Speed vs HP

[tim schoeny]

I believe this topic has been discussed before(many times),but I really need a SIMPLE formula to predict changes in speed based on changes in hp.For example,if I know that 145hp = 134mph what mph will 200hp yield?
                                                        Tim

[aswracing]

I believe this topic has been discussed before(many times),but I really need a SIMPLE formula to predict changes in speed based on changes in hp.For example,if I know that 145hp = 134mph what mph will 200hp yield?
                                                        Tim

Horespower required goes up as the cube of the speed increase.

Or conversely, speed goes up as the cube root of the horsepower increase.

So in your example, take 200hp divided by 145hp = 1.3793, or in other words you're increasing the hp by 37.93%

The cube root of 1.3793 is 1.1131  (if your calculator doesn't have a cube root function, raise it to the 1/3 power)

Therefore the vehicle can go 11.31% faster on the additional power, assuming it's geared right.

1.1131 times 134mph = 149.15mph that you can go on 200hp.

[Sumner]

I believe this topic has been discussed before(many times),but I really need a SIMPLE formula to predict changes in speed based on changes in hp.For example,if I know that 145hp = 134mph what mph will 200hp yield?
                                                        Tim

I have a spreadsheet for that ( HERE ).  It will do exactly what you want for any speed and/or HP.

There are also some spreadsheets there to help you figure what HP might be needed to run a speed if you don't have a reference point.

If they don't make sense PM me.

c ya,

Sum

[JackD]

UMM , TOUGH NUT EH ?

[hitz]

  Someone said the white dyno will tell you!

  Someone else said you can't have too much horsepower.

  It's fun to have an idea how fast you can go but it's so complicated, formulas can lead you astray and  to surprises. Maybe good, maybe not so good. It's really hard to aquire all the correct information for the the formulas. Cd on mine is a wag, So is horsepower (at the wheels please), rolling resistance on (salt), wet or dry, traction etc. Once you have a speed and a horsepower rating you have something good to work on. Throttle full on?
 
  My Doctor told me my engine in the Saturn car was probably good for 100 mph so it should do a 150 in a lakester. He was an engineering major drop out!  I'm taking those figures and going to Sumner's spread sheet and then Tim's formula. I'll put some nice numbers in for Cd when I need them and use the numbers my doc gave me. I have more of a chance to be happier with Sum's spread sheet because my car is realllllly slick. . Just kidding with you, Sum!

  Harv

[Seldom Seen Slim]

"Throttle full on?"

Harv -- you hit the nail on the head there.  My mechanic taped over the speedo and wrote on it this little reminder for the rider:

Tuck In
W.F.O
Have Fun

I always worry that at the end of the run we'll be looking at the data -- and I'll be busted for not having the throttle at 100%.  "No wonder it didn't go fast, Jon..."

I spend a good portion of each run re-checking to see that I've got it at full pin.

[narider]

I've got the opposite problem Jon.. I tend to stress the throttle cable(now that I think of it with the little bit of HP I make, I could have a solenoid open my throttle WFO of the line I suppose). I really like my Tommaselli 1/8 turn throttle that has an adjustable stop as it keeps me from using the cable or slide as it's stress point.
Todd

[jimmy six]

Jon, I thought the note would say "don't sit up at the 5, your not done yet" ........J.D.

[Bob Drury]

How would you bikers know if your running at full throttle?  You guys certainly must ride with your eyes closed or you wouldn't be going that fast.  Didn't any of you guys listen to your Mother?  Sign me Ilovemyrollcage Bob.......

[Harold Bettes]

You know that they call the guys on side hacks "monkeys" on those road race adventures. Perhaps at Bonneville they would be called "ballast" or "drag" or maybe just "not legal". 

Those bike guys have some kind of grande huevos! 

Regards to All,
HB2