Why is drive Train loss a %?(technical observation) [Archive]

RedNOSceli

08-03-2003, 02:30 PM

Ok...Celica STOCK makes 180hp, averages about 160hp to the wheels bone stock....

thats about a 12%(give or take) 'drivetrain loss' or, the car looses 20hp from the flywheel to the motor.

Now it would make more sense to me that we no longer use a % at this point because the question I ask is, why would an engine making more, loose any more thru throu the tranny?

Shouldnt that loss stay the same reguardless of FLYwheel HP? Do we just use the 15% loss as a rule of thumb? If we do its kinda of silly...

Stock Supra makes @ 300hp - 15% = 255 at the wheels, difference of 45hp.

So anothe supra dynos at 500hp at the wheels..Now according the 15% rule that car makes est 590hp at the flywheel, but that doesnt make any sense because the tranny only sucks up 45hp, so LOGIC would rule that car only makes 545 HP at the flywheel, and these are pretty small numbers...

Imagine the differences between 1000hp cars....a 1300hp car would loose 300hp to the drive train to put 1000hp to the ground? Doesnt sound right to me....

LaW

08-03-2003, 02:43 PM

I don't agree with your logic

XYRCNCP

08-03-2003, 02:54 PM

Originally posted by LaW
I don't agree with your logic

:werd: according to your logic, it seems that you are putting 45hp as a constant loss

Originally posted by RedNOSceli

Stock Supra makes @ 300hp - 15% = 255 at the wheels, difference of 45hp.

So anothe supra dynos at 500hp at the wheels..Now according the 15% rule that car makes est 590hp at the wheels, but that doesnt make any sense because the tranny only sucks up 45hp, so LOGIC would rule that car only makes 545 HP at the flywheel, and these are pretty small numbers...

the 500 whp Supra would in fact make 575 at the flywheel. 75hp would be 15% loss.

in a 1000 flywheel hp engine, due to tranny loss the whp would be 850

LaW

08-03-2003, 03:20 PM

Originally posted by XYRCNCP
:werd: according to your logic, it seems that you are putting 45hp as a constant loss

exactly what I was thinking... when you make that 500hp supra its a different engine.... you cant just make the 45 it loses stock as "constant".... doesn't work that way

pokgai

08-03-2003, 03:42 PM

i kinda understand his reasoning.

the more power an engine makes (flywheel hp), the more it loses in its tranny then?

so based on the % system, a 50 crank hp engine would lose 12%, or 6hp, through the transmission, making it run 44 hp the wheels. is that right?

GTSROLL

08-03-2003, 03:52 PM

Not very good reasoning here rednos. There are too many variables to take into consideration when calculating something like this. some supras may put more power to the flywheel but can have close to the same wheel hp as the other supra putting down less flywheel hp. Not all drive trains are the same. Could be more than 15% is what i am saying.

Blue Bomber

08-03-2003, 03:55 PM

Just think of it as a sales tax. No matter what price (or hp) something is, the same percentage is always used as tax (or the transmission), no matter how much or little the price is. Only instead of adding tax, you're removing hp.

BadTOYO

08-03-2003, 04:01 PM

Originally posted by RedNOSceli
the car looses 20hp from the flywheel to the motor.
:confused: you mean from the crank to the wheels... factory numbers are at the cranck, the flywheel is already taking power away...
R

XYRCNCP

08-03-2003, 04:15 PM

Originally posted by pokgai
i kinda understand his reasoning.

the more power an engine makes (flywheel hp), the more it loses in its tranny then?

so based on the % system, a 50 crank hp engine would lose 12%, or 6hp, through the transmission, making it run 44 hp the wheels. is that right?

ur right, 6hp loss, leaving a net whp of 44.

Originally posted by Blue Bomber
Just think of it as a sales tax. No matter what price (or hp) something is, the same percentage is always used as tax (or the transmission), no matter how much or little the price is. Only instead of adding tax, you're removing hp.

that's a good comparison Blue...:thumbup:

RedNOSceli

08-03-2003, 04:59 PM

Originally posted by LaW
exactly what I was thinking... when you make that 500hp supra its a different engine.... you cant just make the 45 it loses stock as "constant".... doesn't work that way

Why Not?

