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How to: Making Accurate Dyno Graphs for LFS!
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(44 posts, started )
Here is a dyno chart I made for the FZR. This is the torque 'at the wheels'. I used RAF data, and approximated that the diameter of the wheel is 0.45m. This is with the default setup in 3rd gear too, so that might be why mine is ~30HP different then bobs. Later I will try using the brake to get the boost up on a turbo car, and then see what happens.
Attached images
FZRdyno.jpg
0.45m for diameter? Way too small. The 18 inch wheels alone are just above that, then there's all the tyre height to add on. Try closer to 0.64m. If you download my Excel attachment further up, rather than the PNGs, you can get the values I used for all the (non-turbo) cars.

My tips for getting more accurate values:
* Max out tyre pressure for minimum rolling resistance.
* Use a tall gear ratio as possible to keep minimum acceleration, thus reducing angular momentum.
* On RWD cars with downforce, max out the front wing. This both reduces rear rolling resistance and slows acceleration.

Good luck with the turbos though, I tried back in S1 (as you can see from the earlier graphs) and using multiple data set to grab the whole rpm range, I couldn't get them to match up.
Quote from Bob Smith :If you download my Excel attachment further up, rather than the PNGs, you can get the values I used for all the (non-turbo) cars.

It is too much data for openoffice.org and my comptuer to handle. I will give it another try though.
If it's that much of a problem you can always grab GRC or the test of my new project, that displays the radius for all tyres on all cars, you'll just need to double it.

Alternatively I can just copy them all into a text file and post them here.
Quote from Bob Smith :If it's that much of a problem you can always grab GRC or the test of my new project, that displays the radius for all tyres on all cars, you'll just need to double it.

I didn't think of that, thanks. I tried my method of 'powerbraking' before doing my run. It turns out that it makes a slight difference on longitudinal tire force at lower RPMs, but the two curves meet at max boost (And max boost just happens to be max torque lol). I could try revving the engine until max boost, and then dumping the clutch.
#31 - JTbo
Quote from wheel4hummer :I didn't think of that, thanks. I tried my method of 'powerbraking' before doing my run. It turns out that it makes a slight difference on longitudinal tire force at lower RPMs, but the two curves meet at max boost (And max boost just happens to be max torque lol). I could try revving the engine until max boost, and then dumping the clutch.

You will get just engine damage if you keep it floored too long, ie. when revved to limiter. Better use brakes to keep speed and rpm down and build boost, use lower gear then when you have full boost shift higher gear so that it starts from low rpm and you can accelerate with maximal boost all range. You can't get max boost from 1000-upwards as it takes certain rpm to produce enough exhaust gases that turbine will spin enough fast to generate needed boost.
Quote from JTbo :You will get just engine damage if you keep it floored too long, ie. when revved to limiter.

I made more longitudinal force by revving at the redline. Here is the chart (Not in exel, this is just raw Revs vs Longitutinal Tire force) Additionally, it is interesting how all three curves meet at one point. I think that this is because by a certain RPM, the turbo was fully spooled each time. I didnt bother plugging in my wheel, so I tested with my mouse.

Red = No braking

Cyan = Used brakes, turbo spooled to 6psi

Green = Floored it, 22psi (ignore the swirly part from the autoclutch)
Attached images
dumpvsbrake.jpg
It's not the autoclutch, I had to chop off the start of all my data sets in order to removed the cool swirls. I made sure I never got the engine rpm low enough to active the auto-clutch (it only cuts in at the last moment if you're using a manual clutch).
Quote from Bob Smith :It's not the autoclutch, I had to chop off the start of all my data sets in order to removed the cool swirls. I made sure I never got the engine rpm low enough to active the auto-clutch (it only cuts in at the last moment if you're using a manual clutch).

Here is the SPR of when I just dumped the clutch.
Attached files
XRR_Clutchdump.spr - 4.5 KB - 176 views
Wow, useful curves there Bob. Dunno how I missed them in the past
(And I thought I'd looked very hard...)

Are the (S2) curves still up to date, does anyone know? If not, I might have a go at redoing 'em...

And one question which I don't see the answer to in the thread - how did you get the curves to go past redline revs? They don't look extrapolated...
Nice one, ta. Will have a peek.
(Btw do you have any clue about the way-past-redline torque/power data? :shrug
They are polynomial-calculated curves with infinite end, so just clip them to the redline.
Hmm, I felt certain they couldn't be polynomial-generated curves cos they have lots of fine-scale wiggles, so you'd need a ridiculously high-order polynomial which would explode as soon as you tried to extrapolate with it... No?
I don't remember where that it was confirmed by the developers that they are composed with two polynomial curves attached at max torque, or something like this…
Fair enough, but it's not the underlying LFS model I'm puzzled about, it's the data Bob provides.
I should really hope that Bob will leap in here, cos it's his method I'm querying: how did he end up with data beyond the redline if it comes from the measured performance of the car? And if the data from beyond the redline isn't from actual measurements but rather extrapolation, why is the data all ripply beyond the redline?
(The ripply-ness is why I'm saying it isn't extrapolated... Unless some ripply-ness was added to make it match the appearance of the data below the redline? Nah that's too nuts!:schwitz
I dunno, it seems he found a way to deactivate the redline limit for his measurements…
Check the date of my data. From before rev-limiters.
Ahhhh.
I'm such a noob I didn't know there was a time before limiters
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