AVO have been busy track BRZ and put some time at the track.
You’d expect a little exaggeration when seeing a title like this, but literally, besides driving to and from the track, that’s exactly how the AVO BRZ has been, and is being, broken in. It hasn’t happened overnight, we got the first BRZ sold to the public in Japan 3 months ago. Since then it’s spent an equal amount of time on the lift being used for R&D or at the track being use for R&D.
This is mainly a writeup about what we’ve learnt from being at the track. To start with, it’s been modified from early on. The car we ordered was a RA edition. We corner weighed the car, and boy is it light at a 1172kg (2585lbs). We also threw it on the dyno so that we’d have a baseline to judge all power modifications against.
It came from the factory with steel wheels and rubber that would probably be used as a spare tire on other cars. This was a simple economical decision, we knew both that the car would mainly see track duty, and that whatever standard wheels would be on the car would be quickly be binned. And so the steelies were, with 18 x 8 WORK wheels and 225/40 Bridgestone RE11 tires fitted soon after. We had literally gotten the car two days before the Hyper Meet, so we had to rush to fit the DAMD rear wing in time for the event. We also had the graphics done within those two days as well. This setup went straight to the track, and Ross recorded a 1m14.3sec lap at Tsukuba Circuit during the Hyper Meeting BRZ 5 Lap Race. During this 5 Lap Race he was doing 145km/h at the end of the back straight. This was to be our base line.
Soon after that we fitted the coilovers that we are working on in conjunction with Spirit. These are high-end track specification coilovers, they’d feel a bit stiff on the street, but are quite good on the track. Our lapping times went well with 1m13.1sec laps, though we felt the coilovers still needed fine tuning on the spring rates. Speed didn’t go up, we were still doing a 146km/h at the end of the back straight. We also tested some 700 degree (celcius) brake pads which were a definite improvement over the stock pads, which we will release soon in the future after we finish our testing. The overall impression was still excellent, with great response at the track and clearly superior cornering compared to, say, an STI. Light weight and an ideal balance will do that for you.
A little time was taken off from the track to get into the R&D. The panel filter was sent off to the factory so we could make a high flow version, and the exhaust was taken apart so we could start on that as well. In both cases, it’s not that neither is that bad from the factory, but of course we found areas to improve. We also got the revised springs from Spirit. Finally, we fitted our front lower control arm bushings, the ones at the front, and at the rear our CAB (Caster Adjustment Bushings). They provided a tremendous improvement in turn-in and stability at the front end, and we felt we could push it a lot further at the track.
So that’s what we did, took it back to Tsukuba. We had a host of changes for this run. Front LCA bushings, 800 degree brake pads, newly revised springs, new panel filter and some new exhaust pieces. And around the track, it certainly felt a lot more stable. Ross was able to take it deeper and deeper into the corners before standing on the brakes and bringing it on through under power, with a bit of kick out at the exit. Lap times were very consistent, and it was quite easy to bring the lap times down from the previous best. In fact, by the end of the session, over 3 seconds had been knocked off from the last time, a huge improvement at a short track like Tsukuba Circuit. Our final best time was 1m10.8 seconds at 149.7km/h at the end of the back straight.
Being able to go much harder than before also returned some very valuable data on the mechanical reliability of the car. It’s one thing for Subaru to say it’ll be a good track car, it’s another to actually test it. And this certainly did test it to the limit, and beyond some limits.
One of the first area’s we found some issues with were the front brakes. Admittedly, not everybody is going to spend their first 1000km standing on the brakes at the track, but we did, and they didn’t last quite as long as we’d have liked. The front rotors were shot after our last lapping session – no real surprise there – but the brake calipers also had some issues. As you can see in the photo, the rubber boots on the pistons tore, not something we had expected to see quite so soon.
The other area of concern was the front lower control arms. Installing the new LCA bushings front and rear took a lot of slop out of the arm, reducing unwanted movement tremendously. It also showed that Subaru got the car as light as it is by using as little metal as possible anywhere it could. With less flex in the bushings, the arms now showed more effectively how lightweight they were designed. They were literally flexing when we applied physical pressure to them by hand. This has raised enough worries about long term effects of racing that we sent them out to our factory to get reinforced.
In response to the issues with the front brake calipers and rotors, we removed them completely from the picture and installed our 330mm Big Brake Kit, which utilizes DBA slotted brake rotors with the kangaroo paw design for vastly improved longevity and performance at the track. Fitted to these were our 4-pot calipers, which fit easily under the wheels and use a Porsche 911 size brake pad, which increased the swept area of the pads by a huge percentage. Due to the increase in size and venting of the new rotors, we have gone to a 500 degree brake pad, as this will be a better match.
For the next track session, we will be testing the Big Brake Kit and the DBW throttle controller. Even on these newest Subaru’s, they still suffer from the initial throttle hesitation that Subaru designs in to all of their drive by wire cars. The throttle controller cures this issue and as a big bonus also gives it a quicker, torquier response. We have fitted our Lap Timer to keep track of our times even better. We might test swaybars at this time as well. We are debating changing them out to balance with the springs on the coilovers better.