...Drive Train loss is the Power that is lost in actually making the tranny etc. turn. This is a Constant.

IE, it takes 10lb/feet or torque just to get this input shaft to twist/move.

Changing how much torque the flywheel makes does not make the drive train 'soak' up more power. So because my motor make 200hp or 300hp, the tranny still only requires X torque to make it move. That why I say that the drive train lost is a constant, which would still be different on every car

I dont think you guys are seeing my point. Im not saying EVERY CAR uses a 45hp constant, im saying that to figure your constant per THAT TRANNY in that car youd have to figure your Flywheel HP vs. your Wheel HP and that how much power is lost through your drive train.

As I said, just a question, so somone give me some Logic/Physics why I am wrong and not just 'because thats what everyone else says'

mirconrice

08-03-2003, 05:07 PM

Originally posted by Blue Bomber
Just think of it as a sales tax. No matter what price (or hp) something is, the same percentage is always used as tax (or the transmission), no matter how much or little the price is. Only instead of adding tax, you're removing hp.

i agree with blue bomber, drivetrain lose is just like taxes. If you spend 10 dollars and was taxed 5 percent, that would be .50 cent. So with your logic, if I spend 100 dollars, i would only be taxed .50 cent....not likely, although I wish it was like that, :) Drivetrain lose is the same thing.

RedNOSceli

08-03-2003, 05:12 PM

Originally posted by mirconrice
i agree with blue bomber, drivetrain lose is just like taxes. If you spend 10 dollars and was taxed 5 percent, that would be .50 cent. So with your logic, if I spend 100 dollars, i would only be taxed .50 cent....not likely, although I wish it was like that, :) Drivetrain lose is the same thing.

But see, that is totally differnt. A Drivetrain takes Xamount of power away just to get it to move. That number does not change with the amount of power that is put to it.

Lets make it VERY SIMPLE....

Theres a Pencil sitting on my desk.

I hit the pensil with X amount of force. The pencil sitting still, requires Y amount of force to break its loose and over come gravity holding it down, as well as the friction between the desk and the pencil is holding it in its place.

(keep in mind, Y is different for everything, it takes a differnt amount of force to say move my key across the desk, just like a 6speed supra tranny would take a differnt amount to get it to turn then a TH350 GM tranny)

Now it doesnt matter if X = 10lbs or 20lbs, Y is still Y, the amount it takes to get it to move, so Z(the total amount of force the pencil would give if it smacked into my pencil holder) is not a percentage of of X to Y, but a sum, X - Y...

Thats just my simple math/physics explination if somone would like to say otherwise...

LaW

08-03-2003, 05:31 PM

I just think its not worth the time to argue over something that makes enough sense to use already... you guys have fun with this one

RedNOSceli

08-03-2003, 05:34 PM

Originally posted by LaW
I just think its not worth the time to argue over something that makes enough sense to use already... you guys have fun with this one

So my last post is wrong? How so?

mirconrice

08-03-2003, 05:43 PM

Originally posted by RedNOSceli
But see, that is totally differnt. A Drivetrain takes Xamount of power away just to get it to move. That number does not change with the amount of power that is put to it.

Lets make it VERY SIMPLE....

Theres a Pencil sitting on my desk.

I hit the pensil with X amount of force. The pencil sitting still, requires Y amount of force to break its loose and over come gravity holding it down, as well as the friction between the desk and the pencil is holding it in its place.

(keep in mind, Y is different for everything, it takes a differnt amount of force to say move my key across the desk, just like a 6speed supra tranny would take a differnt amount to get it to turn then a TH350 GM tranny)

Now it doesnt matter if X = 10lbs or 20lbs, Y is still Y, the amount it takes to get it to move, so Z(the total amount of force the pencil would give if it smacked into my pencil holder) is not a percentage of of X to Y, but a sum, X - Y...

