More Spirited Transmission Action?

Discussion in 'Gen 3 Prius Technical Discussion' started by Pollymath, Mar 16, 2020.

  1. Pollymath

    Pollymath Junior Member

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    As a car guy, I hate CVT transmissions. If somehow there was a way of making an automatic transmission less fun, a CVT is it. Prior to my current fossil fuel destroyer of a Toyota Tundra, I had owned 10 vehicles, almost all of them were manual. I've owned Miatas, 240SX, turbo Mopars and economical Escorts, most of them seeing at least a few Auto-X events.

    More so, it also is detrimental to a car that really needs the carbon blown out of it - like the problematic EGR system equipped 3rd Gen Prius. If the car is never allowed to hit redline, or anywhere near it, how can it clear it's throat?

    I've messed with the "Power Mode", and it seems to make the "shifting" (or rather transitioning) of the CVT a little more aggressive, but are there other ways of allowing the Prius to be driven more "spiritedly?"
     
  2. fotomoto

    fotomoto Senior Member

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    Floor it. ;)

    CVT's don't shift "spiritedly" because there are no gears to shift in the first place.

    If you really want a manual trans hybrid, see older model Honda Insight and CR-Z (I'd vote the Z w/6spd).
     
  3. Pollymath

    Pollymath Junior Member

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    Will the transmission ever let the motor rev above a certain RPM?
     
  4. bisco

    bisco cookie crumbler

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    hundai has some regular auto trans i think.

    power mode simply remaps the throttle position sensor so you don't have to push as hard.

    i don't recall anyone doing anything to increase prius driving spirit. most discussion here is about mpg's.
     
  5. fotomoto

    fotomoto Senior Member

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    Software logic controls the whole car; that's why one can floor it in P and it will just purr.......
     
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  6. Pollymath

    Pollymath Junior Member

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    Yea the car doesn't really rev. I would assume that means it's got a rpm limiter at some ridiculously low RPM like 5000 or lower.

    I might have to take a look at the RPMs in OBDII app.
     
  7. bisco

    bisco cookie crumbler

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    i think over revving can damage the tranny
     
  8. Grit

    Grit Senior Member

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    Reb dullet mod. Forces more power causing ice to stay on longer so engine temp will stay closer to 190 F range.
     
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  9. ChapmanF

    ChapmanF Senior Member

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    The ECU in charge of the engine never runs it above its rated top rpm (differs per Prius generation, I think it's around 5000 or 5300 for Gen 3).

    It will happily run right up to that rpm if you ask for full power.
     
  10. meeder

    meeder Active Member

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    You won't blow out the EGR system when flooring it, at full throttle the EGR system doesn't do anything.

    Besides that normal port injected engines hardly suffer from carbon buildup in the inlet of an engine. Direct injected engines do but even then, flooring doesn't always clear that up.

    As long as you keep to the maintenance schedule and use good quality oil and good quality fuel there won't be many issues. The EGR will probably clog up but again that won't be fixed by flooring it.

    I feel that the most important thing is to keep driving the vehicle. No short distances, always get the engine hot whilst driving.
     
  11. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Blowing the carbon out was possible with carburetors.
    Red line for Gen 2 was 5000 RPM, Gen 3 is 5200. I see red line quite a lot. There is pedal under my right foot for that.
    The eCVT in a Prius is a one speed clutch-less* manual. It emulates a CVT in software, but actually never shifts at any time. (There is a pawl that moves to stop the car from moving in P, but it is really still in D)
    When you are in D, the speed of M/G2 is directly tied to the speed of the front tires. At 0 it is not rotating. At 115 it is red lined. (103 for my Prius v as it has a lower final drive for better acceleration. You could drop a v transaxle in a Liftback for quicker acceleration)
    In R it is exactly the same except M/G2 is rotating the other way. Electric motors don't care.
    In N, the Prius just does not give any electricity to M/G1 or M/G2 so the engine has nothing to push against and the car does not move.
    B is another software change, which adds engine braking, lowering gas mileage, but keeping the HV battery and the brake rotors cooler on long descents.

    Professor John Kelly has an almost infinite number of youtube videos on the Prius transaxles. My favorite is below.

