Horsepower sells cars, torque wins races.

[jinx]

Honestly therein lies the flaw with most people's logic. You're assuming that horsepower measured at a singular RPM is a good indicator of how much work an engine can do in a car

Bingo!!

Chad's understanding of this concept is flawless

No its not! Why you think he poses such a ridiculously silly question ?

"why don't we shift at 2500 RPM where the stock torque peak it at? "

 

One dimensional thinking. NO understanding whatsoever, of the purpose and outcome of keeping a motor in the "meat" of its torque curve throughout the run.... or worse the fundamental behind the use of bigger displacement engines, evidenced by the honda 1.8 powered 7000 pound dually I baited him with - lol.

Why do u think eipquest was so dam quick ????? I'm sure he also didn't know what he was doing

 

Both ligenfelter and Banks quoted "Hp sells motors, but tq will win the race".

They are renowned race engine builders, with the clientelle and record to prove it.

Think those guys r idiots... or don't know what they're sayin ?

Enzo, Banks, Ligenfelter : all built their cars for drivability, not maximum acceleration

that is frikkin hilarious.... so the mind boggling acceleration and ETs of their street cars were just an insignificant byproduct then ? heheh

[bmx152]

i vote broad power curve ftw!

[chiplee]

Bingo!!

 

No its not! Why you think he poses such a ridiculously silly question ?

"why don't we shift at 2500 RPM where the stock torque peak it at? "

 

One dimensional thinking. NO understanding whatsoever, of the purpose and outcome of keeping a motor in the "meat" of its torque curve throughout the run.... or worse the fundamental behind the use of bigger displacement engines, evidenced by the honda 1.8 powered 7000 pound dually I baited him with - lol.

Why do u think eipquest was so dam quick ????? I'm sure he also didn't know what he was doing

 

Both ligenfelter and Banks quoted "Hp sells motors, but tq will win the race".

They are renowned race engine builders, with the clientelle and record to prove it.

Think those guys r idiots... or don't know what they're sayin ?

 

that is frikkin hilarious.... so the mind boggling acceleration and ETs of their street cars were just an insignificant byproduct then ? heheh

 

You're kind of arguing a different topic because you're just missing one subtle element of what chad and I are trying to say. Horsepower IS torque, except with RPM factored in. HP isn't actually a force at all. It's the product of an equation. It's a mathematical representation of an engine's ability to make TQ at any given RPM. For this simple reason, HP contains more information than TQ. In short, we agree, but you don't seem to want to use the same language to make the point. That's fine, but don't ignore the mathematical facts you're being presented with.

Edited February 3, 2011 by chiplee

[bmx152]

You're kind of arguing a different topic because you're just missing one subtle element of what chad and I are trying to say. Horsepower IS torque, except with RPM factored in. HP isn't actually a force at all. It's the product of an equation. It's a mathematical representation of an engine's ability to make TQ at any given RPM. For this simple reason, HP contains more information than TQ. In short, we agree, but you don't seem to want to use the same language to make the point. That's fine, but don't ignore the mathematical facts you're being presented with.

 

 

actually the origional question was what will prevail: hp based cars or torque based cars.

 

then chad posted about the corvette with more hp beating the corvette with more torque. so what is better?A higher revving high hp and lower torque or lower revving higher torque both optimally geared was the basis of our discussion

 

i may be wrong but im just saying it like i see it.

Edited February 3, 2011 by bmx152

[Chad]

actually the origional question was what will prevail: hp based cars or torque based cars.

 

then chad posted about the corvette with more hp beating the corvette with more torque. so what is better?A higher revving high hp and lower torque or lower revving higher torque both optimally geared was the basis of our discussion

 

i may be wrong but im just saying it like i see it.

 

That's entirely subjective though...

 

Do you want a fun stoplight to stoplight car that you don't have to flog, or do you want maximum acceleration?

 

"Torque motors" are suited to stoplight to stoplight because they tend to make that torque at a low RPM.

 

Maximum aceleration is purely a function of avaialble power, so a "horsepower motor" will win.

