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Going on JKM's Dyno-Dynamics rollers when my Revo Stage1 was installed, plotted smooth healthy curves with 236 bhp and just under 300 ft lbs. In late September, Revo HQ loaded Stage2 and we went out on the road and everything was fine and dandy - A subtle but strong linear power. Subsequently, in early October about 20 of us met up for a social rolling road session at JKM and I was very surprised to plot less than 230 bhp with Stage2.
My VW dealer had spotted earlier that my Milltek cat was deteriorating and so Milltek kindly replaced the whole downpipe and sportscat but a diagnostic session on JKM's dyno a few days afterwards still showed only 228 bhp. Keith at JKM thought it was likely to be a boost leak because of data logging the boost request levels.
So another session followed and Jim took the car apart as follows : -
- Spotted oil blow by leak on seals by Turbo Discharge to Intercooler. Inlet seals removed and cleaned and all ok in that area now.
- Forge DV removed and checked. Seals renewed anyway and no faults found.
- DV vacuum lines checked with vacuum gauge and all ok.
- PCV valve checked and all ok. PCV valve blank-off used for testing - No differences to performance/boost response.
- Air box removed and car run - No changes to performance/boost response.
As there are no apparent boost leaks at this stage JKM said they would like to mechanically inspect the turbocharger for any internal damage or potential cracks on wastegate housing etc. They were fairly confident it's the turbo but of course couldn't be 100% sure yet.
So, my options were : -
1) - Inspect the turbo but have to hire a car while it's sent away to a specialist if no damage is obvious. This would have a cost and would also probably not be financially viable to repair.
2) - Buy a new K03 turbo (about £650) with 2-year warranty. BUT....That warranty would be ineffective because VW would claim that my car is too modified by its remap and exhaust.
3) - Buy a hardly used K03 which has done less than 4,000 miles and which both JKM and Revo knew to be in top notch condition. It was taken off for a K04 conversion. Cost £400. Swop turbo's in the same day.
4) - Spend several thousand pounds (£3.5K) on the K04 conversion and end up with around 300 bhp but all the potential problems that could bring to a stock GTI engine internals (not Ed30).
So I decided to go for option #3 and I bet lots of you would say go for option #4 the K04 conversion!!
Meanwhile, I decided it wise to run around in stock map and it did feel rather dull by comparison, though of course it's not!
Initially it's easy to think that none of this would have happened if I hadn't modded my car, but as she's only down on the power she should be (should be closer to 260 bhp instead of the 236 bhp), without being modded and going on the rollers etc, I might not even suspect anything was wrong and the situation become worse as the heat contractions make the crack bigger.
Apart from the obvious benefit of the quasi-religious experience of driving a fast modified car, I am convinced that running a modded car responsibly encourages far better care and maintenance.
^ Showing the wastegate housing cast with the exhaust manifold. K03 turbo is silver.
^ Showing inside the wastegate housing.
^ The crack was found on the rim as shown by the yellow broken circle.
It isn't possible yet for me to reopen the port to photograph the failure without special tools.
^ The arrow shows the connecting rod which opens and closes the wastegate (on my 'new' turbo).
JKM removed and inspected my turbo&manifold (it's one assembly) and, as suspected, the casing around the 'Penny Valve' Wastegate has a small crack. When I was chatting with VW Racing about my problem, they said it was probably in the Wastegate area or Penny Valve as JKM had already exhaustively tested other possibilities.
My original turbo is a Rev C, whereas my 'new' one is Rev G but there's no obviously visible difference!
Instead of trying so hard to meet boost requests that we were seeing >90% effort in the data logs, we are now seeing as little as 65% and mostly in the 70's - So now there's plenty headroom (tolerance).
JKM also set my Revo to Boost 6 instead of 7. It'll run 7 fine but we decided 6 just as an extra margin of safety.
So initially she making just over 240 bhp with a very healthy torque curve but we need to let the whole ECU learn the new setup and settle before another dyno session.
The dyno has been invaluable as a tool for assessment and diagnosis and then checking everything afterwards. Jim did some road testing with the laptop as well.
JKM are a great team - Jim is the mechanical expert and Keith the electronics expert and they specialise in VAG cars.
The probable cause of the crack is heat - Turbo's are subjected to extremely high temperatures - And a weakness in the metal casing. At first it's easy to regret that it didn't happen while still under warranty but I doubt very much if VW would have accepted my issue with my other modifications being present. There have been cases of metal failure in the K03 turbo on standard 2.0T FSI engines, so it's not a problem exclusive to remapped engines.
It's great to have that extra power back!
So far, so very good - But I shall have another dyno run at JKM to double check all is well after everything is more settled.
