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Throttle position and un-expected number of revs

Discussion in 'Automobilista' started by Stingraymx, Apr 15, 2016.

  1. Stingraymx


    When stationary in my road car if i hold the throttle at 25%, the engine revs sit about a quarter of the way around the rev range. And the more i push, the more revs i get, in a linear fashion.
    In AMS my throttle looks linear in the controller setup (both in Logitech profiler and in AMS) as the red bar gradually rises as the pedal goes down.
    However when in the car, holding the throttle at 50% doesnt equal the revs sitting at around 50%. As you can see from this picture, the throttle is at less than 20%, yet the revs are almost at max, which appears to suggest the throttle is not very progressive...its almost like a switch - on/off
    I also noticed its nearly impossible to hold the revs at say 50% as its either 0% or 100%.
    The pedals are ancient, but the fact that they look linear in the Profiler and in the Controller setup in AMS seems to suggest they are working ok. As there is no load on the engine is it normal that the revs are high even at low throttle ?
    Any ideas ?

    Attached Files:

  2. Yes, I posted about this in the rFactor 2 forums maybe a year or so ago as I've noticed it for the past 10 years or so. It's yet another seeming issue with the ISI engine that has been around since the 90s or early 2000s.

    If it happens when stopped then the phenomenon must also happen to a certain extent while you're driving and you spin your rears (leading to the revs rising too relatively quickly during power-wheelspin) so I bet it doesn't just have an effect when the car is stopped but while driving as-well. That may be partly why it often feels like cars gain 6000 horsepower when the rears start slipping in the ISI engine.
    Last edited: Apr 15, 2016
  3. Stingraymx


    i guess that makes it a "feature" then rather than a bug (as we say at work in IT) !
    As you say, it is highly likely that the ability to smoothly accelerate is compromised by this. Shame that the clever guys at Reiza cannot engineer something around it !
  4. Yes, it would be interesting to know if this effect is also happening while in gear. It doesn't appear to (try chugging along staying in 1st gear), but unexpected throttle blips or rises could explain the loss of grip Spinelli is talking about when the rears spin or slide a bit. If that effect that we see sitting in the pits in neutral engages during rear grip loss or wheel spin while in gear....!?!
  5. Don't loose hope. Unlike ISI who seem not to care and do nothing about issues in their physics engine for 15 whole years (from at-least F1Ch 99-02 to RF2), I feel Reiza have a completely different mentality and really want to improve the core source-coding of the ISI physics engine so I have faith they will really start making deep, core changes to the physics engine itself. Reiza got the rights to make changes to the core engine (which I'm assuming and hoping includes all aspects of the ISI pMotor) a few months back so hopefully they start really evolving and improving pMotor (although it already does some things very good don't get me wrong). On the other hand, sometimes there are things you can't do through updates/modifications and you're left with the only option of starting from scratch (part of the reason why Kunos started from scratch with the AC physics engine rather than updating/modifying the NKP one) but I hope that's not the case here.
    Last edited: Apr 16, 2016
  6. PicoBp

    #26 | HSRC - Banzaaaiii Touring Car Crew Premium

    Whoever has driven a real car can confirm that real throttles are the same. When you don't have any load on the engine, it can rev up easier, therefor you don't need 100% throttle input for 100% revs.
  7. Stingraymx


    That is true, but I think the real car is more linear. I can hold revs in my road car at 1000 rpm, or 3000 or 5000 etc but find it next to impossible to hold the revs mid-way in AMS. It's either nothing or max. When doing a clutch start off the grid I seem to always have max revs, whereas maybe it would be better to have 70% revs....trouble is I cannot hold the revs at 70%. Maybe my pedals do not have enough fine control?
  8. PicoBp

    #26 | HSRC - Banzaaaiii Touring Car Crew Premium

    I had no issues with holding a specific throttle with my G27, and neither do have with the T3PA. But if you need a finer curve at the low end, try to decrease the sensitivity of the throttle axis to 25% in-game. :thumbsup:
    • Agree Agree x 1
  9. Stingraymx


    Will do. Am hoping to get a new wheel/pedals in next 2-3 months so it's good to know that decent kit works better than my ancient one. Will test the sensitivity this afternoon, as that may well help. Cheers
    • Like Like x 2
  10. Yes, the issue is that the linearity setting in the controller profile doesn't seem to get applied the same when in neutral than when in gear. In gear, it behaves like a real vehicle. In neutral with no load, it is exaggerated, so that instead of red line occurring with say 50% throttle, it's happening at 15%. If you adjust the linearity to fix the neutral issue (which is important if you do not use auto-clutch), you suddenly have too-dull and unresponsive throttle while driving/racing.
    • Agree Agree x 1
  11. Who knows what the issue is. There's no need to dismiss everyone's thoughts and concerns about sims as if any and every sim out there is perfect from a physics, or any area for that matter, point of view (couldn't be further from the truth).