 

FYI, a propperly geared "horsepower motor" will beat a "torque motor" in a stoplight to stoplight race if it's geared correclty, problem is, most aren't.

[Chad]

You're kind of arguing a different topic because you're just missing one subtle element of what chad and I are trying to say. Horsepower IS torque, except with RPM factored in. HP isn't actually a force at all. It's the product of an equation. It's a mathematical representation of an engine's ability to make TQ at any given RPM. For this simple reason, HP contains more information than TQ. In short, we agree, but you don't seem to want to use the same language to make the point. That's fine, but don't ignore the mathematical facts you're being presented with.

 

Exaclty.

 

One dimensional thinking. NO understanding whatsoever, of the purpose and outcome of keeping a motor in the "meat" of its torque curve throughout the run.... or worse the fundamental behind the use of bigger displacement engines, evidenced by the honda 1.8 powered 7000 pound dually I baited him with - lol.

 

Take that honda vs. cummins example. I proved your understanding wrong by using your own example. Breaking it back down to JUST a torque argument, why is it your belief that the cummiins with 2100 ft/lb of axle torque will out-accelerate the honda with 4200 ft/lb of axle toruque? We have used horsepower information to derive that instantanious axle torque, but we are not comparing horsepower at this point, just axle torque. Why does the bigger motor with 1/2 less axle torque win? Show me where I'm wrong here.

 

Why is it that all the online 1/4 mile calculators never ask for your torque peak, they only ask for your horsepower peak and wieght of car? Cause in a pure acceleration contest, just torque is irrelivant. Where that torque exists is relivantand to yiled the best horsepower, you need it to be at the highest RPM possible. Big motors with huge low end torque that nose over at 4000 RPM are not going to make much horsepower.

 

Take a calculator from this site for example : http://www.wallaceracing.com/et-hp-mph.php (from http://www.wallaceracing.com/Calculators.htm), or any ohters you find).

 

Use the 2 example honda and cummins motors and plug in teh specs you used, you will find the honda wins no matter what.

 

600 HP honda in 7000 pound dualy : 13.21 seconds and MPH of 101.42 MPH.

400 HP cummins in a 7000 pound dualy : 15.12 seconds and MPH of 88.60 MPH.

 

Like I said, not even close.

 

the trick to maximum acceleration is to make high torque at a high RPM, that is where the maximum acceleration is at.

 

If you can make that cummins produce 600 HP at 2000 RPM, than the race will be a tie, and you will have a far more enjoyable truck to drive. Problem is, it will take 1576 ft/lb to do that (http://www.wallaceracing.com/HP-TQ-RPM%20Calc.php).

[Chad]

Honestly therein lies the flaw with most people's logic. You're assuming that horsepower measured at a singular RPM is a good indicator of how much work an engine can do in a car. Maybe if this was in a generator or a boat where engine RPM is maintained fairly constant. However, in a car the engine is constantly varying RPM. Especially considering most vehicles are not optimally geared for acceleration. I don't disagree with your math. You are exactly right in saying 300 hp is 300 hp, no matter what the torque or RPM is. However, my contention in my other post above is that power curve along with peak power is a more important factor when looking at automotive engines.

 

Which of these two engines do you think would do better in a drag race? The engine that makes nearly 300 hp for over 1500 rpm or the one that makes it over 500 rpm? They both have the roughly the same peak horsepower so they should both be equally fast, right?

 

 

So in a race, any kind of real race, when does the motor drop below 4500 RPM? If you will note, both those graps show the same power peak of ~300 HP, but one has 130 ft/lb more torque and noses over at about 5500 RPM. OK, so that "high torque peak motor", what RPM is that flat spot and peak at? 4000-5000 RPM, still a narrow shift window. On that horsepower motor, it has a very desirable flat torque curve but doesn't have much torque at any time, and the power peak is out at redline. So why not just drive it at redline? Gear shifts are only ~1500 RPM part, if you build a horsepower motor, you just raise your shift point. Axle torque is still the same as the much higher "torque motor" right? from an acceleration standpoint that's all that matters.

