GR86 Importing my 2023 JDM BRZ

I had a call today from Fensport, who have installed my HKS GT2 supercharger and are now tuning it. They said that boost with the standard restrictor supplied with the kit was only modest, with the fuel injectors running at 50% duty cycle. We discussed it and they wanted to install a 2nd air temp sensor by the throttle body so that they can tune more accurately. I gave them the go-ahead to do that. They are prepared to take the stock fuel injectors to 80% duty cycle by opening up the hole in the air restrictor. I gave them the go-ahead to do that, too.

We agreed that around 280whp (about 330bhp) would be a nice power number while preserving reliability. I'd be very happy with it. The MCA Traction Mod has been installed, too - perfect for traction with the additional torque. More news on Friday when I pick up the car.
 
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Just for fun, Copilot suggests the following...

Short version: with a ~50 mm opened-up restrictor and keeping injector duty around 80%, you’re realistically in the ~300–320 whp ballpark on a healthy FA24 with the GT2 and stock pulley, which is roughly 340–360 crank hp depending on dyno type and drivetrain loss.

A bit of context so the number isn’t just hand‑wavy:

Boost/airflow: opening the restrictor to ~50 mm will move you noticeably closer to the “no‑restrictor” behaviour—expect a solid step up in airflow and 1–2 psi more boost than the stock restricted setup, but not quite as aggressive as a fully deleted plate.

Fuel side: targeting ~80% IDC is exactly where most tuners like to sit for a street car; that IDC typically lines up with low‑300s whp on pump fuel on these motors with a decent intercooler and sensible timing.

Why it’s a range: intercooler efficiency, exhaust backpressure, fuel quality (your 99 RON vs 95), and how conservative your tuner is with timing and lambda will easily swing things by ±10–15 whp.

So: if everything is working properly and your tuner is honest rather than optimistic, I’d mentally anchor it at ~310 whp as a realistic expectation, with 300 being “it’s a bit conservative” and 320 being “conditions and hardware are really on your side”.
 
@tyu yes indeed, the HKS headers, HKS front pipe and Fujitsubo exhaust remove that as a bottleneck and the Cup Car intake helps on the intake side. No GPF and no charcoal filter in the airbox help, too.
 
Interim report from Fensport
They have opened up the restrictor hole to 44mm, giving 276g/s airflow with the injectors running at 66% duty cycle. This is producing 0.7 bar of boost, or 10.1 psi. They need a bit more dry road tomorrow and will eke out some more airflow and duty cycle before I collect it in the afternoon. To be honest, that's even more boost than I'd hoped for already. The good news is that the car is responding to it well, so all the exhaust mods were worth it.
 
The HKS supercharger installation is complete. Fensport did a superb job of installation and tuning.

Tuning Essentials
Final restrictor hole size 45mm
304g/s peak airflow
Injectors running at 70% duty cycle max
Boost 0.72 bar = 10.4 psi
Power 380bhp, 323whp (approx.)

Driving Notes
The immediate driving experience is exactly as with my previous two superchargers (Sprintex, Harrop), essentially feels like a 'bigger engine'.
From just under 3000rpm, pickup is strong and continuous in a virtual straight line ramping up to the red line. There are no dips or glitches, just continuous pull.
On the road, it drives as before when taking it easy in suburban areas. On the open road, it's a different entity as soon as the pedal is pressed further, revving keenly and pulling strongly in any gear, even in 6th and utterly animal-like in 3rd. I've set my rev warning at 6500rpm so that I just have time to change gear before hitting the limiter.
The sound is a whoosh of air quite like the Harrop, with the overrun making a different tone of whoosh (possibly the bypass).
It's a beautiful installation, OEM-like in quality and running in an OEM-like manner without any idiosyncrasies that I have noticed.

Photo
HKS Supercharger.webp
 
MartinT said:
The HKS supercharger installation is complete. Fensport did a superb job of installation and tuning.

Tuning Essentials
Final restrictor hole size 45mm
304g/s peak airflow
Injectors running at 70% duty cycle max
Boost 0.72 bar = 10.4 psi
Power 380bhp, 323whp (approx.)

Driving Notes
The immediate driving experience is exactly as with my previous two superchargers (Sprintex, Harrop), essentially feels like a 'bigger engine'.
From just under 3000rpm, pickup is strong and continuous in a virtual straight line ramping up to the red line. There are no dips or glitches, just continuous pull.
On the road, it drives as before when taking it easy in suburban areas. On the open road, it's a different entity as soon as the pedal is pressed further, revving keenly and pulling strongly in any gear, even in 6th and utterly animal-like in 3rd. I've set my rev warning at 6500rpm so that I just have time to change gear before hitting the limiter.
The sound is a whoosh of air quite like the Harrop, with the overrun making a different tone of whoosh (possibly the bypass).
It's a beautiful installation, OEM-like in quality and running in an OEM-like manner without any idiosyncrasies that I have noticed.

Photo
View attachment 41473
Click to expand...

That sounds great, I was not expecting that much whp from it. I bet it feels much faster.
Did they say anything about the clutch? Are you going to get wider tires? Did they remove the cold start?
 
Grblue86 said:
That sounds great, I was not expecting that much whp from it. I bet it feels much faster.
Did they say anything about the clutch? Are you going to get wider tires? Did they remove the cold start?
Click to expand...
Neither was I. Yes, it feels a whole lot faster (and it wasn't slow before).

They said the clutch should be ok but if it fails I will have an Exedy stage 1 installed, the same as in my old BRZ with the Harrop supercharger. No, I think the 225/40 Goodyear F1 on the stock 18" wheels have a good level of grip and I'm trying to retain the balance between handling and ride quality. The MCA traction mod definitely gives me more rear wheel grip and the STi springs are just right for the car. The cold start is minimised and only lasts about 20s.
 
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