    Noobody said you can't ever hold steady RPMs, and I think most people know that engines are easier to spin up when under no load but I personally think it's still quite wrong in-game. I even have a friend (he comes over often to simrace) who commented on it and, although not the most experienced simracer around, he definitely knows a thing or two about fast cars and motorcycles.

    Something doesn't seem right.
    Last edited: Apr 17, 2016
  12. Niels_at_home

    Reiza Studios

    Reality is probably somewhere in the middle. The throttle doesn't purely control revs and the revs you reach don't have to say much about the torque the engine produces at that time.

    Its however an area where improvements are possible and already quite clear in my mind... But I can't say much more about it at this stage.
    • Like Like x 2
  13. oh jeez. at this point i feel i have to involve myself in this.

    The torgue coming out of crankshaft is composite of 2 torgues engine produces. Combustion torgue and inertial torgue.
    These 2 combined are called COMPOSITE torgue. Which is NEVER linear with throttle input, as you can only infuence combustion torgue directly with your throttle.
    As the revs get higher, the inertial torgue rises very fast, but combustion torgue keeps rising in quite linear manner with your throttle input.
    Higher tuned the engine, less linear throttle you will have. High revving engine in it self, plus high compression ratio combined to light&well balanced pistons and other moving engine parts, make the inertial torgue curve become less linear with combustion torgue curve.

    If you look at craphs of these two torgues, taken from highly tuned engine, (like a 1000cc sports bike) they actually cross each other usually even before the halfway, which after the inertial torgue rises in allmost vertical manner, while the combustion torgue keeps rather "flat" progression.

    If you have a friend who owns a 1000cc sports bike, like suzuki GSXR 1000rr or similar, ask if you can try the throttle when the bike is running in neutral. You'll see that 1/5 of the throttle input is enough to make it reach the limiter (12-14000 rpm).

    But it's not like it haven't been tried to make it more linear in the real world. 2006 yamaha came up with crossplane crankshaft engine design in their MOTO GP bikes, just to get the throttle more linear with the power output, and 2008 they implemented it in to the R1 lineup.
    Now i haven't spoken to anyone who have had a ride in the yamaha YZR MOTO GP bike, but users of the R1 reported that the advertised linear throttle isnt a magic trick yamaha says it is, and made the engine "only" feel like a V4 instead of inline 4 which it actually is. None of the other big japanese manufacturers have adopted this technology.

    Here's a yamaha ad from 2008, what im talking about starts at about 2min30sec:
    Last edited: Apr 19, 2016
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  14. 1/5th ie. 20% throttle? Interesting.

    I don't imagine it would take Niels and co. much effort to get a Stock Car Brasil driver to comment on how much throttle it takes to reach limiter in neutral.
  15. On the inline 1000cc bikes i would say even less than 20% is enough.

    In inline engine the composite torgue comes more from inertial torgue in relation, which makes it the worst of the lot throttle/power linearity wise.
    The best would be radial engine, where the combustion torgue affects the crank from "all" directions (instead of 1 or 2), making the combustion torgue bigger part of composite torgue.
    Basically, bigger part the combustion torgue is OF composite torgue, more linear the throtte input and engine power are.
    Last edited: Apr 19, 2016
  16. Niels_at_home

    Reiza Studios

    Spinelli, those sims/cars that reach redline at say 20% throttle, put the car in top gear and see what happens at 20% throttle, you probably won't go very quickly, i.e. there is only enough torque to spin the engine up, not to 'drive' any load.
    • Like Like x 1
  17. YES! it's inertial torgue most of it when on neutral.
    As soon as you start to load it you start to spend it, rapidly.
    Now that inertial torgue is one sob from drivers/riders point of view, even more so in sims as it is very hard to get feel of. It follows combustion torgue with latency, yet you still allways have to have enough combustion torgue to keep the inertial torgue (revs) up enough to have power, so you basically have to adjust combustion torgue in advance because of this.
    It also explains those violent spins (no pun intented) very often. As your rear wheels lose a little grip, the inertial torgue is enough to make them spin rapidly without any change in combustion torgue (throttle).
    In engine brake it's that inertial torgue trying to keep your wheels spinning while you are trying to slow them down with brakes.
  18. *torque :p
  19. I hope you're right and that the phenomenon only happens when in neutral or the clutch pressed in.

    Great! Looking forward to core-engine improvements.