Over the past 7k miles I had noticed an issue becoming more apparent. I heard what sounded to me like air leaking inconsistently. The issue happened when under moderate engine load between 2-3k rpm. This was initially rare but became more common as time went on. It also seemed to happen when at WOT but wasn’t as loud or consistent. The other odd thing was the issue would happen less as the engine got warmer. My initial theory was heat caused whatever was leaking to expand and seal better.
Troubleshooting the issue
At first, I thought it was a diverter valve leak or an intercooler pipe that had a split in it. After doing some logs, boost looked good. I compared specified vs actual boost as well as manifold pressure and no noticeable loss was happening. Performance still felt good so I wasn’t losing any significant amount of power if any. I decided to change the diverter valve anyways, it’s a quick job. The OEM J reversion diverter valve was switched with the Turbosmart EM DV. As I expected this didn’t solve the issue, but it was an easy change so worth trying.
At this point, I have determined it’s likely not a boost issue. I pulled off the turbo inlet pipe to check the intake side of the turbine wheel of the turbo. There was some movement in the turbine wheel both in and out and side to side. The blades looked intact and I didn’t see any noticeable scoring on the sidewall. It was an odd angle though and the lighting wasn’t the greatest. This wasn’t a good sign but also wasn’t an exceptional amount of movement either. Checking the exhaust turbine side would need the downpipe removed and I didn’t have the setup for that at the moment.
While getting my valve cover resealed I asked the shop to give it a quick look. They came back and said it was definitely the turbo but the issue wasn’t too bad yet. They said to keep on running it and monitor the sound to see if it gets worse. I am not comfortable with having such an important piece failing catastrophically when it could have been prevented. If it failed it could take out my catalytic converter or worst put metal shrapnel through the oil or coolant lines into the engine.
So whats actually happening?
When the turbo is at a high RPM building boost fast to meet ECU targets the turbine is hitting the sidewall of the turbo housing inconsistently. This is not unheard of on earlier reversions of the turbos in the GTI/R. My turbo was a reversion G (06K-145-722-G) with a car build date of 07/15, so it’s an early production unit for sure.
The issue is a bearing breaking down and causing the shaft of the turbine wheel to have more movement than it should. The turbine is then scraping the sidewall of the turbo housing but only when the bearing isn’t holding the shaft straight. This is what caused the inconsistency of the noise which threw me off. So even a little movement in the shaft is a problem for the blades hitting the sidewall. My turbo had not completely failed yet, but it was going to if I keep running my car in this state. I don’t like the idea of a ticking time bomb in my car.
How should we fix the issue?
I briefly thought about upgrading to a bigger turbo but don’t want to deal with a non-OEM downpipe due to California laws. This makes deciding against going for something like an EQT Vortex Standard or IHI IS38 easier. I also prefer my torque down low and the bigger the turbo the more the power range moves up on the RPM scale. I would also have to redo all my tunes and that’s just too much money for me. So I ruled this option out rather quickly as financially not viable and inconvenient.
I could send the turbo off to be rebuilt but that means having a shop take out the turbo and hold the car on their property while that’s being done. Downtime would be weeks for sure. I would also have to research places to get it rebuilt which is another rabbit hole I rather not go down. Downtime would be too long and would inconvenience the shop I use more than I would like. It also didn’t seem like it would be much cost savings.
I also for a short second debated buying a used IS20 as they are so cheap. Many upgrade to something bigger leaving the market flooded with them. But who knows what reversion of the turbo I would get, how many miles are on it, and if it was abused? It’s just not worth the risk and labor to go this route. So I will just get a new IS20 turbo instead.
Pricing and which turbo/vendor
A new VW branded reversion M Part# 06K-145-874-M which is the latest IS20 at the time of writing goes for $1350 from VW. An unbranded one by IHI rev M is about $950 from ShopDAP but sadly this was out of stock. The OEM one from ShopDAP is $1100. A VW rev M IS20 from FCP Euro is about $1300. A few things to note here.
The OEM manufacturer of the OEM IS20 is IHI and the only difference to the unbranded one is that it doesn’t have VW logo’s on it and the warranty doesn’t go through VW. The VW IS20 also comes with a diverter valve though. The IHI turbo has a warranty of 1 year through ShopDAP. FCP Euro has an interesting policy where it warranties the items it sells for the lifetime of the car. You just have to send them back the broken one after purchasing its replacement and then they will give you a credit once received. You can read more about the warranty here.
Finalizing the plan and now to fix it
I wasn’t going to purchase the OEM IS20 from VW since it’s more money with no benefit. Going over tax/shipping/discounts there is a $400 difference between purchasing the OEM IS20 through ShopDAP and the OEM IS20 through FCP Euro. It took 5 years for my Rev G (06K-145-722-G) IS20 to fail. Which was a reversion known for the issues. So I decided to go with the cheaper OEM IS20 from ShopDAP. I do like their YouTube videos and am happy to support them.
The car went to my usual shop that I trust to do the job correctly. They switched out the turbo without issue and I had the car back to me the next day.
Noise is now completely gone. Everything feels great and got a nice drive in yesterday. The car is now just like it was before.
I don’t feel this issue was caused by any of my modifications, they may not have helped but did not cause the failure. I believe this was just a manufacturing issue that finally reared its ugly head. With the checkered past of this turbo model reversion, I am not surprised it had an issue and am just glad I caught it early enough not to cause serious damage.
Sorry if this seemed like a boring resolution for a failing turbo. There was no catastrophic failure, no real surprises, and I replaced it with the same thing. I have thought about this exact issue a lot over the years as I speculate about it here so I was prepared for this. In the end, I am really happy with my current setup and didn’t want to change it. It’s a great car and even though the GTI is well known I still think it’s underrated in the performance world.