Interesting Concept on Drivetrain Loss...
Too bad we don't have an engineer with enough time to explain it or maybe dig up an SAE paper that covers this.
I still maintain that a large part of what the percentage loss proponents count as drive train loss is due to the use of an inertial dyno, and would go away if they used an absorption dyno.
I'm with you Carl. We covered this in that the thread I posted on the last page. I'll explain more later (gotta work).
The 90 HP delta is about average....it just happens to be close to 15%. My point is now that is established (the delta between flywheel and rearwheel HP), if you added a blower and picked up 200 HP at the crank, I'm betting you will have damn close to 200 additional HP at the tire....not 170 (85% of 200).
I would like real world proof and hard data that shows the "percent theory" might be valid (from TeeKay or anyone else who hangs their hat on that theory)...and/or "expert" opinions that would contradict the few I obtained. I would think Harold Bettes, an engineer and THE lead guy over at Superflow, a company that manufactures both types of dyno's in question might have a pretty good idea about the mechanics and the forces in play here. It seems that there is no hard data backing the percentage theory you guys are touting....just heresay and "opinions". I've given you guys testimony from a veteran dyno operator, my own test with a small hit of NOS (an .051 oriface will NOT produce close to 150 extra HP) which backs the fixed loss theory, and opinion from a veteran engineer at a company that builds and manufactures the very machines we are debating.
Lets do more homework and try and to find something more substantial to back our respective theories....We can all just keep typing our own opinions but that won't lead any of us to possibly consider the other side. This is good stuff and certainly warrants a little more effort and some digging to learn which theory actually holds water. My dyno testing in the next month (and subsequent testing in the vehicle) should be very interesting but not perfectly conclusive....the headers and exhaust will be different but besides that it will be a pretty good test starting with a baseline of my current combination on the engine dyno.
Will keep you guys posted....
Tony
Your n20 test doesn't hold any more water than Mike's 590/500 HP example. You don't know exactly how much HP that n20 shot gave you at the flywheel, so it's just hearsay as well. As I said, guys will spray a 100 shot from a TNT kit and gain 140 rwhp. It's a 100 hp nozzle, yet delivers 140 rwhp.
I think we have many good theories that support the percentage idea. As you make more power, tranny coolers, etc. are required to keep everything in tact. The heat generated is generated from friction and an increased load on transmission/driveline parts. You need stronger parts once you start making more power. This suggests that there is more friction/load on the driveline parts...friction/heat = power consumption in this case. The one idea I continue to come back to is the fact that you can turn a drivetrain with your HANDS. It doesn't take 90 HP to turn the drivetrain. In fact, you could take a 60 HP engine out of an older Civic and easily turn the drivetrain. I'd venture to say that a 10 HP engine could turn the drivetrain with ease. This example is very simple, but I think it really gets to the core of this debate. I still haven't seen any response that counters this argument.
Still, an intriguing thread. Let's see some more ideas and hopefully some more concrete examples.
The lawnmower has applied enough power to overcome the frictional coefficient of the drivetrain at a low rate of speed. The frictional coefficient will remain the same, but speed will increase and in turn, increase the energy required to turn the drivetrain.
I'm going to use an arbitrary example here:
Let's say the frictional coefficient of the drivetrain is 5 HP (this is to say a 5 HP engine would just provide enough power to turn the drivetrain). With 5 hp as your frictional coefficient, we know at high HP levels, more than 5 hp is required to turn the drivetrain. Let's say, 75 HP is required to turn the drivetrain at 450 HP at 6k RPM. The only other variables you have introduced here are increased rotational speed and increased HP. However, we know the frictional coefficient has remained at 5HP (pretend we did a test to obtain the true frictional coefficient of the drivetrain) at lower RPMs. Now, when we turn the drivetrain at 6K RPM we are losing 75 HP. That additional 70 HP has come from somewhere.
I'm sure exactly where I'm going with this right now, but it may provide some more food for thought.
Using your example, 5 HP is required to turn the drive train at low RPM and 75 HP at high RPM. How can you say 5 HP is the frictional coefficient? It is true that with an M6 will have more loss at high speed than low from churning the trans oil and an M4 has pumping losses that will increase with RPM, but the power required to churn the oil will increase the friction on the gears and thus make the frictional coefficient vary with RPM along with the pumping loss. Now throw acceleration in there and more power dissapears due to accelerating the rotational mass, and that loss varies with both rate of acceleration and the mass of the components. But, that acceleration will also increase the load on the gears which will increase the frictional loss, changing the frictional coefficient again with an amount that is dependent on the rate of acceleration and the mass. Of course the viscosity of the oil will affect the pumping losses too ...
