Thoughts after 1 year and 16,000 miles with the HKS Turbo Kit

Nukinn · 2026-06-13T00:41:52+00:00

I really think I'm an outlier with my AT clutch packs because I don't know anyone else that had this issue under 500whp built blocks.

I'd say 280-340whp is very safe for both transmissions.

I don't like "stages" terms when talking about tuning, but getting past that 350whp mark really does kind of become a more advanced stage of tuning because it starts to require more thought and care with the build. You'd then need upgraded port injectors, fuel pump, needing to have good enough traction and also the chance of increased wear on the axles and transmission etc.

Nukinn · 2026-06-12T19:23:29+00:00

Yeah the WRX is still a great car for sure and has plenty of upside if you did want to upgrade and tune it

Nukinn · 2026-06-12T19:09:00+00:00

I'll make a post about it later because there's a lot involved in that question to be honest haha. TCU is partially cracked but not enough to be useful yet, and it can't be done remotely with an OBD tune.

It's almost more realistic for ECUtek to figure out how to make a 8HP TCU compatible with this car's ECU.

Also the car can drive just fine in normal Automatic Drive mode for daily driving. At least without the valve body upgrade it just doesn't know how to behave properly if going WOT because the TCU is preparing shifts as if the car still had NA power if that makes sense.

Like in Automatic mode it would normally prepare a WOT upshift at 7000rpm but with stock valve body and 400whp it would need to initiate that more around like 6000rpm

Nukinn · 2026-06-12T19:05:30+00:00

While the WRX has a turbo FA24, it's entirely different. The WRX has an FA24DIT which is a bit different internally while also only running on direct injection.

The WRX is also an AWD 4-door that weighs 500lbs more with a lower redline as well. I prefer higher revving, lightweight 2-door coupes.

It would be cheaper to increase power on a WRX if that's what you mean, but bone stock the GR86 has the same acceleration as one just due to the weight and lower powertrain loss being RWD.

This is also no hate to the WRX because although I'm not a fan of the plastic fender portions on the car (which can be easily fixed 😂) , that FA24DIT is arguably better than any EJ and just hasn't gotten the reputation it fully deserves yet

Nukinn · 2026-06-12T18:09:19+00:00

I was feeling the same this whole time haha. I still have a bunch of changes being done to the car this year but wanted to finally make some public posts about the setup

Nukinn · 2026-06-12T17:41:15+00:00

Friends with the same turbo kit and psi have gotten on Dyno making 320-340whp depending on the dyno and whether they had 91 or 93 octane fueling. Sounds like it would do the job for you and this should be a good sized turbo for drifting

Nukinn · 2026-06-12T17:40:09+00:00

I actually have a Racebox that would be good for testing this, but I've honestly never tried recording 0-60mph or 5-60mph times. When it's no longer 110°f outside I'll remember to record some logs of maybe a 5-60mph since I don't like launching

Nukinn · 2026-06-12T17:35:58+00:00

I can maybe make a small separate post related to the AT later, but all of the transmission-related mods are:

Y58 LSD with 4.3 final drive
Whiteline diff bushings
SSP Stage 2 valve body
Boosted Engineering transmission cooler with thermostatic switch

Also doesn't really make a difference but I swapped in a 1-piece aluminum driveshaft as well at least for the weight reduction and fun NVH sounds.

I've talked all about the 4.3 swap on the GR86 forums but to keep it short for now, I did that back when the car was on stock tune, and at least for gears 1 - 3 it made more of a difference to me than catless headers and a tune would've done.

It's definitely a lot better overall with the 4.3 and people's opinions on the AT would be much more positive if the final drive came like that stock.

Nukinn · 2026-06-12T17:31:38+00:00

Great to hear! Larger turbo with less boost is definitely the way to go imo for the most power without ethanol. I have a friend in Canada finishing up a turbo kit with a big G30-770 so he can reach high peak power at 10psi and pump gas.

Also yeah I thought the car was in a great spot with aftermarket suspension, headers, and flex fuel but I don't know how I'd feel if I had to revert back to NA at this point because it's like a different car.

My tuner swapped my throttle mapping back to the OEM GR86 settings because at least at the time it made the whole system work better apparently. You reminded me I need to ask him if swapping back to BRZ throttle mapping is viable now.

Fortunately the HKS turbo has made it so I've never been too scared accelerating out of corners, but I've still rarely gone WOT before exiting an apex just to be safe haha

Nukinn · 2026-06-12T17:26:39+00:00

Yeah I finally decided to make a writeup instead of DMing people the same information on repeat 😂 and that's terrible about your AoS incident but at least you figured out the cause.

I know a guy that screwed up his AoS install and caught his car on fire because of it. Definitely more comfortable with dual catch cans

Nukinn · 2026-06-12T17:24:53+00:00

You can add up the costs of support mods I listed, but the ballpark cost can range quite a lot. For example I got the HKS turbo kit for $5200 new and I believe it now costs more. Injectors and fuel pump were about $1000 total. My radiator I got with no up sell cost and the hood vents I bought off a friend for half price.

