Due to emission regulations, Subaru has put restrictive catalytic converters in the exhaust system. These restrictive catalytic converters do not allow for optimal exhaust flow to the turbo, thus top performance of the exhaust system cannot be achieved. Also, removal of the catalytic converter helps prevent the possibility of damaging the turbo if the catalytic converter breaks apart. GrimmSpeed’s Up-Pipe eliminates the restrictive catalytic converter and provides a larger diameter pipe that helps spool the turbo in a quick and efficient manner. There is a 10+ whp gain when using the Up-Pipe.
Adding a non-cat'd up pipe is one of the first things you should do to your Subaru. Arguably one of the best $/HP ratios. Another great feature of the GrimmSpeed up pipe is that the inlet is gasket matched so you have a perfectly smoothed out exhaust flow compared to the big step that that tiny stock inlet has.
The GrimmSpeed Up-Pipe is specifically created without an EGT bung. An EGT sensor is not necessary. If you would like to keep tabs on EGT temperatures the correct place to do it is on the exhaust manifold right after the exhaust ports, this is the only place where the correct temperatures can be taken.
The entire Up-Pipe is made of 304 SS and has a pipe-wall thickness of 2.0mm. The inlet size is 1.93" and the outlet size is 1.72". The pipe tapers down to 1.72” and acts as a funnel as it moves into the turbo allowing for the smoothest transition and best air-flow quality. The flex joint is not located in the bend, which adds to the life expectancy of the flex section. Our outlset size is a perfect match to the most common stock location turbos allowing for a smooth transition into the turbo. Since we are a porting company we make sure to have the smoothest transitions between pipes to allow for maximum flow and quickest spoolup(we call this "quality" airflow).
Quick Facts:
Quality Flex Joint - We've sold well more than 600 pipes with flex joints and have never had an issue with any stock Grimmspeed pipe.
Flow through Flex - There are no big steps in the flow path of the flex joint. The flex is not located on a bend so there is very minimal flow loss(if any) through the flex.
2.0mm Piping Thickness - almost all pipes on the market use a 1.5mm thick piping wall, not GS. We use a 2mm thick piping wall(33% thicker than all of our competition!)
Pipe to Flange Connection - Much smoother connection. Piping is ported flush with flange so there is no step into the pipe.
1.92" Inlet = perfect match to gasket allowing a little room for gasket movement(anything bigger, ie 2", will almost be guaranteed to put the gasket in the flow which is horrible for flow)
1.75" Outlet = Narrowing down from 1.92 to 1.75 acts as a funnel. Also very close match to most common turbos so you have much less step going into the turbo(unlike a straight through 2" which creates a huge step going into most common turbos vf's, tdo4s, etc)
Flex joint that is NOT located in the bend which adds life expectancy to the flex section. many other up pipes have a flex right in a sharp bend so all the exhaust/turbulence is hitting up against it.
Reduce turbo lag
Increase exhaust flow to turbo
The porting that is done on this product ensures the smoothest transitions between pipes and allows for maximum flow and quickest spool-up.