There is no simple formula that will predict power loss under all conditions. The variable are not independent - they depend on each other. At the very least you need to agree on the conditions - static load, velocity, acceleration, viscosity of the fluids, etc., before you can even hope to approach a solution.
The simple answer is that the "power train loss" is neither a fixed percentage nor a fixed amount of the flywheel horse power. This is obvious because of no definition of conditions and the interaction of the variables that causes. If you want a number, define your conditions and listen to the guys that know what they are talking about or get a book and learn. You will never get there with endless argument. Or maybe the argument is the point here and the answer is immaterial ...
Anyhow, back to the topic. Friction forces are based on friction coefficient times the normal load (speaking of driveline, not tires). So, if X% more torque/power appears at the rear end, that should give X% more pressure between the teeth. Won't there necessarily be X% more friction?
Tony Mamo @ AFR, next time you discuss this topic with any of your roadracing contacts, please include the following question: "As you've increased your car's power, did the tranny and rear-end fluids get hotter?"
Perfect.
Have you ever used a gyroscope? (not you Carl, just trying to explain the concept further). You can easily throw a gyroscope a rather long distance (anyone here, you just pick it up and toss it). But, when you wrap up the string and give it an easy pull, it spins up to a moderate speed and you didn't use much force to do it. Now, try to pull as hard as you can (without destroying it). This will accelerate the weight of the "flywheel" in the gyroscope to a much higher speed and you will be trying to do it in less time. The same gyroscope that you could easily throw 50 feet, has now absorbed all the muscle you could put into it (and it hasn't even gone anywhere).
Why?
Because it takes power to accelerate rotating weight. The faster you try to accelerate the mass of the drivetrain (wheels, tires, driveshaft, transmission internals, flywheel, etc), the more power it absorbs (on inertia dyno, like a dynojet). So, you add hp, that lets the car accelerate faster (the whole vehicle), as a side effect, you are accelerating the mass of the driveline faster. The weight of the rotating bits absorbs more hp the faster you try to accelerate them. If you run 0-60 in 6 seconds, you accelerated the driveline from 0-60 in 6 seconds. You add hp, the car now runs 0-60 in 5 seconds, you just accelerated the drivetrain from 0-60 in 5 seconds. It takes more hp to spin that weight to the same speed in less time (on a dynojet).....remember the gyroscope?
On a load cell based dyno, you don't have to worry about driveline weight. You accelerate to a specific rpm and load the motor with the dyno to get a torque reading. You remove the weight of the drivetrain from the picture. However, in a race, the weight is a real factor, so you may as well use a dynojet for your "real world" numbers.
Using your example, 5 HP is required to turn the drive train at low RPM and 75 HP at high RPM. How can you say 5 HP is the frictional coefficient? It is true that with an M6 will have more loss at high speed than low from churning the trans oil and an M4 has pumping losses that will increase with RPM, but the power required to churn the oil will increase the friction on the gears and thus make the frictional coefficient vary with RPM along with the pumping loss. Now throw acceleration in there and more power dissapears due to accelerating the rotational mass, and that loss varies with both rate of acceleration and the mass of the components. But, that acceleration will also increase the load on the gears which will increase the frictional loss, changing the frictional coefficient again with an amount that is dependent on the rate of acceleration and the mass. Of course the viscosity of the oil will affect the pumping losses too ...
There is no simple formula that will predict power loss under all conditions. The variable are not independent - they depend on each other. At the very least you need to agree on the conditions - static load, velocity, acceleration, viscosity of the fluids, etc., before you can even hope to approach a solution.
The simple answer is that the "power train loss" is neither a fixed percentage nor a fixed amount of the flywheel horse power. This is obvious because of no definition of conditions and the interaction of the variables that causes. If you want a number, define your conditions and listen to the guys that know what they are talking about or get a book and learn. You will never get there with endless argument. Or maybe the argument is the point here and the answer is immaterial ...

