why do lower gears show less hp numbers?

 

they should show higher numbers i am pretty sure on that

 

4.10's will show lower hp then 3.42's from what I have read. running heavy wheels is supposed to show lower hp too.

 

a dyno measures how many ftlbs of tourque it takes to stop the motor to hold a steady rpm you put lower gears you gain false tq

 

Uhhhhh none of that is true ! You lose tr and hp because of frition! You wont gain anything trq or hp any where ! and you wont get a false reading as long as you dyno in same gear each time 1.0 to 1.0 ratio

 

dynamometers measure torque by use of a brake Brake torque is simply a measurement of how much resistance is needed to hold the engine at a steady rate of speed This is commonly referred to as a step test

changing to a lower gear is the same thing as using a 1ft tq wrech with 50lbs on the end or a 1.5ft tq wrench with 50lbs on it changing gears is essentialy creating more fore with the same lbs of tq

HP = torque x speed

torque = lever arm x force

Horsepower

The definition of 1 horsepower is the ability to do 33,000 pounds-feet of work in one minute. So horsepower is a measurement of torque over time. The measurement of horsepower was invented by James Watt when he replaced horses turning a water pump with a steam engine and wanted to know how many horses the engine could replace in order to rate the engines power. He figured that a horse could pull with 180 lbs. of force. The horse traveled in a circle with a 12 ft. radius, and could make 144 complete revolutions in 1 hour. This means that the horse traveled 181 feet per minute. 180 lbs. of force times 181 feet equals 32,580 pounds-feet of work in 1 minute. Watt rounded that up to 33,000 pounds-feet of work in 1 minute.

Figuring Engine Horsepower

Watt's definition of horsepower is a horse pulling on lever, so the power was applied to the lever. An engine does not work like this, the power is made at the crankshaft. So to know the horsepower of an engine you will need to imagine a 1 ft. lever at the crankshaft and figure the circumference of that one ft. lever and how many rotations per minute it is traveling. A 1 ft lever will have a circumference of 6.2831853 ft., so the formula for hp would look like this:

HP = (6.2831853 × RPM × Torque) ÷ 33,000

And can be simplified to:

HP = (rpm × Torque) ÷ 5252

 

He didn't ask how you calculate everything. just wants to know the relationship between 2 different gears on the dyno.
Nothing in that equation calculates a gear ratio difference on a vehicle.

 

its physics you are using more force with a lower gear just like using a longer tq wrench like going from inch pounds to foot pounds 1lbs of force on a 1 inch bar or 1lbs of force on a 1 ft bar still using 1 lbs to tighten but it applys more force with a longer bar so your motor is the constant say 350lbs of tq its just like doing a dyno run in 3rd gear 1,0 to 1.0 ratio or in first gear say 3.0 to 1.0 you will put more power down in first gear not less. so say in 3rd gear you are 1.0 with 3.43 gears your actually 3.43 to 1.0 motor to tire revolution now with 4.10 gears your 4.10 to 1.0 motor to tire revolution so your motor is spining 4 time to rotate the tires once witch create a "false" tq kinda like using a breaker bar... i hope you understand what i am trying to say i am not very good at explaining over a computer...

 

I'm going to TRY to simplify that for you. Let me know if i get this right.
I THINK what your trying to say is this:
The 4.10 gear is increasing your engine RPM's compared to that of the lower gears.
using the equations Slide posted Here's what i get.
Say a 4.10 dynos 400ftlbs at 5000rpm (400*5000) / 5252 = 380.8 HP
While a 3.42 may dyno 400fltbs at 4800rpm (400*4800)/5252 = 365 HP

Is that accurate to your description?

 

close but it dose not have to do with rpm the tq at rpm will stay a constant variable.. if your gears are 25% shorter you should theoreticly put 25% more power out but it actually wont come out like that due to other variables but its kinda like this

350lbs tq @ 4000 with 3.43 gears
change to a 20% higher ratio 4.11
you should in in a perfect world have
420lbs tq at 4000 with 4.11 ratio
real world would actually come out to be
380lbs tq @ 4000

make any sence sorry i am so confusing lol