1327 replies to this topic

[gruntguru]

Quote

Originally posted by cheapracer
awwww, you took number 1200, I was too slow

It was a crap post too, but this makes it worth it. Hmmm #1200 eh - wow! Makes me feel kinda important.

[johnny yuma]

Quote

Originally posted by gruntguru
It was a crap post too, but this makes it worth it. Hmmm #1200 eh - wow! Makes me feel kinda important.

you too like the moon and the stars have a right to be here

Just don't post anymore fictional graphs ,and continue to "explain" why maximum torque in Joe's road rocket coincides with maximum g forces,not maximum power, if ,as you say ,power is not an abstraction.

[gruntguru]

Quote

Originally posted by xxchrisxx
Go on. How do you measure heat in? Or indeed heat out?
(where im going with this is that you dont hook up a heat'o'meter and get out a nice sexy figure)

You can measure work (but again not dirctly).

As its fairly well known that measuring the thing known as 'power' or 'energy' directly is impossiible.

As that answer you gave is cryptic and bollocks. Lets take this through to the end shall we and not casually dismiss the most important parts of the points.

Power is never really irrelevent in any context(anyone saying so should be beaten), but for the physical process it is abstract. the point follows that so it torque. but you can feel torque and not power, which makes torque far less abstract to talk about when decribing motion. which as you so kindly skipped over was the most important part of the post.

now talking about the thermo stuff when you want to decribe efficiencys is fine and dandy. which then follows for bsfc. however this is not terribly useful at helping us with decribing how the car moves along the road.

Agree - although power is the most useful single number for rating any engine.
I hope you didn't think I was implying any of these things can be measured directly. I struggle to think of any properties outside the seven fundamentals that can be measured directly.

Measuring heat input is simply fuel massflow times heating value.

Waste heat output as I said is difficult because there are several sources. The easy ones are cooling water for coolant and oil (massflow x delta T). Exhaust is a little more difficult, can use a calorimeter and extrapolate or meausure massflow (inlet air + fuel is easier than direct measurement of exhaust flow) and use tables, but composition needs to be measured or estimated. The hardest to measure is radiant and convection losses from the engine exterior - a small number but significant. This is the one that is usually considered to be "whatever is left" after heat balance calculations. No doubt McGuire will have plenty to add (or subtract) on this subject when he reads this.

As far as definitions of abstract - I don't think it advances the discussion to dismiss things as abstract simply because human beings can't sense them directly. Electric current is something you can't sense but it is a fundamental quantity and we all accept it as a unique way of measuring an everyday phenomenon.

[gruntguru]

Quote

Originally posted by johnny yuma
and continue to "explain" why maximum torque in Joe's road rocket coincides with maximum g forces,not maximum power, if ,as you say ,power is not an abstraction.

Could you re-phrase this bit? I'm not sure of your meaning.

[Dmitriy_Guller]

Oy, back to abstract vs. not-as-abstract? How many times have we had that discussion already?

Can anyone explain to me why the level of abstraction of power is so important? There is a lot of abstraction in sciences like physics, that's how we grow the knowledge and understanding.

I also don't buy the argument that thinking abstractly can lead to poor understanding of the physical process involved. In this thread, for example, the people who got the physical process wrong belong exclusively to the torque camp, so they're not exactly making a good argument for that theory. In fact, the abstract power theory is what helps you sanity-check your arguments.

[Dmitriy_Guller]

Quote

Originally posted by johnny yuma


you too like the moon and the stars have a right to be here

Just don't post anymore fictional graphs ,and continue to "explain" why maximum torque in Joe's road rocket coincides with maximum g forces,not maximum power, if ,as you say ,power is not an abstraction.

Are you from Australia?

[gruntguru]

Quote

Originally posted by Dmitriy_Guller
Are you from Australia?

I assume he means Eastwood - a suburb of Sydney. Now where are you going with this?

Signed
Proud Aussie.

[Dmitriy_Guller]

Quote

Originally posted by gruntguru
I assume he means Eastwood - a suburb of Sydney. Now where are you going with this?

Signed
Proud Aussie.

I'm trying to figure out why his posts are so incomprehensible. If he's not an English speaker, then it's understandable. If he is a native English speaker, however, then there is no excuse for writing so poorly, and making other people work hard to try to decipher what he's trying to say.

[gruntguru]

Quote

Originally posted by Dmitriy_Guller
I'm trying to figure out why his posts are so incomprehensible. If he's not an English speaker, then it's understandable. If he is a native English speaker, however, then there is no excuse for writing so poorly, and making other people work hard to try to decipher what he's trying to say.