Which 'experts' do we listen to? There are experts on both sides of the debate.
If you read all my posts, you'll see that we are both saying nearly the same thing.
The Best V8 Stories One Small Block at Time
The one idea I continue to come back to is the fact that you can turn a drivetrain with your HANDS. It doesn't take 90 HP to turn the drivetrain. In fact, you could take a 60 HP engine out of an older Civic and easily turn the drivetrain. I'd venture to say that a 10 HP engine could turn the drivetrain with ease. This example is very simple, but I think it really gets to the core of this debate. I still haven't seen any response that counters this argument.
You can spin it by hand, but to spin it at a faster speed and accelerate it at a faster rate requires more HP. This argument supports the percentage loss theory, which if you haven't figured out yet, I'm a proponent of. 
I don't think some of you are reading the entire thread.
Go ask another ME (mech engineer) and they will tell you the same.
You can spin it by hand, but to spin it at a faster speed and accelerate it at a faster rate requires more HP. This argument supports the percentage loss theory, which if you haven't figured out yet, I'm a proponent of. 
I don't think some of you are reading the entire thread.

That's what I said, I wasn't disagreeing with you. Yes, we agree that it takes more power and that we don't have sufficient math to calculate all of it. Exactly. Sorry for the confusion.
Shoot I wish I could get a constant hp loss, our power gains would be phenominal,, oh well I can dream .
On a standard "Load Cell" dyno, you'd be correct. You're missing (or I think you are, maybe I misread your post) the fact that you have to accelerate the weight of the drivetrain more quickly on an inertial dyno (dynojet).
The weight of the drivetrain, or it's moment of inertia could be measured/calculated (if someone wanted to). You could then get a reasonable formula that would be close until you reached the point of film failure in the transmission and rear end and saw friction loads increase (and gear deformation, etc). Those little things will keep us from being exact, but it could be calculated to be reasonably close if we measured the weight and knew the MOI of the drivetrain.
The weight of the drivetrain, or it's moment of inertia could be measured/calculated (if someone wanted to). You could then get a reasonable formula that would be close until you reached the point of film failure in the transmission and rear end and saw friction loads increase (and gear deformation, etc). Those little things will keep us from being exact, but it could be calculated to be reasonably close if we measured the weight and knew the MOI of the drivetrain.
i stand on my points before...
tony, something sits wronge with me even more now.. the fact that you contacted these 2 "sorces" is great, however .....
1. they provided you with no NEW information, or proof...
2. there opinions , until backed by proof, are just that.... opinions.
3. they are as you said respected names in the biz... however there are other names just as big who disagree...(you might find one or 2 in the links i provided.
so the input they gave holds the same weight as anyone elses here... until backed by proof it is nothing more then an educated guess... educated... but still a guess...
has no one found any PROOF yet???

Gale Banks Engineering (father of turbos and his shop has multiple engine and chassis dyno's) for the practical hands-on opinion
And
John B Heywood
Sun Jae Professor of Mechanical Engr., Director of Sloan Automotive Lab
Department of Mechanical Engineering,
MIT University
for the cutting edge research-oriented automotive lab's possible information.
I may or may not get a response, but it would be interesting if we could!

BTW, I don't consider a 50 hp (15%) increase small (04-05 GTO baselines posted here in this forum). Both show about an 85% efficiency. Of course that's only 1 of 2 data points we have in this thread where both engine and wheel hp were actually measured. Both those show a consistent percentage ME with hp increase on virtually the same drive train. Time will tell.

<edit>
</edit> Last edited by TeeKay; May 25, 2005 at 02:56 PM.
", im smarter than you.prrrr!!! 

(guys just having fun, not picking on anyone, well mahbe myself...hehehe)Anyways, the "truth" that we seek only gets filled with uncertainty the closer we get to our desired destination. I have been hold on this idea for a long time and i will say that this thread totally rocks, seriously.....it has a few stabs in the dark but handled with a polite gesture before the blade makes contact with skin,but overall enlightening....
But wat is it that we seek? Wat is the purpose? I hope it is not to proves one prowness for we all know the truth behind any ruling body, it will not last for there will always be that apprentice (known or not) that will out shine you..... nevertheless, i keep asking myself this and i keep getting the same answer....
An undestood, unified concept of absolute differences agreed upn by the masses....(wow big words!!! hehehe) if we all had like minds than this, like the borg, than this wouldnt be such a heated topic on ls1tech....furthermore, there wouldnt be an ls1tech since "we no need no stinking cars" (badgers!!) since we have teleportation devices and cool looking eye gear!!!
BAck to the topic though....
So i decided to go a step further in my own head and ask myself why is it being said that we cannot possibly have an answer for this. That is grabage!! Of course we have the answer and it is right there infront of us...that edison story was great and it got me thinking. The world was thought to be the center of the universe. Lightning bolts were coinsidered the finger tip of god doing his bidding.... Alchemist have tried to turn coal into gold but didnt realize that it would take about a few million years to achieve their goals without a really big pressure cooker!!!!!
Ah, alchemy. Anyone who watches adult swim will know that in-order to achieve a specific goal you must inturn introduce a body of equal proportions. But the drivetrain of our vehicles arent obvious alchemaic circles and dont really behave in the same fashion.
So here is a little table i decided to do that might help from the given points and options of the points given in this thread.. (though they may not be exact formulas, its my interpretation and i hope i can stir the pot a bit to keep this going.....
Ok guys, im at work and i do have to go. but tonight i will add my ideas here the best i can so bear with me, it might/might not be of interest and hopefully a few will disagree to add a bit of flavor to this already tasteful thread!!!
see you there..


