Yamaha Power Valve System

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The Yamaha Power Valve System (YPVS for short), more rarely Power Roller (PW for short), is a performance-enhancing exhaust control system for two-stroke engines that was developed by the Japanese motorcycle manufacturer Yamaha in the late 1970s.

Development and Background

In 1977 the system was used for the first time in the YZR500 during the race for the motorcycle world championship . In general, "sharp" timing results in a high output in the high speed range. At lower speeds, on the other hand, “tame” timing is required so that power and torque can develop. In the powerful two-stroke engines, long exhaust valve timing led to a loss of fresh gas at low and medium engine speeds. As a result, the pressure in the outlet dropped sharply and the compression was reduced. The combustion of the mixture was not optimal, which had a negative impact on efficiency and fuel consumption. The YPVS should act on the timing when the engine is running and increase the torque in the lower and middle range. This should give the motorcycles decisive advantages over the competition when accelerating out of bends in racing.

functionality

Immediately above the outlet, Yamaha used a roller that tapered towards the center and was controlled by the ignition via a Bowden cable driven by an electric motor. The roller has a recess in the area of ​​the outlet channel in order to enlarge or reduce the outlet channel by means of a rotary movement. So sharp and tame timing could be implemented depending on the engine speed. The increase in performance of the system can be clearly seen using the Yamaha RD 350 as an example . If the first model came in 1980 (RD 350 LC type "4LO") on 36 kW / 49 PS, the model with YPVS (RD 350 LC YPVS type "1WW") reached 46 kW / 63 PS. Without the YPVS, the engine would only have this output in a very narrow speed range that cannot be used in practice. Since the system was in the open position when it was started, the system could be perceived by a low whirring sound. However, the increased technology also resulted in higher maintenance costs.

  • Yamaha two-stroke engine with the Power Valve System

  • The very successful RD 350 with YPVS

  • Structure of a two-stroke engine

  • Schematic representation of Honda's V-TACS system

Control systems from other manufacturers

  • AETC and Super AETC ( A utomatic E xhaust T iming C ontrol) from the manufacturer Suzuki :
    First used in 1987 in the RM 250 crossers and in the further development as Super AETC in athletes such as Suzuki RGV 250 Gamma , the height of the exhaust ducts varies by means of speed-dependent controlled slide. First there were these two, then in the Super AETC their three.
  • ATAC ( A utomatic T orque A mplification C hamber) from the manufacturer Honda:
    Below a certain speed in the exhaust, a valve opens an additional resonance chamber, which changes the pressure through resonance vibrations in the outlet of the cylinder. This has a positive effect on the filling of the combustion chamber with fresh mixture. The system was first installed on the NS 500 in the Motorcycle Grand Prix in 1982 . Initially, the system worked mechanically using centrifugal force . Electromagnets controlled by the ignition voltage took over this task later. The system was used in series production in the NS 400 R from 1985 .
  • V-TACS The ( V ariable T orque A mplification C hamber S ystem) from the manufacturer Honda:
    The system built into low-displacement engines such as the FC50 scooter from 1983 onwards was operated by the driver using a foot lever. An additional resonance chamber could be opened over 5500 min −1 via a valve, which provided more throughput. If the driver operated it below this speed, the chamber matched to the exhaust system would have the opposite effect.
  • Honda Power Port Valve of manufacturer Honda:
    The system found in competition machines like the Honda CR 250 R use. Centrifugal force controlled valves influenced the exhaust port. Due to the large number of components, it was very maintenance-intensive and had to be readjusted after 7 or 12 hours of operation and did not establish itself in series production.
  • Honda RC ( R evolution C ontrol) Valve manufacturer Honda:
    In principle, the system works, which approximately in the Honda NSR 125 R was very successful, as the AETC system with slides. However, these are controlled here by means of electric servomotors.
  • KIPS ( K awasaki I ntegrated P ower V alve S ystem) of the manufacturer Kawasaki :
    The system was first inserted into the KX-models from 1984th Auxiliary outlets were controlled by the centrifugal force via rollers, depending on the speed. A secondary outlet was closed at low speeds. The second opened into a chamber with an additional volume. At speeds above 6000 min −1 , the roller closed this chamber and at the same time both auxiliary outlets opened, which enabled better filling of the cylinder.

Individual evidence

  1. ↑ Yamaha Technologie 1980: YPVS (Yamaha Power Valve System). Internet presence of the manufacturer Yamaha, accessed on April 15, 2017 .
  2. ↑ The YPVS explanation, function, components, setting and more. RD 350 LC Forum, September 13, 2013, accessed April 15, 2017 .
  3. ↑ 1988 Suzuki RM250. pulpmx.com, accessed April 12, 2017 .
  4. ↑ Suzuki AETC and super AETC. Concordia University, Semesterreader "Industrial 6230", Winter 2016, February 27, 2017, accessed on April 12, 2017 .
  5. ↑ Motorrad, Reisen und Sport 14/85: Honda's ATAC exhaust system on the NS 400 R increases the torque online
  6. ↑ Honda V-TACS. Concordia University, Semesterreader "Industrial 6230", Winter 2016, February 27, 2017, accessed on April 13, 2017 .
  7. ↑ Power Valves. Dan's Motorcycle (www.dansmc.com), 2005, accessed April 15, 2017 .
  8. ↑ What is an rc-valve? thumpertalk.com, August 9, 2006, accessed April 15, 2017 .
  9. ^ KIPS Valves Explained. dirtrider.net, June 19, 2014, accessed on April 12, 2017 (English).

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