So who wants to take me up on my bet then....I see nobody highlighted this part of my post nor the part about Harold Bettes from SuperFlow....Aaaaah....what the hell does he know.

ZeeOsix....Your obviously an intelligent guy and a strong believer in the percent theory. How about a $50 dollar gift certificate to Outback steakhouse or something to make it interesting (after the smoke clears from all the testing).

We will have to wait MONTHS for the results (probably six of them at this rate) but none the less I'm confident that my car will show very similar losses to the rear wheel (within a few HP) from engine dyno to chassis numbers (once again) all using the exact same driveline and test vehicle (my own car).

Starting from 550 HP(with the 346) to 615 HP(with the 383) to potentially 675 HP or so (with the 447 Im building)...I ask you, HOW could I keep losing similar figures to the rear wheel if the percent theory is closer to the truth versus the theory I subscribe to (being closer to a fixed number based on every one's individual driveline). This of course assumes I pull off a hat trick with the 447's results backing up my former two combinations I might add.

I mean even at 15%....if the big motor makes 125 more ponies than the 346 I would need to see a loss of around 100 HP to the rear wheel, versus the 80 or so I hope to see.

Also as I mentioned previously NONE of the percent loss advocates bring real world examples to the table...no reference to actual testing that proves it might be the case. Everyone could theorize all they want about trucks rolling down hills or pressing palms together and feeling the heat generated but none of it relates to our cars and doing engine swaps with time invested testing both flywheel and chassis numbers. I spend alot of time around dyno's and tech oriented professionals (a few of them extremely bright individuals) and I'm in a better position than most to see and sometimes experience real world results from various changes and combinations.

Do you realize how much heat would have to be generated to equal say 20 HP just to pull a number out of the air....Its a lot and I think someone could convert that perhaps into BTU's but Im not about to try.

Anyway....let me know if we have a friendly dinner bet. I wont skew the numbers...I promise (My word and my reputation is everything). Plus, you cant really hide if the car doesn't run the number and I assure you it will backing the power figures with appropriate trap speeds when you factor in my raceweight.

Why do I always get sucked into these threads....LOL

I must write ten times....no more power loss threads.....no more power loss threads....no more power loss threads

-Tony

 

How's about we do the test in real world conditions like the truck pulling a load example I gave earlier?

If the tranny and differential temps don't increase between not pulling a trailer and pulling a trailer up a long hill then your theory would be correct.

I already know the answer ... might as well send me the $50 now.

You have never replied to any of my detailed examples why the HP loss in the drivetrain is not a constant amount of HP.

Have you ever crawled under your car and felt the diff or tranny after even driving it down the highway at 60 mph for an hour? It's so hot that you can't keep your hand on it for over a 1/2 second.

You must also realize that heat is constantly being shed from the diff and tranny too. They are not insulated components. Convective cooling is in effect.

The thermodynamic examples I've given (truck pulling and race car - Post #37) clearly show that if you add HP to a mechanical system it will produce more friction and heat, which can only mean it is creating more lost HP. Also, the efficiency of the system is pretty much a constant as long as nothing is changed. So if it loses 15% it's going to remain basically 15% no matter how much HP is transmitted through the system.

If you could invent a mechanical system that become more efficient as more HP is transmitted through it you'd be one rich dude, as that application could be used to same tons of energy in the world.

 

OK....I will bite

What does an extended duration tow of a truck pulling a load up a long hill have to do with a timed (brief) acceleration run of a performance driveline. Where does the heat come from that is so enormous 20, 30, 40+ HP is vanishing into thin air (lost mysteriously in the driveline) in a burst of 8-12 seconds on the dyno? Of course a truck pulling a load up a hill will increase the heat in the driveline some but over an extended period of time and it wont increase by huge percentages. Not to mention none of this really apply's to with what we are discussing which is brief timed acceleration runs from one RPM point to another.

Think about a driveline as a fixed rotating mass....which is exactly what it is.


