I'm hoping to 2.5 swap my 2006 NC sometime, so I'm looking to do some upgrades this summer to make that better when it happens. I'm envisioning a mild-cam naturally aspirated 2.5L at this point. This is my summer daily driver, so I'd like to keep it nicely streetable while still making it as capable at autocross as I can. So far, I've swapped in a set of Bilstein B6 shocks and 58 White/58 Red GWR bumpstops, a Hotchkis front sway bar, and a Roastersport Street Single muffler. I'd like to work with those existing mods and add the following mods to prep for the 2.5L:
- Improve total exhaust system flow
- Wider Tires
Improving the exhaust flow should be easy. I'm thinking the Roadstersport MAX Power 1.8 header and Roadstersport Helmholtz Midpipe will nicely improve the exhaust system's flow, knock down the drone from my Street Single, and maintain a catalytic converter (since I'm just not crazy about totally removing them). Does that seem reasonable?
An LSD should also be relatively straight-forward. I'm leaning towards one of the Tomei options at this point since they are cheaper, and I don't plan on going bonkers with the 2.5L power. Again, does that seem reasonable? Would you recommend the 2-way or 1.5-way?
Tires get a bit more complicated. As I understand it, to fit the widest tires I can without flares (245), I need to lower the car some to improve camber to ~2 degrees. I'd like to stick with the B6 shocks if that's reasonable as they only have about 5k miles on them. To that end, I'm looking at lowering springs. The options I can find available today (unfortunately not all on GWR) are:
Progress Technology - 126 lb/in front 116 lbs/in rear - expect 1/2" drop
Racing Beat - 145 lbs/in front 112 lbs/in rear - expect 1/2" drop
Flyin' Miata - 300 in/lbs front 196 lbs/in rear - expect ~1" drop
H&R - 235 lbs/in front 155 lbs/in rear - expect ~1 1/3" drop
Eibach - 140 lbs/in front 70-120 lbs/in rear - expect ~1 1/2" drop
This leads me to several questions.
- Would you expect 1/2" drop on an 06 to be enough to get the requisite camber to fit a 245 tire?
- The rates on the FM springs seem very high. Would you expect these to work with B6s? I'm guessing they would be stiffer than I want for daily use...
- Would 1 1/2" of drop be too much on stock length B6 shocks?
- Which of these options would you recommend for my application (as much grip as possible for autocross while still being a great daily driver)?
Thanks so much for your help and advice!