Interesting Concept on Drivetrain Loss...
04-28-2005, 09:06 AM
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Interesting Concept on Drivetrain Loss... Maybe we’ve been wrong all along. You generally hear 15-18% drivetrain loss for a manual and 18-22% loss for an automatic. So basically as you add more power, the loss through the drivetrain is greater. I believe this may be true for a stock vehicle, but why does that percentage hold constant with added power? The drivetrain remains the same. Lets just say you have a stock vehicle that loses 20% through the drivetrain, which on this vehicle equates to 20 RWHP lost, then the drivetrain takes 20 RWHP to operate. Now if you increase engine horsepower by 50%, nothing in the drivetrain changed, so it would stand to reason that it still takes 20 RWHP to operate it.
You don’t see a lot of engine vs. chassis dyno runs in the LSx community, but it would be nice to see an engine get strapped to an engine dyno and measured, then have that same engine dropped into a vehicle and dynoed again. I bet you wouldn’t see as drastic of a loss as we all have been told to expect and calculate for if you want a roundabout number for flywheel horsepower.
All of this was brought up by a buddy of mine who is into Miata performance. The Miata community does a lot of both engine and chassis dyno runs apparently. On a stock engine, they generally see a 26 RWHP drop from flywheel to rear wheel horsepower. Now they build up a turbo motor that’s making 100% or more horsepower than the stock engine, and they still see that 26 RWHP loss. It doesn’t increase to 52 RWHP loss just because the engine is making more power, because the tranny, driveshaft, and rear only take that 26 RWHP to get moving.
Just an interesting concept that maybe we’ve been wrong all along, and maybe our cars aren’t putting out the engine HP we think they may be. Thoughts as to why this may be right or wrong? Just something interesting that I heard that couldn't hurt to look into.
You don’t see a lot of engine vs. chassis dyno runs in the LSx community, but it would be nice to see an engine get strapped to an engine dyno and measured, then have that same engine dropped into a vehicle and dynoed again. I bet you wouldn’t see as drastic of a loss as we all have been told to expect and calculate for if you want a roundabout number for flywheel horsepower.
All of this was brought up by a buddy of mine who is into Miata performance. The Miata community does a lot of both engine and chassis dyno runs apparently. On a stock engine, they generally see a 26 RWHP drop from flywheel to rear wheel horsepower. Now they build up a turbo motor that’s making 100% or more horsepower than the stock engine, and they still see that 26 RWHP loss. It doesn’t increase to 52 RWHP loss just because the engine is making more power, because the tranny, driveshaft, and rear only take that 26 RWHP to get moving.
Just an interesting concept that maybe we’ve been wrong all along, and maybe our cars aren’t putting out the engine HP we think they may be. Thoughts as to why this may be right or wrong? Just something interesting that I heard that couldn't hurt to look into.
04-28-2005, 09:15 AM
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Here is what my buddy posted exactly in another forum where this debate was going on...
Just some interesting stuff to think about. I dont know how true this would be on an unlocked automatic transmission due to the added slippage when more power is applied, but for a "locked" drivetrain like a locked automatic or a manual with no clutch slippage, I can see some very solid evidence in his arguement.
I would like to put a theory in yalls brain, and see what sticks, because I believe it it correct and that this 15% est drivetrain loss, etc is a bunch of BS that makes a cause for over inflated #'s.
Example: You and a buddy grab an ice cold beer with a twist off top, you are a HUGE body builder, and your buddy is derek (a weak quivering mass of girly man jello). In getting the cap off, you need to provide 25 ft/lb of torque to twist the cap off. Derek is capable of 50 ft/lb, you are capable of 300 ft/lb. both of you twist, and both use exactly 25 ft/lb to remove the top....both succeed.
how does this relate? well, take two motors, connected to same type of transmission, the trans takes 25 ft/lbs to spin all gears/etc. If one motor makes 200HP, and the other motor makes 250, both are still going to take 25 ft/lbs to spin, not more....
so if you look at it that way, 200 HP * 1.2 = 240, now you add a intake/exhaust and redyno and find 50HP at the wheels, does that mean your motor now makes 250*1.2 = 300??? I don't buy that in the least.
Drivetrain losses are a fixed value, not a percent.
-Greer
================================================== ===
sure, there is variation from trans to trans, never questioned that, but what is termed "drivetrain losses" is generally closer to a fixed # than a percentage.
