DVUSz06

Hi all, maybe this has been hashed out on here before but I want to know what you think of my thought process reguarding powertrain and percent of loss. I just read an old post where a guy said he made x amount of hp at flywheel with his mods because he dynoed at xhp at the wheels, and figured an 18% loss in powertrain. Now most of what I read in past tells me the average stock LS6 in a Z puts around 360-365 to rear wheels, thats 40-45hp lose and that = 10-11% hp lose in powetrainn meaning it takes 40 hp to move my car down the road. Why do people always use a rediculas hi percentage when talking power gains and loss. If I mod and dyno x amount of hp at wheels then I only gained x amount above 360-365 not apercentage of total hp output. Because it still only takes 40-45 hp to move my car down the road, right? Is this 18-22% thing a marketing gimmick or am I missing something?

road pilot

I don't know much about numbers and percentages. But I do
know that engines are run on engine dynos out of the car and
that is the number published for general consumption. Because
of varying factor's politics, insurance, etc sometimes those
horsepower numbers are decreased and at times (for marketing)
increased. So in a lot of ways the crank horsepower number
is not a exact number ; just as a rwhp is not a exact number.

Some other guys can explain the 18/20 percent rule better
than I can . Just remember the numbers are not a exact
number just a number that can go up or down depending on
a host of variables.
See--I told you I don't much about numbers.

HardcoreABN

the loss factor has a LOT to do with your trans/diff combination. an auto will always have a higher parasitic loss than a manual. Some diffs are more parasitic than others.

gimp

Some mods also introduce their own parasitic loss - superchargers are common.

The figures I've seen are usually a 20% loss at around 500+ flywheel hp.

romandian

over here its very simple. i get the power loss plot with the rwhp plot, which adds up to the din/ec hp numbers. it comes with every dyno run. no guessing involved.