That's OK then - lots of Aussies are illiterate.

[johnny yuma]

Quote

Originally posted by gruntguru
That's OK then - lots of Aussies are illiterate.

Yeah mate, spoze that explains why neiver of us can get our ideas across !

My perception of this topic (when I came in late from a roo- shooting bush-bashing grog-on) was people were saying power was as fundamental as torque.Others seemed to say it was "even more fundamental"--pardon my colonial convict English ! I thought "thats a crock of crap",torque is a fundamental to calculating power "readings".Thus power is an abstraction .Perhaps torque is also an abstraction ,but it's higher up in the chain than power.

Just how this relates to year zero/ post#1 , I shudder to think. Anyhow she'll be right mate ,no worries Bruce, let's hit the frog 'n' toad.Last one to the Ari shouts.Didja hear the one about the Pom,the Yank and the Kraut ? It's still goin on !

[Joe Bosworth]

While thinking about Grunt’s Summary list of 9 items it suddenly came to me where much of the mis-information and false statements contained in this thread derive from. Let me share with you in the hope that doing so can/will allow more people to understand the issues being discussed so passionately. (Actually this came to me during a long bicycle ride, when one’s mind is cleared of extraneous matters and the sub-conscious works at its best.)

IMHO one of the problems with this thread largely comes from the thinking that,

7. To achieve this limiting value at ALL speeds would require either a CVT to maintain the engine at peak power rpm, or an engine that maintains peak power over a sufficiently wide range of RPM so that it can be operated at peak power before and after each gear shift. (e.g. WRC restricted turbo engines, Electronic Diesel truck engines, Diesel Electric locomotives . . . .)

is actually true. It is true for some engine configurations but not all engine configurations. Much confusion exists because there are some who argue from the position that the statement is for every engine and therefore is absolutely true.

I think that we have all progressed to the point that we can agree that acceleration is a direct function of the thrust at the rear wheels. I think that we all have also progressed to the point that rear wheel thrust is a direct function of rear wheel torque, which in turn is directly a function of engine torque and the gearing between engine and rear wheels.

Let me use my daily driver engine as an example. My torque figures are:

at max torque 413 Kn at 3500 rpm

at max HP 350 Kn at 5120 rpm

This is the reason that in any given gear that I find the maximum acceleration at the point of max torque.

But now lets attach Grunt’s CVT to the engine in place of my gearbox. I will compare the rear wheel torque for two situations; one is to maintain engine speed at max HP and the other to maintain engine speed at max torque. To be comparable for the same road speed I need to use a dif ratio numerically lower ratio when using a constant 3500 rpm than when using a constant 5120. And of course that numerically lower ratio reduces the available rear wheel max torque to a point that is now only 81% of the torque available at max HP. Grunt’s hypothesis is correct!! (By the way I also look at a point 55% of the way between 3500 and 5120 ant the picture is better being only 4% lower but still less.)

Let me now keep the same shape of HP and T curves but lift the max torque point to 4000 rpm as happens when I higher state of tune is achieved. Re-gearing again for equivalent road speeds we now find rear wheel torque at max revs only 8% below the T at 5120 but the rear wheel torque at the interim point (4710) now equals that found at 5120. Grunt’s hypothesis is now looking shaky!

Lets do some more tuning and raise the max torque point to 4500 and the interim point to 4850, still with max HP at 5120. Lo and behold, after adjusting the dif ratio again to keep tings equal we find RWT at 4500 to be 4% over that at 5120 and the interim to be 5% greater. Grunt’s hypothesis is now blown to smithereens!!!

Summary point 7, complete with the capitalised ALL, is incorrect.

The controlling factors in the choice of speed to run a CVT for max acceleration are the percentage change in T/HP vs percentage change in RPM. The best RPM will msot likely be found between the RPM of max T and Max HP but this again is curve shape controlled.

What does this tell us? First and foremost that making broad general statements on this subject is very fraught with problems unless one sticks very close to very good science. Another point shown is that one better go back to basics and analyse for rear wheel thrust/torque in order to fully understand the nuances of HP/T/gearing questions.

PS: Since the situation of bicycle gearing has been raised elsewhere in this thread I would be happy to provide a very sound treatise on that subject if enough people are interested. Human power output is quite a subject in its own right. But very OT.

