Hi everyone,myoo uk recently broke a rod and smashed a hole in the crank case.I had a few mods,turbo smart dump valve/k&n 57i kit,boost bleed valve and full magnex de-cat.The car was still under warranty but was'nt much use as the garage came up with this explanation why the car went bang,it goes like this.The removal of the forward cat on this vehicle removes any restriction through the exhaust and as such the computer that fuels the engine for full throttle even at idle and creates full boost to quickly,thus dumping fuel into the crank case via the piston rings.The engine and computer are designed to run on back pressure through the exhaust and this can only be rectified properly by re-mapping the computer. (surley this is bull s**t). Also i was told that the fuel was also mixing with the engine oil.Can anyone help? is this true? are there going to be thousand's of scoobies about to blow up?

 

There are a few grains of truth hidden in there amongst a whole beach of b*ll*cks.

If that is exactly what the garage has told you, they are pulling your chain a bit.

Decatting a UK car will not cause it to explode or fuel at idle as it does on full throttle (God, I'd love to see that if it did), neither does the car/engine/ecu/whatever NEED back pressure. If it did, why would thousands of turbo car owners decat their cars?

What is a more likely cause is running too much boost through the bleed valve. What boost was it running? and/or using crap fuel.

Whilst the full benefit of a decat can be exploited by a remap it is by no means necessary.

 

If this rod failure was based on a rich fuelling problem, the only thing in your post that stands out to cause that is the dump valve. I'm assuming it vents to atmosphere...? VTAs have been known to cause bore wash, but would that result in the snapping of a rod...?

The failure was probably due to the exact opposite of their diagnosis - lean fuelling, leading to det. There are a couple of possibilities that could have caused it...

1. As Rich says, excessive boost. And what is classed as excessive depends on supporting mods and octane level of fuel. If the only mods you've done are what you've posted, I'd say excessive boost would be anything over standard (assuming using normal Unleaded), anything over 16psi (assuming using only Esso Supreme or Optimax), or anything over 18psi (assuming Supreme/Optimax + good octane booster like Millers or NF). But those are rough estimates...!

2. Failing MAF sensor. Quite likely given that yours is a MY00. Do you know when it was changed last? What panel filter was being used prior to the induction kit? Is the induction kit secure (ie. no vibration)? Or have you oiled it recently...?

I'm guessing you don't have any monitoring equipment, such as Knocklink, AFR gauge, boost gauge? These would have given you advance warning of the pending failure (assuming it was caused by lean fuelling).

Personally, just to satisfy curiosity, I'd ask them to inspect the piston crowns for signs of det. Is this a Subaru dealer? I'm surprised they even remotely entertained the idea of a warranty claim, considering the mods you'd made...