S2 underestimated quality process demands:
This is a short list of it. I am not aware of what was user and what is Skunk2 related, but there were built rumours of a bad quality. But remember these guys were one of the first in the market and always went big and were quite successful with their parts NHRA, NOPI and other stuff. They gone through hard times and are still on the market, some improvements on the quality side were done. The Ultra Series is a step forward in design and material quality. For me I made with all US aftermarket companies, I ever bought parts, not the best experiences.
I won't compare them, but it seems to me there are several points causing it: time to market, lack of competence or wrong partners, not finished design process and what almost always is the case, customer does not intentionally the endurance testing for them. We have to remember, this is an enthusiast driven scene, which is valid for the aftermarket companies too. They have all no time and may also not the budget to finalize the design process properly, but of course their approaches to get there and their level of reaching it is different. It doesn't matter were you buy, there is a risk, which I price up into products when I buy from the US aftermarket for revise design or quality issues. But finally, there are parts, which saves a lot of time and money.
Compared to that, I never had quality issues with parts from Japan. Why that? Their market and culture is different. For an Japanese company reliability and reputation is cultural immanently of an much higher value, also there market is more based on circuit racing then on 1/4 mile like in the US. There design approaches align much more the durability factor and therefore their designs are not as extreme as and of better quality. You won't find e.g. cams specs from Japanese companies which compare to that of the US companies. JUN, SPOON, TODA, all of them have no high speed valve lift higher then 13 mm. Why? It is not necessary for their market, but durability is a demand on it, which is not the case for the 1/4 mile driven US market. There seems to count 3 numbers: peak values for power, torque as well as the 1/4 mile time. The curve shape of the torque is almost not of interest. Which is, if you run around a circuit for hours and gears count is lower then 100
.
So I wouldn't point to any of these brands and companies, just to parts, which are known to have a lack in design or quality, e.g. like the S2 Tuner-series camshafts, which are too hard on the seating ramp. The S2 Ultra series is are an improvement over those.