Supporting Arg: In the miata community, one engine shop has an engine dyno and a chassis dyno, in testing, they have found a 26ish (give or take a HP or two) loss in the drivetrain no matter the power the motor makes, from 116 (stock motor) to 300+ HP turbo setups.
yes differential and other losses happen, but they are closer to a fixed # than a %.
You aren't changing the other factors, so why assume 20%....each model/type has a specific loss, and to assume 15-20% is not right. I know some that say "oh well RWD loses more than FWD" (and yes driveshafts can help to support that arg BUT) to assign a fixed % to every trans is guessing at best.
A better formula (albeit still flawed) is to say at stock a car rated for 305 HP loses 25HP (take acutal measurement over rated) which means 280/305 = 91% or a 9% loss (giggles and grins, play along, percent doesn't matter, which is my point). Now, when I go back to the dyno, I know that my drivetrain loss is X number of HP, and my new dyno shows that instead of 280, I made 305 + my 25HP to drivetrain makes 330 at the engine. However, following the theory, if I still lost 9% that would be 305 * 1.09 = 332. Pretty close, but lets expound that....say in stead of 280, you make 380 or 400HP. a 9% drivetrain loss is now = 436 vs 425 that we said. already in 100 HP gain we have seen an error of 11HP. and that measurement is ONLY at 9%. lets say we break this down at 20% and say 60HP loss:
305-60 = 245/305 = 80.3% or 20% driveline loss.
245 upgraded with a supercharger (or something) now makes 400 at the wheels. using the 60HP loss we agree that it would be 460 at the wheels.
but, using the driveline loss of 20%, the car would actually be making 480. we are off over 20HP...which is pretty significant when you are elephant walking
miatas time in and time out make 26HP less on the stand than in the chassis. so we make around 90 on the stock 1.6 at the wheels (rated 116 at the motor or 23% driveline)...when dynoed mine made 150 (long time ago at 7psi and crappy fueling system) does that mean that the engine made 150*1.23= 184ish? no, it made 176, an 8HP difference.
The differences aren't huge in the 100Hp range, but if you go from a 100HP car and upgrade it to a 300HP or more engine, you aren't losing the same %
-Greer
Example: You and a buddy grab an ice cold beer with a twist off top, you are a HUGE body builder, and your buddy is derek (a weak quivering mass of girly man jello). In getting the cap off, you need to provide 25 ft/lb of torque to twist the cap off. Derek is capable of 50 ft/lb, you are capable of 300 ft/lb. both of you twist, and both use exactly 25 ft/lb to remove the top....both succeed.
how does this relate? well, take two motors, connected to same type of transmission, the trans takes 25 ft/lbs to spin all gears/etc. If one motor makes 200HP, and the other motor makes 250, both are still going to take 25 ft/lbs to spin, not more....
so if you look at it that way, 200 HP * 1.2 = 240, now you add a intake/exhaust and redyno and find 50HP at the wheels, does that mean your motor now makes 250*1.2 = 300??? I don't buy that in the least.
Drivetrain losses are a fixed value, not a percent.
-Greer
================================================== ===
sure, there is variation from trans to trans, never questioned that, but what is termed "drivetrain losses" is generally closer to a fixed # than a percentage.
Supporting Arg: In the miata community, one engine shop has an engine dyno and a chassis dyno, in testing, they have found a 26ish (give or take a HP or two) loss in the drivetrain no matter the power the motor makes, from 116 (stock motor) to 300+ HP turbo setups.
yes differential and other losses happen, but they are closer to a fixed # than a %.
You aren't changing the other factors, so why assume 20%....each model/type has a specific loss, and to assume 15-20% is not right. I know some that say "oh well RWD loses more than FWD" (and yes driveshafts can help to support that arg BUT) to assign a fixed % to every trans is guessing at best.
A better formula (albeit still flawed) is to say at stock a car rated for 305 HP loses 25HP (take acutal measurement over rated) which means 280/305 = 91% or a 9% loss (giggles and grins, play along, percent doesn't matter, which is my point). Now, when I go back to the dyno, I know that my drivetrain loss is X number of HP, and my new dyno shows that instead of 280, I made 305 + my 25HP to drivetrain makes 330 at the engine. However, following the theory, if I still lost 9% that would be 305 * 1.09 = 332. Pretty close, but lets expound that....say in stead of 280, you make 380 or 400HP. a 9% drivetrain loss is now = 436 vs 425 that we said. already in 100 HP gain we have seen an error of 11HP. and that measurement is ONLY at 9%. lets say we break this down at 20% and say 60HP loss:
305-60 = 245/305 = 80.3% or 20% driveline loss.
