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Thread: The perfect Sequentiel Downshift

  1. #1
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    The perfect Sequentiel Downshift

    Just talked an hour to a very interesting man.
    He is a lifelong race-driver and a racing-instructor on the nürburgring.
    He told me that the perfect downshift in a GT-car
    (with sequentiel-gearbox, no computer-assistance syncing the gears, dog-clutch and a clutch-pedal for first gear and reverse)
    looks like this:

    -foot of the accelerator
    -brake
    -wait till revs are as low as possible without compromising lap-time
    -press the clutch a bit (different in every car)
    -shift down (with paddle of course)
    -release the clutch immediately
    -accelerate out of corner

    This is done to go easy on the dog-clutch, because by just pulling the downshift-paddle
    without using the clutch the (usually high) revs put a lot of stress on the drivetrain/clutch.
    The same when shifting up: lift the accelerator a bit before shifting to reduce power
    grinding on the clutch.

    I never heard that before, but after googling a bit this is like most race-drivers do it.


    NOW MY QUESTION:
    Can anybody tell me if this is simulated in project cars?
    Do you need to get of the accelerator for upshifts
    and use the clutch for downshifts to reduce damage on the clutch?
    Or can you just shift up and down without increased wear and tear?

    Thanks!
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  2. #2
    WMD Member RomKnight's Avatar
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    Wear is simulated, yes but maybe not enough.

    The autoblip/lift might be present in some cars and obviously not others and some just have auto-lift for flat shifting.

    If you disable autoclutch you'll notice differences. Actually, driving with auto-cluch on as a negative impact on this for me because it seems to be tied with auto-lift/blip so it works against simulation (for me) more often than not.

    Your call really but for me, auto-clutch OFF and the use of clutch will be dependent on the car even on H pattern cars assuming you get the timming correct and blip/lift yourself
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  3. #3
    GT3 Pilot hkraft300's Avatar
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    Don't some cars have the ignition/fuel cut on shifts?
    I thought modern race cars would have that to not necessitate the clutch/throttle lift.
    "Slow is smooth, smooth is fast."
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  4. #4
    Superkart Pilot ashasha's Avatar
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    From what I understand after each race (or even a restart) the car's damage is reset to zero so unless you were doing hundreds of laps in a race you'd probably never have this particular wear become an issue.

  5. #5
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    Alright.
    Thanks everyone!

    Just tested a few GT3 cars.
    In the BMW the downshifts are a lot less noisy when you use the clutch.
    Hard to measure if your faster with it, but it sounds/feels better.

  6. #6
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    I think it's probably a bit difficult to describe, so take those words with a grain of salt. If you listen to the cars carefully at a race, you can hear that the drivers use far less engine braking (they downshift very late) than most of the players in pCARS. They wait until late in the deceleration zone, then blip of the downshifts rapidly.

    I never knew they were floating the clutch, but it makes sense. Basically, that would allow for some slip on the input shaft as the gears engage, which dramatically reduces the reciprocating mass that must be dealt with. Even with automatic rev-matching from the engine, a dogbox downshift is a violent thing.

    Understanding the mechanics of a manual transmission really helps. I wish a had a good resource for a really detailed review of how a manual works, but I'd really strongly recommend reading up on how a manual transmission works. Even if you learn about synchromesh transmissions, the mental leap to a dogbox is super simple; you basically eliminate the synchro cones and beef up the interlock sleeve.

    Keep in mind that this really isn't going to improve lap times in pCARS. The reason actual race car drivers do this is because their team is paying to replace gearboxes, and that gets expensive. The profession of race car driving is about a lot more than just turning the fastest possible lap time. Sometimes it's about managing wear & tear. This technique serves that end.

