Exhaust Time-FlowArea

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Exhaust Time FlowArea Programme

This programmme calculates the specific time-flowarea and specific blowdown time-flowarea for the exhaust 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.

TorqSoft - Exhaust Time-FlowArea Programme


Time-Area calculated by the traditional method of using the exhaust 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.


TorqSoft - Exhaust Time-FlowArea Programme


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 port diameters of less than 32 mm. A larger Venturi Flow Meter - V27 is suitable for cylinders with exhaust port diameters between 30 and 40 mm, and is shown below.


TorqSoft - V27 Venturi Flow Meter


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AM6 50cc Cylinder

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 port timings - exhaust and transfer. The final two lines show the potential power output based on the calculated specific time-flowarea, both blowdown and total. This engine dyno tested at 15.6 bhp at the rear sprocket - equivalent to 16.95 bhp at the crank - and correlates closely with the computed specific time-flowarea potential.


TorqSoft - Exhaust Time-FlowArea Programme


Once the first calculation is carried out, it is very easy to carry out some what if calculations. For example, we can raise the cylinder by adjusting the piston position parameter. Shown below is the computed output for the same cylinder raised by 0.5 mm. It can be seen that the potential power has risen from 17.52 bhp to 18.21 bhp, an increase of 0.7 bhp.


TorqSoft - Exhaust Time-FlowArea Programme


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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.


TorqSoft - Exhaust Time-FlowArea Programme, Yamaha TA125 cylinder


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 exhaust 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.


TorqSoft - Exhaust Time-FlowArea Programme, Yamaha TA125 cylinder


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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.