HKS Hi Power reduced HP on Nismo cars?
 

I saw a comment.... that the HKS Hi Power exhaust resulted in a reduction of HP when installed on a 370Z Nismo. Can anyone confirm? It would be surprising to me if true.

nismo exhaust was made by HKS, (at least the one I had was)
Doesn't seem possible they would make their hi power more restrictive.

This isn't unheard of especially if you do not retune after a full exhaust system install. Sometimes the so-called "hi power" exhaust systems are made with much wider diameter piping which sometimes is overkill for a stock engine resulting in a reduction of low end torque and/or high end HP. What's also interesting is that most of the 18 HP gain on the Nismo cars was achieved by the exhaust system redesign. So the OEM Nismo exhaust is not too shabby, just quiet as f**k.

I believe the HKS is a full 2.5" design through and through. I'm not entirely sure on the "stock" Nismo exhaust that comes on Nismo cars. I wanna say I recall that even the Nismo cars "stock" exhaust has pinch points for clearance? Leading to some points in the exhaust being under 2.5", which the car is tuned for. So if you put a full 2.5" exhaust on a car that isn't tuned for it, NA at least, there's a possibility that power could be lost because tune optimization? Spit balling here, not preaching facts, just thinking out loud.

60mm piping or 2.36
https://www.hksusa.com/products/32009/BN004/1496

I've got the Hi Power on my Nismo. When my car was supercharged, I upgraded my supercharger and while it picked up a ton more boost, it lost hp. While trying to figure out if there was a restriction somewhere. The shop that built and tuned it disconnected the exhaust and ran it on the dyno. It only gained a few hp with the exhaust disconnected. With my FI tt kit, the car made 745whp with the Hi Power. I love the exhaust. Quiet, no drone and has a great tone.