Thats just my simple math/physics explination if somone would like to say otherwise...

yes but that is incorrect. You can't say X is equal to whatever and that a constant force of Y can move any size object. That is totally wrong. The physics of what you are trying to explain is called potential and kenetic energy. The pencil sitting there is holding potential energy. The reason why the pencil is just sitting there is because of static energy. The force it takes to move that pencil has to be greater than the static energy which includes friction and what not. That pencil is holding an equilibrium of energy which include static energy. So to move that object, you have to overcome that equilibrium. So it does matter what the object, X equal to, and the amount of force it takes to move that object. It is portional to each other so therefore lets say the pencil weigh in at 10 lbs and it takes 20 Newton to move that object, with your thinking, that 20 newton force that you apply to the 10 lbs, you can apply to a 20 lbs object and it would move. But that is totally wrong. You can't use the same force that you move a 10 lbs object to a object that weighs 20 lbs. I hope I explain that right. Its been 4 years since I took physics.

FL Honda Stompr

08-03-2003, 05:43 PM

too many variables, each car has its own percentage of drive train loss, you could easily decrease the drivetrain loss by lightening up the entire drive train assembly.

nudge1201

08-03-2003, 05:46 PM

I see your reasoning you just because an engine is making more power, why does it take more power to move the drive train part. They seem like they should be a consant variable. I just would like a techinal explination, not just an "it is because it is."

pokgai

08-03-2003, 05:48 PM

i think im the only one who is understanding rednos' reasoning.

if you go back to my example of the 50 crank HP engine car, it only produces 44 WHP, because 6hp is lost through the transmission. So the transmission sucks out 6hp right? Now, lets add on an XS turbo kit onto that motor, and pump its crank HP up to 150hp. So now the motor makes 150 crank HP, but is still transferring all the power through the same transmission.

If using the % rule, now, the car would be putting out 132 wheel HP, losing 12% of the crank hp, or 18 HP. How come the transmission sucks out 18HP versus 6HP? Did the gears become tougher to spin, which require it to suck out 12 more HP to turn? But I thought the transmission was left alone... it wasnt changed through the whole XS turbo process. So why would the transmission now take out 18 HP?

XYRCNCP

08-03-2003, 05:48 PM

Originally posted by LaW
I just think its not worth the time to argue over something that makes enough sense to use already... you guys have fun with this one

lol, finally! this is gonna be the replacement debate for the shortshifter explanation....:D

Blue Bomber

08-03-2003, 05:49 PM

What RedNOSceli is trying to say is, if the transmission weighs 100lbs (not a clue if weight is correct or not), it only takes 20 hp to move, which will always be the same no matter how much power the engine puts out. Therefore, you can have 180 or 1000 hp, but you only need 20 hp to move the transmission.

nudge1201

08-03-2003, 05:52 PM

Originally posted by mirconrice
It is portional to each other so therefore lets say the pencil weigh in at 10 lbs and it takes 20 Newton to move that object, with your thinking, that 20 newton force that you apply to the 10 lbs, you can apply to a 20 lbs object and it would move. But that is totally wrong. You can't use the same force that you move a 10 lbs object to a object that weighs 20 lbs. I hope I explain that right. Its been 4 years since I took physics.

I think he meant the wieght of the object is the same and the force is different. so why would it take more force to move the same object(s) "the drivetrain" just because the force put on it is greater "engine power"??

RedNOSceli

08-03-2003, 05:56 PM

Originally posted by pokgai
i think im the only one who is understanding rednos' reasoning.

if you go back to my example of the 50 crank HP engine car, it only produces 44 WHP, because 6hp is lost through the transmission. So the transmission sucks out 6hp right? Now, lets add on an XS turbo kit onto that motor, and pump its crank HP up to 150hp. So now the motor makes 150 crank HP, but is still transferring all the power through the same transmission.

If using the % rule, now, the car would be putting out 132 wheel HP, losing 12% of the crank hp, or 18 HP. How come the transmission sucks out 18HP versus 6HP? Did the gears become tougher to spin, which require it to suck out 12 more HP to turn? But I thought the transmission was left alone... it wasnt changed through the whole XS turbo process. So why would the transmission now take out 18 HP?