Regards

[cheapracer]

Quote

Originally posted by Dmitriy_Guller

I'm trying to figure out why his posts are so incomprehensible. If he's not an English speaker, then it's understandable. If he is a native English speaker, however, then there is no excuse for writing so poorly, and making other people work hard to try to decipher what he's trying to say.

You want me to correct your shocking grammar in this paragraph?

Another proud Ozzian.

[cheapracer]

Quote

Originally posted by gruntguru
That's OK then - lots of Aussies are illiterate.

I'm not illiterate, my Mum and Dad were married 3 weeks before I was born.

[gruntguru]

Quote

Originally posted by Joe Bosworth
Lets do some more tuning and raise the max torque point to 4500 and the interim point to 4850, still with max HP at 5120. Lo and behold, after adjusting the dif ratio again to keep tings equal we find RWT at 4500 to be 4% over that at 5120 and the interim to be 5% greater. Grunt’s hypothesis is now blown to smithereens!!!

Impossible !!!!! Rear wheel torque is proportional to engine power divided by road speed, so if road speed is the same in both cases, rear wheel torque will be higher for the case where engine power is higher.

[gruntguru]

Quote

Originally posted by cheapracer


I'm not illiterate, my Mum and Dad were married 3 weeks before I was born.

[gruntguru]

Quote

Originally posted by Joe Bosworth
The controlling factors in the choice of speed to run a CVT for max acceleration are the percentage change in T/HP vs percentage change in RPM. The best RPM will msot likely be found between the RPM of max T and Max HP but this again is curve shape controlled.

Best CVT acceleration occurs at max power RPM. Same with finite gearboxes - best acceleration occurs when RPM is maintained as close as possible to max power RPM. Max torque RPM is irrelevant to shift point selection.

[johnny yuma]

Lets do some more tuning and raise the max torque point to 4500 and the interim point to 4850, still with max HP at 5120.

Regards [/B][/QUOTE]
As much as I love your work Joe,that is a very fictional engine hot-up which puts peak torque up to 4500 rpm, without simultaneously raising the power peak a single rpm ! Reminds me of gruntguru's fictional graphs.And those diff ratio changes are a worry too.gruntguru is a moving target,I think you've missed him !

Love to hear more on Human Powered Vehicles !

[johnny yuma]

Quote

Originally posted by McGuire


What is the proper technical term for the physical property that accelerates the crankshaft?



No, they are saying exactly what they mean, with perfect technical precision. You are merely translating it into your own preferred terms, which requires an additional level of abstraction.

McGuire,2 YEARS AGO ! He was right then,he's still right,he's still fightin the good fight.

ABSTRACTION ! Power is an abstraction.Say it loud ,say it proud.

[johnny yuma]

Quote

Originally posted by Dmitriy_Guller

I'm trying to figure out why his posts are so incomprehensible. If he's not an English speaker, then it's understandable. If he is a native English speaker, however, then there is no excuse for writing so poorly, and making other people work hard to try to decipher what he's trying to say.

I'll fill you in Guller,you find it difficult because your perfect storm of knowledge won't allow you into the still calm of looking at something from my point of view.You seem comfortable enough to disagree,but that has no value if you don't know what I'm saying.

[gruntguru]

Quote

Originally posted by johnny yuma
McGuire,2 YEARS AGO ! He was right then,he's still right,he's still fightin the good fight. ABSTRACTION ! Power is an abstraction.Say it loud ,say it proud.

Nonsense. Peak power output is the single most useful number to describe any engine.

[Joe Bosworth]

John

You are correct that HP and T will likely move up with the fictional changes that I used on a real engine. But I carefully kept proportions in keeping with the original. Heaven forbid that I am ever accused of creating the blatantly contrived engine curves used to demonstrate some of the points trying to be made in this thread.

Frankly, using a CVT in the situations in which it is being used in this thread is a gross contrivance in itself.

However, it is a mathematical certainty that when the torque measurement of an engine at max T is a greater percentage above T at max power than the percentage differenece between the two rev points that the CVT will provide greater acceleration when operated at the lower T revs than the higher P revs when both are geared to provide the same top speed.

I hope this concept is clearly enough stated for all to understand despite my half fictional attempt to demonstrate it with numbers.

Regards

PS: The fictional changes will be the likely result of my next planned engine mods of increasing the cam timing duration to something closer to 280 degrees.

[gruntguru]

Quote

Originally posted by Joe Bosworth
However, it is a mathematical certainty that when the torque measurement of an engine at max T is a greater percentage above T at max power than the percentage differenece between the two rev points that the CVT will provide greater acceleration when operated at the lower T revs than the higher P revs when both are geared to provide the same top speed.

