While I meant for a series of upgrades to be featured in one single mid-season post, so many things got in the way that it just makes sense to split things into parts, starting with my new cams – a set of GSC S2s.
These are a slightly more aggressive cam than I have had in the past (GSC S1), but as far as I understand, still run fairly smoothly with the right amount of tuning. According to GSC, no low end power is lost with these cams on Evo 9s. From what I have seen on the forums, this is true, even for the stock turbo. In addition to the cams, GSC valve stem seals were added to help cope with the higher heat. GSC beehive springs with titanium retainers (part 5040) were also required with these cams. These springs go to 8,500 rpms (vs 10,500 rpms for part 5041), but I will never be going that high anyway. These are lighter and more durable than OEM, and should rev faster with less wear on the valvetrain. Finally, Topline lifters were added. These are the updated version with larger oiling holes. These should get rid of the ticking noise common with lifters on the 4g63.
All-in, this setup can rev to 8,500 rpms safely, but the rev limiter will be set to 8,200 rpms. For the most part, I still expect to shift around 7,000 rpms. The 8,200 rpms will primarily just be used as an over-rev feature, to allow me to stay in 3rd or 4th for those moments where I briefly need to upshift, only to downshift immediately after. Adding the additional mphs (i.e., 108 to 123mph in 4th) should really help in circumstances that do not otherwise warrant an upshift, costing me precious tenths. Below are some calculations for max speed per gear based on the gear ratios and tire height – based on my experience, these are spot on. I didn’t pick up any power from these cams, but should still be worth a good bit of time on track.
Previous setup with stock cams (7,200 rpms):
New: Where I will usually shift up to (8,000 rpms). This gets me to 92 in 3rd and 120mph in 4th – just about perfect for track:
The 8,200 rev limit will add about 2-3mph in 3rd and 4th in case I need it, but those instances should be rare – and again, this is just for straights before corners that I’m upshifting or sitting on the rev limiter for:
Calculations from apexgarage.com – http://www.apexgarage.com/tech/gear_ratios.shtml