Fuc*king Thank You...

LaW

08-03-2003, 05:57 PM

Originally posted by RedNOSceli
So my last post is wrong? How so?

Man I am not getting dragged into this **** :)

RedNOSceli

08-03-2003, 05:59 PM

Originally posted by Blue Bomber
What RedNOSceli is trying to say is, if the transmission weighs 100lbs (not a clue if weight is correct or not), it only takes 20 hp to move, which will always be the same no matter how much power the engine puts out. Therefore, you can have 180 or 1000 hp, but you only need 20 hp to move the transmission.

Not exactly. Im saying how much force it takes to Spin the inputshaft of the tranny, not physicly slide it across the floor. I used my Simple Pencil thing because it shows that to make somthing move, whether it be sliding, spining, etc....it takes a specified amount of force to do it.

If you guys have ever seen a tranny sitting on the floor, and actually tried to spin the inputshaft, good chance you couldnt, they are very tight in their bearing journals, and it takes a significant amount of torque to twist the shafts wich are in turn attachced the gears and then twist the output shaft. But this shows why there is 'drive train loss' because of the amount of force that is lost just getting the damn thing to move. The tranny doesnt become harder to turn just because the motor makes more power.

LaW

08-03-2003, 06:09 PM

ok fine i'm going to try to make some kind of explanation....

Rednos you are right, there is a constant that you speak of. I agree with that. The constant is the percentage however. Hmm where to start on this one......

Basically horsepower loss through the drivetrain has always been a constant percentage and not a constant amount of power. However you have to figure that a manual tranny does take about 35hp to move the tranny. There should be your "constant" but thats not exactly how you can do it...

First of all, when there is frictional force the amount of power needed to move an object increases. If you apply 10 lb/ft of torque on a gear it will produce a given amount of friction. If you change the force from 10 lb/ft to 100 lb/ft more friction will be generated by the turning gears. In a transmission this increased friction is generated by heat. That should make some sense.....

If you tie a board to a rope and drag it across a wood floor and then drag it across a carpeted floor it will be harder to pull on the carpet. If you put a stack of bricks on the board it will be even harder to pull. If you were to drag the same board for the same distance at the same speed and took a temperature measurement on the bottom of the board it would get hotter as you added weight. The heat generated would increase linearly as compared to the amount of weight you put on the board. The force required to move the board would also increase linearly.

This is an example that I read somewhere a while back....

LaW

08-03-2003, 06:14 PM

As more proof from physics you know that energy is transformed into another state because it cant be destroyed. Energy can not be destroyed, only transformed. So, if your transmission is generating more heat, where do you think this heat is coming from? The heat is a direct result of power being transformed in the form of heat. The more power you produce, the more power you lose in your drive train.

RedNOSceli

08-03-2003, 06:15 PM

Originally posted by LaW

First of all, when there is frictional force the amount of power needed to move an object increases. If you apply 10 lb/ft of torque on a gear it will produce a given amount of friction. If you change the force from 10 lb/ft to 100 lb/ft more friction will be generated by the turning gears. In a transmission this increased friction is generated by heat. That should make some sense.....

Thats all you had to say = )

Ive been proven wrong.

I was actually thinking that in the back of my head. If you have a friction I.E. bearings in a Tranny, the harder you twist the shaft, the more the more friction is generated at the beaings/journals IE losing more HP...so I see where the general 15% comes in, varries per Driveline efficiantcy.

Done and done

LaW

08-03-2003, 06:19 PM

yeah I mean I read what you said and it made sense and all but I actually read most of this info off of a website months ago when I was wondering the same thing....

ah well answer found :)

Keyshawn

08-03-2003, 06:38 PM

Very good explanation, LAW. Hehe, I was just about to cite that carpet example also. I found it on this site here: http://www.superstang.com/horsepower.htm .

Here's another interesting link about the topic:
http://www.mustangdyne.com/Articles/CHP0603-article-03.htm

LaW

08-03-2003, 07:21 PM

KEYSHAWN!!!! That is the same exact site I read a while back! Or at least its the same exact article!!!

