formula for calculating weight change by moving engine

JuicedBu · Post by **JuicedBu** » Tue Oct 24, 2006 10:42 pm

Is there anyway to figure out the change in front end weight by moving an engine back? I would assume you would need to know the wheelbase and weight of the vehicle, percent of weight on front, weight of the engine, distance from the center of gravity of the engine to the front wheels, and the change in that distance but am unsure of what else.

BillyShope · Post by **BillyShope** » Wed Oct 25, 2006 7:47 am

distance = LPW/w where "L" is the wheelbase, "P" is the percentage change in rear wheel weight divided by 100, "W" is the total weight, and "w" is the weight of the component being moved.

JuicedBu · Post by **JuicedBu** » Wed Oct 25, 2006 6:27 pm

My car weighs 3150 pounds with me in it. 54% of the weight if on the front. Lets say the engine is about 500 pounds. Moving the engine back 2 inches would change the rear end weight by 3.4% dropping about 111 pounds off the front of my car. That sounds like a lot to me but I've never actually done it. Does that sound right?

2 = 108.1 x P / 100 x 3150 / 500
2 = 6.8103 x P
P = 3.40515

BillyShope · Post by **BillyShope** » Thu Oct 26, 2006 6:56 am

JuicedBu wrote: 2 = 6.8103 x P
P = 3.40515

Here's where you went wrong. You DIVIDE both sides by 6.8103 and the change is 0.294%.

JuicedBu · Post by **JuicedBu** » Thu Oct 26, 2006 7:20 am

Doh, I divided by 2. So I would actually lose like 10 pounds.

mike walker · Post by **mike walker** » Thu Oct 26, 2006 10:14 am

Billy,
when using this equation, should'nt transmission weight be a factor also since it will move with the engine?
but then would'nt you have to consider how the eng/trans asm is mounted? because the asm will have a weight bias of its own dependant on its mounting points. ex: motor plate, mid plate, trans mount??

BillyShope · Post by **BillyShope** » Thu Oct 26, 2006 11:24 am

mike walker wrote:Billy,
when using this equation, should'nt transmission weight be a factor also since it will move with the engine?
but then would'nt you have to consider how the eng/trans asm is mounted? because the asm will have a weight bias of its own dependant on its mounting points. ex: motor plate, mid plate, trans mount??

The equation applies to the NET weight moved.