245 upgraded with a supercharger (or something) now makes 400 at the wheels. using the 60HP loss we agree that it would be 460 at the wheels.
but, using the driveline loss of 20%, the car would actually be making 480. we are off over 20HP...which is pretty significant when you are elephant walking
miatas time in and time out make 26HP less on the stand than in the chassis. so we make around 90 on the stock 1.6 at the wheels (rated 116 at the motor or 23% driveline)...when dynoed mine made 150 (long time ago at 7psi and crappy fueling system) does that mean that the engine made 150*1.23= 184ish? no, it made 176, an 8HP difference.
The differences aren't huge in the 100Hp range, but if you go from a 100HP car and upgrade it to a 300HP or more engine, you aren't losing the same %
-Greer
04-28-2005, 09:19 AM
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Those loss percentages sound very high to me.
I've always heard it 12-15% for a manual and 15-20% for an automatic (depending on the combo of course... IRS, inefficient torque converter, big nasty rear-end, etc.)
It might have something to do with the stock clutch being worn or a piece of **** and exaggerating loss numbers on the initial dyno pull.
If that stock Miata had 150 hp (no idea what those turd cars produce), then 15% drivetrain loss would be 22.5 hp loss.
I've never seen a manual lose more than 15% unless going through a big nasty rear-end or having a worn clutch.
My guess is a weak clutch initially, then moving to an aggressive clutch design for the buildup.
Mike
I've always heard it 12-15% for a manual and 15-20% for an automatic (depending on the combo of course... IRS, inefficient torque converter, big nasty rear-end, etc.)
It might have something to do with the stock clutch being worn or a piece of **** and exaggerating loss numbers on the initial dyno pull.
If that stock Miata had 150 hp (no idea what those turd cars produce), then 15% drivetrain loss would be 22.5 hp loss.
I've never seen a manual lose more than 15% unless going through a big nasty rear-end or having a worn clutch.
My guess is a weak clutch initially, then moving to an aggressive clutch design for the buildup.
Mike
04-28-2005, 09:34 AM
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Originally Posted by Kraest
Those loss percentages sound very high to me.
I've always heard it 12-15% for a manual and 15-20% for an automatic (depending on the combo of course... IRS, inefficient torque converter, big nasty rear-end, etc.)
It might have something to do with the stock clutch being worn or a piece of **** and exaggerating loss numbers on the initial dyno pull.
If that stock Miata had 150 hp (no idea what those turd cars produce), then 15% drivetrain loss would be 22.5 hp loss.
I've never seen a manual lose more than 15% unless going through a big nasty rear-end or having a worn clutch.
My guess is a weak clutch initially, then moving to an aggressive clutch design for the buildup.
Mike
I've always heard it 12-15% for a manual and 15-20% for an automatic (depending on the combo of course... IRS, inefficient torque converter, big nasty rear-end, etc.)
It might have something to do with the stock clutch being worn or a piece of **** and exaggerating loss numbers on the initial dyno pull.
If that stock Miata had 150 hp (no idea what those turd cars produce), then 15% drivetrain loss would be 22.5 hp loss.
I've never seen a manual lose more than 15% unless going through a big nasty rear-end or having a worn clutch.
My guess is a weak clutch initially, then moving to an aggressive clutch design for the buildup.
Mike
But yes, if the car did have a slipping clutch or an unlocked auto tranny, they are going to be losing more, maybe some sort of exponential percentage in relation to the input power. Even with a big 9" rear or something, it will take more power to operate it, but it will be more like a fixed number (10 more HP over a stock rear) than a percentage (per the theory).
04-28-2005, 09:43 AM
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This is all more of my own curiosity but I think it could be beneficial to others to learn more about this, so if you want to learn, go ahead and read...
