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

We are still progressing on our R35 GT-R harness bar and the second revision will be tested for the first time in another customer’s car at Laguna Seca on Thursday.  This newest revision should make the installation of the harness bar itself even easier for owners at the track and we can’t wait to test it out.  It should be installed by early afternoon today.  As before, we are holding off on showing pictures of the bar until it is ready to be fully released.  Hang in there friends.

Getting back to the ZCG GT-R… The car is still at SSP as it seems they have run into some issues when the car hit the 700wtq mark.  I’m still waiting to hear more on the situation and I will update you when I find out.

We also received a set of COBB Tuning sway bars for our car when it comes back from SSP.  They are high quality bars with two levels of adjustment for the front and three for the rear.  These will be put on as soon as possible because we have a few track days planned for this car as well in the near future.  It will be interesting to see how these change the handling characteristics of an already amazing car.

The VQ35HR engine in the ’07-’08 350z just continues to impress us here at Z Car Garage.  This last generation of the VQ35 responds so well to bolt on modifications that the sky is the limit when it comes to producing normally aspirated horsepower.  Yesterday we bolted on another Injen intake system and an Unorthodox Racing pulley to accompany the Nismo exhaust that was already installed on this customer’s car.

The Injen intake now grabs air from in front of the radiator almost directly in the high pressure air stream.  The quality and appearance of the intake is top notch and fit and finish is up to the standards of a company that has been around as long as Injen.  The pulley from Unorthodox Racing is a high quality piece machined out of aluminum and is supposed to weigh around seven pounds less than the stock piece (8.25 vs 1.32lbs.)  We actually weighed both pieces and found the stock pulley on this HR to weigh only 4.8lbs, go figure.  Maybe they had two on the scale?  Anyways, the pulley is the stock diameter so all benefits come from reduced rotational mass rather than an under-drive system.

They dyno results were right were we expected them to be, but that doesn’t make them any less amazing!  While the main horsepower gain comes on the top-end, there are notable gains throughout the mid-rage on the torque side of the equation.  From looking at the graph you will also notice that the modifications cause the torque curve to not drop off as quickly past 5,500 rpm.  The car now makes twelve more foot-pounds of tourqe at peak horsepower, you will certainly feel that in your butt dyno!

Since the two modifications were carried out at the same time I can’t say for sure how much of a difference the crank pulley alone made, but if you look back at the first Injen intake we did on an HR you will see what the intakes did by themselves on that car.  I know, different day, different car,  but can be used as some sort of a comparison.

We are patiently waiting to see more aftermarket suppoort for the HR engines to see what sort of power we can extract.  I want to see cams, intakes, new headers, and more ideas that I’m going to save for our shop to make.  Hopefully more is on the horizon.

The 350z with the built 3.8L VQ, Cosworth cylinder heads, and GReddy twin turbos fired up on the very first try today.  This combination has a super meaty exhaust note that leads me to believe that it will make killer power once we get in on the dyno.  Next are going to modify the exhaust system before we do anything else to take full advantage of the quick spooling GReddy kit.  Currently the car is only running a custom set of 3″ down pipes and 3″ catalytic converters out of a Dodge Viper.  I should have more information on the exhaust sometime tomorrow.

The rest of the car was finished some time ago, so it is really nice for the power-plant portion to come to a close as well.  As far as the interior, the car already boasts the latest in audio technology with an awesome double-din head unit form Alpine with a removable hand held GPS unit that is self contained in the head unit when not on foot.  This 350Z also boasts a host of Defi gauges to keep tabs on the vital engine stats as well as a Tein EDFC unit to control the shock valving in the Type Flex coil-overs.

I will have more pictures and some dyno info in the next few days.  I will also have my first drive in the car with the new twin setup in the next day or two so I will report back with my impressions then.  Good talk.

Now that our GT-R is making almost 650 whp, with more coming everyday, the drivetrain parts are certainly being over-stressed in their stock form.  SSP have decided to upgrade the axle shafts on the car in an effort to strengthen the system before any catastophic failures happen.   This is only one of many parts that SSP plans on releasing for the R35 drivetrain.  With this addition we are one step closer to having the world’s most powerful GT-R that won’t grenade it’s internals as soon as we put the power to the ground.

The new axles have an advanced design that increases the CV bearing cage strength and a couple other improvements.  SSP have been building high power AWD cars for some time now and it is nice to see their experience prove useful in the modified GT-R world.  The axles are made in house at SSP and they plan to keep them in stock and ready to ship at a moments notice.  Although they aren’t cheap, $2,399.00 isn’t too bad if you are trying to find the limit of what your GT-R can take.  Happy hunting.

The entire press release can be found after the “read more.”

…[read more]