VForce and 31K-Exhaust

Measures

  • VForce-Membran
  • YPVS Exhaust
  • 1.5 mm copper base gasket acting as an additional cooling fin
  • squish gap 0.75 mm
  • electronic ignition system of PowerDynamo
  • ignition timing by Zeeltronic
  • self-constructed air filter box
  • exhaust whistle cut and sealed
  • Intake bridge

 

Setup

  • Main Jet # 200, idle # 30
  • needle 5I4, Position # 3
  • Nozzle O8
  • throttle 2.5
  • Ignition curve 

                   rev        degree before TDC

  • 1500    20
  • 3000    22,5
  • 5000    21
  • 7000    17,2
  • 9000    1

Result

  • 21 kW on the wheel

 

Widen Membrane case and VForce membranes

To assemble the VForce membrane, the membrane box has to be widened by 8 mm (from 45.5 to 53.5 mm. This will end up in  remaining wall thicknesses below 1 mm. To be on the safe side it is recommended to increase the wall thickness of the membrane box by filling the spaces between the ribs with cold metal. I also use a 5mm spacer between the membrane and membrane Box. The complete action is a lot of work, but takes 10% more power.

 

Fig.: Membranes: RD 250, YPVS, VFORCE                                                         Fig.: Membrane Spacer

Fig.: Wall thickness of the membrane box increased by filling with cold metal Wall thickness of the membrane box increased by filling with cold metal

Bild: Membrankasten original und auf 53,5 x 51,5 mm aufgeweitet
Bild: Membrankasten original und auf 53,5 x 51,5 mm aufgeweitet

Fig.:Cylinders with studs                                                            Fig.:  Pack of spacer and V-Force-membrane

 

To get the new membrane package sealed, the screws must be tightened properly. To minimize the stress in the aluminium block studs should be used that can be easily produced from a 6 mm threaded rod. For the above shown modification studs with a length of 50 mm are ideal.

Fig: Performance with standard membranes and Boost-Bottle, 17 kW
Fig: Performance with standard membranes and Boost-Bottle, 17 kW
Fig.: Performance with V-Force membranes and cross over pipe, 19 kW
Fig.: Performance with V-Force membranes and cross over pipe, 19 kW
Fig.: 21 kW with YPVS exhaust and V-Force
Fig.: 21 kW with YPVS exhaust and V-Force

The engine after the Classic Race in Wallduern

At Walldürn 3 + 4 June 2011 the engine ran over 60 km on the race track. Main Jet # 200 was installed. Temperatures was between 24 and 27 degrees.

On the piston you can see very clearly the effect of different squish gaps left and right. The carbon deposits are a sign of the piston temperature. The left piston, i.e. the one with the 0.85 mm squish gap clearance has no coking all around the edge. That means the piston remains cool at the edge. Unlike the right piston with 1.2 mm squish gap. Coking is seen from 9 o’clock to 3 o’clock. It is much warmer on the edge as the other piston.

                                      right                                                                                  left
Figure 10: Piston after 160 km, of which 60 km race mode