Tatsu333's 2020 BRZ Sport Tech RS

[Compelica]

To add - got this info someplace else. Left is 1st gen, right is 2nd gen. Thanks @Jianlun

[Tatsu333]

OK - FA24 OEM headers and over pipe are on! I've reflashed my ECU back to 100% stock (I had been running some changes for cold start only with the ACE headers to try and quiet it down a bit), and went for a bit of a drive.

First impressions are as expected. It feels a bit more linear through the power band on full throttle pulls (I did 4 pulls from 2,000 rpm to redline - three in 3rd gear, and one in 2nd) with a *slight* soft spot just before 4,000 rpm, and it also pulls more strongly up top right to redline than I remember with the stock header. Driving some of my normal around-town roads, I don't notice any significant loss of low-end torque either. It pulls strongly away from stops / traffic lights / tight corners, even uphill from low revs. The sound is a little bit deeper toned in the mid-range than I remember with the stock FA20 header, but otherwise just as quiet (again, as expected).

Bear in mind that this is all still with the Billet Power Blocks installed, which shift the power curve down the rev range a bit, so someone else's experience with the FA24 headers on an FA20 might be a bit different. Also worth remembering that it's been four months since I had the stock headers on, so my recollection of how they felt and sounded may be hazy...LOL.

Vs. the ACE headers, I'd say it doesn't feel quite as strong in the midrange and maybe a *little* more restricted up top, but feels like it pulls away from stops and low revs more smoothly.

Anyway - overall, I'm happy with it so far.

I'm going to do a BUNCH of driving around under various conditions over the next week or so to give the ECU some time to make adjustments, and then I'll try to see about getting it on the same dyno as my previous pulls to see how it does on the stock tune.

EDIT: Darn - I just found out that the shop where I had done my previous dyno runs has closed down. So, no apples-to-apples comparison is possible, unfortunately.

[Tatsu333]

OK - on to the next project! Since I have five days where I don't have clients in my garage, I'm going to try and get everything outstanding done on my car.

Next up after the header swap is refinishing my MCA Traction Mod brackets.

With at best 16,000 kms on the car since they were installed in November 2021 and very little winter driving, I was a little shocked to see how badly rusted they were when the car was up on the lift back in May, so this has been on my mind for the last four months.

Here are some pics of them after removal:










...and here are a couple of pics after cleaning them up the best I could with solvent and a wire brush and then brake clean:






After letting them dry, I hit them with a coat of Tremclad Rust Reformer, and now they have to dry / cure for 24 hours before finishing:




I'll be finishing them with 2 or 3 coats of Tremclad Professional rust paint tomorrow, reinstalling, and then I'll probably spray some Kleen Flo Honey Goo around the assembly for a bit of extra protection.

While I'm waiting for the Rust Reformer to dry, on to my next project... (I'll update this post with further progress on this project tomorrow)

UPDATE 2025-09-28: Refinishing is done, and MCA Traction Mod brackets are reinstalled. The driver's side went in no problem, but for some reason the passenger side one was VERY difficult to get back in place. Took a lot of swearing and levering to get it to seat up in the stock bracket and align the holes, so of course my nice new finish got all scratched up.

Here's a couple pics of them before reinstalling:





Anyway, it's all back together, and I sprayed the whole assembly with Kleen Flo Honey Goo afterwards as a further layer of protection against corrosion. While I had the car up, I also increased the ride height all around to the maximum ride height supported by the RCE SS1's to give me a little more leeway with driveway ramps, etc. It's only 5-10 mm higher than before, but it's something!

[Tatsu333]

My next project today was to try the MAC Lifter Kit for fixing the bumper sag / gap / alignment issues. For context, I broke one of the loops (the one nearest the headlight) on the bumper side of the driver's side after hitting a driveway ramp a little too quick and smacking the bottom of the bumper on it.