Masayver

08-03-2003, 07:59 PM

Originally posted by Keyshawn
Very good explanation, LAW. Hehe, I was just about to cite that carpet example also. I found it on this site here: http://www.superstang.com/horsepower.htm .

Okay, I'm a little baffled here. In that article, they show a comparison between a dyno done in 1st gear and 4th gear. 1st gear showed lower power numbers than 4th gear, because of time (I understand their point), but why is it that in the REAL world, a car will accelerate faster in 1st gear than in 4th gear? Is it because of the increased air resistance a car will face at 4th gear speeds as opposed to 1st gear speeds? And if that's the case, then theoretically, a car running in a vacuum would accelerate faster in 4th gear than in 1st?

Keyshawn

08-03-2003, 08:45 PM

Originally posted by Masayver
Okay, I'm a little baffled here. In that article, they show a comparison between a dyno done in 1st gear and 4th gear. 1st gear showed lower power numbers than 4th gear, because of time (I understand their point), but why is it that in the REAL world, a car will accelerate faster in 1st gear than in 4th gear? Is it because of the increased air resistance a car will face at 4th gear speeds as opposed to 1st gear speeds? And if that's the case, then theoretically, a car running in a vacuum would accelerate faster in 4th gear than in 1st?

In discussing air resistance, I think you answered your own question. The author says something similar in his article: "If you take a stock Mustang six cylinder and try and obtain a top speed rating it will probably be around 110 mph._ Now get in a V8 Mustang and it will go faster._ For an average vehicle to break 200 mph it takes around 500-600 horsepower._ As an item accelerates it becomes harder and harder to push it because of the drag induced by the wind."

Masayver

08-03-2003, 09:51 PM

So again, I pose the question: In a vacuum, a car would accelerate faster in 4th gear than in 1st?

LaW

08-03-2003, 10:03 PM

Not necessarily I believe gearing comes into play here as well no?

bagodoosh

08-04-2003, 11:19 AM

i dont know if people dont pay attention or flat out dont want to put the effort into thinking or argueing? it took how many posts to settle around a reasonable argument?

without reading those articles, my guess is loss = a + x*P. "x" is like a frictional loss which is multiplied. "a" is the initial force needed to turn the tranny. so rednos is thinking of "a", while law was trying to explain "x". let's say for a given tranny, you need 6hp to turn it and it has a 10% friction loss. with a 100hp engine, loss = 6 + 10 = 16. with a 200hp engine it'll = 6 + 20 = 26. so the loss at 100hp = 16% while at 200hp = 13%. it does lessen with increased HP as rednos was hinting at (assuming i am correct).

Masayver

08-04-2003, 06:37 PM

Well, what I was suggesting by my previous posts, I think that dyno may be off. Didn't someone here dyno their car in 1st gear and they got similar numbers (a bit lower) to others who dyno their cars in 3rd/4th gears

I have no problem with the idea that frictional force is a %, but I don't think it remains constant, as bagodoosh put it. I believe it lessens as power increases, to a point. But what if the drivetrain was equally efficient from say 180 hp peak to 220 hp peak, and then it started losing efficiency? The only way to know for sure would be to dyno @ the flywheel and then dyno at the wheels before and after mods.

djm221

08-05-2003, 06:30 AM

I don't buy that Mustang dudes explanation. Sounds like a bunch of hand waving and speculation crap to me. A tranmission is not the same as pulling a board across a carpet. And putting more weight on the board is certainly not the same as putting more power through a transmission. More power means things move faster. That carpet analogy is like you put molasses in the tranmission instead of oil. Bagadoosh's idea sounds alot more reasonable. There will be slight increases in power absorbtion from increased friction losses because the parts are moving faster.

And I thought RedNOSCeli's orignial question was easy to understand; I don't know why some people had such a hard time comprehending what he was insinuating.

FutureMatrixXR

08-05-2003, 07:27 AM

djm221

08-05-2003, 08:15 AM

Acutally, that was a terrible comparison. All that demonstrated is the concept of percentage loss, which RedNOSceli was not asking about.

