Article: BHP vs HP vs kW and other power conversions

[stradlater]

Yeah, there is no conversion, but people typically use about a 30% drive line loss, but that's not a rule by any stretch of the imagination..

[crowncustom]

Great contribution Strad...

If you, or anyone, has the time to do some more research ...
I'd be keen to see a reliable flywheel to rearwheel conversion formula & vice versa.

From what I can see around, most people work on rearwheel being somewhere between 70% to 80% of the flywheel power.

I know that this gets complex when you look at various drivetrain configurations, etc, but surely their could be some reliable way of doing this, that would help to resolve a few debates.

It would be great if there was but there definitely is not.Yes there is alot of things to think of in this one.I think I covered some of the things concerned in my last post on this one.
Cheers Brett.

[brett_celicacoupe]

The overall power or torque curve is much more important, as this will determine a vehicle's characteristics. You can get a quicker ET with a lower TV if you accelerate quicker from a lower RPM.

Cheers, Owen

if you wanted to get really technical you could fit a mathematical function to the torque curve and then calc the area bounded by it

i dare say that a 1g would compare similarily with the likes of a commowhore 3.8l engine in this aspect


this may be useful for comparing 1ggte and 1ggze engines....the outcome would indeed be interesting i think the GZE might just scrape in with more though

[o_man_ra23]

Yeah Brett, but you know the 3SGTE would reign supreme in this field (WRT engine capacity of course). The formula you speak of is called integration. If you know the torque reading at points of set intervals (say, 5rpm increments, a good dyno should give you a decent spreadsheet), then feed these discreet values into matlab, use a digital integrator, and hey presto, you have your answer. The more accurate the values given by the dyno, the more accurate the output. Interpolating the points will gain accuracy too.

Cheers, Owen

[crowncustom]

Then it comes down to one big mathematical headache but you are so correct on this Owen.If you want accurate figures this is the way to do it for sure.But it is only usually done with the big race builders.
Cheers Brett.

[o_man_ra23]

shit, i could write the program in a couple of hours that would do it (cant be arsed factor comes into play here). Its not a difficult program, just not really necessary for street use.

Cheers, Owen

[stradlater]

So your saying you integrate the torque curve and you get the work done? is that where your headed?

Surely you couldn't make an equation that directly graphed it, given the variables involved.

[Hiro]

So your saying you integrate the torque curve and you get the work done? is that where your headed?

Surely you couldn't make an equation that directly graphed it, given the variables involved.

Technically integrating power would give you work done, as Power is the rate of work being done (1 Watt = 1 Joule/second, integrate that over 1 second and you get 1 Joule of work)

[brett_celicacoupe]

So your saying you integrate the torque curve and you get the work done? is that where your headed?

Surely you couldn't make an equation that directly graphed it, given the variables involved.

you can do anything with the correct tools

as owen said, you just need a set of ordered pairs (rpm, torque) then you can import them into something like matlab. after plotting it, you can then use a function to interpolate a degree X curve to the data. and there is probably tools to integrate easily in matlab as well.


calculating this integration allows an accurate torque comparison of engines.

example:

say you have a 250cc 2 stroke and a 400cc 4-stroke motorbike, from the manufacturing specs, the 2-stroke may make more peak torque compared to the 4 stroke.

however you know this amount of torque is only useable through a short section of the rpm range (thanks to power band ). and if you wanted a bike with torque, you'd choose a 4-stroke even though it makes less peak torque.

this is where integration comes in. in a nutshell it is measure of how much torque is useable through the RPM range.

back to the motorbikes though, if you integrated the torque curve of both said motorbikes, theoretically, the magnitute of the 4-stroke torque integration should be much larger.

and stradlater; i think your car would score low in this aspect ....even though the car flys. this isnt always a bad thing though.

also depends on application. a towing car would want a high amount

[CussCuss]

also make sure you take a read of this http://vettenet.org/torquehp.html

explains the difference between hp and torque as most people dont know exactly what measures what.

In a single sentence, hp measures how good a torque curve you have and therefore how fast you will go.

[oldcorollas]

http://forums.toymods.org.au/index.p...t=0#msg_125056

[o_man_ra23]

you can do anything with the correct tools

as owen said, you just need a set of ordered pairs (rpm, torque) then you can import them into something like matlab. after plotting it, you can then use a function to interpolate a degree X curve to the data. and there is probably tools to integrate easily in matlab as well.

Why do you need to plot and iterpolate Brett?? Check out the tools in Matlab, you will find you can integrate straight from the ordered pairs. Its part of a digital filter. If you wanted to get really technical you would do an ordered pair for each gear, plot the torque curve against each other relative to speed, not RPM, and you can work out your gear changes. You would want to change gears where the torque curves cross over.

Also, if you are doing this from a dyno sheet on a turbo car, the dyno will prematurely load the engine, which will spool the turbo early, and give you a false reading. You need to factor this in when you compare curves on turbo motors. The engine will not load as quickly on the road, and as such it will not boost as quick.

And CussCuss... dont forget that because the HP reading is factored with RPM, a longer geared low rpm motor with more torque but less power can out accelerate a short geared high rpm motor with more power.

Cheers, Owen

[crowncustom]

And CussCuss... dont forget that because the HP reading is factored with RPM, a longer geared low rpm motor with more torque but less power can out accelerate a short geared high rpm motor with more power.

Cheers, Owen[/QUOTE]
That is so very true Owen.It does not matter how much HP you have it will always come down to the right gearing to match.And thats where most people stuff up when building engines.They dont work out the correct gear ratios to get the most out of there engine.
Cheers Brett.

[RONA]

And thats where most people stuff up when building engines.They dont work out the correct gear ratios to get the most out of there engine.
Cheers Brett.

Someones been watching initial D second stage

[crowncustom]

Someones been watching initial D second stage

um plz explain?