HP vs Torque Discussion (No Jokes, No bantering. Just facts and reality)
02-15-2009 | 09:23 AM
#316
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From: KC
Are the overly complicated equations in this thread wrong? Some clearly are, some are just too convoluted to bother to try to sort out.
02-15-2009 | 09:51 AM
#317
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From: All Ate Up With Motor
nothing like whyning the revs up .....Revs win all the time ...
02-15-2009 | 09:57 AM
#318
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That's the crux of the entire debate. Some folks still are thinking about ENGINE torque ( rotational force) being the "F" in the "F=ma". However, Im talking about the "F" at the rear wheels, not the "F" at the engine, which is almost irrelevant when comparing two equal HP engines in the same car.
Originally Posted by mark kibort
......................I showed that two equal HP engines with different torque can produce the same, greater or less torque to the rear wheels at any vehicle speed.
mk
mk
Nothing new for me here, even 21 pages ago.
02-15-2009 | 10:12 AM
#321
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Going back to this post. Assume that both cars are geared such that gearing is irrelevant. What I mean by that is, each car redlines in each gear at the same speed. To simplify, let's say that's 8K for the Beemer and 6K for the Chevy - er - Caddy. Also assume 27% drop between gears.
Based on the above, I would derive the ideal RPM ranges for each as follows:
BMW: 5,840 - 8K RPM
Caddy: 4,380 - 6K RPM
Using the lower HP curves for each, I then find the point on the HP curve where we will be after shifting to the next higher gear:
BMW: 5,840 RPM, 330HP
Caddy: 4,380 RPM, 325 HP
This bears out your theory in a perfectly ideal situation. However, let's say that we hit that taller gear 500 RPM lower in the band, for any number of reasons. For example, held up in traffic or other situation where the gear change is too costly to be worth doing. Forget about sequential whiz-bang video game transmissions for a second, consider H-pattern and manual clutch, which I think most of us have. The cost of downshifting to use 500RPM to redline, then upshifting again may not be worth paying in some situations.
BMW: 5,340 RPM, 290 HP
Caddy: 3,880 RPM, 320 HP
Whoops, the BMW is down 10% on power in this situation. Not good. In a perfect world, on paper or a whiteboard, these two cars may seem to be equal. However, in the real world where nobody hits their shift point perfectly every single time, where things happen that upset your rhythm, the car with the broader and flatter torque curve (and resulting flatter HP curve) will be more forgiving and will benefit the less-than-perfect driver(just about everyone).
I've seen you go both ways in your videos, Mark. I've seen you hit 1st gear leaving turn 11 at Laguna. I've also seen you stay in a higher gear when on paper, you could have hit a lower gear for ~500RPM and chose not to.
Based on the above, I would derive the ideal RPM ranges for each as follows:
BMW: 5,840 - 8K RPM
Caddy: 4,380 - 6K RPM
Using the lower HP curves for each, I then find the point on the HP curve where we will be after shifting to the next higher gear:
BMW: 5,840 RPM, 330HP
Caddy: 4,380 RPM, 325 HP
This bears out your theory in a perfectly ideal situation. However, let's say that we hit that taller gear 500 RPM lower in the band, for any number of reasons. For example, held up in traffic or other situation where the gear change is too costly to be worth doing. Forget about sequential whiz-bang video game transmissions for a second, consider H-pattern and manual clutch, which I think most of us have. The cost of downshifting to use 500RPM to redline, then upshifting again may not be worth paying in some situations.
BMW: 5,340 RPM, 290 HP
Caddy: 3,880 RPM, 320 HP
Whoops, the BMW is down 10% on power in this situation. Not good. In a perfect world, on paper or a whiteboard, these two cars may seem to be equal. However, in the real world where nobody hits their shift point perfectly every single time, where things happen that upset your rhythm, the car with the broader and flatter torque curve (and resulting flatter HP curve) will be more forgiving and will benefit the less-than-perfect driver(just about everyone).
I've seen you go both ways in your videos, Mark. I've seen you hit 1st gear leaving turn 11 at Laguna. I've also seen you stay in a higher gear when on paper, you could have hit a lower gear for ~500RPM and chose not to.
BINGO... PLUS ONE !!!
In the real World, torque wins races, a higher horsepower rating sells cars.