 

In a arce you are always keeping the motor in the same basic RPM range, even on a road course (except engine breaking). In a race car, a wide power curce us really unnessesary. A driver is always keeping the motor at it's power peak. It is however very desirable in a street car to have a wide curve.

 

So are we talking bout race cars or street cars here, cause I think different arguments are going arorund here. My impression is that it's all about accelerating a mass (a car) as quickly as possible. That takes torque (right) but it also needs to be measured in a distance/time realm. Horsepower is torque with a distance/time refrence. More horsepower = faster acceleration, regardless of the torque used to derive that horsepower. take a turbine engine for example, they ave almost no torque but they spin at 40,000+ RPM. They makes tons of horsepower and are used in 45 ton M1 Abrams tanks. That's right, a 40 ft/lb motor that accelerates a 90,000 pound mass rather quickly. It's all about gearing. Turbines are used due to their compact power-to-size ratio, and thier ability to use lower grade fuels.

[Chad]

"Horsepower sells cars, torque wins races."

-Enzo Ferrari

 

I found this quote and just wanna know your opinion on it

 

 

Modern Ferrari motors:

599 : 661 bhp @ 8250 rpm, with 460 lb·ft of torque @ 6500 rpm

Enzo : 651 hp @ 7800 rpm, and 485 lb·ft @ 5500

458 : 560 hp @ 9,000 rpm, and 400 lb·ft @ 6,000 rpm

F430 : 483 hp @ 8500 rpm and 343 lb·ft of torque @ 5250 rpm

F360 : 400 bhp @ 8500 rpm, with 275 lbf·ft @ 4750 rpm

 

 

Has Ferrari lost their way, or was Enzo wrong?

[Maxzillian]

So in a race, any kind of real race, when does the motor drop below 4500 RPM? If you will note, both those graps show the same power peak of ~300 HP, but one has 130 ft/lb more torque and noses over at about 5500 RPM. OK, so that "high torque peak motor", what RPM is that flat spot and peak at? 4000-5000 RPM, still a narrow shift window. On that horsepower motor, it has a very desirable flat torque curve but doesn't have much torque at any time, and the power peak is out at redline. So why not just drive it at redline? Gear shifts are only ~1500 RPM part, if you build a horsepower motor, you just raise your shift point. Axle torque is still the same as the much higher "torque motor" right? from an acceleration standpoint that's all that matters.

 

In a arce you are always keeping the motor in the same basic RPM range, even on a road course (except engine breaking). In a race car, a wide power curce us really unnessesary. A driver is always keeping the motor at it's power peak. It is however very desirable in a street car to have a wide curve.

 

So are we talking bout race cars or street cars here, cause I think different arguments are going arorund here. My impression is that it's all about accelerating a mass (a car) as quickly as possible. That takes torque (right) but it also needs to be measured in a distance/time realm. Horsepower is torque with a distance/time refrence. More horsepower = faster acceleration, regardless of the torque used to derive that horsepower. take a turbine engine for example, they ave almost no torque but they spin at 40,000+ RPM. They makes tons of horsepower and are used in 45 ton M1 Abrams tanks. That's right, a 40 ft/lb motor that accelerates a 90,000 pound mass rather quickly. It's all about gearing. Turbines are used due to their compact power-to-size ratio, and thier ability to use lower grade fuels.

 

I'd like to think we're talking about race cars here. At least I am.

 

I want to point out that I am not arguing torque wins races. I am arguing that power curves win races. What I have tried to explain in some of my prior posts, and I admit that I likely did not make it very clear, was that a torque motor may generally have a flatter power curve than a horsepower motor. Horsepower is a measure that involves distance and time, but once again that is at a steady state. If the cars maintained a constant engine RPM while accelerating, looking at purely horsepower would be a logical assessment of acceleration potential.

 

To use your proposed figure of 1500 rpm range for one gear to another and assuming both cars are optimally geared for their specific engine, which engine holds the greatest horsepower over a 1500 rpm range? Looking at the graphs, the engine with the quick and peaked torque curve maintains the greatest average horsepower over a 1500 rpm window. The engine with the nice and desirable flat torque curve has a lower average over a 1500 rpm window as it is increasing up to the peak, not peaking and maintaining.