    * there is a clutch, called a torque damper, that never disengages. It is there in case the engine or transaxle locks up, and the torque need to go somewhere. It is just there to break first.

     
    #11 JimboPalmer, Mar 17, 2020
    Last edited: Mar 17, 2020
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  12. Pollymath

    Pollymath Junior Member

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    So to clarify - the motor will rev to redline under full throttle?

    Red Bullet eh? That's a rabbit hole.

    I've heard people mention that turning off traction control can damage the transaxle, yet people do it for autocross and other sporting drives. What's the scoop on that?
     
  13. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Some people choose to damage the transaxle. So long as they don't make warranty claims, I am ok with that.
     
  14. ChapmanF

    ChapmanF Senior Member

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    Some tachometers used to have more than one color of line, depending on how far you wanted to push it. Red would be the last one.

    The ECU in the Prius has a maximum RPM that it will demand of the engine, whether that would be the just-short-of-rapid-unscheduled-disassembly "red" line or some earlier limit.

    The typical output power graph for an engine has a peak at a certain RPM and then starts to decline again at higher RPMs than that, as efficiency is lost to the sheer mechanical work of moving the stuff that fast.

    In a conventional car with fixed gear ratios, you might now and then have reasons for wanting to rev higher than the power peakā€”like because you just want to go faster, and the fixed gearing means the car can't go faster unless the engine spins faster too. Then you're trading off the efficiency to get the road speed you want.

    The Prius never has a reason to do that, because the CVT allows any road speed (within reason) to go with any engine RPM. If the engine is turning 5200 and you want the car to go faster, the CVT just does that. So the car never has to sacrifice efficiency by pushing the engine onto the declining part of the power graph.

    That would explain why the top engine RPMs seen in operation match so closely the "peak power x HP at y RPM" from the engine specs. The RPMs beyond that point just aren't useful.

    As for the traction control, because MG2 is an electric motor with very powerful torque right down to zero RPM, if you punch it from a standstill and traction breaks, MG2 can reach pretty high RPM much faster than the engine speed increases from idle. Because of the way the tranny is built, that difference between engine idle RPM and high MG2 RPM translates into a very high MG1 RPM, also reached nearly instantaneously. MG1 also has a threshold for rapid unscheduled disassembly, and one job of the traction control is to prevent reaching it, because your reaction time would be too slow.

    In the Gen 1 Prius, that was really the only job of the "traction control". Starting with Gen 2, they also gave it individual-wheel braking control and made it more of a system that can actually help with, you know, traction.
     
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  15. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    The 'redline' for M/G1 keeps increasing: 6500 RPM for Gen1 and 17,000 RPM for Gen 4. So the computers need to intrude less in newer Prius. Some one is really working on the bearings!

    There are many third party tachometers, often built into OBDII readers. I bought a ScanGauge II in 2009, it is very nice bit very pricey compared to using Android or iOS.

    www.amazon.com/dp/B000AAMY86
    $140

    I have used Torque software which wants an old Android device and a ELM comparable ODBII to bluetooth dongle.
    Torque Pro (OBD 2 & Car) - Apps on Google Play

    There are tons more
     
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  16. ChapmanF

    ChapmanF Senior Member

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    Somehow, I've had the impression for a long time that the original limitation was the structural integrity of the rotor, which has eight hefty magnets around the outer edge that would travel in straight tangential lines if they had their choice in the matter.
     
  17. Maarten28

    Maarten28 Active Member

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    Yes, but only from about 73 mph. Below that the maximum rpm of the engine is limited because MG1 is limited in speed.
    With MG1 limited at 10,000 rpm, you'll get a maximum of 2,778 rpm at standstil, going in a linear fashion to 5,200 rpm at 73 mph.
     
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  18. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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  19. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    The M/G 2 motor will be at it's red line at top speed, that is why it is the top speed, so M/G2's bearings survive. The amount of throttle does not really do much for the motors, it has more effect on the engine.
     
  20. Pollymath

    Pollymath Junior Member

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    Thanks guys. It sounds like aside from "Power Mode" there really isn't any special mode or setting which makes the Prius more sporting. It's designed in every way to be efficient.

    That being said, it's a decent handling car, but then so was the Vibe/Matrix/Corolla of which it shares platforms.
     
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