AM03GT

08-05-2003, 09:04 AM

Law is correct, and there are many places within the transmission which produces the friction as a function of input power/velocity/acceleration rule... gears being the obvious one, but even smaller details like transmission oil will behave differently as power increases due to the property differences caused by added head, fluid velocity etc...

Xracer729

08-05-2003, 08:02 PM

Originally posted by RedNOSceli
Ok...Celica STOCK makes 180hp, averages about 160hp to the wheels bone stock....

thats about a 12%(give or take) 'drivetrain loss' or, the car looses 20hp from the flywheel to the motor.

Now it would make more sense to me that we no longer use a % at this point because the question I ask is, why would an engine making more, loose any more thru throu the tranny?

Shouldnt that loss stay the same reguardless of FLYwheel HP? Do we just use the 15% loss as a rule of thumb? If we do its kinda of silly...

Stock Supra makes @ 300hp - 15% = 255 at the wheels, difference of 45hp.

So anothe supra dynos at 500hp at the wheels..Now according the 15% rule that car makes est 590hp at the flywheel, but that doesnt make any sense because the tranny only sucks up 45hp, so LOGIC would rule that car only makes 545 HP at the flywheel, and these are pretty small numbers...

Imagine the differences between 1000hp cars....a 1300hp car would loose 300hp to the drive train to put 1000hp to the ground? Doesnt sound right to me....

i agree with you 100% i dont think anybody here understands wat we are thinking. i kno exactly wat u mean and i agree with you.

2002GT_Celica

08-05-2003, 08:14 PM

Originally posted by Xracer729
i agree with you 100% i dont think anybody here understands wat we are thinking. i kno exactly wat u mean and i agree with you.

Yeah, nobody understands because that reasoning is wrong and if you read this thread like you should have, you would realize that RedNOSCeli's original reasoning was proven wrong.

LaW

08-06-2003, 12:02 AM

Originally posted by Xracer729
i agree with you 100% i dont think anybody here understands wat we are thinking. i kno exactly wat u mean and i agree with you.

hehe :chuckles: come back when your older and can read lol jk :)

but yeah his reasoning was proven wrong (well he never said his reasoning was right)....

We got the logical answer in here somewhere though ....

Did you read this thread? lol

djm221

08-06-2003, 05:23 AM

It was "proven" wrong by some nimrod on some Mustang page that used handwaving, speculation, and terrible comparisons.
He even had an article at the end, from a 'reputable' Mustang tuner saying the whole percentage thing was wrong and the Mustang generally loses 35HP.

kaioshin

08-06-2003, 07:50 AM

Originally posted by djm221
It was "proven" wrong by some nimrod on some Mustang page that used handwaving, speculation, and terrible comparisons.
He even had an article at the end, from a 'reputable' Mustang tuner saying the whole percentage thing was wrong and the Mustang generally loses 35HP.

Yeah I agree with djm on this one. The whole plank with bricks on it feels akin to something like swapping in a 40 lb flywheel for the stock one.

For what rednos was asking a better example would seem to be

walking with a plank on a rope behind you and then running with a plank on a rope behind you.

The only factor that should change is the amount of power you apply not increased weight in the transmission.

Not saying that there isn't a frictional % loss, but that example wasn't the best either.

I agree with bagodoosh's post. Seems like the most likely answer. Not that I am a mathmatician though :chuckles:

Keyshawn

08-06-2003, 07:57 AM

Originally posted by LaW
As more proof from physics you know that energy is transformed into another state because it cant be destroyed. Energy can not be destroyed, only transformed. So, if your transmission is generating more heat, where do you think this heat is coming from? The heat is a direct result of power being transformed in the form of heat. The more power you produce, the more power you lose in your drive train.

This reasoning is logical to me. More points about the affects of friction in the tranny are made on page 3 of this Chevy Hi Performance magazine article (http://www.mustangdyne.com/Articles/CHP0603-article-01.htm) that states that: "The drivetrain losses are mainly composed of three loss areas: friction loss, inertia loss, and viscous loss. _The friction loss is largely due to the surfaces of the gear teeth rubbing against each other. _Gear friction is related to the torque being trans_mitted through the drivetrain. _The gear power loss is related to the speed at which the torque is being transmitted."