================================================== ==============
I'm not going to copy and paste all over the place, but here is the thread that I've got going with a discussion on the topic...
http://www.mtfba.org/forum/viewthrea...age=1#pid87160
...and here is a post on camaroz28.com that has already covered the topic with some good info...
http://web.camaross.com/forums/showt...threadid=81279
================================================== ==============
I'm not going to copy and paste all over the place, but here is the thread that I've got going with a discussion on the topic...
http://www.mtfba.org/forum/viewthrea...age=1#pid87160
...and here is a post on camaroz28.com that has already covered the topic with some good info...
http://web.camaross.com/forums/showt...threadid=81279
04-28-2005, 09:56 AM
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Originally Posted by josh99ta
...and here is a post on camaroz28.com that has already covered the topic with some good info...
http://web.camaross.com/forums/showt...threadid=81279
http://web.camaross.com/forums/showt...threadid=81279
Like it was stated before:
In my opinion, it has to do with your initial driveline setup, but the percentages won't vary much on YOUR OWN car/setup.
Mike
04-28-2005, 10:29 AM
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Originally Posted by Kraest
Fred (Injuneer) showed that his car lost around 12% with the manual and 20% with the TH400, regardless if he was on/off the spray making 400+, 500+ or 600+ rwhp.
Like it was stated before:
In my opinion, it has to do with your initial driveline setup, but the percentages won't vary much on YOUR OWN car/setup.
Mike
Like it was stated before:
In my opinion, it has to do with your initial driveline setup, but the percentages won't vary much on YOUR OWN car/setup.
Mike
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04-28-2005, 11:29 AM
#8
Percentage losses are BS....
A particular driveline takes "X" amount of power to accelerate. The whole 15% thing is just a rule of thumb based on some average given power level. Once you have figured out your particular delta from driveline loss whatever power is gained at the flywheel will make it to the rear wheels if there are no other changes present in the driveline (converter swap, rear gear, etc.)
I believe the driveline in my M6 C5 eats up about 75 HP or so, putting my current flywheel numbers around 550 ish. If I were to drop in a solid roller 441 CID engine tomorrow that produced 150 more flywheel HP, I would see the same gain to the tire. My driveline didn't magically increase the power required to accelerate it's mass, which is in fact a constant assuming no other changes.
I will prove this theory out once and for all when I test my current 205 headed 346 on the engine dyno during our 62 cc 225 testing scheduled in the hopefull near future. Once I have my baseline (say 550 flywheel HP for instance) I will then play with the larger 225's and a larger camshaft hoping to see say an additional 30 or so HP (say 580 at the flywheel)....I will then drop that exact combination in my car hoping to see 510 RWHP...exactly 30 more than my current mild mannered 205 combo produces. Assuming that pans out to be true, it helps to validate what I have described above.
When I do testing on either the 383 or 402 I have planned, I would expect exactly the same scenario to play out and it will be easier to verify because the power delta from my current combination will be greater.
Will keep you guys posted regrading the progress of this "test"....
Tony M.
EDIT: If peak power occurs at a significantly higher RPM, you might see a little more loss due to spinning the driveline faster, but it wouldn't be a sizable difference considering you might see a "peak to peak" RPM difference of say 300-600 RPM's assuming the engines in question are even reasonably similar.
A particular driveline takes "X" amount of power to accelerate. The whole 15% thing is just a rule of thumb based on some average given power level. Once you have figured out your particular delta from driveline loss whatever power is gained at the flywheel will make it to the rear wheels if there are no other changes present in the driveline (converter swap, rear gear, etc.)
I believe the driveline in my M6 C5 eats up about 75 HP or so, putting my current flywheel numbers around 550 ish. If I were to drop in a solid roller 441 CID engine tomorrow that produced 150 more flywheel HP, I would see the same gain to the tire. My driveline didn't magically increase the power required to accelerate it's mass, which is in fact a constant assuming no other changes.
I will prove this theory out once and for all when I test my current 205 headed 346 on the engine dyno during our 62 cc 225 testing scheduled in the hopefull near future. Once I have my baseline (say 550 flywheel HP for instance) I will then play with the larger 225's and a larger camshaft hoping to see say an additional 30 or so HP (say 580 at the flywheel)....I will then drop that exact combination in my car hoping to see 510 RWHP...exactly 30 more than my current mild mannered 205 combo produces. Assuming that pans out to be true, it helps to validate what I have described above.
When I do testing on either the 383 or 402 I have planned, I would expect exactly the same scenario to play out and it will be easier to verify because the power delta from my current combination will be greater.
Will keep you guys posted regrading the progress of this "test"....
Tony M.
EDIT: If peak power occurs at a significantly higher RPM, you might see a little more loss due to spinning the driveline faster, but it wouldn't be a sizable difference considering you might see a "peak to peak" RPM difference of say 300-600 RPM's assuming the engines in question are even reasonably similar.