It takes "X" amount of force to sustain say 3000 RPM with that mass

It takes "Y" amount of force to sustain say 4000 RPM (more than "X")

It takes "Z" amount of force to sustain 5000 RPM (More than X and Y)

If you dont change the fixed mass (the driveline) would the force necessary to spin it at those speeds ever change?? (answer....NO)

Ultimately, a more powerful engine (one with more horsepower) will simply spin the driveline from 3000 to 5000 faster (the very definition of horsepower which is torque output in relation to time)....the amount of force required hasn't changed necessary to do the job but if you add more power to the equation, most of that power will be converted into energy by accelerating that mass thru that RPM even faster looking once again at the same test parameters (3000 - 5000 RPM's). If you put an engine three times a powerful in front of it what would cause the fixed mass to require (rob) any additional power if we keep testing in the same RPM range (assuming it was stout enough to handle the additional power)?

A stock LS1 M6 Vette makes 390-395 at the crank roughly with no accessories robbing power on the engine dyno....most M6 vettes in stock trim chassis dyno around 295 or 300 RWHP (this is all proven stuff). About a 90-100 HP loss (not even close to the Internet accepted 15% btw ). Now take that same driveline and add an electric water pump and a lightweight clutch....same car on the same day now rolls 315 with no other changes skewing the percentage loss but landing it coincidentally exactly where my driveline has been proven to lose with a lightweight clutch and EWP (looking at what I believe to be my approximate "delta" or fixed loss based on the mass and circumference of my driveline). Is that another fluke or am I possibly on to something here with the "close to a fixed loss" theory?

Moral of the story and to directly answer the OP's question (are you still here!?!?)....If you drive an M6 car and have an aftermarket lightweight clutch and the rear tires are at least close to stock weight, adding around 80 HP to your chassis numbers (75 - 80 if you run an EWP) will get you damn close to your engine's output at the flywheel.

If you run a stock clutch (heavy), you can add 12-15 or so HP to that to get to the flywheel numbers as your chassis numbers will be reduced by that much having to spin some of that extra mass during the run.

If you have an A4 trans add at least 100 - 110 to your chassis numbers....even more if you have a big stall. A4 cars are alot more difficult to predict crankshaft numbers because you can literally do a converter swap and see 30 more ponies to the ground....to many variables.

Zee....if your still here (and I know you are) please address the situation (question) I had posted and asked you to address at the end of my former post. Dont forget now I am quoting legit hard numbers here (no theory)....If a stock M6 Vette with a lightweight clutch and both my previous combinations with a lightweight clutch, and potentially my next combination with 300 more HP than stock all lose around 80 HP.....HOW CAN THE PERCENTAGE THEORY HOLD WATER?? For me the next combo is the icing on the cake (assuming it plays out with the approximate 80 HP delta) reinforcing what I already strongly believe. To casually dismiss all that REAL data aimed at exactly what we are discussing in leui of theory and truck drivelines getting hotter towing heavy loads seems a bit closeminded.

I take paypal by the way.....

OK....I think Im done now....maybe....probably not

Guys....I apologize for the novels I have written but I get started on this topic and Im like a moth to the flame....LOL



Back to the porting room for me!

PS....OK....before I go here's another thought (told you I wasn't done!). Looking once again at the stock Vette scenario (where we have countless dyno results of cars all laying down within 10 RWHP of one another), being they are making so little power they should have the smallest loss to the rear wheels if you subscribe to the percent loss theory (low power equals low losses on the chassis dyno because its all based on a percentage....15% being the "Internet" accepted for an M6 driveline). Whats funny is the actual results couldnt be further from the truth....stock vehicles are actually the worst offenders if your looking at the percentages. With close to 400 at the crank and 300 at the ground they are losing close to 25% (BUT, have a similar "fixed loss" as modded cars making twice their output ....tell me it isnt so!!)

 

MY head hurts.

 

Stay tuned ... I will have some good answers later. You're longer winded than I am!

Mine too ...

 

I fail to see why numbers (HP#s) matter so much to some people. Bragging rights? I drive a stock A4. Its more than fast enough for the street. IMHO, dynos are good for verifying the effects of a modification but people put too much stock in a number. Anyway, I digress.