    From a pCARS perspective, I've never experienced a gearbox failure in hundreds (thousands?) of hours of racing with mechanical failures turned on, so it's less necessary. The only potential benefit — other than mitigating mechanical failures — would be increased stability of the car. Optimal grip comes when the car "settles in". Rapid changes in directional force disrupt the contact patch and reduce the grip available. That's why the whole "smooth is fast" thing is so important. The problem is that no simulation is 100% accurate, and pCARS tends to favor engine braking pretty heavily. If you use this technique in an online race, you're going to get out-braked in to the corners pretty bad. If you watch enough YouTube videos, you'll see that the really fast guys are leaning heavily on engine braking, down-shifting as early as possible in order to get that extra braking edge.
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  7. #7
    GT3 Pilot hkraft300's Avatar
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    With mechanical failure on, smashing the limiter will damage the engine faster than the gearbox as far as I've seen.
    In LMP cars you'll lose >50HP in a 30 minute race just upshifting with auto clutch on, where the clutch engages on up shifts and the revs spike. I'd imagine silly downshifting would have the same effect. Anyone notice this in GT cars?
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  8. #8
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    Quote Originally Posted by bradleyland View Post
    I think it's probably a bit difficult to describe, so take those words with a grain of salt. If you listen to the cars carefully at a race, you can hear that the drivers use far less engine braking (they downshift very late) than most of the players in pCARS. They wait until late in the deceleration zone, then blip of the downshifts rapidly.

    I never knew they were floating the clutch, but it makes sense. Basically, that would allow for some slip on the input shaft as the gears engage, which dramatically reduces the reciprocating mass that must be dealt with. Even with automatic rev-matching from the engine, a dogbox downshift is a violent thing.

    Understanding the mechanics of a manual transmission really helps. I wish a had a good resource for a really detailed review of how a manual works, but I'd really strongly recommend reading up on how a manual transmission works. Even if you learn about synchromesh transmissions, the mental leap to a dogbox is super simple; you basically eliminate the synchro cones and beef up the interlock sleeve.

    Keep in mind that this really isn't going to improve lap times in pCARS. The reason actual race car drivers do this is because their team is paying to replace gearboxes, and that gets expensive. The profession of race car driving is about a lot more than just turning the fastest possible lap time. Sometimes it's about managing wear & tear. This technique serves that end.

    From a pCARS perspective, I've never experienced a gearbox failure in hundreds (thousands?) of hours of racing with mechanical failures turned on, so it's less necessary. The only potential benefit — other than mitigating mechanical failures — would be increased stability of the car. Optimal grip comes when the car "settles in". Rapid changes in directional force disrupt the contact patch and reduce the grip available. That's why the whole "smooth is fast" thing is so important. The problem is that no simulation is 100% accurate, and pCARS tends to favor engine braking pretty heavily. If you use this technique in an online race, you're going to get out-braked in to the corners pretty bad. If you watch enough YouTube videos, you'll see that the really fast guys are leaning heavily on engine braking, down-shifting as early as possible in order to get that extra braking edge.
    Let's just say i'm always super carefull on my manual shifts, in all of the cars i owned.

    I would never do what i do in pCars, regarding engine braking and clutch splipping, on my cars! That's the beauty of simulation, i can trash my car without any 2nd thoughts!
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  9. #9
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    Quote Originally Posted by poirqc View Post
    Let's just say i'm always super carefull on my manual shifts, in all of the cars i owned.

    I would never do what i do in pCars, regarding engine braking and clutch splipping, on my cars! That's the beauty of simulation, i can trash my car without any 2nd thoughts!
    I keep Mechanical Failure on!!! I have Blow the Motor Many Times Down Shifting to Quick or Missing a Gear... Going from 4th to First Blows the Motor every time!!! LOL.... Practice make perfect tnough.... I Now have a Good Feel for the Shifter so even using VR i rarely Miss a Gear Now.
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  10. #10
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    Just came across this IMSA video from this year's Rolex 24, which illustrates the concept really well:

    https://twitter.com/IMSA/status/841663435322585088

    Notice how late he's downshifting? It's fascinating how differently professionals drive real cars versus how the fast guys drive pretend race cars. You'll also notice that real professional race car drivers seem to hold the gear more often than not. This also preserves the gearbox.

    In sims, there's very little penalty to jamming it down to 2nd, when an IRL race car driver would probably hold 3rd. You'll see this in a lot of Nurburgring 24h in-car footage as well. If you go by traditional recommendations, there's only two or three 2nd gear turns on the whole Nordschleife (Nordkehre, Wehrseifen, and Karussell). Yet, if you race online, you'll see plenty of people dropping to 2nd in places like Hocheichen, Adenauer Forst, Kallenhard, and Eiskurve.
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