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Stillen 370Z exhaust system
Stillen's Nissan 370Z exhaust features quality all stainless construction and makes a pleasant tone

Next we installed Stillen’s Exhaust System. The 370Z is cursed with a corked up stock exhaust and a good exhaust system should free up power. The Stillen system is a high quality part made of stainless steel. High grade polished 304 stainless is used in the muffler bodies and the exhaust tips. The under car tubes average 2.5" in diameter and are made of a mig welded easily formable grade of stainless like 409 with high temp coated for rust resistance, mild steel flanges. The Stillen system uses ultra free flowing straight through perforated core oval twin rear mufflers that are transversely mounted. The oval case allows good interior volume for noise control while still maintaining free flow.

The Stillen exhaust produced good top end gains starting at 5600 and getting proportionally larger all the way to the 8000 fuel cut. Peak power was 279 whp at 7500 rpm a gain of 7 whp with a peak gain of 11 whp at 8000 rpm. Peak torque was identical with gains coming after the torque peak with a peak gain of 6 lb/ft at the fuel cut. These are impressive results for a late model car with this particular dyno.

Stillen Nissan 370Z exhaust dyno sheet
The Stillen Nissan 370Z exhaust produced good top end power gains

Next up was Stillen high flow cats and dowpipes. The Stillen cats have a free flowing 200 cell count spiral wound metallic substrate.  The substrate is the honeycomb-like stuff inside the cat that the exhaust gasses pass though that cleans the exhaust stream.  A metallic substrate has thinner walls with less cross sectional area than the ceramic material used for the honeycomb in most factory cats. Thinner walls mean larger internal passages in the honeycomb and thus less backpressure.  Each passage is called a cell and a 200 cell count means that this honeycomb has large diameter cells for low restriction.  Stock cats usually have cell counts in the 400 range and thicker walls on the cells making for much more flow restriction.

Stillen Nissan 370Z high flow cats dyno chart
Stillen's Nissan 370Z high flow cats, like the exhaust provided good top end power gains


Stillen Nissan 370Z high flow cats
Stillens Nissan 370Z high flow cats have a free flowing 200 cell metallic substrate

The stock cats have a small 46mm inlet with a 60mm outlet, with tiny under 2" tubing.  The Stillen parts are a much bigger 2 1/2" or 68mm in diameter all the way through with smooth mandrel bends to really uncork the system in this area. The Stillen parts are high quality pieces featuring stainless steel construction. The Stillen cats, like the exhausts contributed to gains in top end power with the gains starting at 5600 rpm. The Stillen cats gave 3-4 more whp from 6800 rpm all the way to the 8000 rpm rev limit. This gives quite a bit of area under the power curve and complements the exhaust nicely.

Technosquare Nissan 370Z six speed ecu reflash dyno chart
Technosquare's Nissan 370Z ECU reflash does not give as large gains on an engine with bolt on's as it does on a completely stock car but the gains are still across the board and pretty impressive

Finally we reflashed the ECU back to stock to see what sort of gains the ECU contributes to on a car with bolt on and to better compare the results of the automatic transmission reflash that we tested last month. Although the peak gains were nearly the same as the completely stock car, the area under the curve was slightly less as you can see in the dyno charts. As the automatic transmission reflash gave 5-7 whp over a wide rpm range, the manual transmission reflash gave 10-12 whp over a broad powerband. As you can see, although the reflash is a pretty effective mod for an automatic transmission equipped car, it is more effective on a manual transmission model.

Stay tuned, we will soon be testing the Stillen long tube Gen 3 Intake and a JWT lightweight flywheel and clutch on the Killer Bee. It will be interesting to see how the light flywheel works with the Syncro Rev feature of the transmission.





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