More to the point, I came across this article and sounds a lot like you all's arguments here.....


http://www.superstang.com/horsepower.htm


Very interested in hearing you all's thoughts on it....

 

I think everyone involved in this and previous discussions on this topic agrees wth the quote in bold above.

I also think everyone is trying to get a better understanding of what is actually going on in the drivetrain as power increases.

That is the big question, just a technical discussion.

I have always leaned towards the argument supported by Tony's data and results.
There is enough evidence in his results to suggest he is on to something.

Is he certain?
No, but that is why he plans to test the new engine he is building in the same manner.

Good stuff, Tony.
I had hoped someone had done exactly that kind of testing in the real world.
How come it took you so long and so many threads later to chime in?!!!

However, I also agree with ZeeOSix that there are other factors involved, such as friction/heat/rate of acceleration, that can skew the results a bit as power is increased.

I've read the article you reference, and it does offer some interesting information.

Here is another one for everyone to take a look at.

http://www.pumaracing.co.uk/trans.htm

It offers yet another method of looking at this question.

 

Exactly ... the "gearheads" are getting technical here and are more interested on what's going on then what the claimed numbers are.


The inertial dyno testing has some merit, but to claim that the amount of HP lost in a drivetrain (say a constant 75 HP) regardless of the input power level is ludicrous at best. IMO, the dyno testing methods are not showing the true story. The dyno testing is showing more of the inertial HP loss factor and not the real story on the factor of HP loss due to loading. The examples I gave in the real world more clearly show what really goes on when a drivetrain is loaded lightly compared to loaded heavily. The example of a truck pulling a load vs not pulling a load is a good real world example. If anyone took the time to do a test like that, they would see a huge difference in trans and diff temps, which can only lead to the conclusion that more HP was lost due in the drivetrain from added friction as a result of add HP input to the drivetrain. Again, if the amount of HP lost in the drivetrain was a constant 75 HP, then the trans and diff temps would never change as a result of higher or lower loading. Anyone remotely connected to how a car works knows that can never happen.

The drivetrain losses may not be a fixed constant % of input power -- but my bet is that it doesn’t change drastically with input power levels. But I will certainly say that the theory that drivetrain HP loss is a constant value regardless of the input power level is certainly a far cry from what’s actually going on.

 

Mathematically speaking, nothing mechanical (read: man-made) is ever "constant".

 

Oh, I do agree that more hp is lost as heat in the example you cited.
Even I won't question that !!

There may not have been enough of a change in fwhp amounts in Tony's tests to result in a measureable change at the rear wheels.

I look forward to his new engine results as another piece of information to include, as we beat this issue to a slow, ugly death!!

All in the interest of knowledge, I hope the discussion continues.

 

Nice find. My thoughts are that my viewpoints are basically exactly like his. He has spent tons of time explaining it all in detail, and even gives examples in terms of added heat in the drivetrain as HP levels increase.

Tony Mamo @ AFR -- read that article, as he explains everything in detail. I was working on another detailed reply to your post #43, but that article basically says everything I've said so far and was going to say. Looks like you owe me $50.

 

My pleasure, Sir. I'll accept 50% of the take

 

Yep...

You guys were right

Checks in the mail

And to the poster that questioned "Why I hadnt shared this before now", well....now you know why.

I lay out a "one plus one equals two" scenario with the various Vette drivelines quoting results from both engine and chassis dyno's that no one can argue with (because all the data is legit) where the math points directly to the fact a "close to fixed loss theory" makes ALOT more sense evaluting the real world test data versus the percent loss theory and it is casually dismissed (nor does anyone address that data and pose even a lame *** reason of how that is possible if driveline power losses are governed by percenatges).

I hope I may have given some of you a different viewpoint on this seriously misunderstood aspect of our hobby. I wish Harold Bettes from SuperFlow would take the time to post but honestly I wouldnt want to subject him to the frustration.

I look forward to future when I can hopefully report that my C5 driveline once again mysrteriously defies the laws of "percent loss" physics when now an almost 700 HP package will only lose (hopefully) around 80 HP to the back wheel...AGAIN

Catch you guys later....

