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Originally Posted by Notes from the new iRacing build
Transmission and Shifting Model
We have replaced our model of a car's transmission and how the driver causes the car to shift gears. Previously, clicking out of a gear or into another gear would instantly do just that - regardless of whether or not such a gear change was actually physically possible.
Now, your shifting inputs tell the sim what you're trying to do, and the sim tries to do what you ask - the sim no longer instantly just shifts. Think of your shifting inputs as telling the sim, "I am pushing/pulling on the shift lever." You will often need to hold the shift control for little while as the shift goes through to completion before releasing, if you let go too early the sim will interpret that as you letting go of the shift before the shift completes, probably leaving you hanging in neutral. If you use an h-pattern shifter, then the shifter is automatically holding the next gear which makes it more comfortable.
This is likely to require some time to adjust to, so do not be afraid of turning on the auto-clutch and auto-blip shift aids when you need reliable shifting while you're still learning to feel out shifting with lower levels of aids in practice and testing.
The currently engaged gear will not disengage unless the transmission is sufficiently unloaded:
- For upshifts, full throttle will definitely hold the current gear engaged. You will need to lift, use the clutch, or hit the rev limiter to unload the transmission enough for the current gear to disengage.
- For downshifts, engine braking when fully off-throttle especially at higher rpm may well be sufficient to prevent the current gear from releasing. You will likely need to use a little bit of throttle (which will happen anyway if you are blipping on downshifts), or use the clutch to disengage the current gear. If you are braking while holding down some throttle it will quite likely be too much throttle to allow the current gear to disengage, unless you use the clutch to unload the transmission.
If you are using an h-pattern shifter control to shift with, moving the stick into neutral will ask the sim to try to leave the current gear if it can. Selecting the next gear will tell the sim to attempt to engage that gear once it succeeds in getting into neutral.
If you are using sequential controls to shift with, holding down the shift button is equivalent to pushing on the shift lever to the next gear. If you let go of the button before the shift completes, you may not have even left the current gear yet, or may end up in a neutral between the two gears.
Cars that have a sequential transmission can no longer be shifted with an h-pattern shifter. If you have your h-pattern set as the preferred shifting method, the sim will give you a warning message when you first get into a sequential car to start driving advising you that you will have to use your configured sequential controls.
If you try to engage the next gear when the rpms are too mismatched, the gears will just grind and the next gear will not engage. So that means that smash-it-into-1st race starts don't work any more, as trying to grab 1st at high rpm is not healthy for the gearbox and you will hear nasty grinding sounds. You'll want to engage 1st gear while the motor is not revved up and the clutch is pushed in (the anti-stall clutch conveniently holds the clutch in for you if you are stopped and not revving the motor). Then you do a race start via revving up the motor with the clutch pushed in, and doing some kind of clutch drop. If you use the auto-clutch shift aid, it will hold the clutch in for you while you are revving in neutral, so selecting 1st gear for your launch is acceptable. The auto-clutch shift aid will release the clutch for you, but with a fractional delay.
For a dog-box transmission, the next gear can typically engage when the revs are within a few thousand rpm - a pretty broad rpm range. You don't need to bother with the clutch, just appropriate throttle lifts or blips to disengage the previous gear are all it takes to shift. This also means that you can quite comfortably left foot brake with dog-box cars.
- Upshifts you want to do as fast as possible: press and hold your upshift a moment before you lift to preload the shifter, then do the fastest lift you can for a really quick shift. It is possible to use the rev limiter to unload the transmission and cause the upshift instead of lifting. If you are using sequential controls, remember to press and hold the upshift button until the gear change finishes. Some race cars have a built in throttle cut that engages when it detects pressure on the gear lever. For these cars you don't need to lift at all, just clicking the button will trigger the throttle cut. But make sure not to release too rapidly, or the shift may not be fully completed as you release pressure from the shift lever.
- Downshifts can be done very quickly too. Press and hold your downshift a moment before you blip to preload the shifter, then tap the throttle for a blip of the motor to minimize upsetting the car's balance as the next gear engages. In most cars there will be enough engine braking torque that the gear won't disengage until you tap the throttle for the blip, and remember to press and hold the downshift button until the gear change finishes.
