# dyno-ing your car w/o a machine? **URL:** \ **Category:** NYSpeed Automotive\ **Created:** [March 13, 2008, 6:18pm UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986 "2008-03-13T18:18:10Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![snowracer101](https://avatars.discourse-cdn.com/v4/letter/s/258eb7/32.png) [@snowracer101](https://forums.speedlife.net/u/snowracer101)\ **Post date:** [March 13, 2008, 6:18pm UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986/1 "2008-03-13T18:18:10Z")
I remember reading this somewhere and it actually works… All you need is a car and a stop watch, if I remember correctly You keep the car in 3rd gear (5spd) and accelerate and time it with the stop watch until red line, then you shift into neutral and roll back to your starting speed to measure the rolling resistance. You then plug a bunch of numbers into a formula and you have your cars HP/TRQ Again, I’m not sure the exact steps but I remember reading this somewhere, anyone have a link to the site which explains how to do it? ---
**Author:** ![RedGoober4Life](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/redgoober4life/32/7610_2.png) [@RedGoober4Life](https://forums.speedlife.net/u/RedGoober4Life)\ **Post date:** [March 13, 2008, 6:41pm UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986/2 "2008-03-13T18:41:27Z")
Use: ![http://www.canadaconnects.ca/i9/quantumphysics/config/images/shrodspace.jpg](http://www.canadaconnects.ca/i9/quantumphysics/config/images/shrodspace.jpg) 🙂 ---
**Author:** ![Nikuk](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/nikuk/32/7254_2.png) [@Nikuk](https://forums.speedlife.net/u/Nikuk)\ **Post date:** [March 13, 2008, 7:03pm UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986/3 "2008-03-13T19:03:24Z")
wouldnt it be 4th gear, for 1:1? Of course, you could do any gear, just have to factor the multiplication in ---
**Author:** ![psphinx81](https://avatars.discourse-cdn.com/v4/letter/p/e9a140/32.png) [@psphinx81](https://forums.speedlife.net/u/psphinx81)\ **Post date:** [March 13, 2008, 7:05pm UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986/4 "2008-03-13T19:05:49Z")
wat? ---
**Author:** ![Nikuk](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/nikuk/32/7254_2.png) [@Nikuk](https://forums.speedlife.net/u/Nikuk)\ **Post date:** [March 13, 2008, 7:07pm UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986/5 "2008-03-13T19:07:32Z")
> [@psphinx81](#): > > wat? alot of math. You need to know alot of the details too (weight, cD, gear ratios, exact distances, etc). ---
**Author:** ![snowracer101](https://avatars.discourse-cdn.com/v4/letter/s/258eb7/32.png) [@snowracer101](https://forums.speedlife.net/u/snowracer101)\ **Post date:** [March 13, 2008, 7:13pm UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986/6 "2008-03-13T19:13:28Z")
> [@Nikuk](#): > > wouldnt it be 4th gear, for 1:1? > > Of course, you could do any gear, just have to factor the multiplication in 4th gear in a 6 spd, 3rd in a 5 speed. I was jsut looking for the website that explains it. ---
**Author:** ![SOLITUDE](https://avatars.discourse-cdn.com/v4/letter/s/c37758/32.png) [@SOLITUDE](https://forums.speedlife.net/u/SOLITUDE)\ **Post date:** [March 13, 2008, 7:15pm UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986/7 "2008-03-13T19:15:50Z")
my brain hurts. ---
**Author:** ![psychopjv](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/psychopjv/32/7251_2.png) [@psychopjv](https://forums.speedlife.net/u/psychopjv)\ **Post date:** [March 13, 2008, 7:23pm UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986/8 "2008-03-13T19:23:33Z")
> [@sedlmeier101](#): > > 4th gear in a 6 spd, 3rd in a 5 speed. > > I was jsut looking for the website that explains it. not for 1:1 4th gear is 1:1 in both of those. in a 6 speed the 5th and 6th driven gears are both over drive. in a 5 speed only 5th is OD. ---
**Author:** ![FiftyCheven](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/fiftycheven/32/4950_2.png) [@FiftyCheven](https://forums.speedlife.net/u/FiftyCheven)\ **Post date:** [March 13, 2008, 9:47pm UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986/9 "2008-03-13T21:47:13Z")
Here is the formula i commonly use… Pull wallet out + pay dyno guy = get dyno numbers. ---
**Author:** ![Nikuk](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/nikuk/32/7254_2.png) [@Nikuk](https://forums.speedlife.net/u/Nikuk)\ **Post date:** [March 14, 2008, 5:02am UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986/10 "2008-03-14T05:02:52Z")
:word: > [@psychopjv](#): > > not for 1:1 4th gear is 1:1 in both of those. in a 6 speed the 5th and 6th driven gears are both over drive. in a 5 speed only 5th is OD. :wstupid: ---