Last edited by Tony Mamo @ AFR; 04-28-2005 at 11:57 AM.
04-28-2005, 11:30 AM
#9
Here are a few other points to consider.
When my car was pretty much stock (lid and a catback) and I got it on the dyno. you would agree that it lost 15-20%
now im pushing around a moser 9" rearend and a denny's nitrous driveshaft to hadle the power I now make. My drivetrain upgrades are power sucking monsters. As you increse power you loose MORE do to the increase drag on components.
point #2 increases in rpm and power can sometimes take more energy in an expotential not linear manner. take a 3 phase 460 volt 100hp industrial electric motor. at 1700 RPM it might take 100 amps. at 3400 rpm the power consumption doesnt double it quadruples to 400 amps
When my car was pretty much stock (lid and a catback) and I got it on the dyno. you would agree that it lost 15-20%
now im pushing around a moser 9" rearend and a denny's nitrous driveshaft to hadle the power I now make. My drivetrain upgrades are power sucking monsters. As you increse power you loose MORE do to the increase drag on components.
point #2 increases in rpm and power can sometimes take more energy in an expotential not linear manner. take a 3 phase 460 volt 100hp industrial electric motor. at 1700 RPM it might take 100 amps. at 3400 rpm the power consumption doesnt double it quadruples to 400 amps
04-28-2005, 12:30 PM
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Tony M, I look very forward to reading the results of your test, as thats the theory that is questioning the percentage theory I've always heard.
04-28-2005, 12:50 PM
#11
Yes the % is a rule of thumb. But if you have 300HP and the drivetrain eats 50ft-lbs and you slap in a 600HP engine your same drivetrain, it's going to use more then 50ft-lbs. Why? Through a baseball 30mph, then through it 60mph. It takes a lot more force to through it 60mph because you have to double the ***** acceleration while it's in your hand to get it up to 60mph. With a 600HP engine you accelerate your drivetrain a lot faster so you will see more ft-lbs lost. Probably not the same overall % as you increase HP.
04-28-2005, 01:08 PM
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very intersting stuff, when i discussed this specific topic with a few of my buddies, me and a few others used to argue that the drivetrain lose is more of a fixed ratio, like stated above. Though koolrayz brought up some interesting counter arguments, which could be used in this discussion. Let say the electrical or thermal conductivity efficiency in the wires and circuits resistors in the above mentioned elcetrical motor could be translated to the effieciency of our drivetrain parts and how well they can recieve and tranfser the energy being excerted on them.
However, i totally agree that a fixed percentage could be a simple, generic way to measure power lose much like the lose through drag on a moving object if that object has not been through proper testing. Anyways, i feel that its more of a fix ratio ro number, that can be possibly calculated throught the differnt factors that are involved in our specific situation. (materials used and their specific dynamic properties, weight, total mass, rotational mass and its particular frequency, lubrication and its properties, wear ratio on parts, air density, etc.)
ther seems to be a few factors that could divert this whole "experiment" and i for one dont have the money, time, (which sucks!!) facilities, to do such an experient with differnt types of transmisson parts.
It would be very interesting nd a great find to see the truth behind drivetrain loss for i believe the percentage is a general if not false assumption like people used leaches to balance the bodies three (or four) main fluids....Just and anology, dont take me serious!!!
maybe, a system on jus the weight an material used in transmisson could yield a simplier ratio without going to crazy? nyone want to have some fun?
However, i totally agree that a fixed percentage could be a simple, generic way to measure power lose much like the lose through drag on a moving object if that object has not been through proper testing. Anyways, i feel that its more of a fix ratio ro number, that can be possibly calculated throught the differnt factors that are involved in our specific situation. (materials used and their specific dynamic properties, weight, total mass, rotational mass and its particular frequency, lubrication and its properties, wear ratio on parts, air density, etc.)
ther seems to be a few factors that could divert this whole "experiment" and i for one dont have the money, time, (which sucks!!) facilities, to do such an experient with differnt types of transmisson parts.
It would be very interesting nd a great find to see the truth behind drivetrain loss for i believe the percentage is a general if not false assumption like people used leaches to balance the bodies three (or four) main fluids....Just and anology, dont take me serious!!!
maybe, a system on jus the weight an material used in transmisson could yield a simplier ratio without going to crazy? nyone want to have some fun?