Replacing the clips didn't help, and the regular metal repair plates from Etsy improved things a bit, but it still didn't fit quite right. Then I stumbled upon the MAC Lifter Kit.

The parts arrived from Australia just in time for this weekend, so I thought I'd give them a go. Since I already had the other repair plate installed on the bumper, I decided to just stick with that and only use the body side bracket from the MAC Lifter Kit.

While looking up the instructions for installing the kit, I came across this video, where the guy pretty much fixed the bumper gap by using a bolt and nut in place of the push pin at the top of the side marker bracket. I wish I'd seen this video before spending hundreds of dollars having two different repair kits shipped from Australia! Anyway - here's a link to the video:

So before installing the MAC Lifter Kit, I decided to just give this a try to see how it did. I removed the stock bumper bracket before doing this, and with just the bolt holding things in place, it actually looked OK:





That said, while the vertical gap was nice and tight, the bumper cover still didn't quite align flush with the fender. So, on to the MAC Lifter Kit!

The product page said that trimming of the headlight bracket would be needed for install, which I wasn't really keen on doing. Besides which, with the repair plate in place, that front loop was seating properly below the headlight / above the headlight bracket. Instead, I decided to cut the MAC Lifter Kit bracket short so that it would fit without cutting the headlight bracket:



That allowed it to fit just behind the headlight bracket when installed. I lined it up so that the smooth top edge of the lifter bracket was in line with the top of the headlight bracket, and maintained a consistent gap along the length of the bracket:





That got the bumper cover nice and flush with the fender line. I then installed the serrated flange bolt and nut (one of the stainless-steel M6x1.0 x 16mm sets that came with the MAC Lifter Kit - since I'm only installing the driver's side right now, I used one of the leftover sets) in place of the push pin at the top of the marker light bracket to secure things even more for a little extra insurance, and the fitment is PERFECT!!!





Since I had the side marker light out, I decided to finally get around to upgrading the side marker bulbs to LED's as well (they were the only bulbs not already switched over).

I'm going to keep the other MAC Lifter Kit pieces and previous repair plate for the passenger side for when I eventually need to fix that as well (right now it looks fine).

While my install wasn't typical / as recommended by the instructions, I'm happy to not have had to cut the headlight bracket for fitment. If you're looking to fix your bumper sag, gap or misalignment, I'd highly recommend the MAC Lifter Kit AND the trick of replacing the push pin at the top of the side marker light bracket with a bolt and nut.

Overall, I'd say this was a big win!

[Tatsu333]

I've had the cabin side of the sound tube blocked off with a 3/4" PEX plug since a week or two into owning the car, but just never bothered to remove the tubing, etc. in the engine bay. I figured while I'm waiting for paint to dry (literally) on my other project, might as well get 'er done!

I used the low cost DIY route, buying a 1-1/2" flexible pipe cap from Home Depot (for about $6 CAD including tax). It fit like a glove over the port on the intake tube.

[Tatsu333]

OK - with most of the little annoyances with my car sorted out and ZERO budget until I sell the ACE headers and other bits and pieces, I've started delving into self-tuning on ECUTek again. Available technologies have come a LONG way in the couple of years since I last dabbled on this side of things, most notably the availability of AI tools like ChatGPT, so I'm going to leverage them to hopefully make this easier.

I'm working on building out some project instruction files and prompts to make use of ChatGPT in analyzing my ECUTek logs and making tuning suggestions based on what is found in them. This was one of the most time-consuming parts of my previous self-tuning efforts, and while it's not instantaneous feedback by any stretch of the imagination, it's a LOT better than manually going through a 40 minute long, 53,000 line log file!

One big caveat here - ChatGPT WILL make mistakes and / or make stuff up if you don't constrain it with some very specific instructions or prompting.

For example, on one initial pass on MAF Scaling before building out the instructions, it was telling me to increase the g/s values for a section of the MAF Scaling table where LTFT's showed the ECU was consistently pulling fuel (which would indicate that the feedback from the O2 sensors was saying LESS air was coming in for a given MAF voltage than expected). So what was really needed was a LOWER g/s value (so that airflow was being correctly reported), not higher.