Keyshawn

08-06-2003, 08:38 AM

Originally posted by djm221
A tranmission is not the same as pulling a board across a carpet. And putting more weight on the board is certainly not the same as putting more power through a transmission. More power means things move faster.

A more appropriate analogy than that "carpet analogy" would be someone rubbing their hands together. The faster you rub your hands together, the hotter they get (because of friction). And as LAW asks, "Where do you think this heat is coming from? The heat is a direct result of power being transformed in the form of heat. The more power you produce, the more power you lose in your drive train." It's that Law of Conservation of Energy that everyone learns in grade-school Physics: Energy can neither be created nor destroyed. Energy is always changing from one kind to another. The total energy of an object never changes.

A carpet analogy could still be used, but instead of putting more weight on the board, you could move the board over the carpet at a faster speed to demonstrate the effects of friction. The faster you slide that board over the carpet, the hotter the bottom of that board will get (just like when you rub your hands together faster). Again, The Law of Conservation comes into play: some of that mechanical/kinetic energy is converted into heat energy. If you increase the amount of that mechanical energy (by sliding the board over the carpet at a faster speed), then the amount converted into heat energy will also increase. This indicates that the power loss (or rather the power converted into heat) is a percentage and not a constant number.

SexyCelica

08-06-2003, 08:40 AM

:popcorn:

djm221

08-06-2003, 08:41 AM

I understand the increase of friction comes from moving the transmission faster - but I don't think it's a linear relationship like the mustang guy inferred.

I think the only reason a constant percentage is used is so they can inflate the numbers to make their ****s even bigger.

Keyshawn

08-06-2003, 09:06 AM

Originally posted by djm221
I understand the increase of friction comes from moving the transmission faster - but I don't think it's a linear relationship like the mustang guy inferred.

I think the only reason a constant percentage is used is so they can inflate the numbers to make their ****s even bigger.

Naturally, it's not a perfectly linear relationship. But it IS a much more reasonable estimate than just using a constant number, since the amount of power lost (converted into heat) in the tranny increases as the power applied to it increases. That's why people should consider those drivetrain-loss percentages a decent "rule of thumb" that simplifies crank or flywheel power estimates, but should not consider those estimates as facts written in stone.

There's an easy answer to companies trying to exploit the 15% rule of thumb to inflate their HP numbers: Simply disregard all those HP estimates at the crank/flywheel, and only look at the power actually getting to the wheels.

Keyshawn

08-06-2003, 10:20 AM

Originally posted by BadTOYO
:confused: you mean from the crank to the wheels... factory numbers are at the cranck, the flywheel is already taking power away...
R

Technically, I think you might be right in considering it a misnomer when people quote horsepower figures "at the flywheel." It probably would be more accurate to instead say one is measuring power "right before the flywheel." Nevertheless, for some reason or another, it's become pretty much accepted in the car industry to consider "at the crank" and "at the flywheel" synonymous and interchangeable.

ArchangelX

08-06-2003, 10:36 AM

This is an interesting read. Me Like. :thumbup:

kaioshin

08-07-2003, 06:29 AM

Originally posted by Keyshawn
Naturally, it's not a perfectly linear relationship. But it IS a much more reasonable estimate than just using a constant number, since the amount of power lost (converted into heat) in the tranny increases as the power applied to it increases. That's why people should consider those drivetrain-loss percentages a decent "rule of thumb" that simplifies crank or flywheel power estimates, but should not consider those estimates as facts written in stone.

There's an easy answer to companies trying to exploit the 15% rule of thumb to inflate their HP numbers: Simply disregard all those HP estimates at the crank/flywheel, and only look at the power actually getting to the wheels.

So, according to this line of thinking, you would need to change the type of tranny fluid you are running, b/c it would need to be able to withstand higher temperatures due to increased power? Not sure this is common practice already though.