04-28-2005, 01:17 PM
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Originally Posted by pknowles
Yes the % is a rule of thumb. But if you have 300HP and the drivetrain eats 50ft-lbs and you slap in a 600HP engine your same drivetrain, it's going to use more then 50ft-lbs. Why? Through a baseball 30mph, then through it 60mph. It takes a lot more force to through it 60mph because you have to double the ***** acceleration while it's in your hand to get it up to 60mph. With a 600HP engine you accelerate your drivetrain a lot faster so you will see more ft-lbs lost. Probably not the same overall % as you increase HP.
04-28-2005, 02:50 PM
#15
I don't think it's as simple as saying, "the drivetrain requires 50 hp to rotate". What speed are you acheving with this 50 hp?
When you create HP at the flywheel and run that HP through the drivetrain, you lose a certain percentage of your HP. If you then double the HP at the crank (say from 300 hp to 600 hp) and make a pull on the dyno, it will take more power to accelerate the mass of the drivetrain at the faster rate the increased HP of the engine will produce. The same thing can be said about accelerating a car. You could move a 3500 lb. f-body with a 50 hp engine. Would you move it very fast? No. Same thing with the drivetrain. You may be able to attach a 5hp engine up to the stock drivetrain and rotate it to a certain speed. Try to rotate that same drivetrain to a much faster speed at a much faster RATE, that requires more HP.
The percentage won't remain constant going from say 100 crank HP to 800 crank HP. The drivetrain will obviously require more power to turn at the speeds required by the 800 hp setup.
When you create HP at the flywheel and run that HP through the drivetrain, you lose a certain percentage of your HP. If you then double the HP at the crank (say from 300 hp to 600 hp) and make a pull on the dyno, it will take more power to accelerate the mass of the drivetrain at the faster rate the increased HP of the engine will produce. The same thing can be said about accelerating a car. You could move a 3500 lb. f-body with a 50 hp engine. Would you move it very fast? No. Same thing with the drivetrain. You may be able to attach a 5hp engine up to the stock drivetrain and rotate it to a certain speed. Try to rotate that same drivetrain to a much faster speed at a much faster RATE, that requires more HP.
The percentage won't remain constant going from say 100 crank HP to 800 crank HP. The drivetrain will obviously require more power to turn at the speeds required by the 800 hp setup.
04-28-2005, 03:37 PM
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unfortuantely, i, and this is only my opinion and im not makng an interesting post into a flame war, however would have to disagree.
if all things remain constant, hyperthetically, including for example the amount of force needed to crush a can with a press, and the only variable you are changing is amount of "strength" or force being aplied by that press, than the amount of energy lost when crushing that same exact can is the same when you were crushing the can with 10 lbs of force and 100lbs force.
the percentage theory is only, like you said a rule of thumb, but i fail to see how you would require more energy lost when you are using the same amount of resistance but with more force behind it.
in this case, speed is only a bi product of our experiment and the real test subject is the amount of energy lost after a specific and hyperthetically similar operation or "work"
if all things remain constant, hyperthetically, including for example the amount of force needed to crush a can with a press, and the only variable you are changing is amount of "strength" or force being aplied by that press, than the amount of energy lost when crushing that same exact can is the same when you were crushing the can with 10 lbs of force and 100lbs force.
the percentage theory is only, like you said a rule of thumb, but i fail to see how you would require more energy lost when you are using the same amount of resistance but with more force behind it.
in this case, speed is only a bi product of our experiment and the real test subject is the amount of energy lost after a specific and hyperthetically similar operation or "work"
04-28-2005, 03:56 PM
#17
Originally Posted by obZidian
unfortuantely, i, and this is only my opinion and im not makng an interesting post into a flame war, however would have to disagree.
if all things remain constant, hyperthetically, including for example the amount of force needed to crush a can with a press, and the only variable you are changing is amount of "strength" or force being aplied by that press, than the amount of energy lost when crushing that same exact can is the same when you were crushing the can with 10 lbs of force and 100lbs force.
the percentage theory is only, like you said a rule of thumb, but i fail to see how you would require more energy lost when you are using the same amount of resistance but with more force behind it.
in this case, speed is only a bi product of our experiment and the real test subject is the amount of energy lost after a specific and hyperthetically similar operation or "work"
if all things remain constant, hyperthetically, including for example the amount of force needed to crush a can with a press, and the only variable you are changing is amount of "strength" or force being aplied by that press, than the amount of energy lost when crushing that same exact can is the same when you were crushing the can with 10 lbs of force and 100lbs force.
the percentage theory is only, like you said a rule of thumb, but i fail to see how you would require more energy lost when you are using the same amount of resistance but with more force behind it.
in this case, speed is only a bi product of our experiment and the real test subject is the amount of energy lost after a specific and hyperthetically similar operation or "work"
As Kraest stated, Injuneer performed this test on his car and no matter what the power level was at the motor, he saw a consistent ratio of power lost to the rear tires.
