AFT_B912

DECEMBER/JANUARY 2020 AFTERMARKET 27 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 following a recent track event. The engine idles normally with no obvious problems, no noises and good oil pressure. Depressing the clutch and selecting gears has no effect. Testing Let’s review the images: Fig.1 Normal trace at idle E1 represents the crankshaft frequency, E2 represents the combustion events both values are exceptionally low at 6mg or less, there is a little ambient vibration at 50/60/70hz. The blue trace represents engine speed. The lower plot is the complete data buffer. All is good. Fig.2 Trace at elevated speed Note engine speed at approx. 2586rpm 42.1hz, vibration at crank E1 is still very low however at around E2 there is a broad band contact representing a mass displacement between 55 and 90hz. This represents the failure of the dual mass flywheel secondary mass. Also note the mass displacement is shared across all three dimensions. There is also a broad band vibration at 120hz. This represents an increase in ambient vibration through the vehicle body, remember high frequency equals low mass. So, the fault is a faulty dual mass flywheel. Total diagnostic time around 15 minutes. Solid evidence for the customer. Interestingly, with the flywheel removed it was not possible to determine the nature of the fault.