Komseh,
Excellent information!
I’ve read read several posts in the forums regarding engine damage as a result of adding superchargers. Just by looking at the information you posted I have to think that poor performing injectors could be a direct cause. For example - where a cylinder runs lean under boost. If you are spending the money on a power adder I would think for reliability sake and, at the very least, you should clean your injectors or have them flow matched. Komseh had idle issues in NA but exaggerate this differences under full boost and I can envision damaging lean conditions within the engine. It takes only a second or two to destroy an engine.
To follow up on the OP’s info I found an article which I’m cutting and pasting below to preserve. It basically describes the exact issue that Komseh was experiencing and elaborates a bit more on the theory behind the issues.
http://www.aftermarketonline.net/Technical/2012/28202-/Multiple-problems-hit-cost-of-ownership
Pressure
[i]EVEN THE LONGEST journey begins with a single step’ is an often heard saying used in the context of motivating folk whom are finding it hard to begin a big task. During my feature job this month, a 2007 Audi RS4 V8 FSi with 60,000 miles on the clock, this phrase kept repeating in my mind. In my case though, I was soon wondering how I’d managed to get myself involved with this repair. Well, it started with a fault code.
The initial customer complaint was that the engine warning MIL was coming on and the vehicle was intermittently suffering from rough running – it was hesitating as well as misfiring and it had a flat spot on acceleration. The fault codes related to multiple cylinder misfires and an air flap implausible position. The driver had owned earlier versions of this vehicle type and was prepared for the ‘cost of ownership’. We discussed a few different scenarios and agreed a budget for initial assessment.
The FSi system has its fans and undoubtedly the technology used is top quality. However, there are inherent design flaws in the way it is implemented on this vehicle. In fact, there are three distinct areas for concern. Firstly, is the triple vortex oil separator design used in the crankcase ventilation system. This uses a vortex ‘swirl affect’ to throw oil particles out of the crankcase gasses prior to allowing them into the intake system. In theory this is brilliant but in practice, it doesn’t really work. The oil vapour reaches the relatively hot intake port and valves and makes a ‘nest’. It is not unusual to see the intake restricted to less than half of its original ‘clean’ size. This restricted breathing leads to flat spots in the performance of the engine.
Secondly, there were the problems with the EGR system. The direct fuel injection (FSi) system, when running in lean burn (stratified) mode, suffers from high combustion temperatures, due to the lean cylinder mixture. EGR is required to ‘pad’ the cylinder volume out with inert exhaust gasses rather than air. This means that a lot of hot exhaust gas and combustion particles re-enter the intake system; this bakes the intake system oil residue onto the inlet system. Also the direct petrol injection FSi system does not allow the fuel to act as a detergent on the ports as it is injected, unlike a more conventional system.
Thirdly, the direct in-cylinder fuel injectors face the harsh environment of the combustion chamber. This means that they can suffer from a build-up of carbon on the tips and, due to the higher than normal injector temperatures, lacquer or varnish is said to occur inside the internals of the injectors restricting fuel flow. Direct petrol injection is a great way of ensuring maximum utilisation of the fuel injected with characteristics like great atomisation, precise metering and excellent mixture formation. However, you’d be right if you are starting to think that the FSi engine has the potential for some real issues.
Actuator test
I used the Autologic to run an actuator test on the intake manifold flaps, both sides of the ‘vee’ seemed to be moving. On closer inspection though, the right hand bank wasn’t quite as it should be. Using the borescope, I could see that the flange attaching the actuator to the flap shaft had a large crack which prevented proper movement (access in situ is a real problem). It looks as though the manifold would have to come off to progress the repair.
Next, were the intermittent running problems of misfire/flat spot/hesitation. The plugs had been replaced on a recent service but I chose to remove these and check the coils and plugs for serviceability and signs of mechanical cylinder malfunction issues. All looked good. I used the pressure transducer in the cylinders whilst I was examining the coils and plugs, running a compression test, to rule out valve train malfunctions (sticking valves). The MAF sensor also checked out fine when tested on the scope.
I used the diagnostic smoke leak detector to flush out any minor manifold air leaks, which may cause similar issues, but this test passed O.K. as well. On scoping the ignition system on roadtest, the firing lines were quite high and the spark line voltages were kicking up at the end, indicating a lean mixture even during non-lean burn mode.
Misfire counting
Using the live data cylinder misfire counters, I could see random cylinders incrementing the counter. At the same time, the oxygen sensors were reporting excess air. The gas analyser didn’t show a significant increase in HCs (of course, these may have been cleaned by the cat converter if there were any). At this point, I considered mixture problems (intake coking/injector poor flow) to be the root cause, so I had to take the manifold off after all, just to access the injectors. On removing the manifold, I could see that the intake ports were extremely clogged; they needed remedial cleaning as well as an in-situ de-coke to enable the engine to breathe properly (Figure 2) . I updated the customer and he sanctioned the work.
The fuel injectors were removed and tested on the ASNU fuel injector service machine. The spray patterns from the injectors were uneven; the final flow test (Figure 3) highlighted a large imbalance between injectors. A 40 minute session in the ultrasonic bath, followed by a reflow (with new filter baskets) showed that the flow was much more even (Figure 4) .
Following the intake flap diagnostic trouble code, I inspected the underside of the manifold and could see more clearly where the control rod had detached from the arm. These were not available separately as they come assembled as part of a new manifold, which costs an unbelievable £1,900+vat!
Once the V8 was back together, I reset adaptations and ran through a throttle re-learn. Idle was nice and smooth and there was no misfire. The owner commented that the vehicle pulled much better and was a nicer drive altogether.
Customers often want to know the cost of the repair upfront. This is never easy to do. A staged approach is considered by many to work the best. It is easy though to see how a ‘simple’ fault can end up in a complex repair and communication is the key to maintaining customer confidence. The Audi’s fault was larger than the initial diagnosis but the cost ‘vs’ value equation still balanced, however, it’s easy to see how either lower value vehicle could be easily written off or a higher value vehicle, as the owner who can’t really afford to run it. [/i]
Leads to several questions:
Are there any newer better injectors? Updated spray patterns? Does that even matter?
Per the article is the EGR hot air injection preventable?
Is there a better oil separator design?