 

What this means is that while running through a gear, the engine with the flat power curve is pumping out a steady 300 hp while the engine with the flat torque curve is gradually increasing horsepower up to the desired shift point. Which do you think is better?

 

I've been attempting to graph this relation, but I won't be able to put anything online until tonight. Starting with the starion shift points, I have found one interesting little tidbit: The desired shift point varies depending on what gear you are in. Interesting stuff! I look forward to your response.

[Chad]

A lot of "horsepower motors" peak before redline, they reach internal effency issues like rod speed or intake/exhaust effency walls. there is usualy a flat plateu for them to work with at the top.

 

I get what you are saying man, Totaly. I 'm just stating my arguemnts for others here as well...

 

FYI, when I talked to the owner of the SAKURA 7.41 second 1/4 ET 1000 HP G54B, he told me he shifted at 6800 RPM. Pretty much all highly boosted G54B's I've seen dyno sheets on have this same curve, just higher or lower lines:

 

http://www.starquestclub.com/forum/uploads/1294886318/med_gallery_3386_777_757723.jpg

 

They all have torque peaks arround 4500-4800 RPM. Nobody that takes racing seriously shifts for maximum torque , they shift for maximum power. That is Technologyes power curve, the HP and TQ peaks are ~1000 RPM apart. Will he get a better ET shifting at 6000 (for HP) or 5000 (for TQ)?

 

Building a motor for maximin torque by default yields excelent horsepower, but it must be made at a high RPM to result in superior acceleration. The persuit of maximum horsepower is the study of where that torque is made. Making it in the low end is not going to get the job done. If Technology was able to hold that 459 ft/lb out to 6200 RPM, he'd have dynoed 542 HP. It's not about how high the peak is, it's about where that torque is made in the RPM range.

 

Just like the sledge hammer and jackhammer annology I used earlier. Each revolution is 2 combustion events, those combustion events on the pistons are like blows to a hammer. Lots of medium blows (High RPM) does a lot more than just a few really huge blows (low RPM with high torque), over time. Jackhammer blows are pretty static in force, wop what happens when you turn up the speed of those blows? a lot more work gets done. I've broken sidewalk with both methods, trust me the jackhammer is a lot faster.

[conquestTSIguy]

Modern Ferrari motors:

599 : 661 bhp @ 8250 rpm, with 460 lb·ft of torque @ 6500 rpm

Enzo : 651 hp @ 7800 rpm, and 485 lb·ft @ 5500

458 : 560 hp @ 9,000 rpm, and 400 lb·ft @ 6,000 rpm

F430 : 483 hp @ 8500 rpm and 343 lb·ft of torque @ 5250 rpm

F360 : 400 bhp @ 8500 rpm, with 275 lbf·ft @ 4750 rpm

 

 

Has Ferrari lost their way, or was Enzo wrong?

 

Those are production cars... and I'm sure Ferrari wants to sell them

 

But what's wrong with having both? kind of like the whole "can't we all get along" quote.

[Chad]

Rate of change does not equal acceleration. rate of change is just that, the change in rate. Acceleration would continue to infinity if you had a flat horsepower curve and unlimited redline. It's like gravity, you have an static force downward. jump off a cliff and you will accelerate to the ground at an everincreasign speed. If there were no air resistance and you never actually hit the ground, you would accelerate at the same pace untill you reached infinity speed.

 

I have an altima Hybrid, it can produce a totaly flat power curve and a totlay linear gear change (CVT transmission). Passing up-hill is a rather odd feeling of linear acceleration.

 

If you setup the dyno correclty and added the gear reductions in for the chosen gear, the chart would look identical. the dyno roller would turn more slowly, but expect a higher force to be applied. This is why some people use the road speet dyno chart, that prepresents a more tangable representation of acceleration. There, the steeper the curve the faster the rate of acceleration, but this just shows the maximum acceleration is acchieved at the peak of the power curve, not the bottom or middle.

