   Approximate Torque per RPM curve.
  I'm currently following the http://home.planet.nl/~monstrous/tutcar.html tutorial for making a car simulation for a HMMWV. The problem occured when trying to find the Torque/Power per RPM curves (3:rd graph) for a HMMWV, according to the tutorial this is determined by engine tests and I'm wondering if I'm unable to find these engine tests, if there is a way to approximate this curve relatively realistic with the usually given values of Torque (XXX lb.-ft @ XXXX rpm) and Horsepower (XXX hp @ XXXX rpm). For the HMMWV these are Torque: 430lb.-ft@3400rpm and Horsepower: 195hp@1800rpm. With these 2 values I can transform them and get horsepower and Torque for the other with the 5252 constant. and approximate with straight line the value ~250 hp at 5252rpm wich I take 95% of and then with Lagrange I add the point[0,0](at 0 rpm I get 0 hp) and [195,7600](an experimental point to get the descending of hp at higher rpm) to the 3 existing ones and get an fairly good approximated curve wich altough rampages away at low rpm speed giving a smacking 550lb.-ft@1000 rpm wich isn't that realistic. Any official "this will always work" approach or am I better off trying to find the real engine tests or take something that "looks good".   
  Hi, It's hard to model the torque curve from nothing, it depends on the bore/stroke/weight of the pistons and other engine characteristics. It's a lot easier to model by hand at different RPM intervals, create a table for these RPMs and then just interpolate between those intervals to get an exact torque value... torque & bhp curves for most of the cars are readily availableCheers   ;  Usually games specify the torque curve of the engine. The 'power' the engine is making is largely irrelevant for your purposes, torque is probably what you need to know. As jaimedp said, usually torque is stored as a few data points at different engine speeds, which you interpolate between to find the current engine torque.The Hummer has a large V8, right? Generally V8 engines have a fairly smooth torque curve, which rises sharply around 1200-1500 rpm and then stays fairly constant (usually moving in a flat dome shape) up until it hits its designed maximum speed at around 4000-6000 rpm, depending on how the engine is tuned.   ;  Not sure this works but just wanna ask anyway, all the information I've got on the HMMWV vehicle is:195hp@1800rpm430lb.-ft@3400rpm And with the hp=torque*rpm/5252 formula I get the 2 values~570lb.ft-@1800rpm and430lb.fr-@3400rpmNow I'm guessing this isn't enough for getting the interpolation to work and without more values I just have to imagine some values to get the curve you are speaking of fractoid.   ;  Yeah, you'll probably have to make up some values. Start with dyno charts measured from actual hummers, and make up something similar. That is actually a chart showing power and torque gains from upgrading the engine chip, but you can work off the original torque curve - as you can see, it's pretty flat from 1500rpm to 5000rpm. Basically if you don't get it perfect no-one will ever notice, as long as its not too far off. Also remember that these figures are at the wheels - the figure at the engine could be 20% to 40% higher, depending on the efficiency of the transmission and whether the test was done in 2wd or 4wd mode.   ;  The whole power thing's a bit wierd. In that article Marco says that you want to have your rpm at the maximum power to get good acceleration, but surely you want the engine to be at maximum torque?   ;  No. That's what the V8 metalheads always say, but what you really want is to have the engine producing the maximum torque at the wheels. In a perfect world, with ideal gearing, you achieve that at the maximum engine power point. If you're running at maximum engine torque, chances are you could be in a lower gear at higher revs, making more torque at the wheel. For instance, in my car peak torque is at around 4500rpm, but even though the torque drops off after that, it doesn't drop fast enough for the power (torque x rpm) to drop until after at least 6000rpm. So I could be doing 4500rpm in 3rd or I could be in 2nd doing the same speed but getting more acceleration.The only exception (and the point where the V8 guys are right) is when you take into account the limits of tyre traction. If your engine has enough torque to spin the wheels off the line in first gear, then there's no point in gearing down any further since you can't make use of the extra torque. You're better off with a taller gear ratio, which in turn means you can change gears (with the attendant waste of time) less times to get to any given speed. Then again, when you're at this point your engine is no longer the weakest link and you should be paying more attention to suspension setup, tyres etc. (and obviously brakes, handling and so forth if you're not building a dedicated drag car).   ;  Ah that makes sense, I think. Maybe I'll put a guage for engine torque and torque on the wheels alongside the engine rpm guage in my game and see what they do...   