02-15-2009 | 10:18 AM
#322
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From: All Ate Up With Motor
A point which was amply made in the PREVIOUS 20+ page thread on this subject, only to be bloviated into oblivion by sanctimonious condescending naysayers (I mean that in the nicest possible way, no personal slight intended, take only as directed, your mileage may vary, call your doctor if you have an erection lasting longer than 4 hours, etc.).
All in good fun, but the FACT remains, Trumper and SharkSkin are 100% correct.
Last edited by Veloce Raptor; 02-20-2009 at 07:12 PM.
02-15-2009 | 02:02 PM
#323
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Oh, so now we are looking at driver mistakes as a factor? Hmm, a stretch, but Ill go there. While Brian is absolutely correct, it only is true if the driver selects the wrong gear. I can honestly say, I cant remember having selecting the wong gear in any race, at least in the last 5 years. and Brians point of me being in a slightly taller gear, simulating his comparison is true, but in the REAL world this would be a small difference, however a difference and one only found at one slow corner on the track.
Now, I ask you to look at the V8 vs I6 comparison and do the same test. These curves are clearly different and certainly look to favor the higher torque engine in most all circumstances. Now, even if the high torque engine has the advantage as Brian has shown, IN THIS OTHER CASE, it would be negated by the same type of advantage at the high end of the RPM curve, where you will actually spend more time on a road course. again, it depends! its not a rule.
and, HP wins races, due to it determining the rear wheel torque.
He has the most HP-seconds over a lap, wins. (all other things being equal)
mk
Now, I ask you to look at the V8 vs I6 comparison and do the same test. These curves are clearly different and certainly look to favor the higher torque engine in most all circumstances. Now, even if the high torque engine has the advantage as Brian has shown, IN THIS OTHER CASE, it would be negated by the same type of advantage at the high end of the RPM curve, where you will actually spend more time on a road course. again, it depends! its not a rule.
and, HP wins races, due to it determining the rear wheel torque.
He has the most HP-seconds over a lap, wins. (all other things being equal)
mk
02-15-2009 | 02:08 PM
#324
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Ha ha. you know Dave, leave it to you to do this! 
Ok, you are right. Good points. But, now you are making a decision of which vehicle is better based on a drver mistake. I guess if that is the criteria, you have a valid point. By the way, which one would you buy, even if you were going to buy it for the track?
By the way, to be fair, do the same "mistake" comparison evaluation on the V8 vs I6 curves. I havent looked, but i suspect there would be no place where the V8 would have the advantage, even with 75ft-lbs of higher engine torque.
Mk
Ok, you are right. Good points. But, now you are making a decision of which vehicle is better based on a drver mistake. I guess if that is the criteria, you have a valid point. By the way, which one would you buy, even if you were going to buy it for the track?
By the way, to be fair, do the same "mistake" comparison evaluation on the V8 vs I6 curves. I havent looked, but i suspect there would be no place where the V8 would have the advantage, even with 75ft-lbs of higher engine torque.
Mk
Last edited by mark kibort; 03-16-2009 at 09:45 PM.
02-15-2009 | 02:15 PM
#325
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After all this, you make your point based on a possiblity of a driver error??
I guess if that is the way you want to look at it, sure you are right. all you had to say, 20pages ago was just that. You could have said, " If two equal hp cars, one with greater torque than the other are compared, acceleration at all normal operation of the race car will be the same. If you get caugth in the wrong gear or make a mistake (kind of the same) the higher torque engine could provide a saftey net of available torque and HP". I would have agreed, up and down. Thats why this conversation could be done on a napkin in a few minutes with no argument, even with varying points.
Im glad we finally agree.
mk
I guess if that is the way you want to look at it, sure you are right. all you had to say, 20pages ago was just that. You could have said, " If two equal hp cars, one with greater torque than the other are compared, acceleration at all normal operation of the race car will be the same. If you get caugth in the wrong gear or make a mistake (kind of the same) the higher torque engine could provide a saftey net of available torque and HP". I would have agreed, up and down. Thats why this conversation could be done on a napkin in a few minutes with no argument, even with varying points.
Im glad we finally agree.
mk
Yup.
A point which was amply made in the PREVIOUS 20+ page thread on this subject, only to be bloviated into oblivion by sanctimonious condescending naysayers (I mean that in the nicest possible way, no personal slight intended, take only as directed, your mileage may vary, call your doctor if you have an erection lasting longer than 4 hours, etc.).