 

300 HP in 1st gear is the same as 300 HP in 5th, its just at a different axle speed, where 1st is applying a higher torque with a lower speed. the acceleration of the car is faster, but only because the axle torque is higher. you go though the gears to continue the acceleration process whithout having to change the RPM's of the motor out to infinity. Each time you change gears, you reduce your axle torque and give up some rate of acceleration. The engine horsepower/torque is the same, you have just changed the gearing and subsequent axle torque.

 

Steep horsepower or torque curves just equal an unpredictable car, which is why wide semi-flat-curve cars are very desirable in street driving, or some types of road course driving (as Max explained). In an all out race, if you are doing it right, you only see a small RPM band, and it's well past the upward portion of the curves. Steep curves suck in a street car, they make it squirly and hard to handle during transitions in and out of a corner.

[Ironside]

I wasn't aiming on starting an arguementhttp://www.starquestclub.com/forum/public/style_emoticons/default/blink.gif I was just wondering who would win?

[Chad]

I wasn't aiming on starting an arguementhttp://www.starquestclub.com/forum/public/style_emoticons/default/blink.gif I was just wondering who would win?

 

Depends on how many varraibles there are to consider.

[Ironside]

Depends on how many varraibles there are to consider.

 

 

All depends on what varraibles you are talking about, winning races or argueing?http://www.starquestclub.com/forum/public/style_emoticons/default/blink.gif http://www.starquestclub.com/forum/public/style_emoticons/default/laugh.gif http://www.starquestclub.com/forum/public/style_emoticons/default/laugh.gif http://www.starquestclub.com/forum/public/style_emoticons/default/laugh.gif

[Maxzillian]

I wouldn't say it's an argument at all. I've learned a lot of things from this discussion, including points that haven't been brought up. I've been playing with some data in excel and found some rather interesting things. Hopefully I'll post them up later tonight.

[tim si]

I wouldn't say it's an argument at all. I've learned a lot of things from this discussion, including points that haven't been brought up. I've been playing with some data in excel and found some rather interesting things. Hopefully I'll post them up later tonight.

i think this is some of the best stuff thats been in the b.s.section in a long time.theres alot of good stuff coming out of this.

[Maxzillian]

Ok, so I finally got a little time to make some mischief. I took the data from the two dyno charts I had posted earlier and plotted them in Excel. In addition to that I corrected the flat torque curve dyno chart so that the peak horsepower is the same between the two. After accomplishing that I "geared down" the flat torque dyno chart so that peak horsepower occurred at the same RPM as the flat power dyno chart. This would be akin to gearing them down to the same wheel speed, I'm just skipping the extra unnecessary math.

 

As expected, the torque at this point is both exactly equal on both charts. That is to say that since both charts display 308 hp at 5500 rpm, they now both display 294 ft-lbs of torque at the same engine speed. So, by some of the logic stated before, once gearing is taken into consideration, both engines should be equal matches, right?

 

Well, not quite. While they are both equals right at 5500 rpm, a quick peak at the torque and power curves shows that the engine with the flat power curve produces more torque and horsepower over a wider RPM range. I have highlighted in green the gain in torque and in red the gain in horsepower. What this shows is that despite both engines producing the same horsepower and being geared to spin at the same speed, the broader power curve will always have more acceleration all the way from 3800 rpm to 5500 rpm.

 

To put this into numbers, averaging out the horsepower over this range yields an average of about 299 hp for the engine with the flat power curve and an average of 159 hp for the engine with the flat torque curve.

 

http://maxzillian.com/starion_files/powercurve1.jpg

 

So what does this mean? Is an engine with more torque than horsepower better than an engine with more horsepower than torque?

 

Well, not really. Ultimately you really can not focus solely on one peak figure or the other. A torque engine may generally have a flatter power curve, but there are certainly cases where a horsepower engine could have a flat power curve as well.

 

While peak torque and horsepower will generally give you an idea of how an engine will behave, what you really want to focus on his how much horsepower is made over a range of engine speed. As the chart shows, even when comparing peak power to peak power, it hardly tells the full story.

 

Coming next: Analyzing when you should shift

[Chad]

I "geared down" the flat torque dyno chart so that peak horsepower occurred at the same RPM as the flat power dyno chart. This would be akin to gearing them down to the same wheel speed, I'm just skipping the extra unnecessary math.

