Pictures of Big Shots

VGT Turbo Lifespan

It was my second turbo, factory one snapped the shaft at 387k miles and it wasn’t violent – 2 hours later (before it even had a chance to cool down) I was back to the road with reman from Cummins. That updated VGT lasted exactly 50% longer, which is kinda nice increase  but… not really. Problem is, they don’ t explode nearly as often as old, non-variable  turbos were and keep spinning beyond it’s own lifespan despite being out of whack and robbing you from fuel for who knows how long.
I was dealing with elevated by 100-200 F EGT (Exhaust Gas Temperatures) for at least half a year. At first I was blaming hot summer air (nonsense but thats when it started anyway) then I was suspecting my still original mufflers possibly being stuffed with soot buildup (they were, just a bit though and replacing them didn’t help). Then over time my pyrometer started creeping up to 900 F and when it started hitting 1000 F I went to talk to Ray Righetti, North-California Cummins guru to talk about it. He asked me how many miles on the turbo I got – 583k I said. He made a sound like something stabbed him in the back and said “come, I need to show you something” And being good friend of mine he took me to his engine room where they X-Ray blocks for whole Bay Area and pointed to two open  ISX turbos: „they wore out those nozzles and can’t be properly positioned by ECM anymore. With the miles you have put it’s not even worth diagnosing, you need new turbo, there is nothing that could have more bad influence on ISX EGT than worn turbo
Then doing oil change at Speedco I have met a produce hauler from TN who at 810k miles still had his original turbo (no kidding, I checked the part number) and not complaining  – he actually loved his 530 ISX for being almost troublefree. I hate replacing things that still work but then… I got under lighter load and still was hittin 1000 F on pyro and seing some inconsistences on Insite (like occasional 56,000 rpm pulling hills) – I decided I’m fed up with this.
Below are pictures of that turbocharger – Ray was absolutely right about the nozzles being worn and sticky plus the shroud late was loose from its housing (could be the latest development) and the sliding nozzles base was cracked from high temperatures probably or maybe how it all started – from that crack. All this mess must have been causing not only higher drive pressure but boost problems aswell since it didn’t really close nor fully open but max boost reamained almost unaffected. Its actually quite interesting it didn’t blow being the sad junk it was for months and the only gauge to reflect that was pyrometer because Insite software was showing Turbocharger Control Valve being actuated – problem is there was no feedback from turbo on actual position until 2007+ motors (with electric turbo actuation and DPFs) so ECM didn’t even know how far off turbo was from where it wanted to be.
Another culprit of dying variable geometry turbo is weak jake-brake performance. It was working but you’ll be seeking higher rpms, up to 2000 instead of usual 1700 and then, over time you still have to use air brakes to compensate for its under-performance. Which is obvious sign of turbo not being able to close fully – I used to be able to run coast-to-coast fully loaded without touching brake pedal (I’m still on original brake shoes on drives). Thing is… weaker jake started… 200k miles ago. It wasn’t nearly that bad as lately and fairly OK for long time – but it means that wonderful piece of modern diesel technology started walking out of specs at around… 400k miles. In other words you need 2 of them for the miles of non-variable turbo which used to be also 3 times cheaper.
Now, here is another kicker – I have lost probably around 7% of fuel mileage last year and that means I paid for that turbo 3 times compared to what it could’ve cost me if I knew what I know now year ago: placing moving parts in stream of diesel exhaust is poor engineering  idea and works for everyone but the truck owner

Holset VGT Turbo 5 Holset VGT Turbo 4 Holset VGT Turbo 3 Holset VGT Turbo 2 Holset VGT Turbo 1 Holset VG Turbo 6

 

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