A VERY basic logic error that you'd think a "smart" AI wouldn't make, but it did.

So - short version: AI tools like ChatGPT have the potential to save a lot of grunt work when it comes to data analysis without purpose-built software, but don't trust them to necessarily provide you with the right answer. You need to build in some checks and balances with your instructions / prompting, AND spot check things to make sure it's on the right track!

Once I have things built out and tested, I'll be happy to share the project files for other people to try.

EDIT #1: And of course, now that I've decided to go this route, my laptop decides to die... Looks like one of the hard drives failed. Trying to repair it now, otherwise I have to spend money I don't have to get a new laptop. To be fair, I guess, it IS eight years old. Just annoying, and not in the budget at the moment.

EDIT #2: After many hours of fighting with it to try and get my laptop back up and working, I decided to just bite the bullet and picked up a new (to me) laptop instead. Now getting that set up, and then I'll be back on my way with self-tuning...

[Tatsu333]

I'm making really good progress with building out the instructions, etc. for ChatGPT to assist with self-tuning using EcuTek. So far I've dialed in the process for tackling MAF Scaling and instructions for evaluating performance improvements based on before / after logs.

I've also got some preliminary work done on the process for adjusting cam timing for NA mods like headers, BPB's, etc. based on before / after logged data. I'll be testing out the cam timing changes the next time I have free time on a good weather day to do back-to-back WOT pulls.

Once that's done, I'll move on to dialing in ignition timing next.

[Tatsu333]

Between this reported failure and my experience with corrosion of the brackets despite very low mileage, I've gotten really nervous about the durability of my MCA Traction Mod V1. So, I've decided to replace it with something else.

In searching around this morning, I came across this option that I had never seen before:

https://www.justengineering.ca/shop/...traction-arms/

With it using a similar configuration to the MCA's but with what looks to be MUCH more robust materials and finish (and it being a Canadian shop in Quebec producing it ), I decided to pull the trigger. It's a bit pricey, but both relocates the pickup point and replaces the trailing links, so it saves the cost of the STI trailing links as well.

Of note is that it moves the pickup point both down by 50mm AND forward slightly, and the new trailing link is longer as a result. They say the forward position and longer arm are "to reduce the toe gain curve as much as possible to so it became more linear."

Anyway - there's a little over $600 CAD I didn't really have available now gone, but it will give me a bit more peace of mind...LOL.

[Tatsu333]

My new replacement for the MCA Traction Mod brackets just arrived - the Adjustable Traction Arms from Just Engineering. They have a design that combines elements from the MCA and GP Sports designs, and replaces the trailing links as well.

The construction is pretty beefy, especially compared to the thin stock used for the MCA brackets, and they have a heavy silver powder coated finish as well, so I'm hoping for much better weather durability than my MCA brackets.
Here are some initial pics now that I have them in my hands.

Very well packaged to protect them during shipping:


The brackets and trailing links unwrapped:


The BEEFY adjustable trailing links:


The key change - moves the trailing link pickup point both down AND forwards, and the new trailing link is therefore longer than the stock arm:



The forward end of the trailing arm has a spherical bearing that connects to the bracket here. Hardware all looks high quality (unlike my blurry photo...LOL:


I likely won't have an opportunity to get these installed until sometime in mid-January...or *maybe* I'll get them on tomorrow...

[Tatsu333]

OK - got these installed this morning, because I wasn't willing to wait until late January (which would have been my next opportunity)...LOL.

Install was very easy.