 

Moving the horsepower peak is in effect changing the torque peak, since horsepower is torque. Can you elaborate as to what you changed? if you moved it much, you pretty much nullified the graph you made. Why not just leave the numbers where they are? they obviousy aren't the same motors due to the sahpe of the curves, so why try to make the numbers come out the same?

[jinx]

real truck ETs

6870 pounds, 600hp 5.9L cummins goes 12s.

7780 pounds, 650hp 5.9L dodge ram et 13.19

6800 pounds, 650hp 6.6L duramax, et;12.0

so much for "formulas", eh. Not accurate at all.

 

now for analysis;

6780 pounds, 542hp 6.6L duramax goes 12.50

 

so Chad, what you're saying is, if I swap a turbocharged 542hp D16 1.6L honda civic motor into this 6780 pound truck, all I have to do is gear it correctly and this monster would ET 12.50 ?

Or conversely, the 'math' says that a 180hp 2260 pound civic would ET 12.50 ? (thats 1/3 the weight & hp)

[Chad]

real truck ETs

6870 pounds, 600hp 5.9L cummins goes 12s.

7780 pounds, 650hp 5.9L dodge ram et 13.19

6800 pounds, 650hp 6.6L duramax, et;12.0

so much for "formulas", eh. Not accurate at all.

 

now for analysis;

6780 pounds, 542hp 6.6L duramax goes 12.50

 

so Chad, what you're saying is, if I swap a turbocharged 542hp D16 1.6L honda civic motor into this 6780 pound truck, all I have to do is gear it correctly and this monster would ET 12.50 ?

Or conversely, the 'math' says that a 180hp 2260 pound civic would ET 12.50 ? (thats 1/3 the weight & hp)

 

So you don't acknowledge that the 350 ft/lb honda motor at 8000 RPM has twice the axle torque as the 700 ft/lb 2000 RPM cummins?

 

It's all about torque, so there is your torque. the honda wins.

[Maxzillian]

Now to tackle another question. Is it better to shift at peak torque, peak power, or something else?

 

This, unfortunately is a very subjective question. Technically if you wanted to talk purely theory I would say the shift point should occur somewhere after peak power so that you maximize the most horsepower you can in the rpm window you have for each gear.

 

Realistically it is largely going to be determined by your power curve and the gear ratios you have available. So that I can be a little more relevant, I decided to use Technology's dyno chart as an example and used the gear ratios of the stock Starion transmission. We don't need to factory in rear end ratios or tire size as these all effect how the car accelerates, not when you should shift.

 

To start we create a table of dyno data for the engine. Then we use the transmission ratios to create a number of columns showing what the engine RPM and torque is after exiting the transmission for 1st through 5th gear.

 

(Now right away some of you are going to notice I am only using the torque figures here and not horsepower. There's good reason for that. Torque is a measure of force that directly relates to the amount of thrust exerted by the wheels and causing the car to accelerate. Horsepower, being a measure of power, can not be used in this sense as it is used to illustrate the amount of force or work that has been done over a measure of time. In other words, horsepower is telling how quickly we are getting work done, but doesn't tell us what the amount of work is.

 

Other keen eye people will notice I stretched the power range to 7000 rpm. I'll cover this point later.)

 

http://maxzillian.com/starion_files/shiftpoint1.jpg

 

Using this data we can then create a chart to illustrate what the effective torque curves look like after being multiplied by the transmission reduction ratios and their relation to each other.

 

http://maxzillian.com/starion_files/shiftpoint2.jpg

 

What you should notice right away is the wide gap between first and second and how the gaps tighten up as you get to higher ratios. To find the ideal shift points, we want to jump from one torque curve to the next while maximizing the most torque possible.

 

Using yet another chart, we can plot what happens when we shift at peak torque, peak horsepower, the RPM limit, and the best possible RPMs.

 

http://maxzillian.com/starion_files/shiftpoint3.jpg

 

If you notice, shifting at peak torque yields the worst results. While we are shifting at the point where the car stops accelerating any harder, we are also shifting into the base of the next torque curve and have to repeat the process all over again.

