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Automatic Transmission Exporter tuning


#1

This is a suggestion for the devs who mostly work on the exporter. I noticed that cars fitted with any automatic transmission, (Both advanced and regular, as well as Dual Clutches) when exported exhibit some very unrealistic behavior. Now, I understand BeamNG automatic transmissions aren’t perfect by any means, however the ones imported from Automation are particularly odd acting. Most of them do not like to shift up in gears when cruise control is activated, and often will stay in a much lower gear than a car usually would. This is usually very prevalent cars where there is a low final drive ratio, where the engine should be turning very slowly at highway speed. What I think the issue to this is after pulling up the shift debug in BeamNG, is that the default aggressiveness is far too aggressive, especially on advanced automatics. The game both holds the aggressiveness in too high of a state for too long. For example, in the scenario of accelerating on a highway with a long geared 5 speed box, the transmission will hang in 3rd gear for far too long before down shifting in to 4th gear, and then once cruise speed is attained, the transmission may shift down into 5th gear, however it will immediately blip back to 4th because the load on the engine is increased, and will continue the cycle of up shifting to 5th and down shifting into 4th. Another scenario is that the transmission will sit in 4th gear and refuse to shift down into 5th gear unless you are doing an unrealistic speed, because the default aggressiveness doesn’t drop the down shift speed to a large enough extent.

I hope this makes some sense to y’all and if you have any questions, please do ask so I can explain myself better.


#2

Makes perfect sense to me, I mess with every autobox in BeamNG to make it realistic. I know exactly what you mean.

However there really isn’t a way around it, the only thing you can really do is turn down the one parameter, I think it’s called gearboxDesicionSmoothingUp. Just make that number way smaller, maybe 1.0-1.5. Also turn down agressionSmoothingUp to about the same.

Hope this helps!


#3

Check out camso_engine.jbeam

Find:
“lowShiftUpRPM”:
Low shift up controls on which RPM the transmission upshifts when you are driving slowly. Adjust these to lower number. I generally use 1800-2000 for larger displacement vehicles, 2200-2600 for smaller displacement vehicles. You can use a single number or make a table which controls upshift for all gears. For example I have a 6 speed auto trans, my shift up table is “[0,0,2500,2500,2450,2400,2350]” (P,R,1,2,3,4,5). Gear 1 to 2 is at ~2500 RPM, gear 3 to 4 is at ~2450, gear 5 to 6 is at ~2350 RPM.

“highShiftUpRPM”
High shift up controls on which RPM the transmission upshifts when you are driving aggresively. I generally adjust these at rev limiter minus 200 to 300 RPM. You can also set it up as a table like the example above.

“lowShiftDownRPM” and “highShiftDownRPM” controls on which RPM the transmission downshifts. Same as above, lowShiftDownRPM controls the downshifting when you are driving slowly, highShiftDownRPM when you’re driving aggresively. You can set it up as a table too.

“gearboxDecisionSmoothingUp”:
Controls how fast the transmission reacts to throttle to determine upshifting (lowering aggression factor). Higher value means when you ease off the throttle, the transmission will be faster to upshift (faster to lower aggression factor). Realistic value would be around 0.75 (slower transmission) to 2 (faster transmission)

“gearboxDecisionSmoothingDown”
Control how fast the transmission reacts to throttle input to determine downshifting (increasing aggression factor). Higher value means when you mash the throttle, the transmission will be faster to downshift (increasing aggresion factor). Realistic value would be around 0.75 (slower transmission) to 2 (faster transmission)

“aggressionSmoothingUp”
Controls how fast aggression factor to increase. When the aggression factor is high, the transmission will upshift at higher RPM and downshift early to maintain engine power. I usually use 0.5-1.

“aggressionSmoothingDown”
Controls how fast aggression factor to decrease. When the aggression factor is low, the transmission will upshift at lower RPM making the engine operate at lower RPMs to maintain engine comfort and economy. I usually use 0.15-0.25. Making this too high will make the engine upshift too much when you’re trying to drive fast.

Use the transmission shift debug in BeamNG UI apps to see what your transmission is thinking and see the aggression factor value the transmission is in.