Author Topic: Engine values in the .cfg: Engine inertia  (Read 574 times)

Asdrael

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Engine values in the .cfg: Engine inertia
« on: February 05, 2017, 10:18:00 AM »
Hi,

Trying to figure out proper engine importing in your engine PiBoSo. I am however dumbfounded by this value:
Code: [Select]
engine
{
Inertia = 0.005

What is it? Where does it come from? I'm hoping to understand why you have the values you are using, which are:
250f: 0.004
350f: 0.005
450f: 0.005 (? same as 350?)
250: 0.005 (a 2 strokes with more inertia than 4 stroke of same cc?)

Both models that have ? are marked as WIP in the bikes page though.

I'm running a few tests right now, but not sure what I should be looking for nor where I should start from. Any help appreciated.
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тғc

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Re: Engine values in the .cfg: Engine inertia
« Reply #1 on: February 05, 2017, 11:02:00 AM »
I'm not smart enough to figure out which discussion on the PiBoSo board is relevent, but there are a few interesting / hopefull looking bits of information on there if you search for 'inertia'..
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Asdrael

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Re: Engine values in the .cfg: Engine inertia
« Reply #2 on: February 05, 2017, 11:08:31 AM »
Tried that. There is a lot about weight inertia (mass of the chassis etc) but barely anything on engine inertia. Which seems to have a massive influence on how a bike revs up and revs down by itself.

I have a "perfect" .engn file of a 125 2s along with perfect gear ratios etc. I happen to have more or less the same bike IRL. An engine with inertia of 0.004 feels like a blocked air filter, 0.003 feels like a well set up 125 engine.

Then again I could be talking out of my ass and seeing things I want to see, since I have no idea what the number represents or comes from.
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pacopastor34

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Re: Engine values in the .cfg: Engine inertia
« Reply #3 on: February 05, 2017, 11:19:43 AM »
If I remember good that inertia makes engine to raise rpm easier or harder.

Asdrael

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Re: Engine values in the .cfg: Engine inertia
« Reply #4 on: February 05, 2017, 06:50:07 PM »
Good way to gauge your inertia value:

Stay in neutral. Hit the rev limiter. Time how long it takes to decay to idle rpm. Compare to youtube video of an idiot doing that on a real bike.

0.005 seems good for a 450. 0.004 a tad high for a 250F, I'd say 0.0035 would be closer but it's tough to say.
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HornetMaX

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Re: Engine values in the .cfg: Engine inertia
« Reply #5 on: February 06, 2017, 05:52:44 PM »
Good way to gauge your inertia value:

Stay in neutral. Hit the rev limiter. Time how long it takes to decay to idle rpm. Compare to youtube video of an idiot doing that on a real bike.
Hmmm ... that would be affected by the braking torque too, not only by inertia no ?

Asdrael

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Re: Engine values in the .cfg: Engine inertia
« Reply #6 on: February 06, 2017, 05:56:43 PM »
Hmmm ... that would be affected by the braking torque too, not only by inertia no ?

tbh I can't really say. I will stick to default values (except 125 2 stroke for which 0.003 is a good value) until I figure out how this works. I suppose brake torque affects it slightly, but I was under the impression brake torque was affecting more the resistance of the engine to external forces, not its own.

Then again might be talking out of my poophole.
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HornetMaX

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Re: Engine values in the .cfg: Engine inertia
« Reply #7 on: February 06, 2017, 11:32:14 PM »
Hmm .. I'm not sure either on this one ...thinking ...                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     

Asdrael

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Re: Engine values in the .cfg: Engine inertia
« Reply #8 on: February 15, 2017, 05:16:24 PM »
After quite a lot of experimenting, I am settling for this when doing "custom replica" engines.

Inertia:
- 125 at 0.003
- 250 at 0.004
- 250f at 0.004
- 450f at 0.006

Engine breaking torque:
- stock 250 and 250f
- 125 adapted / rescaled from 250
- 450f adapted / rescaled from 250f

At least that's what I am using in my latest "OEM" stuff and so far the feedback has been good but sparse :P
« Last Edit: February 15, 2017, 05:18:00 PM by Asdrael »
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