 

Shifting at peak HP yields better results, but time is still spent trying to climb the curve of the next gear. While this largely means that the transmission isn't geared right, we need to be practical and realize that none of us have the money to build a one off transmission made to match our specific engine. For that reason let's continue and focus on how to make the best of what we have.

 

Once we ignore peak torque, peak hp, and the fact we won't find the perfect transmission, it quickly becomes apparent that for 1st and 2nd gear the engine has to be ran to redline to maximize the torque curves of 1st, 2nd and 3rd. It isn't until the shift into 4th that we finally find an ideal shift where the decline of 3rd gear torque leads perfectly into the 4th gear torque curve (in other words, where they intersect).

 

It is at this point that I will explain just why I interpolated Technology's power curve to extend to 7000 rpm. While this may not be a perfect or realistic power curve, it illustrates that despite a drastic drop in engine power of 146 hp from peak power, if we can drag the engine out to 7000 rpm, we can make the best of 1st, 2nd and 3rd gear before finally falling into where the gear ratios begin to match up as we go into 4th and 5th.

 

The reason it works this way is that as you go from one gear to the next, you encounter a drastic drop in output torque available. For this reason it is actually beneficial to drag out some gears because despite the drop in horsepower, we still have more torque available out of the transmission than if we had shifted into the next gear earlier.

 

To bring this to a close, if Technology's car is limited to 6150 RPM, his shift points should be:

 

1st to 2nd: 6150 rpm

2nd to 3rd: 6150 rpm

3rd to 4th: 6150 rpm

4th to 5th: 6150 rpm

 

However, if he can get his engine to reach 7000 rpm, and assuming that the torque falls off linearly:

 

1st to 2nd: 7000 rpm

2nd to 3rd: 6715 rpm

3rd to 4th: 6392 rpm

4th to 5th: 6150 rpm

 

Confused yet? I know I have a headache.

[Maxzillian]

Moving the horsepower peak is in effect changing the torque peak, since horsepower is torque. Can you elaborate as to what you changed? if you moved it much, you pretty much nullified the graph you made. Why not just leave the numbers where they are? they obviousy aren't the same motors due to the sahpe of the curves, so why try to make the numbers come out the same?

 

Because as you've said before, the focus needs to be placed on the torque available at the wheels if we really want to compare engines and horsepower.

 

While I didn't calculate the Rpm and torque at the wheels, I did the next equivalent thing and equalized the RPMs of the two curves. This is akin to your example:

 

So you don't acknowledge that the 350 ft/lb honda motor at 8000 RPM has twice the axle torque as the 700 ft/lb 2000 RPM cummins?

 

It's all about torque, so there is your torque. the honda wins.

 

All I did to the flat torque chart aside from bumping it up by a percentage to make the peak horsepower equal was divide the RPM and multiply the torque by the same ratio. The horsepower curve remains the same, but now we've pulled RPM and torque into a range where it can be compared. This is no different than picking the gear that works best for an engine and focusing on the torque sent to the wheels.

 

In other words this is akin to two cars, side by side, picking their best gear and accelerating from a rolling start.

 

Edit: I altered the flat torque curve so that the climbing edges of the power curves line up better. What this shows is that now the cars may be pretty well equal up to a point, but eventually the car with the flat torque curve will need to shift to another gear. Unless the car has extremely short gears and quick shifts, it is not going to be able to match the torque curve of the other engine and keep up.

 

http://maxzillian.com/starion_files/powercurve2.jpg

Edited February 4, 2011 by Maxzillian

[Chad]

Because as you've said before, the focus needs to be placed on the torque available at the wheels if we really want to compare engines and horsepower.

 

This is no different than picking the gear that works best for an engine and focusing on the torque sent to the wheels.

 

In other words this is akin to two cars, side by side, picking their best gear and accelerating from a rolling start.

 

Thanks for clarification.

 

the torque statement was direceted at Jinx.

[Maxzillian]

Heh, I know. I was being lazy and didn't want to dig back for your original example of Honda Vs. Cummins.