You are correct - this is a mathematical certainty. Unfortunately the scenario is an impossibility because if you raise the torque at max T enough to achieve this, the power at max T will be higher than the power at max P. See the contradiction?

[xxchrisxx]

Quote

Originally posted by gruntguru
Agree - although power is the most useful single number for rating any engine.
I hope you didn't think I was implying any of these things can be measured directly. I struggle to think of any properties outside the seven fundamentals that can be measured directly.

Power is the most useful number to see what an engine CAN do, which is why I have referred to it as 'potential' for the car to do something.

I understand that you know it can't be measured directly (which as you probably detected the how do you measure heat is a leading question). But a lot of people do think it can for two reasons. A rolling road spits out a power figure and it slips neatly into the formula. Acceleration = Power / (Mass * Velocity).

So even though the mathematical relation is solid and can be used to find acceleration, it gives a slightly cloudy view of the physics. Which is what i've got the bug up my arse about.


On a tangent, for comparison of how different engines (and especially ones that are very different) are performing relative to each other, a power output isnt the most useful thing. Comparing something like BMEP and volumetric efficienies are. (This isnt really a respose to the question, its just a rambing)

Quote

Originally posted by gruntguru

Measuring heat input is simply fuel massflow times heating value.

As you've said its not one of the big seven so can't be measured directly. And what you measure is acutally those two things (i'll stop bashing on about it now).

Quote

Originally posted by gruntguru


Waste heat output as I said is difficult because there are several sources. The easy ones are cooling water for coolant and oil (massflow x delta T). Exhaust is a little more difficult, can use a calorimeter and extrapolate or meausure massflow (inlet air + fuel is easier than direct measurement of exhaust flow) and use tables, but composition needs to be measured or estimated. The hardest to measure is radiant and convection losses from the engine exterior - a small number but significant. This is the one that is usually considered to be "whatever is left" after heat balance calculations. No doubt McGuire will have plenty to add (or subtract) on this subject when he reads this.

This is same as above. not direct measuring as you say.

Quote

Originally posted by gruntguru

As far as definitions of abstract - I don't think it advances the discussion to dismiss things as abstract simply because human beings can't sense them directly. Electric current is something you can't sense but it is a fundamental quantity and we all accept it as a unique way of measuring an everyday phenomenon.

Touch yourself with two wires connected to ac. Just because people dont tend to feel electric current doesnt mean they cant. However I am utterly crap at all things electronic and electric so im not going to go there as i've probably already used the wrong words.

This is the problem that many people have, they cant sense the electric properties and therefore have applying them. So for example, lots of people may think that "MORE VOLTS WILL KIL YUOS!!!" when its acutally an increase in current ususally. But keeping the resistance the same will make more current = more volts. And what comes first voltage or current.

Theres an analogy to this thread in there somewehere.

[xxchrisxx]

Quote

Originally posted by Dmitriy_Guller


I also don't buy the argument that thinking abstractly can lead to poor understanding of the physical process involved. In this thread, for example, the people who got the physical process wrong belong exclusively to the torque camp, so they're not exactly making a good argument for that theory. In fact, the abstract power theory is what helps you sanity-check your arguments.

People talking about phsyics of motion in terms of forces and torques can easily be corrected by making them go away and do it. As torque and that can be measured directly the fact taht they've made a mistake becomes plain to see.

As power cant be measured directly it tends to be more difficult to correct people who have the physics wrong in that camp.

[gruntguru]

Quote

Originally posted by xxchrisxx
On a tangent, for comparison of how different engines (and especially ones that are very different) are performing relative to each other, a power output isnt the most useful thing. Comparing something like BMEP and volumetric efficienies are.

BMEP and VE and TE are great for comparing engines in terms of "how good a job did the engine designer do?" But if you want to know "how well will engine A or B go in my racecar?" and you only get to look at one number, the number to look at is "peak-power".

[gruntguru]

Quote

Originally posted by xxchrisxx
Touch yourself with two wires connected to ac. Just because people dont tend to feel electric current doesnt mean they cant.

In that case I suppose you can also feel power in the sense that you can feel the heating power of a bar heater or the sound power from a loudspeaker. You could even pretend you are a dyno-brake and grab a rotating driveshaft to estimate the power in terms of how hot your hand gets.

[cheapracer]

Quote

Originally posted by xxchrisxx


Power is the most useful number to see what an engine CAN do, which is why I have referred to it as 'potential' for the car to do something.

