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- Transfer Time FlowArea Programme
- Example - AM6 50cc Cylinder
- Example - Yamaha TA125 Production Racer Cylinder
- Example - Yamaha TZ250 Production Racer Cylinder
- Example - Puch Maxi 50cc Cylinder
Transfer Time FlowArea Programme
This programmme calculates the specific time-flowarea for the Transfer port of an engine, based on actual flowbench data. From this information the programme calculates the potential power capability of the engine. If you require an increase in power from your engine, you can quickly ascertain what modification will give you the required increase.
Time-Area calculated by the traditional method of using the Transfer port actual dimensions is a fantastic tool. However, there are engine cylinders that just do not flow as well as the calculated time-area would suggest resulting in poor performance and often a lot of wasted development effort. Using the Torqsoft time-flowarea programme will actually give more reliable power predictions numbers.
The heart of the equipment required for flow testing is the venturi flow meter, the black item in the above photo. This item can be purchased from here Venturi Flow Meter - V20 and is most suitable for cylinders with bores less than 50 mm. A larger Venturi Flow Meter - V27 is suitable for cylinders with bores between 45 and 80 mm, and is shown below.
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AM6 50cc Cylinder
The image below shows the engine details entered for this engine fitted with an after market high performance 50cc cylinder. These include the Bore, Stroke, Rodlength and Peak Power Speed. The piston distance ( at TDC ) relative to the top of the cylinder is also entered. Notice that in this example the value is -1.7, with the minus sign indicating that the piston timing edge is below the top of the cylinder at TDC. Note that if the timing edge of the piston protrudes above the top of the cylinder at TDC then the number will have a positive value.
Next the distance from the top of the cylinder to the opening of the transfer ports is entered as shown below.
Next the measured data from the actual flow tests is entered. The image below shows the measured flow data for 3 piston positions. The distance from the top of the cylinder to the timing edge of the piston is entered in the first column. The measured pressure differential across the venturi ( measured in units of mm of H2O ) is entered in column 4. The measured pressure at the inlet to the venturi is entered in column 3.
The image below shows the computed output for an after market high performance 50cc cylinder for a Minarelli AM6 engine. The first line shows the calculated transfer port timings. The final two lines show the potential power output based on the calculated specific time-flowarea. This engine dyno tested at 20.6 bhp at the rear sprocket - equivalent to 22.9 bhp at the crank - and correlates closely with the computed specific time-flowarea potential.
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Yamaha TA125 Production Road Racer Cylinder
The image below shows the exhaust port of a Yamaha TA125 cylinder - a twin cylinder, piston ported inlet, air-cooled production road racer produced in the 1970's. The engine has a bore and stroke of 42.00 mm.
The image below shows the exhaust port of a Yamaha TA125 cylinder being flow tested using a Torqsoft Venturi Flowmeter. The raw flow data collected from the 15 piston positions tested were input into Torqsoft Flow-Time-Area programme. The computed output indicated that the TA125 cylinder Transfer port flows very efficiently and has a high potential power output.
The programme also allowed us to "lift" and "lower" the cylinder in order to optimise both the transfer and exhaust timings for maximum power.
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Yamaha TZ250 Production Road Racer Cylinder
The image below shows the exhaust port of a Yamaha TZ250 cylinder - a v-twin cylinder, reed valve inlet, water-cooled production road racer produced in the 1990's. The engine has a bore of 56.00 mm and a stroke of 50.6 mm.
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Puch Maxi 50cc Cylinder
The image below shows the transfer ports of a Puch Maxi 50cc cylinder - a single cylinder, piston ported inlet, air cooled moped engine - being flow tested. The engine has a bore and stroke of 38.00 mm and 43.00 mm respectively. This particular cylinder has 1 exhaust port, 2 transfer ports and 1 inlet port.
The programme calculated power potential for the transfer ports based on the flow tests is 4.28 bhp. This is considerably lower than the 10.5 bhp potential off the exhaust port. This information is invaluable for the Mofa Tuner as they now know to direct all their efforts to improving the flow of the transfer ports.
