November 2019

NOVEMBER 2019 AFTERMARKET 29 EYEBROW www.aftermarketonline.net TRAINING COURSES OFFERED &%$#"! " #% % # " % % &% #%! % % &% % % % &% # % % % &% ! "% "! % # " #% % &% # # % # #"% %"! % % &% ! % " %" " # % % &%$ # " #% " % # " % % &% %" " # %! ! %! # ! " #%" # % % &% ! "%" " # % # % % !% ! &% ! ! " % # % %"! # # Frank Massey is one of the UK’s leading experts in vehicle Diagnostics with over 40 years of industry experience. He is renowned in the motor industry for his unrivalled expertise and knowledge as well as running a successful commercial workshop. +*)( ')&%$%$#( "!*) ( &) ( ! * &) ( *% %$#( !' ( )% $" ( &$ ( "!$ $" ( %$( &( ( +( ( & )!&" ( ( "! )( &( % ( )&$# ( ! ( * "' ( %$')! *"%$#( '!! ( &$ ( ' " $% * ( ! (%$(' ( ( !) ! !% ! % # ! " #% % #" "% ## "" &% % annette@ads-global.co.uk % %% | %% !$ % 01772 201597 www.autoinform.co.uk conducted. This engine employs variable camshaft timing on both cams with lift extension on the exhaust cam. With this in mind, I was especially interested to examine the valve piston relationship and the valve pocket profiles. The results immediately confirmed significant errors to the intake and exhaust valve pockets with excessive exhaust pressure. This engine variant should have little or no pressure above 1 atmosphere, or 1,000mb. during the exhaust stroke, my test results confirmed over 1,700mb absolute. Valve pockets represent the pressure differential across the four-stroke cycle and accurately represent the mechanical efficiency of the Otto Cycle. This is often referred to as pumping losses. So, we have a restriction in the exhaust stream, turbo, catalyst or exhaust system? Removing the flange pre-catalyst enabled examination of the turbo hot side and catalyst intake. Reduction of boost pressure The catalyst substrate was detached and turned through 90 degrees. In this way, we discovered the symptoms. A restricted exhaust was reducing both air intake volume, therefore load calculation, and turbine volume. The result was a reduction of boost pressure. Next, we needed to discover the cause. Excessive heat and expansion, followed by the catalyst detachment. This was interesting, not least because a recent upgrade to the fuel priming system resulted in the fitting of an upgrade in tank pump. The result of which only became known after a track session where a drop-in top-end power resulted in a DTC rail pressure negative deviation. The pump module, a specific upgrade from a respected independent VAG tuning specialist, had been supplied with the incorrect o ring. This resulted in a slight drop in both flow and pressure together with cavitation causing a lean mixture ratio at extreme load. So now we have the complete trio, fault, symptoms, and cause. Happily ever after? That is not the end of the story however, as this particular VW Golf R returned just a week later. The good news was the owner’s report of exceptional performance. However, the bad news was that with the returned power came horrific vibration. That’s a story for another day though. Right: Restricted exhaust