.

30 years or so ago I went through a succession of various engines in my Datsun 1000 Coupe all rated at around the same power, 110hp - Mazda 12A rotary, Datsun L20 2.0, Fiat 1608cc TC.

If you think these 3 examples with the same power rating were anything close to similar in what they CAN do, you are delusional.

[cheapracer]

Quote

Originally posted by gruntguru
Nonsense. Peak power output is the single most useful number to describe any engine.

Oh, I answered this one above ...

[gruntguru]

Quote

Originally posted by cheapracer
30 years or so ago I went through a succession of various engines in my Datsun 1000 Coupe all rated at around the same power, 110hp - Mazda 12A rotary, Datsun L20 2.0, Fiat 1608cc TC.

If you think these 3 examples with the same power rating were anything close to similar in what they CAN do, you are delusional.

I am certainly not saying that - merely that max power is the most important single number. Next most important is the width of the power peak.

You mention three very different engines that would all have a different width of power peak, different final drive requirements, different rotating inertia etc etc.

[McGuire]

Quote

Originally posted by gruntguru
In that case I suppose you can also feel power in the sense that you can feel the heating power of a bar heater or the sound power from a loudspeaker. You could even pretend you are a dyno-brake and grab a rotating driveshaft to estimate the power in terms of how hot your hand gets.

You can hear sound and you can feel heat, but you cannot hear or feel power. I hope I am not being too obvious in noting that heat, sound, and power are totally different qualities.

There is a very good reason you cannot experience power in an automotive engine. Here, power is the product of two dissimilar properties, one a quality and the other a quantity: torque and rpm. So power is indeed an abstract value, no getting around it. This is not to say power does not exist as a useful property, simply to advance an understanding of what it is.

[gruntguru]

Quote

Originally posted by McGuire
I hope I am not being too obvious in noting that heat, sound, and power are totally different qualities.

Obvious but incorrect. Heat and sound are both forms of energy and therefore are expressed as power when measured as a rate or as a time derivative.

[gruntguru]

Quote

Originally posted by McGuire
Here, power is the product of two dissimilar properties, one a quality and the other a quantity: torque and rpm.

Pardon my ignorance. Which one is not a quantity and when did this change of status occur?

[xxchrisxx]

Quote

Originally posted by cheapracer


30 years or so ago I went through a succession of various engines in my Datsun 1000 Coupe all rated at around the same power, 110hp - Mazda 12A rotary, Datsun L20 2.0, Fiat 1608cc TC.

If you think these 3 examples with the same power rating were anything close to similar in what they CAN do, you are delusional.

Oh im ever so sorry. Your experience with three engines means the world should redefine what power is.

Forget that power is the rate of work, forget that work is thing that something does. because you had three labels that said the same thing yet acted differently all of that if rather obviously wrong.

Have you ever considered that three engines, that have a rated power output. may not be acutrally putting ou that power, and that power is delivered with a different characteristic. and that the the characteristics make them feel different.

no?

oh well i guess we wont chage the definition of power then... DAMN!

[xxchrisxx]

Quote

Originally posted by gruntguru
In that case I suppose you can also feel power in the sense that you can feel the heating power of a bar heater or the sound power from a loudspeaker. You could even pretend you are a dyno-brake and grab a rotating driveshaft to estimate the power in terms of how hot your hand gets.

then you would be feeling temperature, not heat, not power. you could attampt to calibrate how hot your hand gets to power output. thats still not measuring or indeed feeling power.

Mac is dead right on this one, they are totally different qualities. I suspect you are now arguing with increasing absurdity simply to be obtuse.

[McGuire]

Quote

Originally posted by gruntguru
Obvious but incorrect. Heat and sound are both forms of energy and therefore are expressed as power when measured as a rate or as a time derivative.

Heat and sound may both be expressed in terms of the energy required to produce them, but that does not make them the same thing. Try to heat your home with your loudspeakers.

[xxchrisxx]

Quote

Originally posted by McGuire


Heat and sound may both be expressed in terms of the energy required to produce them, but that does not make them the same thing. Try to heat your home with your loudspeakers.

Theres a funny image, I can just see the neighbours compaining and the coppers rolling up.

"I'm sorry but your heating system is too loud"

[cheapracer]

Quote

Originally posted by xxchrisxx


Oh im ever so sorry. Your experience with three engines means the world should redefine what power is.

