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Dyno Tune Thursday – Does a stock cat-back restrict power on a turbo car?

Here we had the ability to compare, in relatively close succession, the same car dyno tuned with a 3″ downpipe and stock cat-back and then with a 3″ cat-back.  The results were quite surprising considering we had expected to see maybe 5HP difference at the most.  While this is only one test I believe it goes to show that any restriction in the exhaust of a turbo car will hurt power.  This car gained 15WHP and 15WTQ peak.

Event: Dyno Tune
Location: Touge Tuning, Mississauga Ontario
Ambient Temp:
Elevation: 249 ft.
Weather: 18C
Car: 2013 Subaru WRX STi
Tuner: Sasha from OnPoint Dyno
Dyno Info: Dynapack
Transmission: 6-speed
Gear: 4th
Stock Cat-Back Peak HP at RPM: 276 @ 5325RPM – SAE J1349 (2004) Corrected –
Stock Cat-Back Peak Torque at RPM: 310 @ 3800RPM – SAE J1349 (2004) Corrected
3″ Cat-Back Peak HP at RPM: 291 @ 5175RPM – SAE J1349 (2004) Corrected –
3″ Cat-Back Peak Torque at RPM: 325 @ 3700RPM – SAE J1349 (2004) Corrected
Baseline HP/TQ for Stock 2010 STi on same dyno: 228WHP/240WTQ
Target Boost: 19PSI
Fuel: Petro 94

Mod List:
-Custom Dyno Tuning by OnPoint Dyno
-3″ Catted Downpipe
-Stock Cat-back
-T1R Cat-Back Exhaust

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