Just wondering is it possible to calculate a car's wheel horsepower without running on dynos? Say if you are reading tru the ECU? I believe by recording the rpm together with the speed the same time you can find out the power band? But do the ECU log speed or just the speedometer, for non electronic speedo?

Butt dyno got!

No need any equipment!

It won't be accurate but you can try with those 1/4 mile softwares to calculate your engine BHP base on engine capacity and etc etc

just use back your engine's official hp (from manufacturer) and deduct 20% (for manual) or 25% (for auto), then deduct 1hp per year of usage and u'll get an estimated whp of the car. But this kind of calculation is NOT accurate of course, because there are just too many variables that can't be calculated like how is the condition of your engine and gearbox and the mileage etc. etc.

This post has been edited by stormlcc: Nov 8 2011, 04:17 PM

So if you reading tru the ECU you won't get the data required to calculate or plot the graph?

use your iphone if you have one

That sounds strangely logical.

there's an app for that

Of course there is

5 years ago ppl will think you're crazy to use your phone to measure bhp .

Nowadays can do so many things.....

i wonder how u use "iphone" to get hp ?

plug in iphone into .... CAR OBD Socket ?

or what ... ? How iphone Detect ur hp ?

by tire spinning rate ? speed rate ?

Who has done before??

Basically it is like a 1/4 mile app
You key in your engine data inside, hook your Iphone (make sure it is straight)
Then just hentam
The app will calculate your engine BHP base on how fast your 1/4 mile base on your engine capacity

used OBD2 socket, but u need to buy OBD2 wifi /Bluetooth transmitter and need to install apps like "torque" for Android and "rev" for I Phone..

the transmitter is like this.. :

I have one which looks exactly like this!

Unfortunately car running OBD1.

What about car's weight?

that's the first thing to key in. weight with driver.

that method to calculate is using any device with a gyro. which all smart phones have now. not reliable. too many variables to effect the results. to me, totally useless.

i bought dynolicious, i used it once. garbage.

Might as well just send for dyno?

Where do you connect this to, the ECU? Is it standard for most cars? What kind of data does it log other than RPM?

The weight of the car can be calculated by measuring the tyre ground area & tyre pressure.

There is a plug under the dash that this can be connected to and is linked to the ECU....

Huh? Can calculate in this way meh?

wana sell to me?

I thought vehicle's curb weight is often specified in the car brochures (Heck, you can even find it in Wikipedia)?

Empty your boot and just add driver's weight to it can?

I got the software. Its completely useless.

Sure,I have no use for it!

Shoot me a pm!

If have wider tyres will be different again.....

Different countries have different accessories. In Europe Aircon is optional so it would be lighter than Malaysia version.

So, actual dyno will still be the most accurate.....

If you have your engine rpm & speed logged, together with car + driver weight, & aerodynamic drag you can calculate relatively accurate data, not sure how often the dynos are calibrated.

Just a sidenote for dynos where do they plug in the engine to read the rpm?

To me, benchmarking solely on hp alone is pure crap. In the real world, Power to weight ratio, 0-100 or quarter mile time are the benchmark. Whats the use having a 300 hp with a 2.5 tonne weight, when a sub 1tonne car with half the HP can easily out maneuver and perform better than the big hp car? Not to mention, a low HP car with a high torque makes urban driving much more fun.

also depends on the dyno. so far innertia based ones are most accurate. like dyno dynamics.

Very true......

Anybody know how to get dyno? Can share with me please =)

go to sunway and ask around "where got dyno?" and u'll find it...............

The problem now is I am living at Sabah now.

Somehow a bit of a problem there. I have some members from Labuan, Kuching also, and some mention have to travel further to source for service or parts also....

Because there is no much highways for us to speed. Our highways just have two lines only plus our roads are too good already until I don't know how to say. 3months need to alignment a times.

Understand, as I was in KK a few years back for an assignment, but for a few days only.
As far as I know the sales personnel who took me around, mentioned the road to Sandakan very winding so good to play but dangerous......

Ya... Tat's y most of the people here r driving 4X4 cars... Small car nid to alignment everything especially sportcars..

Actually that's how inertia dyno like Dynojet works. Instead of car+driver weight, it uses the roller's fixed weight.

I've done this to my Exora Bold CFE. Using home-made Excel. Something like this :



The formulas are explained here : http://www.herberts.org/wayne/valk/valktorque.htm

I added aerodynamic drag & rolling resistance formulas for final values. Looks pretty accurate to me.

How do you log the rpm and time it properly with velocity?

I use ELM327 Bluetooth OBD2 reader to log OBD2 data (RPM,speed,boost etc) directly.

alternatively : www.gtechpro.com

GTech Pro is much more expensive than 1 dyno run.

They're IPhone apps than can calculate hp based on accelerometer data like Dynolicious & Track Day. Same concept as GTech Pro, much cheaper, pretty accurate, but only hp value no torque value.

Iphone apps are crap. I've tested it and the results were far from actual after dyno. The gyro is not industrial spec tool. They rely on acceleration of the movement (which has a high tolerance) and GPS data (which is also crap AGPS & low frequency) to work out the estimation value. If you drive a 200hp car which weight less than 1 tonne, your HP indication will be higher due to power to weight ratio.

Dynolicious & Track Day doesn't use GPS data. Probably it boils down to putting the correct info (vehicle weight etc), putting the Iphone in correct orientation (and stationery), and no jerking movement. Or the apps don't count aerodynamic drag / rolling resistance.

I'll stick to my OBD data then

If you retune your car ten times due to bad tuning/mechanical failure/upgrades, it's a whole lot of different story. Mind you, I am the sole distributor of gtechpro in SEA

I don't think any reader that only monitors acceleration will be accurate as there's no other input to the data.

Important parameter other than acceleration should be time synched rpm. With this 2 data you should be able to tune the engine properly, even if the weight data is not available, just you won't get the real horsepower but good enough for tuning.

Use a videocam to record the RPM, speedometer and a stopwatch. Calculate offline during video playback.
Get the car rolling at top gear, and do full throttle until desired top RPM is reached.
Only works for manual.