Forget that power is the rate of work, forget that work is thing that something does. because you had three labels that said the same thing yet acted differently all of that if rather obviously wrong.

Have you ever considered that three engines, that have a rated power output. may not be acutrally putting ou that power, and that power is delivered with a different characteristic. and that the the characteristics make them feel different.

no?

oh well i guess we wont chage the definition of power then... DAMN!

Leave sarcasm to Ozzies, we rule in that area, amateur.

I pointed out those 3 engines because they all had 110hp ratings from the manufacturers (thats the people who make them and give out the hp ratings based on their own testing and loose International agreements, not mine) and it's not such a common situation that that occurs, how many times can anyone here say they have compared 3 different engines with the same hp rating in the one chassis? I could give you my resume but I could also piss into the wind and get the same results.

You posted a very stupid comment, again, you can not choose an engine and know what it will, sorry CAN do in a car based on it's power output - take out a 3300cc 150hp Holden 6 out of a Commodore and throw in a 1300cc 180hp Suzuki Hybusa engine and see how much slower you go with 30 more hp.

[Bill Sherwood]

Quote

Originally posted by cheapracer
take out a 3300cc 150hp Holden 6 out of a Commodore and throw in a 1300cc 180hp Suzuki Hybusa engine and see how much slower you go with 30 more hp.

The Suzuki just needs a stroker crank, like this one, fitted by tiny little mechanics.

[cheapracer]

Quote

Originally posted by gruntguru
I am certainly not saying that - merely that max power is the most important single number. Next most important is the width of the power peak.

You mention three very different engines that would all have a different width of power peak, different final drive requirements, different rotating inertia etc etc.

I wish, I was an apprentice spanner at the time working part time at a wreckers and sometimes I would take an engine instead of wages and the diff stayed the same the whole time. If memory serves me correctly all 3 used a 4.1:1 diff standard and I had a 4.3:1 in a Datsun 1600 SW diff.

I like the way you say "width of power peak" and skirt mentioning torque

Of those 3 the L20B was the grunter pulling in any gear very strongly from low revs to about 5000, you had to rev the FIAT up more than 6000 and the Rotary had a strong flat feeling in the mid range which tapered off quickly despite you could rev it to more than 8000. All were bog standard.

Ahh good (read wasted) days with my little Dato, the first year I changed engines 7 times!

[cheapracer]

Quote

Originally posted by Bill Sherwood


The Suzuki just needs a stroker crank, like this one, fitted by tiny little mechanics.




Yes, the many-times-posted Sulzer diesel ship engine; 98,000hp at 100rpm. I'd say that this is a lot of torque but I dare not.

[

> "tiny little mechanics"

Great pictures, I got that one somewhere on my puter.

And looking at the drive plate it's obviously an auto ;)

[xxchrisxx]

Quote

Originally posted by cheapracer


Leave sarcasm to Ozzies, we rule in that area, amateur.

I pointed out those 3 engines because they all had 110hp ratings from the manufacturers (thats the people who make them and give out the hp ratings based on their own testing and loose International agreements, not mine) and it's not such a common situation that that occurs, how many times can anyone here say they have compared 3 different engines with the same hp rating in the one chassis? I could give you my resume but I could also piss into the wind and get the same results.

You posted a very stupid comment, again, you can not choose an engine and know what it will, sorry CAN do in a car based on it's power output - take out a 3300cc 150hp Holden 6 out of a Commodore and throw in a 1300cc 180hp Suzuki Hybusa engine and see how much slower you go with 30 more hp.

Oh you crazy tool.

The power output, shows how work can be done in a set time.

The Hybusa doesnt have the torque to drag the enormous lump that is the Commodore and you know it. Yet this has no impact on the work being done by the engine in a set amount of time.

The deliberate and rather lame attempt to dig your way out of an idiotic comment, suggesting that power is somehow not a measure of what work can be done by the engine in a set time. Purely on the basis that your had three different engines with the same 110hp rating but didnt do the same thing to your car. OH NOES!

Now I know the Ozzies just dont get subtlty but, engine work and moving down the road are two different things (connected, yes. but still different). I said that it shows wha the engine can do and this is the 'potential' for what a car can do, not what it will actually do. This is important becuase me ang gg were talking about otto cycles at the time you decided to wade in blindfolded and start shouting about something totally irrelevent.

To make this clear for the less mentally sharp. The above does NOT mean you can take it from power alone, only that power shows the work that CAN be done by the engine. To acutally know what will happen you need a torque fugre showing WHAT work is done. ie moving little lump very fast, or big lump slowly.

