Yesterday we installed a set of Stillen high-flow catalytic converters (HFCs) onto the 350z that received the Injen Intake system and the Unorthodox Racing lightweight pulley last week.  We’ve seen how these HFCs have improved the power band in the past on other cars but it’s always nice to back up good results.  Again, this car is equipped with a Nismo exhaust system, unlike the other car with these mods which has a Bassani exhaust.

The Stillen high flow cats are a high quality piece but as with all exhaust modifications where the stock catalytic converters are removed we were interested to see if there would be any increase in exhaust rasp.  As you remember this was a small issue that we had to resolve on the red HR car that had the Bassani true dual system with an x-pipe.  The Nismo system is much different, it comes from the cats into a 2.5″ to 3″ Y-pipe (stock is 2″ to 2.5″.)  From there is a single 3″ pipe, with resonator, back to a factory style (but larger diameter) rear muffler.

This car with the HFCs installed exhibited almost none of the rasp that has become associated with the dual exhaust cars.  While the exhaust note was very nice, you can see from the dyno graphs that this car was a few horsepower short of the Bassani 350z.  The cars were dyno’d on different days but all the results are SAE corrected to get them on as even a playing field as possible.  In their uncorrected forms, both of these cars are putting down over 300hp to the wheels. Very impressive.

Below you can see the run comparison with and without the HFCs.  The Stillen cats gain around 10hp and 10lb/ft of torque at the wheels throughout the rev range.  That’s certainly power you will feel on the road which makes this change almost mandatory from a performance aspect.

Here are the graphs that show this customer’s entire power gains over the past week or so and the comparison between the this car and the earlier Bassani equipped car.

We are trying to get the ball rolling with a header and camshaft comparison for the HR engines and maybe an turbo install in the near future to show all of you what is really possible with all available modifications.  We can’t wait to make more “RELIABLE” power from the HR series.

Link:  Other HR related posts