I just want to provide some insight from a different opinion so please don't think I'm flaming but I am going to add some fuel (pun intended
) to this discussion.
In regards to the internals of the 2.0T FSI:
There has been some discussion about the rods and pistons only being able to handle 300'ish chp or whp.
Its important that everyone understands in regards to pistons this only applies to AXX engines which are the early 05 2.0T FSI engines sold as European spec only that had the crowned pistons and were true FSI and lean burn. The crowns on the pistons and casting techniques used to make them resulted in a weak piston with low heat tolerances.
The current engine and all 06+ engines have abandoned the crowned pistons, true FSI and lean burn. This results in a more traditional style piston manufactured more traditionally as well and has made the issues associated with the AXX or crowned pistons a moot point. Proper calibration techniques will yeild 350whp+ safely on the oem pistons.
The rods are good in both applications to 350whp+ as well.
In regards to Ko4 turbochargers and FSI fueling:
During our calibration of the S3 ko4 we have found that egt's like to shoot up very quickly. The reason is the close proximity of the turbine to the exhaust housing. This makes for a great spool but up top things get hot pretty quickly.
Due to high egt's, its then necessary to add more fuel to cool things off so you can keep adding boost and making more power. At about 280whp and 290wtrq the egt's begin to surpass the oem fueling's ability to keep it nice and cool. On oem injectors the on time is way beyond spec at this point and S3 injectors start to head that way a little north of 310whp.
Enter upgraded fuel pump. As you increase the S3 injector on time, fuel pressure begins to decrease more rapidly and it is then necessary to upgrade the fuel pump so you have plenty of fuel available for peak torque and to also keep the injectors supplied with enough fuel to lower egt's in the high rpm's. This leads to 310whp-330whp and 310wtrq-330wtrq.
Summary:
In order to maintain proper injector on time and low egt's with the s3 ko4 you are either limited to 300'ish chp with s3 injectors or oem injectors and no fuel pump or you can upgrade fueling to get closer to 330-340chp.
If you want to offer a warranty for a turbokit as an aftermarket or oem company it is very important that you are able to keep egt's down and injector on times within safe specs. If you can't do this to the tune of 330-340chp with a ko4 then you have to settle for what you can accomplish which seems to be about 300'ish chp if you can't find a reliable fuel pump upgrade that you feel you can offer a warranty with.
Modified by Keith@APR at 11:54 AM 1-22-2008