For the Solstice and other cars with synchromesh gears, the synchros do all the work when the revs are mismatched. You won't hear a grind when you select the next gear while the synchros are doing their thing, so the neutral timing isn't the same as a crash box. You don't absolutely have to use a clutch for a synchro box - but the synchros are not even remotely close to being strong enough to overcome the entire motor when trying to rev match so you have to get the entire motor to match the correct rpms for the next gear yourself, but if you use a clutch pedal then the synchros can easily match the transmission input shaft for you and make shifting a much faster and reliable experience.
When shifting with a real synchromesh gearbox, you engage the next gear's synchros by lightly pulling the stick against the next gear, until the gear clicks into place. Unfortunately, the sim has no ability to know that you're trying to select the next gear until you actually select the next gear, and only then can the sim start working the simulated synchros. With sequential controls, the sim knows you are trying for the next gear up or down, so you just need to press and hold the shift button until the gear engages. With an h-pattern you need to actually click your next gear into place quite quickly so the sim can start pushing it's simulated shifter against that gear's synchro. The timing of the shifting process feels a little different to a real car. You'll have to get used to the timing of your shift request but continuing to hold the clutch in until the gear finally engages before letting the clutch out, unlike in a real car where you can feel the shifter clicking into place as the gear finally engages.
- Upshifts you typically want to do as fast as possible, but it's not as fast as a dog-box transmission can do it: press and hold your upshift a moment before you lift to preload the shifter, then lift the throttle while pushing in the clutch. As the next gear engages, you can push the throttle down again and release the clutch. You could also choose to not lift, and just push in the clutch pedal until the next gear engages. This method of power shifting will not make your clutch want to be friends with you for very long. Or you could not use the clutch at all, but you have to lift off the throttle and wait for what will feel like forever and ever until the engine drops enough rpm for the next gear to engage. Remember to hold the shift button until the gear shift completes.
- Downshifts you will also want to shift as quickly as you can, to start working the next gear's synchro. Press and hold your downshift a moment before you blip to preload the shifter while braking with your right foot, then press the clutch pedal in with your left foot and roll your right foot somehow to blip the throttle while maintaining smooth brake pressure at the same time, and when the next gear catches, release the clutch pedal smoothly. This is called heel-toe downshifting, and it's very hard to get a good feel for in the sim due to not being able to physically feel the response of the car and the shift lever. It is possible to left foot brake and not use the clutch on downshifts, but it's hard work on the synchros and you must make sure to blip the engine rpm well enough to match revs or you'll be stuck in neutral fishing for a gear. Remember to hold the shift button until the gear shift completes.
Sometimes if you mis-time your synchromesh gear shifts (particular if you don't use a clutch) you can clear the synchro but still miss the gear engagement, and you will hear nasty grinding sounds from your gearbox.
Some of the higher end race cars with sequential gearboxes can have fully automated shifting. You just bang the shifter button and it does whatever it needs to do with the throttle to get the next gear for you in a very short amount of time.
Here is a list of the cars we currently have and the type of transmission they have so you know what style of shifting you will want to use with each:
Fully automated sequential:
- Dallara
- Jetta TDI
Dog-box sequential with throttle cut:
- Corvette C6R
- Ford V8SC
- Radical SR8
- Riley DP
- Star Mazda
Dog-box sequential:
- Legends Ford34C
- Skip Barber
Dog-box h-pattern:
- Impala A
- Impala B
- Latemodel
- Lotus 79
- Silver Crown
- Silverado
- SK Modified
Synchromesh h-pattern:
- Mustang FR500S
- Solstice
- Spec Racer Ford
Key points:
- If you are struggling to adapt to shifting with no shift aids, don't be afraid to turn on the auto-clutch shift aid and perhaps even the auto-blip shift aid for important sessions where you need reliable shifting. Like any physical activity you may have been doing for a long time it can take a while to unlearn your old muscle memory habits and learn new ones.
- Sequential cars will not allow the use of h-pattern controls, like the Jetta has been doing for a while now.
- Remember to think "press and hold" for sequential shift buttons until the shift is complete, it's not just "click".
- Practice your timing so you press and hold the shift button before you blip on downshifts or lift on downshifts.
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