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ATV Race Engines |
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DRG Porting Services |
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Single Stage Anti Reversion (SSAR) is tuned 'stepped' exhaust integrated porting to assist in ‘exit-only’ exhaust gas flow. Exhaust port 'steps' enhance the exiting exhaust flow prohibiting exhaust gasses from being pulled back into the cylinder during camshaft overlap. Undesirable reverse exhaust gas flow in the exhaust port occurs on camshaft overlap when the piston is accelerating toward crankshaft bottom Dead center (BDC); negating the intake strokes ability to completely fill an contaminant free cylinder. DRG’s anti-reversion porting has designed and tested to reduce the negative effects of reversion to enhance low end engine performance. DRG, being the first to integrate anti-reversion porting in motorcycle/ATV applications, is offered to every cylinder head DRG ports.
Dual Stage Anti Reversion (DSAR), coupled with SSAR technology, is designed to 'store' the positive pressure at the intake valve backings to 'ram-air' the intake charge into the cylinder upon valve opening. Because the intake valve closes at near 450 degrees of crankshaft rotation, a positive pressure builds at the back of the intake valve due to the ramming effect known as rarefaction. These rarefaction waves are elastic in nature with its energy damping over time. DSAR 'stores' this pulsed energy within the 'traps' of the intake porting and inhibit backward pressure flow out the intact tract. As opposed to the stepped design on the SSAR, the DSAR intake port with integrated 'traps' permits forward flow but 'traps' outward flow toward the air filter. Without DSAR intake 'traps', the reverse pressure at the back of the intake valve easily flows back to the carb where it stalls the carbs fuel metering circuits. DSAR intake anti-reversion uses the energy of the refracted waves to constructively interfere with FORWARD waves providing gains throughout the power curve. |
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The chart above is an example of the flow-rate graphical representation that is recorded on every cylinder head ported. Customers are provided with flow gains obtained as verification. Each graph displays the intake flow rate before porting and after porting, along with before and after exhaust flow rates. |
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DRG, LLC. 608 Sand Road Severn, Maryland 21144 |
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To contact us: |
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Phone: 301-910-9850 E-mail: info@chad502ex.com
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All DRG porting is validated for flow prior to assemble or shipping to the customer. Unlike other shops that can not repeat flow rates, DRG consistently reproduces flow for the desired power curve on every cylinder head ported.
DRG’s flowbench is fully calibrated by NIST and digitally controlled for precise valve lift recreation using electric motors capable of pulling over 600 cfm’s at over 35” of water column (H2O). While recording flow rates and/or velocity speeds, handheld pitot tubes can be used to probe the port for locate areas in the port needed to be port mapped.
All cylinders heads ported at DRG are flowed as part of the porting services and the flow record is stored graphically. Before tests and after tests are done to document gains obtained.
Every DRG ported head gets: · Adjusted port volume and cross-sectional area · SSAR exhaust · Short-side radius roll-back · Deep pocket porting · Bowl blending · Intake guides sunk · Seat throat proportioning · Compression Chamber shaping · Valve job -cleanup · New valve seals · Flow bench tested |