You are getting good and responding to posts with 'answers' so far removed from the discussion at hand that nobody knows that the hell is going on.

Like I said correct tool for the job. Meaty engines for meaty cars, thimble sized revvers for bikes.


Read the above several times before launching into a tirade of drivel please.

[Dmitriy_Guller]

Quote

Originally posted by Joe Bosworth
While thinking about Grunt’s Summary list of 9 items it suddenly came to me where much of the mis-information and false statements contained in this thread derive from. Let me share with you in the hope that doing so can/will allow more people to understand the issues being discussed so passionately. (Actually this came to me during a long bicycle ride, when one’s mind is cleared of extraneous matters and the sub-conscious works at its best.)

IMHO one of the problems with this thread largely comes from the thinking that,

7. To achieve this limiting value at ALL speeds would require either a CVT to maintain the engine at peak power rpm, or an engine that maintains peak power over a sufficiently wide range of RPM so that it can be operated at peak power before and after each gear shift. (e.g. WRC restricted turbo engines, Electronic Diesel truck engines, Diesel Electric locomotives . . . .)

is actually true. It is true for some engine configurations but not all engine configurations. Much confusion exists because there are some who argue from the position that the statement is for every engine and therefore is absolutely true.

I think that we have all progressed to the point that we can agree that acceleration is a direct function of the thrust at the rear wheels. I think that we all have also progressed to the point that rear wheel thrust is a direct function of rear wheel torque, which in turn is directly a function of engine torque and the gearing between engine and rear wheels.

Let me use my daily driver engine as an example. My torque figures are:

at max torque 413 Kn at 3500 rpm

at max HP 350 Kn at 5120 rpm

This is the reason that in any given gear that I find the maximum acceleration at the point of max torque.

But now lets attach Grunt’s CVT to the engine in place of my gearbox. I will compare the rear wheel torque for two situations; one is to maintain engine speed at max HP and the other to maintain engine speed at max torque. To be comparable for the same road speed I need to use a dif ratio numerically lower ratio when using a constant 3500 rpm than when using a constant 5120. And of course that numerically lower ratio reduces the available rear wheel max torque to a point that is now only 81% of the torque available at max HP. Grunt’s hypothesis is correct!! (By the way I also look at a point 55% of the way between 3500 and 5120 ant the picture is better being only 4% lower but still less.)

Let me now keep the same shape of HP and T curves but lift the max torque point to 4000 rpm as happens when I higher state of tune is achieved. Re-gearing again for equivalent road speeds we now find rear wheel torque at max revs only 8% below the T at 5120 but the rear wheel torque at the interim point (4710) now equals that found at 5120. Grunt’s hypothesis is now looking shaky!

Lets do some more tuning and raise the max torque point to 4500 and the interim point to 4850, still with max HP at 5120. Lo and behold, after adjusting the dif ratio again to keep tings equal we find RWT at 4500 to be 4% over that at 5120 and the interim to be 5% greater. Grunt’s hypothesis is now blown to smithereens!!!

Summary point 7, complete with the capitalised ALL, is incorrect.

The controlling factors in the choice of speed to run a CVT for max acceleration are the percentage change in T/HP vs percentage change in RPM. The best RPM will msot likely be found between the RPM of max T and Max HP but this again is curve shape controlled.

What does this tell us? First and foremost that making broad general statements on this subject is very fraught with problems unless one sticks very close to very good science. Another point shown is that one better go back to basics and analyse for rear wheel thrust/torque in order to fully understand the nuances of HP/T/gearing questions.

PS: Since the situation of bicycle gearing has been raised elsewhere in this thread I would be happy to provide a very sound treatise on that subject if enough people are interested. Human power output is quite a subject in its own right. But very OT.

Regards

Joe, frankly that was a disappointing post. First of all, how can you raise the rpm of the torque peak while keeping the same shape of the curves? That's mutually exclusive, by definition you change the shape of the curve when you change the peaks.

By far the bigger error is that when you moved the torque peak to 4,500 rpm, you've actually given your car more power at that point than it has at power peak! That's what happens when you assume that the curves stay the same while at the same time heavily modifying them. Of course the car is going to accelerate better with a CVT set to that RPM, it's got more power there than at "power peak".

With all due respect, and I do respect you, that was not a well-thought out post.

[Greg Locock]

McGuire - you are wrong on both counts.

Check out sound intensity and heat flux, both of which are measures of energy transmitted per second (ie power) per unit area. Both of which I have measured.