All in good fun, but the FACT remains, Trumper and SharkSkin are 100% correct.
A point which was amply made in the PREVIOUS 20+ page thread on this subject, only to be bloviated into oblivion by sanctimonious condescending naysayers (I mean that in the nicest possible way, no personal slight intended, take only as directed, your mileage may vary, call your doctor if you have an erection lasting longer than 4 hours, etc.).
All in good fun, but the FACT remains, Trumper and SharkSkin are 100% correct.
02-15-2009 | 02:42 PM
#326
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Brian?? 
Mark, are you saying that you have never in 5 years had your car on the track and been outside of the "ideal" RPM range for any reason whatsoever? I find that hard to believe, I'm pretty sure I have seen you in a taller than "ideal" gear more than once in your vids -- but I don't have time today to go through them and cite specifics. I'm not talking about picking 3rd when you meant to pick 2nd -- I am talking about leaving it in 3rd when it was possible -- just not ideal -- to drop it in 2nd(or pick any two gears for the discussion).
Mark, are you saying that you have never in 5 years had your car on the track and been outside of the "ideal" RPM range for any reason whatsoever? I find that hard to believe, I'm pretty sure I have seen you in a taller than "ideal" gear more than once in your vids -- but I don't have time today to go through them and cite specifics. I'm not talking about picking 3rd when you meant to pick 2nd -- I am talking about leaving it in 3rd when it was possible -- just not ideal -- to drop it in 2nd(or pick any two gears for the discussion).
02-15-2009 | 02:45 PM
#327
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"Bingo, Plus 1" for one look? How about another. All we are trying to prove is that its not the rule and takes a little more anaylsis. (even in real life)
Now look at Brians analysis on the V8 vs the I6.
quite a different outcome.
using the same conditions of a miss shift or election to not shift around a turn where you might have some indecision, or a shift might cost more time, look at the results:
V8 4600rpm to 6300rpm
I6 5600rpm to 7700rpm
You dont downshift, getting caught in traffic, or are in the wrong gear for whatever reason and now you have
V8 3700rpm
I6 4600rpm
You could downshift, but you dont. who has the advantage . the big torquey V8 or the little I6?
V8 HP at 3700rpm is 190HP
I6 HP at 4600rpm is 200HP
I6 , low torque engine wins with MORE rear wheel torque at the lower rpm. It wins in this equal conditions to the caddy, M5 comparison, but more importantly, the lower torque engine has a flatter hp curve up top, creating more rear wheel torque at that range as well.
Hey, I even did a near 1000rpm drop to make the point too! (18% rpm drop)
See how easy that was?
Again, the point of 20 pages is that it depends on the shape of the HP curves.
HP-seconds wins races!
mk
Now look at Brians analysis on the V8 vs the I6.
quite a different outcome.
using the same conditions of a miss shift or election to not shift around a turn where you might have some indecision, or a shift might cost more time, look at the results:
V8 4600rpm to 6300rpm
I6 5600rpm to 7700rpm
You dont downshift, getting caught in traffic, or are in the wrong gear for whatever reason and now you have
V8 3700rpm
I6 4600rpm
You could downshift, but you dont. who has the advantage . the big torquey V8 or the little I6?
V8 HP at 3700rpm is 190HP
I6 HP at 4600rpm is 200HP
I6 , low torque engine wins with MORE rear wheel torque at the lower rpm. It wins in this equal conditions to the caddy, M5 comparison, but more importantly, the lower torque engine has a flatter hp curve up top, creating more rear wheel torque at that range as well.
Hey, I even did a near 1000rpm drop to make the point too! (18% rpm drop)
See how easy that was?
Again, the point of 20 pages is that it depends on the shape of the HP curves.
HP-seconds wins races!
mk
Last edited by mark kibort; 02-15-2009 at 03:06 PM.
02-15-2009 | 03:00 PM
#328
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BMW OTOH I recognize as offering a quality product with great performance(in certain models) but IMHO their image is tarnished by the fact that 99.9% of the people who own them are posers who, aside from the status factor, would get just as much out of a Kia.
"BMW - The ultimate posing machine".
02-15-2009 | 03:01 PM
#329
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No never, and i have racing videos for every race for the last 10 years! ( probably 4-5 miss shifts or hesitations that cost a lot of time that can be seen on the videos.) With braking, comes shifting so its pretty hard to not be in the right gear.
