000-6000rpm as possible.
All makes perfect sense now.
Yay me!