[gruntguru]

Quote

Originally posted by McGuire
Heat and sound may both be expressed in terms of the energy required to produce them, but that does not make them the same thing. Try to heat your home with your loudspeakers.

They are both forms of energy. You could heat your home with loudspeakers but since just 10 Watts of sound power is quite deafening, I wouldn't recommend it.

[xxchrisxx]

Quote

Originally posted by Greg Locock
McGuire - you are wrong on both counts.

Check out sound intensity and heat flux, both of which are measures of energy transmitted per second (ie power) per unit area. Both of which I have measured.

Before I respond to this, i'm going to have to say I know very little about the above so i'm quite possibly/probably wrong, so be gentle.

The word flux chagnes things a bit from heat and sound. You can measure the flux of something its not a direct measurement.

Take heat flux, from what I can remember heat flux sensors mesure temperature difference of a known material (so you know the thermal conductivity) and set area.

Making temperature the measured property not heat. And then then power per unit area inferred.

It kind of makes it like the dyno, you measure 'something' and a power is spat out.

[gruntguru]

Quote

Originally posted by cheapracer
I like the way you say "width of power peak" and skirt mentioning torque

I don't say it to be obtuse. "width of power peak" is actually more technically correct than saying "broader torque band".

[gruntguru]

Quote

Originally posted by cheapracer
take out a 3300cc 150hp Holden 6 out of a Commodore and throw in a 1300cc 180hp Suzuki Hybusa engine and see how much slower you go with 30 more hp.

If those power numbers are real, the Hyabusadore will out-accelerate the Commodore. Only proviso is that gearing is suitably altered and the power band is wide enough for the engine to be maintained above 150hp through the gears. The Suzuki engine doesn't even need to be lighter weight.

I have donned my bullet-proof vest and await your responses!

[xxchrisxx]

Quote

Originally posted by gruntguru
If those power numbers are real, the Hyabusadore will out accelerate the Commodore. Only proviso is that gearing is suitably altered and the power band is wide enough for the engine to be maintained above 150hp through the gears. The Suzuki engine doesn't even need to be lighter weight.

I have donned my bullet-proof vest and await your responses!

Although this is true, cheapracer was talking about doing it practically. With the lack of torque that the Hybusa engine produces it would require a hell of a lot of gears to keep it up in the power band and keep the rear wheel thrust the same.

[gruntguru]

Quote

Originally posted by xxchrisxx
Before I respond to this, i'm going to have to say I know very little about the above so i'm quite possibly/probably wrong, so be gentle.

The word flux chagnes things a bit from heat and sound. You can measure the flux of something its not a direct measurement.

Take heat flux, from what I can remember heat flux sensors mesure temperature difference of a known material (so you know the thermal conductivity) and set area.

Making temperature the measured property not heat. And then then power per unit area inferred.

It kind of makes it like the dyno, you measure 'something' and a power is spat out.

Its a pity Greg mentioned the word "flux" because its not really necessary. Both heat and sound can be measured/expressed in total power terms ie Watts, in fact this is the most common unit used for heat or sound-producing devices. Heating devices are generally 100% efficient (except RC aircon which is more like 300% and referred to as Coefficient of Performance not efficiency) so the rating in Watts refers to the electrical power used and the heat power produced. Loudspeakers are rated by the electrical power used but are generally only 1% to 10% efficient so the sound power produced will be a fraction of the rating in Watts. The remainder of the electrical power appears as heat in the driver coils and the crossover circuitry. Interestingly the sound power also ends up as heat - some in the house and some outside - depends if you have the windows open etc etc.

[xxchrisxx]

Quote

Originally posted by gruntguru
Its a pity Greg mentioned the word "flux" because its not really necessary. Both heat and sound can be measured/expressed in total power terms ie Watts, in fact this is the most common unit used for heat or sound producing devices. Heating devices are generally 100% efficient (except RC aircon which is more like 300% and referred to as Coefficient of Performance not efficiency) so the rating in Watts refers to the electrical power used and the heat power produced. Loudspeakers are rated by the electrical power used but are generally only 1% to 10% efficient so the sound power produced will be a fraction of the rating in Watts. The remainder of the electrical power appears as heat in the driver coils and the crossover circuitry. Interestingly the sound power also ends up as heat - some in the house and some outside - depends if you have the windows open etc etc.

Edited to cut the crap

I'm starting to get tired and i'm making posts that dont make sense, so i'll respond to this tomorrow.

Bugger you already responded, oh well.