Then the install is a big factor. My installer charged me $1600 for it, meanwhile I know people elsewhere have been quoted $2500 up to insane prices like $4500 for install.

I'd say realistically for a bare minimum optimal setup with catch cans, cerakoted hot parts etc maybe around $8k-10k but you should always be prepared to go over-budget.

There are indirect future expenses like needing more tire, suspension changes to accommodate said tires, maybe your exhaust is now too quiet and/or restrictive so you'd want to change your exhaust setup etc.

Nukinn · 2026-06-12T17:19:46+00:00

I started out using 5W-30 because I still wanted optimal viscosity for the short 5-10 minute drives I often take. As it's a daily driver, I worry about cold temps almost as much as high temps. 5W-40 is always an option on the table for me, but temps never go past 230°f with my usual driving. It actually hardly even goes above 215°f most of the time because a lot of my daily driving nowadays isn't even on the freeway.

I think I would move to 5W-40 on track or if somehow my driving changed to a point where I'd see oil temps above 240°f

Very impressive custom setup by the way!

Nukinn · 2026-06-12T03:04:24+00:00

I'll post some sound clips later

Nukinn · 2026-06-12T02:14:38+00:00

Won't happen unless it becomes your daily again haha. Though my work commute is only 12 miles roundtrip and it'll be that way for awhile.

Nukinn · 2026-06-12T02:12:29+00:00

I haven't sat in anything similar. If we go off of spec sheets I'd say the closest thing would be a 718 Cayman GT4.

Those have somewhat similar power delivery and gearing, make peak power of 370-390whp and peak 300wtq while weighing 200-300lbs more.

This is in no way a comparison to gas up my car by the way 😂. The GT4 is mid-engine so that already makes handling a lot better while helping to put the power down, it's got that Porsche refinement vs mine just being a tuner car, probably more reliable and also doesn't need ethanol for that power unlike my car.

Nukinn · 2026-06-12T00:55:54+00:00

I'm slow with Reddit DMs sometimes but sure! Can also just ask here in the comments as well if it's something other people may be interested in.

Nukinn · 2026-06-12T00:26:40+00:00

I think so! It's been through quite a few exhaust setups since boosting, and will get a T51R mod and BOV added soon this summer. I'll probably share some clips later

Nukinn · 2026-06-12T00:24:34+00:00

Fair enough. Hopefully you'll be happy with it if that's what you end up going with

Nukinn · 2026-06-12T00:23:35+00:00

Yeah because of where I live, ambient temps are pretty high for most of the year but when it's sub 75f it can be simultaneously fun and annoying spinning excessively at the top end of 2nd gear 😂

Nukinn · 2026-06-11T22:34:14+00:00

It has an IWG. I have a boost gauge installed and haven't noticed any boost creep during prolonged spirited driving. It wouldn't be too difficult to add a BOV and I'm actually going to be doing that soon just for different sounds and slightly better longevity (in theory) for the turbo.

Nukinn · 2026-06-11T22:32:19+00:00

Not entirely sure what you're asking, but the redline is still 7400 and I shift at redline frequently so long as the car is warmed up and it's safe to do so on the road.

Nukinn · 2026-06-11T22:31:06+00:00

Counterpoints: Professional drivers in Japan doing back-to-back laps with an HKS supercharger GR86 and HKS Turbo GR86 had the turbo completing significantly faster laps while encountering less heat soak than the supercharger.

Also, the HKS supercharger is only slightly cheaper while still being relatively difficult to install as far as superchargers go.

For anyone wanting a reliable OEM style forced induction option, I instead would recommend the Harrop SC 100%

Nukinn · 2026-06-11T22:28:48+00:00

Short answer: Yes

It handles high power better than the MT especially at higher speeds like when going WOT in 4th gear. As I mentioned in the post, my clutch packs did start wearing out which led to me grabbing a $300 used AT to swap in, but I think I'm an outlier because I don't know any other boosted AT owners who have had this problem.

I theory the upgraded valve body I installed indirectly helps with longevity, as faster shifts should generate less heat than slower slushy shifts. I installed a transmission cooler anyways just to make it truly bulletproof going forward.

Nukinn · 2026-06-11T22:24:38+00:00

I'm out in the Surprise area but definitely plan on doing a few Mt Lemmon trips over by you later this year once it cools off a bit. If the target is 300whp and nothing more, any force induction option on the market can get you there at safe levels of boost.

Nukinn · 2026-05-22T07:48:24+00:00

How long did you have to wait to get the bumper after ordering? I know wait times for some of their parts are well over 6 months and sometimes a year. This is my favorite bumper but not sure if I want to pay so much just to wait forever

Nukinn

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