On May 28th, I decided to go on a drive with Mia without checking the dipstick in a while. Suffice to say, she was short on oil, and a short while later her BP4W decided it had enough, and started to knock.
After initially feeling really upset that I basically blew up a motor due to negligence on such a simple task, I decided it’s also a good time to rebuild her into a car that can take on the giants and beat them. To do that, a lot of upgrades are going to be needed, and because of how expensive everything is, I think the best approach to this massive project is going to be doing it in stages.
This is the current proposal for Stage One, the first of three stages to build her into what will eventually be a 300hp road and track monster:
Tear down the motor inside her and see if it’s rebuildable. If so, great; if not, do the VVT swap. To do that, I’ll take her motor completely apart and see if the cylinder walls are scorched/damaged in any way. If they are, the whole motor needs to be replaced. If I can get away with rebuilding her current heart, that’s a nice lump sum of money saved; if not, then I’ll do the VVT swap – the 2001 and newer Miatas added Variable Valve Timing, which basically allows the car to control the camshaft’s position to optimize midrange torque and high end power. Another advantage is the beefed up crank support plate, which will come in handy for stage three. The only thing needed to be done to accommodate the new motor will be some splicing of wiring; not that hard.
Total cost: $700/$1200, depending on if the BP4W inside is rebuildable.
Blackbird Fobworx Lowered Engine Mounts. They lower the BP motor by about 1/2″ – and make the oil pan flush with the subframe. The lowered motor will improve the center of gravity and the stiffer mounts will keep the engine more solidly mounted, stiffening the car up. There are two versions – street and track. I’m getting street because track would be so stiff the car would shatter your spine on the street.
Total cost: $310.
Manual Transmission Swap. The automatic was fun and got me over the fear of performance cars, but it’s time to go. A car like Mia needs a manual not just for pure enjoyment, but because the slushbox won’t be able to keep up/handle the abuse of track work; it also has its own radiator which makes the car’s already too small radiator even smaller. The question then becomes of whether to use the Mazda 5 Speed gearbox or the Aisin 6 Speed box; the 6 Speed box is more expensive, but I’m told can hold the high HP/torque I’m planning in stage three. That said, a phone to call to Fast Forward Superchargers revealed that their test car uses the 5 speed box, and is currently making over 300hp to the wheels, so I suppose the 5 speed box isn’t too bad.
Other parts needed will be an ECU from a manual car, clutch lines, pedal assembly, (aftermarket) clutch, lightened flywheel, and other parts outlined here.
Total cost: ~$1000, give or take.
Torsen Differential Swap. A Torsion differential will come in handy by limiting the maximum amount of slippage; good for slippery conditions. That said, this is also at this time optional given my limited budget; I can reuse my open differential with the 6 Speed box because both of their differentials use the same gearing.
Total cost: ~$800-$1000.
Hard Dog Sport Double Diagonal Roll Bar. A roll bar is required for track events and AutoCross; plus, not only does it look cool, it also means that it won’t be the end of Mia if she ever rolls over for whatever reason.
Miscellaneous Parts. These include door bushings, a Momo quick release steering wheel, racing seats, and some extra gauges (namely oil temperature and hacking the semi functioning oil pressure gauge to make it completely functional).
Total cost: ~$1000, give or take. Varies by what wheel and what seats I intend to use.
Stage One Total Cost: ~$6000, depending on how much each part costs. Bear in mind that this is just napkin math; I can give you a final cost once Stage One is complete. Also, this cost can be brought down with the sale of the automatic transmission, the stock suspension that I already removed, and the other automatic parts.
Fun fact: I bought the car for $4000, so I’m going to be throwing more money in than it’s worth. A part of me hesitated on this because of that simple fact; that said, if we really cared about numbers, we’d all be driving Camrys.
Special thanks to /r/miata for encouragement and advice.
At the time of this writing, I’m leaving for Europe in a few days; when I return, I can get to work on Mia.