help with horsepower formula
Feb 15, 2010, 07:36 AM
#1
help with horsepower formula
its late and my brain is mush.... but for some reason i cant get this formula to evaluate properly
HP=(5280/3600)^2*(3500/32.17)/(87.7)^2*(curr rpm - prev rpm)/(curr time - prev time)*(curr rpm + prev rpm)/2/550
prev time=85.14
curr time=85.17
prev rpm=2763
curr time=2777
obviously i am missing a cpl brackets as Excel evaluates it properly but if i do it by hand i get a completely wrong answer.
can someone please help me with the order of the formula? the result should be 65..or 71 but i get 1.14159E-08 or even 101.... which is very very wrong.
HP=(5280/3600)^2*(3500/32.17)/(87.7)^2*(curr rpm - prev rpm)/(curr time - prev time)*(curr rpm + prev rpm)/2/550
prev time=85.14
curr time=85.17
prev rpm=2763
curr time=2777
obviously i am missing a cpl brackets as Excel evaluates it properly but if i do it by hand i get a completely wrong answer.
can someone please help me with the order of the formula? the result should be 65..or 71 but i get 1.14159E-08 or even 101.... which is very very wrong.
Feb 15, 2010, 12:13 PM
#3
Evolved Member
iTrader: (22)
Join Date: Nov 2003
Location: Northern KY near Cincy
Posts: 2,408
Likes: 0
Received 6 Likes
on
6 Posts
Yep....71.52 when i do it. Based on the low RPM this seems to be correct.
Shouldn't the first value be 5250 rather than 5280 ? ?
Shouldn't the first value be 5250 rather than 5280 ? ?
Last edited by Appauldd; Feb 15, 2010 at 12:19 PM. Reason: adding question
Feb 15, 2010, 02:41 PM
#4
would u mind explaing the order, its been a long time since i did these currently i calculate
HP=(5280/3600)^2*(3500/32.17)/(87.7)^2*(curr rpm - prev rpm)/(curr time - prev time)*(curr rpm + prev rpm)/2/550
hp=2.1511 * 108.797 / (7691.29 * 14) / (0.03 * 5540) / 2 / 550
or
hp=234.033 / 107678.06 / 166.2 / 2 /550
or
hp=1.14159E-08
so i am obviousily doing something wrong... and I even tried to do it in VB and the wrong answer there to... hence the request to put the above in brackets or if u dont mind telling me the order. i also get 99.33, if i order them like:
234.033*166.2*550/107678.06*2=99.33
HP=(5280/3600)^2*(3500/32.17)/(87.7)^2*(curr rpm - prev rpm)/(curr time - prev time)*(curr rpm + prev rpm)/2/550
hp=2.1511 * 108.797 / (7691.29 * 14) / (0.03 * 5540) / 2 / 550
or
hp=234.033 / 107678.06 / 166.2 / 2 /550
or
hp=1.14159E-08
so i am obviousily doing something wrong... and I even tried to do it in VB and the wrong answer there to... hence the request to put the above in brackets or if u dont mind telling me the order. i also get 99.33, if i order them like:
234.033*166.2*550/107678.06*2=99.33
Last edited by ziad; Feb 15, 2010 at 02:44 PM.
Feb 15, 2010, 03:09 PM
#6
Evolved Member
iTrader: (22)
Join Date: Nov 2003
Location: Northern KY near Cincy
Posts: 2,408
Likes: 0
Received 6 Likes
on
6 Posts
HP=[((5280/3600)^2)]*[(3500/32.17)/(87.7)^2]*[(curr rpm - prev rpm)/(curr time - prev time)]*[(curr rpm + prev rpm)/2/550]
That is how I did it. Basically break the equation into pieces. Once you solve each piece...then solve for the multiplication.
That is how I did it. Basically break the equation into pieces. Once you solve each piece...then solve for the multiplication.
Trending Topics
Feb 15, 2010, 03:16 PM
#8
would u mind explaing the order, its been a long time since i did these currently i calculate
HP=(5280/3600)^2*(3500/32.17)/(87.7)^2*(curr rpm - prev rpm)/(curr time - prev time)*(curr rpm + prev rpm)/2/550
hp=2.1511 * 108.797 / (7691.29 * 14) / (0.03 * 5540) / 2 / 550
or
hp=234.033 / 107678.06 / 166.2 / 2 /550
or
hp=1.14159E-08
so i am obviousily doing something wrong... and I even tried to do it in VB and the wrong answer there to... hence the request to put the above in brackets or if u dont mind telling me the order. i also get 99.33, if i order them like:
234.033*166.2*550/107678.06*2=99.33
HP=(5280/3600)^2*(3500/32.17)/(87.7)^2*(curr rpm - prev rpm)/(curr time - prev time)*(curr rpm + prev rpm)/2/550
hp=2.1511 * 108.797 / (7691.29 * 14) / (0.03 * 5540) / 2 / 550
or
hp=234.033 / 107678.06 / 166.2 / 2 /550
or
hp=1.14159E-08
so i am obviousily doing something wrong... and I even tried to do it in VB and the wrong answer there to... hence the request to put the above in brackets or if u dont mind telling me the order. i also get 99.33, if i order them like:
234.033*166.2*550/107678.06*2=99.33
It should be:
/7691.29 * 14 and /0.03 * 5540
There are no parentheses there
Thread
Thread Starter
Forum
Replies
Last Post
smanders
Evo X Engine Management / Tuning Forums
5
Mar 30, 2012 10:54 AM
djkmod83
Lancer Tires, Wheels, Brakes & Suspension - Sponsored by The Tire Rack
4
Aug 22, 2008 01:48 AM