rec.autos.simulators

I'm looking for torque curves shape.

Its hard to find torque curve. but it's easy to find max torque and rpm
for max torque, and also max power and rpm for this max power.
What i want to do is to compute the torque curve from thos information +
engine type (V6 V8 4iniline, 6inline, 4boxer, etc )  and engine size  (
2L , 3L, etc.. ).
So i'm looking for torque curves so i could ty to find out specific
curve shape for each engine type/size.

Do you know where i can find that ?
regards,

--
--- Ocrana.Racing.Ati|MagicFr#6 ---      www.ocrana.com        ---
---      Sebastien TIXIER       --- Dynamics and Car Physics   ---
---        Eden Games           ---   www.eden-games.com       ---

The method to choose depends on how accurate of a result you want.  The easiest
way would be to buy an engine simulation program.  My drag racing program has a
simple engine model built into it that would take care of it with reasonable
accuracy.  There are other programs out there that are more involved as well.
They need quite a lot more input info so I'd recommend them only if you're
pretty knowledgable about engines already.  

http://www.motionsoftware.com
http://www.performancetrends.com

Calculating the torque curves or writing your own engine model is not a simple
task.  There are a lot of variables involved and it's not so simple as asking
"what's the torque curve for a 5.7L V8?"  Power/torque curves can go all over
the place depending on cam timing, header selection, heads, and a zillion other
things.  There are 170 HP units up through 600HP+ for that size alone.

Google for "dyno graph" and you'll find tons of torque curves for all kinds of
engines.  You'll see a general shape to the torque curves and of course power
is just a function of that, so you might create a sort of fixed torque curve
that you can move left/right and up/down according to the engine parameters you
want.  That'd be the easiest way probably, but accuracy wouldn't be as good.
As very rough approximation, you'll see a certain amount of torque per liter
and it doesn't depend a whole lot on the number of cylinders.  Generally more
cylinders will mean you can run the engine at a higher speed because the stroke
is shorter, so you'd end up moving the torque curve to the right.  That would
increase power.

Todd Wasson
Racing Software
http://PerformanceSimulations.com
http://performancesimulations.com/scnshot4.htm

But i must prepare myslef to minimum info :)

I finish a 1st version of my dyno graph maker :)

In input i have =>

        Max torque + rpm
        Max Power + rpm

wich already give me 2 points on the torque curve ;)

The curve is made of 3 bezier curves.

1st from 0 rpm to max torque.
2nd from max torque to max power.
3rd form max power to redline.

I have also other parameter to change the curve shape :
-flatness at max torque : at max torque the tangeant of the curve is
perfectly horizontal, with this parameter i can increase the with of
this tangeant, so the curve is more round or sharper at max torque
-flatness at max power
-start tangeant, i can change the start tangeeant at 0 rpm, so the
torque curve will be more like an exponential or logarithm curve
-end tangeant

i post the exe if you wanna take a look and give me feedback :)
I post it on alt.binaries.simulators.autos

--
--- Ocrana.Racing.Ati|MagicFr#6 ---      www.ocrana.com        ---
---      Sebastien TIXIER       --- Dynamics and Car Physics   ---
---        Eden Games           ---   www.eden-games.com       ---

Bezier curves are a good solution.  Chances are if the car companies will give
you dyno data they'll provide a torque/power point at every 500 or maybe 250
rpm point.  If that's the case a simple linear interpolation will work quite
nicely (just connect the dots with straight line segments).  I do that for the
drag racing sim and acceleration times are very close to reality.  I also do
this in Virtual RC Racing and the telemetry matches up with the real car very
closely.  I just make a big array with 10rpm or so resolution and precalculate
everything.  Nice and fast.

You could also use those data points to make a hermite spline through it
automatically as well without having to play around with bezier control points
at all.  In my experience it's possible for bezier curves to throw off the
curve quite a bit in some areas, creating bulges and dips in places where there
really aren't any in reality.  In the end we got the best results with the
linear interpolation.  But anyway, there is more than one way to skin a cat and
beziers will work nicely too :-)

If you'd like to email me the program that'd be fine, I'll be happy to take a
look.

What sim are you guys working on now?  VRally 4? :-)

Todd Wasson
Racing Software
http://PerformanceSimulations.com
http://performancesimulations.com/scnshot4.htm