if you have a 1000hp car, im sure you have the money to upgrade the tranny and tc, and whatever else you need to minimize hp loss.

 

got to it first, but yea thats where my vote goes too

 

if you have a 1000hp you probibly have a beefier trans and rear end and bigger axles. more mass, more surface area, more driveline loss.

 

when you look at the physics behind acceleration and force, you will see that drivetrain loss IS a percentage and not a fixed number.

The ability to accelerate a mass requires force, and as you increase the rate of acceleration, the force required to achieve that acceleration rate requires even more power.

What you have to account for is not the power needed to just simply "turn" an object, but you have to realize that you are ALSO accelerating a mass in the drive train parts. To accelerate that at a faster rate will require more power, thus the loss is a percentage.

 

well put.

 

Also at 1000 hp your friction levels will be higer on every single bearing / gear throu the whole drive line...

 

if friction increased with speed or acceleration then there would be a point everything would seize.

Friction is a constant, the energy required to overcome friction for a bearing is the same at 300hp as it is for 600hp.

Now whether or not a part can survive to such power or speeds is another matter. Take the stock driveshaft. That will not survive an engine that can pull off 8k rpm. (which would be an amazing feat to have the ls1 pulling such rpm in the first place...). It would hit its critical rotational velocity and boom goes the dynamite!

 

I highly doubt friction would be the same on a bearing that is subjected to 250hp as one that is subjected to 1000hp

take the rear end in your car... the pinion and carrier are allways trying to seprate under power and they cant because the bearings are holding them there... now when you quadruple the the power going throu the gears you dont think this will increase the load on your bearing???? Bearings do create friction, and as the load increases so does the friction..... It has nothing to do with speed but more so the increased load on the components..... The same goes for your transmission, those gears are always trying to separate and the bearings are what keep them in mesh.....

Also there is a point where any bearing will fail... to think that a bearing will survive unlimited rpm's is ludicrous... and the reason that they will fail would be heat do to friction.....

 

there is a point with friction vs load where the bearing will not dramatically increase in terms of firction vs load applied. this happens about 50% to 100% of its rated load capacity. at 150% the firction generally only increases around 5-10%. but the as the bearing failrs friction can and will quadruple. so what your saying might be true lets not look at driveline loss in percentages. Because the higher the ouput of the engine the lower the percentage of the output will be used to turn the driveline. IE a 345hp motor make 300hp to the tire thats 15%. but that same engine at 500hp make 465 to the tires a 5% loss. the ratio is inverse.

 

Do you even realize what you just said??? That simply increasing the power will make a drive train increasingly more efficient ...

HP isn't just a function of moving a mass. It's also a function of how quick you move that mass.

Take your example 300HP and 500HP ... say both are at 6000 rpm. They are both at 6000 RPM and both are turning the same mass so whay is one 300HP and the other 500HP? It's time. One got up to 6000 RPM in - say 20 seconds. The other say - 15 seconds.

The quicker you spin up the drive train the more inefficient becomes ...

 

If you would like i can start posting chassis dyno vs engine AB tests done with the same vehicle to prove my point or you can just accept the fact that if your making 500rwhp your only making 575ish flywheel in a m6 fbody with accesorys. Not 650. providing the drivetrain isn't exccesivly heavier than stock.


So in your world an 8000hp top fuel car at %15 loss only make 6800hp at the rear tire correct ?

 

I'm not disputing how much the loss is for a given motor and drive train ...

What is in dispute is your belief that drive train loss is fixed and therfore ever increasing power on a given drive train results in an increasingly more efficient transfer of power ... sorry but there is no free lunch in physics.

As for a 8000 hp top fuel ... run any of the HP calculators put in the specs for a top fuel ... say 2300 lb, 4.4 ET and 335 mph and you come up with a rwhp somwhere between 5300 and 6800 ... and on my own car the calculator is high by a factor of about 12% ... so a 8000 hp top fuel could be putting as little as 4400 to the wheels ... so yes the loss is at least 15% and as much as a 42% loss for a top fuel ...

 

You are both right but Sean is stating it in different terms. He is a dyno tuner and see these numbers all of the time. Before, after, engine and chassis.
hypathetical
340 fwhp LS1 shows 300 rwhp = 13% lost (40hp) to turn the trans, driveshaft, rear end.
Now bump the engine to 500 fwhp - 13% = 435 rwhp that would mean that the drivetrain now requires 65 hp to make it do exactly what it did before only a little quicker. Physics are laws and it isn't going to take another 25 hp to turn the same exact drive train due to extra frictional losses. Let's say that it does take 10 more hp to overcome the extra friction of bringing it up to speed faster.
So now we have a 500 fwhp motor that puts out 450 rwhp = 11% of the 500 is lost in transmission to the wheels.
The percentage of loss shrinks because the drive train stays the same as the engine power goes up.

 

dont top fuel cars just run a huge clutch and no transmission? i think with the clutch fully locked you end up with a pretty efficent drive train minus the weight of all the components

 

There was quite a big discussion about this ls1tech.com.

http://ls1tech.com/forums/showthread...4&page=1&pp=20

Drivetrain loss is based on a percentage, but it is not a linear increasing percentage at higher power levels. A drivetrain does not suck up a specific static amount of hp. If you took Camaro drivetrain, and stuck it in some 50hp car, does that mean the drivetrain won't move? Because it will (although not quickly). It is explained much better than I can do at the moment in the link.