-Tony

 

There is no mystery involved ... physics and engineering principle don't morph into whatever someone wants it to be based on their beliefs. Go find a dyno that has the ability to put much more load into the drivetrain and see what kind of HP loss you see. I bet if you just put the car on jackstands, and could measure the rwhp, the drivetrain would only lose about 20 HP - all due to just the inertia and the HP required to spin up the mass.

If you read the article linked a few posts above, it actually explains why the chassis dyno gives the illusion that the drivetrain HP loss is constant ... and it explains why in real life it really is close to a fixed percentage loss.

We may very well be that a chassis dyno gives the illusion that the drivetrain loses a constant HP amount which is what you say you see. But I would also have to say that you have your blinders on also when it comes to the real world examples that clearly show that the more HP you put into the drivetrain, the more HP is eaten up and turned into heat. You seem to not believe that and can't correlate the fact that all the heat that shows up is a direct indication of lost HP.

At this point all we can do it agree to disagree. There are a few who think a drivetrain always loses the same amount of HP regardless if the engine puts out 100 HP or 1000 HP, and there are the majority who think its close to a fixed percentage loss regardless of how much HP the engine puts out. The former is much more easily shot down than the latter IMO. So be it ... everyone is entitled to their beliefs.

 

I guess I should address some of your comments. The truck towing example is actually very related to this discussion. It's an example that clearly shows that the more HP you put into the drivetrain, the more HP is lost and turned into heat. Where does it go? ... well obviously the heat goes to increasing the temperature of mainly the trans and diff mass. They get very hot with extended amounts of high HP going into the drivetrain. Ask anyone who tows large trailers or anyone who races high HP cars. Don't you think there is a reason NASCARs and other high performance race cars use trans and diff coolers? When they are cruising at 200 mph at WOT around the track they are putting 800+ HP into the drivetrain and it's eating up a lot more than a "constant 75 HP". Do you think those same NASCARs would need a trans and diff cooler if their engines only made 100 HP and leisurely cruised around the track at 70 mph?

Not quite sure what you were saying in the red text above. In order to accelerate the dyno drum faster between 3000 - 5000 RPM it takes more force (ie, torque) on the drum. It's the higher force that makes it accelerate faster.

An engine 3 times as powerful will basically be putting out 3 times the amount of torque. When 3 times more torque is put into the drivetrain that has the same load on the rear tires (ie, the inertia of the dyno drum in this case), then it should cause added friction and heat in the components, which in turn should rob some additional HP from the rear wheels. The other end result of putting more power to the rear wheels is that the dyno drum accelerates faster. If the car was on the road, the end result would be the car accelerates faster down the road.

I'm not sure where you came up those numbers in red above. For instance, a bone stock C5Z is rated at 405 fwhp, and the avg dyno numbers come in somewhere around 345 ~ 355 rwhp. That's right in the 13 ~ 15% loss range. Call it a 55 HP loss (405 - 350).

It will be interesting to see where the new ZR1 comes in since the drivetrain is basically the same design as the C5Z. If the constant HP loss theory is true, then we can expect to see about 581 rwhp (636 - 55). If the 15% loss theory is true, then we can expect to see about 541 rwhp (636 x 0.85). That is a large enough difference between these (40 HP) to see what theory is closer to the truth.

 

Deal

 

More information to peruse.....

http://www.welltall.com/ymc/discover...rivetrain.html

http://www.motortrend.com/roadtests/..._the_dyno.html

http://craig.backfire.ca/pages/autos/horsepower

 

Drive train loss varies with temperature, tire pressure, and other variables. You can not also assume that all drive train loss is 15%. This also can vary greatly even on same model cars.

Another thing you have to realize is that horsepower is not a real figure, it is simply the result of a formula used to compare power output of engines. The real HP of an engine can only be figured using the brake torque figure via a real engine dyno.

The only true way to tell your HP number is to use the following forumla wth the results of a engine dyno.

horsepower = rpm x torque / 5252

Anything else is guess work.

 

This one example will help us all to better understand the relationship that is being discussed.

Shouldn't be too many more weeks before the results start to roll out.

 

http://auto.howstuffworks.com/question622.htm