**Author:** ![MaximaSE98](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/maximase98/32/7600_2.png) [@MaximaSE98](https://forums.speedlife.net/u/MaximaSE98)\ **Post date:** [March 14, 2008, 5:25am UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986/11 "2008-03-14T05:25:07Z")
> [@sedlmeier101](#): > > 4th gear in a 6 spd, 3rd in a 5 speed. > > I was jsut looking for the website that explains it. really depends on the car…my 4th isnt quite 1:1 but its close both 5spd and 6spd Sentras are 4th gear 6 Spd Sentra 1st 3.416 2nd 1.944 3rd 1.258 4th 0.947 5th 0.772 6th 0.630 5 Spd Sentra 1st 3.153 2nd 1.842 3rd 1.258 4th 0.947 5th 0.772 ---
**Author:** ![Fry](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/fry/32/7284_2.png) [@Fry](https://forums.speedlife.net/u/Fry)\ **Post date:** [March 14, 2008, 5:38am UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986/12 "2008-03-14T05:38:34Z")
Only taking into account acceleration and drag: F=m((v2-v1)/t) + .5_rho_v^2_A_Cd Good luck getting any sort of accuracy out of it. Well, that just gives you average force and at this point I’ve lost interest. ---
**Author:** ![Viper966](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/viper966/32/7268_2.png) [@Viper966](https://forums.speedlife.net/u/Viper966)\ **Post date:** [March 14, 2008, 5:48am UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986/13 "2008-03-14T05:48:23Z")
or buy a used Gtech for less then 30 bux and VOILA ---
**Author:** ![ultradriver10000](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/ultradriver10000/32/7397_2.png) [@ultradriver10000](https://forums.speedlife.net/u/ultradriver10000)\ **Post date:** [March 14, 2008, 6:39am UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986/14 "2008-03-14T06:39:08Z")
I’ll sell my G-tek for $30 if you want it! ---
**Author:** ![66impalass](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/66impalass/32/7429_2.png) [@66impalass](https://forums.speedlife.net/u/66impalass)\ **Post date:** [March 14, 2008, 6:50am UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986/15 "2008-03-14T06:50:42Z")
you forgot to include rolling resistance of the tires, probably have to take into account the air density to get a more accurate F resulting from air… shit if you actually know what you are doing in regards to this, but I doubt many people would want to actually sit down and do the math to this, and you might want a program like mathcad where you only have to define the variables. EDIT: and you have to also take into account your lack of reaction times for the timing system ---
**Author:** ![Fry](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/fry/32/7284_2.png) [@Fry](https://forums.speedlife.net/u/Fry)\ **Post date:** [March 14, 2008, 6:57am UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986/16 "2008-03-14T06:57:37Z")
> [@66impalass](#): > > probably have to take into account the air density to get a more accurate F resulting from air… Rho sukka! The math is easy. It’s just plain old freshman year kinematics. It’s getting accurate inputs to the variables that’s going to be hard. Well, naw maybe not that easy. Drag force will be increasing exponentially the entire time you’re accelerating. Time to do calculus. :hang: ---
**Author:** ![Nikuk](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/nikuk/32/7254_2.png) [@Nikuk](https://forums.speedlife.net/u/Nikuk)\ **Post date:** [March 14, 2008, 6:58am UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986/17 "2008-03-14T06:58:24Z")
For the third time… anything can be solved with math, but you have to know the variables. ---
**Author:** ![Fry](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/fry/32/7284_2.png) [@Fry](https://forums.speedlife.net/u/Fry)\ **Post date:** [March 14, 2008, 7:01am UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986/18 "2008-03-14T07:01:33Z")
If you can get the Cd and frontal area of your vehicle, the rest is pretty much cake. Would you even have to take into account rolling friction? It’d be there on a dyno too. Well, it would for the drive wheels. So yeah you’d have extra resistance from the non-drive wheels. Fuck just guess. ---
**Author:** ![66impalass](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/66impalass/32/7429_2.png) [@66impalass](https://forums.speedlife.net/u/66impalass)\ **Post date:** [March 14, 2008, 7:16am UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986/19 "2008-03-14T07:16:14Z")
> [@Fry](#): > > Would you even have to take into account rolling friction? It’d be there on a dyno too. Well, it would for the drive wheels. So yeah you’d have extra resistance from the non-drive wheels. There is a slipping factor from the fact that the road doesn’t move like the rollers of a dyno, and what if it was a hub dyno? ---
**Author:** ![Nikuk](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/nikuk/32/7254_2.png) [@Nikuk](https://forums.speedlife.net/u/Nikuk)\ **Post date:** [March 14, 2008, 7:18am UTC](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986/20 "2008-03-14T07:18:23Z")
PJs & KENNEDYS & SPINA’s all have Dynos. Just not for AWD. [Next page](https://forums.speedlife.net/t/dyno-ing-your-car-w-o-a-machine/44986.md?page=2)