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”.
 
I wonder due having headers, and the lack gpf must help a bit at least for tuning purposes
 
@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.
 
Now i know why everyone was nagging me for an update an hour after i got my car tuned. C'mon, spill the beans!
 
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
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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?
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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.
 
That really is a lot of power. I'm quite suprised they've managed to get that much on the standard fuel system.
I bet it feels great to drive. Do you have a dyno printout? Also, did they do anything with the rev-hang? I recall them saying they can dial that back too.
 
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GRistopher said:
That really is a lot of power. I'm quite suprised they've managed to get that much on the standard fuel system.
I bet it feels great to drive. Do you have a dyno printout? Also, did they do anything with the rev-hang? I recall them saying they can dial that back too.
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No dyno chart. Yes, no rev hang but I didn't have much on the previous Abbey tune either.
 
MartinT said:
COST
I had set a drive-away cap of £32,000 with Torque GT before they bid in the auction. They reverse calculate all the costs (auction fee, mark-ups, shipping, registration) so that you know exactly what you will pay with no surprises and this system works very well. In the end, because they got a low bid price on the car (the Japanese love automatics and consequently manuals are not popular), my drive-away price, excluding the additional work I asked Torque GT to perform, was £28,800. I was extremely pleased with this price for a car that looked and smelled brand new.

INSURANCE
UK insurers uplift the insurance on all JDM cars, for reasons that have never been well explained to me. I knew it was coming, but the first quote from Adrian Flux, my existing insurer, shocked me with £1,800. For comparison, they were insuring my supercharged BRZ for £590. This was with zero no-claims bonus because it was a 2nd car to start with. I rejected the quote and looked around elsewhere. Torque GT recommended Howden and, sure enough, they were more reasonable starting with £1,400 with zero NCB. Now that I have sold the old BRZ and transferred the NCB over, I am looking at around £1,100 annually.

These are fully comprehensive, declared value £28,800, performance mods declared, I am 66 years old and garage the car overnight, living just outside a countryside village near Basingstoke.

ROAD TAX
This one surprised me. I thought Torque GT had made a mistake classifying the BRZ as a 'PLG' - Private Light Goods vehicle. When I queried it with Darren, he said they classify all their imports as PLG otherwise the DVLA reject them. Huh? Consequently, the road tax is twice the cost I had expected. I have sent the relevant forms to the DVLA to reclassify it as a car and will see what transpires. If they argue, I'll try sending photos and asking them where I should load up the goods? The BRZ has a 199 CO2 rating so just comes into a lower road tax band - if it's classified as a car.

SERVICING
I continue to have Abbey Motorsport perform all of my servicing and bigger mods. They use LiquiMoly Toptech 4200 oil and only proper OEM parts. They have a dyno and Hawker alignment facilities and a local friendly MoT station. My first service is due soon and will only be an oil change.

FUEL ECONOMY
My economy is running at 10.2l/km which translates to around 29mpg. It's a bit worse than the old car but my driving pattern has changed now that I don't commute 80 miles a day any longer.
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How did you get on with DVLA for the roadtax? My Alphard is classified as PLG too and being a Hybrid is way below the CO limit for £200 tax instead of the fixed £375 I had to pay on first reg.
 
ninjin said:
How did you get on with DVLA for the roadtax? My Alphard is classified as PLG too and being a Hybrid is way below the CO limit for £200 tax instead of the fixed £375 I had to pay on first reg.
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I could not win with them - they insisted that my BRZ had to be on the European database for emissions and, despite my pointing to the main Subaru CO2 data in their website and telling them that the GR86 is on the database and it's the same car, they wouldn't move. So PLG it remains.
 
I'm starting to think about wheels. While I like my stock 18" wheels with 15mm spacers, a true lightweight Japanese wheel beckons. I have always liked an odd number of spokes and, while I like 5 spokes on smaller cars, a 7 spoke design appeals. Enter the Wedsport SA-75R in 18 x 7.5. The weight saving by getting ET35 wheels in place of stock 18 x 7.5 ET48 and spacers is about 3kg per corner. I don't want to go wider than 225 tyres as the Goodyear F1 are outstanding, even with boost. I think my preferred finish is HBCII but I wish I could see them for real.

Does anyone run Wedsport wheels? Does this sound like a plan?
 
MartinT said:
I'm starting to think about wheels. While I like my stock 18" wheels with 15mm spacers, a true lightweight Japanese wheel beckons. I have always liked an odd number of spokes and, while I like 5 spokes on smaller cars, a 7 spoke design appeals. Enter the Wedsport SA-75R in 18 x 7.5. The weight saving by getting ET35 wheels in place of stock 18 x 7.5 ET48 and spacers is about 3kg per corner. I don't want to go wider than 225 tyres as the Goodyear F1 are outstanding, even with boost. I think my preferred finish is HBCII but I wish I could see them for real.

Does anyone run Wedsport wheels? Does this sound like a plan?
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I do not. I run SSR which they are also pretty light. Also run 225 width on them.
With your power i will be aiming to run wider wheels/tire, even more so if you are going to widen the supercharger restrictor.
 
Grblue86 said:
With your power i will be aiming to run wider wheels/tire, even more so if you are going to widen the supercharger restrictor.
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Interesting. I am amazed at how much grip the Goodyear F1 have, even with boosted power.
I'm reluctant to go with wider wheels and 235 tyres as all the effort to reduce weight will come to nothing.
 
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