I have always been in the operational range of the engine. as brian says, I have elected to be in 1st through turn 11 at laguna, but have experiemented with both on occasion, but the reason that this is not a fair comparison(actually to the contray to the arguement) is going around turn 11 in 1st gear im still at 4000, only 500rpm below the optimal rpm range. due to my engine's torque, Its still ok to leave it there. If I was driving the BMW, I would select a lower gear as it is an easier shift for it. I leave it in gear due to difficulty of most 928s to hit 1st gear, and a trade off of shfting time. in a heated battle, and good concentration, ill hit first from 5500rpm to redline. All other places, Im at optimal speed ror the given gear. I think ive only seen a couple of times where a competitor has been in the wrong gear. If you are ever in the wrong gear, through traffic, etc, its the kiss of death. with our close racing, two guys will go right buy. heck, even a hesitation or a miss shift for a split second, a competitor will fly right buy as you can see one of those on my videos (M3 in the 928 sounds video)
mk
I have always been in the operational range of the engine. as brian says, I have elected to be in 1st through turn 11 at laguna, but have experiemented with both on occasion, but the reason that this is not a fair comparison(actually to the contray to the arguement) is going around turn 11 in 1st gear im still at 4000, only 500rpm below the optimal rpm range. due to my engine's torque, Its still ok to leave it there. If I was driving the BMW, I would select a lower gear as it is an easier shift for it. I leave it in gear due to difficulty of most 928s to hit 1st gear, and a trade off of shfting time. in a heated battle, and good concentration, ill hit first from 5500rpm to redline. All other places, Im at optimal speed ror the given gear. I think ive only seen a couple of times where a competitor has been in the wrong gear. If you are ever in the wrong gear, through traffic, etc, its the kiss of death. with our close racing, two guys will go right buy. heck, even a hesitation or a miss shift for a split second, a competitor will fly right buy as you can see one of those on my videos (M3 in the 928 sounds video)
mk
Brian??
Mark, are you saying that you have never in 5 years had your car on the track and been outside of the "ideal" RPM range for any reason whatsoever? I find that hard to believe, I'm pretty sure I have seen you in a taller than "ideal" gear more than once in your vids -- but I don't have time today to go through them and cite specifics. I'm not talking about picking 3rd when you meant to pick 2nd -- I am talking about leaving it in 3rd when it was possible -- just not ideal -- to drop it in 2nd(or pick any two gears for the discussion).
Mark, are you saying that you have never in 5 years had your car on the track and been outside of the "ideal" RPM range for any reason whatsoever? I find that hard to believe, I'm pretty sure I have seen you in a taller than "ideal" gear more than once in your vids -- but I don't have time today to go through them and cite specifics. I'm not talking about picking 3rd when you meant to pick 2nd -- I am talking about leaving it in 3rd when it was possible -- just not ideal -- to drop it in 2nd(or pick any two gears for the discussion).
02-15-2009 | 03:15 PM
#330
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No never, and i have racing videos for every race for the last 10 years! ( probably 4-5 miss shifts or hesitations that cost a lot of time that can be seen on the videos.) With braking, comes shifting so its pretty hard to not be in the right gear.
I have always been in the operational range of the engine. as brian says, I have elected to be in 1st through turn 11 at laguna, but have experiemented with both on occasion, but the reason that this is not a fair comparison(actually to the contray to the arguement) is going around turn 11 in 1st gear im still at 4000, only 500rpm below the optimal rpm range. due to my engine's torque, Its still ok to leave it there.... ...I leave it in gear due to difficulty of most 928s to hit 1st gear, and a trade off of shfting time.
I have always been in the operational range of the engine. as brian says, I have elected to be in 1st through turn 11 at laguna, but have experiemented with both on occasion, but the reason that this is not a fair comparison(actually to the contray to the arguement) is going around turn 11 in 1st gear im still at 4000, only 500rpm below the optimal rpm range. due to my engine's torque, Its still ok to leave it there.... ...I leave it in gear due to difficulty of most 928s to hit 1st gear, and a trade off of shfting time.
See the bold above -- you are contradicting yourself. The latter part of your statement that I quoted above simply helps drive home the point that I was making, that a broader powerband can be beneficial. Whether by mistake or intent, you occasionally drive outside the "ideal" RPM range and the broad powerband benefits you in these cases.