04-28-2005, 04:09 PM
#18
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So far we've got my buddy (reliable) with the Miata who sees a consistent 26 rwhp loss from engine to chassis dyno, and we've got Fred (Injuneer) who is seen a consistent 12% drivetrain loss, so Tony's results will be very interesting.
04-28-2005, 04:15 PM
#19
Originally Posted by josh99ta
So far we've got my buddy (reliable) with the Miata who sees a consistent 26 rwhp loss from engine to chassis dyno, and we've got Fred (Injuneer) who is seen a consistent 12% drivetrain loss, so Tony's results will be very interesting.
Yes, will be interesting to see some third party results.
04-28-2005, 08:05 PM
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Originally Posted by Tony Mamo @ AFR
Percentage losses are BS....
A particular driveline takes "X" amount of power to accelerate. The whole 15% thing is just a rule of thumb based on some average given power level. Once you have figured out your particular delta from driveline loss whatever power is gained at the flywheel will make it to the rear wheels if there are no other changes present in the driveline (converter swap, rear gear, etc.)
I believe the driveline in my M6 C5 eats up about 75 HP or so, putting my current flywheel numbers around 550 ish. If I were to drop in a solid roller 441 CID engine tomorrow that produced 150 more flywheel HP, I would see the same gain to the tire. My driveline didn't magically increase the power required to accelerate it's mass, which is in fact a constant assuming no other changes.
I will prove this theory out once and for all when I test my current 205 headed 346 on the engine dyno during our 62 cc 225 testing scheduled in the hopefull near future. Once I have my baseline (say 550 flywheel HP for instance) I will then play with the larger 225's and a larger camshaft hoping to see say an additional 30 or so HP (say 580 at the flywheel)....I will then drop that exact combination in my car hoping to see 510 RWHP...exactly 30 more than my current mild mannered 205 combo produces. Assuming that pans out to be true, it helps to validate what I have described above.
When I do testing on either the 383 or 402 I have planned, I would expect exactly the same scenario to play out and it will be easier to verify because the power delta from my current combination will be greater.
Will keep you guys posted regrading the progress of this "test"....
Tony M.
EDIT: If peak power occurs at a significantly higher RPM, you might see a little more loss due to spinning the driveline faster, but it wouldn't be a sizable difference considering you might see a "peak to peak" RPM difference of say 300-600 RPM's assuming the engines in question are even reasonably similar.
A particular driveline takes "X" amount of power to accelerate. The whole 15% thing is just a rule of thumb based on some average given power level. Once you have figured out your particular delta from driveline loss whatever power is gained at the flywheel will make it to the rear wheels if there are no other changes present in the driveline (converter swap, rear gear, etc.)
I believe the driveline in my M6 C5 eats up about 75 HP or so, putting my current flywheel numbers around 550 ish. If I were to drop in a solid roller 441 CID engine tomorrow that produced 150 more flywheel HP, I would see the same gain to the tire. My driveline didn't magically increase the power required to accelerate it's mass, which is in fact a constant assuming no other changes.
I will prove this theory out once and for all when I test my current 205 headed 346 on the engine dyno during our 62 cc 225 testing scheduled in the hopefull near future. Once I have my baseline (say 550 flywheel HP for instance) I will then play with the larger 225's and a larger camshaft hoping to see say an additional 30 or so HP (say 580 at the flywheel)....I will then drop that exact combination in my car hoping to see 510 RWHP...exactly 30 more than my current mild mannered 205 combo produces. Assuming that pans out to be true, it helps to validate what I have described above.
When I do testing on either the 383 or 402 I have planned, I would expect exactly the same scenario to play out and it will be easier to verify because the power delta from my current combination will be greater.
Will keep you guys posted regrading the progress of this "test"....
Tony M.
EDIT: If peak power occurs at a significantly higher RPM, you might see a little more loss due to spinning the driveline faster, but it wouldn't be a sizable difference considering you might see a "peak to peak" RPM difference of say 300-600 RPM's assuming the engines in question are even reasonably similar.
