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« Last post by pudding on Yesterday at 12:48:04 pm »
Yeah I wouldn't go past 1.6 bar personally. The journal bearings don't like it and it's starting to surge out of its efficiency zone at that pressure ratio, but should be OK if you do regular oil changes and have a better intercooler.
I found 1.5 bar to be the sweet spot for the power to lifespan compromise. Stock S3s ran 1.2 bar for 265hp, so there's not a massive amount of headroom. Borg Warner quote a sustainable 300hp max for the K04 but they're capable of more in short bursts. Poor tuning can crack them around the wastegate as bad tuners they don't control the EGTs properly, or turn off component protection completely. I've seen a complete fracture of the entire housing as a result of that.
Is your throttle body a VDO one? If so, I would swap it for the newer Continental one. I had surging and throttle valve flutter issues with the gen 1 VDO throttle after it was tuned.
How many grams/sec at idle are you seeing? Normally around 2.5 - 3 g/s at hot idle. When my MAFs used to go, it would dip below 2 at cut out. Surging from the turbo used to fling PCV oil up into the turbo intake pipe and soak the MAF. It's a really poor location. VW moved it much further away from the turbo on MK6s onwards for that reason.
VW just close the injectors on overrun and open them again around 1200rpm to give the idle control map time to kick in. The HPFP being mechanical will still be making pressure.
Need to be careful with the rail pressure drops as 25% lambda is the maximum compensation. Below 80-90 bar it runs out of options, retards the ignition (which also has an adjustment limit) and then it detonates because it's too lean.
You definitely need pump internals, and maybe the RS4 pressure relief valve as well as the stock one cracks open at 128ish bar.
I never had any problems with a Revision D, but there are some silly myths about them being 'designed to leak', which is nonsense. My DV+ failed. The rubber pad unglued itself and fell off. Really poor design.
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