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Torque curves - where?
(13 posts, started )
Torque curves - where?
Anybody know where to get the torque curves for each engine in LFS?

I know a gear-ratio-calculator was once working (dead now I understand), which means that the person who wrote it must have had access to the torque curve, as far as I can figure out...

TIA!
#2 - J@tko
Look for Bob's VHPA
Curves in VHPA are estimates, not measured. One day I'll re-measure them...

If you want to do it yourself, you can extract them from RAF data.
How can I extract them from RAF data?
...does not create a RAF file.

To extract the torque curve from a file, go to the drag strip in single player, and drive down to just before the finish line. LFS won't start outputting data into the RAF until you have crossed the line, so nothing before this point matters. Roll across the line in a medium gear at the lowest speed that won't stall, and then floor the throttle and keep the car straight until you crash into the barrier at the end of the drag strip. If the gearing is perfect, you'll hit the rev limiter just before you crash.

Now, save a replay of this, watch it, and before you cross the finish line, select output RAF data from the menu and enter a file name. Once you have watched yourself reach the rev limiter / crash, you can end the replay, minimise LFS, and open the RAF file in a replay analyser (I've always used F1perfview for this purpose although I don't know if it still works with latest versions of LFS). From here you will need to output the force at the driven wheels, along with engine rpm and throttle, to a text file (csv). This can then be opened in a spreadsheet package. Limit this data to only the region where throttle is 1.0, and perform a little maths* to convert the force at the wheels to engine torque and power.

Also note you will want a setup that uses maximum tyre pressures and, where applicable, minimum downforce. This will minimse the effect of rolling resistance on the results.

*See here for some old examples. IIRC, you need to sum the forces, divide by the wheel radius, divide by the combined gear ratio (individual gear ratio multiplied by final drive), and then divide by drivetrain efficiency, to obtain engine torque.

If somebody creates these, please post them, and I can then include the revised curves in the next release of VHPA. It's tedious and time consuming to repeat this process 20 times, hence I haven't got around to doing it yet.
#6 - alxf1
Thanks for the info, all!

I've now tried VHPA, and was wondering where it got the torque curves from, and then I read Bob's post. (Wow, dedication!) It's a seriously nice, and complex tool, for which I hope there's good documentation :-) (Only scratched the surface last night.)

However, given the info in Bob's post, it seems like the easiest thing to do would be simply to ask the devs to provide the torque curve though, no? Reverse-engineering it from the force data in the replay data seems a bit extreme, unless of course the devs have already declined to provide the data...

Unless of course, the BIN file contains the torque curve, as the other posts seem to hint.

(Btw, does the replay actually provide contact-patch force, or does it have to be inferred from the acceleration? In which case how does the acceleration get corrected for wind resistance...?)
Quote from Neilser :Unless of course, the BIN file contains the torque curve, as the other posts seem to hint.

This is the car info format. Nothing about the torque curve, I don't think.
http://www.lfs.net/?page=CAR_INFO_BIN

Quote from Neilser :(Btw, does the replay actually provide contact-patch force, or does it have to be inferred from the acceleration? In which case how does the acceleration get corrected for wind resistance...?)

See screenshot...
Attached images
tehoutput.png
Quote from wheel4hummer :This is the car info format. Nothing about the torque curve, I don't think.
http://www.lfs.net/?page=CAR_INFO_BIN

Aha - thanks. Yes indeed, no hint of torque curves in there . Shame.

I have to presume somebody asked for the torque curves before engaging in heroics to extract the curves from the replay files... No?
Can't imagine why the devs wouldn't be happy to distribute them...
#10 - xtm
Sorry, I'm not sure whether this has been mentioned before, but how can I find out the tyre sizes of LFS cars?
That's available from the .bin format files. VHPA has a reader for those files built in (in fact the .bin format was created specifically for VHPA), or even easier, just look at the data tabset in VHPA, where that info is listed in the wheels & tyres tab.
Is there anyways someone who really really knows there way around LFS and the many ohter related programs can go though and find the torque curves for each car in LFS, I think many racers would like it and very much appreciate it. Myself, I would be eternally grateful for something like that, I just don't have the time or experience with all this to do it myself. I think it would be a huge favor to the community. People can than adjust their gearing for each car and track perfectly, man, it would be incredibly awesome, I mean this is something real racers do, it's actually very important.

When I tuned and dyno'd my '04 Cobra I was able to see my engines curves, however the powerband was very linear, since it's such a large, blown engine, with a very broad powerband. But with the cars in this simulator, especially with the turbo cars, it would be very helpful, because the powerbands are anything but linear.

Edit: I guess it's possible to kinda of, guestimate, judging by the G's, and just watching the boost climb and speed climb, where about your power band starts and ends, but this is kinda ghetto.

Torque curves - where?
(13 posts, started )
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