1. I landmarked the distance between the stock trailing arm pickup point and the connection to the knuckle so I had a point of reference for setting the length of the adjustable trailing arms once installed. Measurement in my case was just shy of 30 cm.
2. Undid the 10mm rear bolt and two outside clips holding the underbody panel in place so the panel could drop down for access
3. Unbolted the stock trailing arm from the MCA Traction Mod bracket and from the knuckle. These were 17 mm bolts / nuts both ends.
4. Removed the MCA Traction Mod bracket by unbolting the 19 mm subframe bolt and the 19 mm nut and bolt holding the bracket to the original pickup point
5. Removed the stock subframe to chassis bracket / brace - there was a 12 mm bolt holding the brake line bracket to the brace and two 14 mm bolts at the front edge bolting the bracket to the chassis
6. Installed the Just Engineering bracket, making sure the brake line bracket was aligned above it. Hand-threaded the 19 mm subframe bolt first to make sure it was not cross-threaded, then tightened it up about halfway. Did the same with the 12 mm brake line bracket bolt and two 14 mm bolts at the front edge, then secured the upper mounting point of the bracket to the stock trailing arm pickup point using the stock 17 mm nut and bolt.
7. Snugged things down by hand, then torqued the 19 mm subframe bolt to 107 ft-lb, the two 14 mm bolts at the front edge to 52 ft-lb, and the 17 mm upper mounting bolt and nut to 81 ft-lbs. (as per stock torque specs I could find). The brake line bracket bolt, I just left snugged up by hand.
8. Took me a while playing around with the adjustment on the new trailing arm to get the overall length correct to match up to the original measurement from the stock pickup point to the knuckle. Weirdly (or maybe not?) the correct length centre to centre on the new trailing arm ended up being right around 30 cm too. That was pretty near as long as I was comfortable setting the adjustment, because that left only about 15 mm threaded in at either end (of 50 mm total length into the arm and 40 mm total length at the rod end into the adjuster body). The adjuster body required a 7/8" wrench and the locknuts were 15/16". Once I figured out the length, I set the other trailing arm exactly the same in preparation for doing the other side, and set it aside.
9. After much back and forth with adjustments, connected the rod end to the new forward pickup point using the supplied hardware (bolt and nut were 19 mm), and the end of the trailing arm to the knuckle using the stock 17 mm nut and bolt. Snugged everything up hand tight.
10. Loaded the suspension to about normal ride height by raising the trailing arm with a jack, then torqued the 19 mm forward bolt and nut and 17 mm bolt and nut at the knuckle to 81 ft-lb. Then I tightened the locknuts on the trailing arm adjuster as tight as I could, making sure that the rod end was properly aligned vertically in the bracket.
11. Reinstalled the underbody panel with the rear nut and the forward clip. The new bracket doesn't have a hole for the more rearward clip to attach, but the panel sits OK without it, so I didn't bother doing anything about it.
12. Gave the adjuster mechanism, the rod end and the fasteners either end of the trailing arm a light coat of Honey Goo for some weather protection.
13. With all the measuring, adjusting, re-adjusting, etc., being very careful and deliberate about things, looking up torque specs and taking pictures, the first (passenger) side took just under 2 hours.
14. Repeated the whole procedure on the second (driver) side in about 25 minutes...LOL.

Here are a few pics of the parts during / post install:

The new bracket installed in place of the stock brace and MCA Traction Mod:


The new bracket and adjustable trailing arm installed:


And of course, new parts mean new stickers...LOL:


Initial Driving Impressions

Doesn't feel any different in terms of ride or NVH vs. the MCA Traction Mod and stock arms. The subframe being tied in a bit more with the new bracket seems to have reduced a little bit of drivetrain bounce when accelerating away from a stop, but other than that, no really noticeable difference. Maybe felt like it put the power down a little better than even with the MCA Traction Mod installed, but that could totally be in my head, and I didn't push things too hard, because I'm on my snow tires right now.

Everything feels straight (LOL), but I'll definitely get an alignment done sometime between now and spring when I'll be putting new all-seasons on the car, because this will almost certainly have had some effect on toe at the rear. No rush since I only drive about 300-350 km per month, and won't be pushing hard on my snow tires anyway.