Leaderboard

I currently have these tyres (got them cheap as chips through a mate) They have surprisingly good reviews online - especially when compared to other tyres at a similar cost Previously had the neuton nt sport 2 tyres too which were mint and lasted the distance

So I have been giving some thought over the weekend to why stock location turbos on Subarus always deliver relatively mediocre results. Why is it that turbos that routinely deliver 300wkw+ when installed in a rotated/twisted setup (i.e. GT/GTX3071R) get more like 250-260wkw when installed in the stock location? I believe the answer is all in the turbine housing. In order to retain "stock" fitment, the turbo cannot alter the relationship between the location of the uppipe flange and downpipe flange. This in turn forces the position of the turbine wheel; this is also forced by the location of the turbo's inlet having to go under the intake manifold. Because these locations are fixed, there is a hard limit on the size of the volute (the channel the exhaust gas takes through the turbine housing), which also limits the size of the turbine wheel. Furthermore, if you increase the size of the turbine wheel you take up space that is needed for the volute, so you just shoot yourself in the foot - either you have a big, high-flowing turbine wheel and feed it with a straw, or you open up the volute and then choke it at the turbine. This gets a little bit disguised by manufacturers claiming, for example, that their stock location GTX3071R has a 0.84AR turbine housing, but this is simply a ratio of two sections of the volute, it has nothing to do with the actual size of the housing. I guarantee you a bog standard Garrett T3 0.84AR housing for that turbo has a way, way larger cross-section. Twin-scroll does slightly resolve this, depending on the turbo, as you can have two volutes side-by-side and thus gain considerably more area. When you choke the exhaust flow you end up with high pre-turbine exhaust backpressure; I have a theory about this causing exhaust reversion at certain boost/EBP levels where the exhaust valve spring pressure isn't high enough to completely close the valve, causing knock and crap power. EDIT: Side note on why US cars seem to do better on stock location: completely aside from how half their dynos are just complete works of fiction, I believe that a lot of the US "stock location" turbos just completely ruin the position of the downpipe; something we can't do because of steering/brakes components in that area, and then they just don't talk about how none of the downpipe brackets line up any more and the midpipe fitment is a bit S***. I tried to install a US-spec "stock location" turbo once and the fitment was utterly S***. Feel free to tell me I'm dumb