HomemadeTurbo - DIY Turbo Forum - My Turbo Setup Plans

Hello everyone. I'm new to HMT. I have a 99' base miata. It's a 1.8 L DOHC I4. Right now it has an Edelbrock direct port nitrous kit 100 shot with progressive controller, dual stage window switch, separate fuel system for the nitrous, and running MegaSquirt II. I was planing a custom supercharger setup utilizing 2 millenia twin screw SC's, but I'm abandoning that idea (for now) because it will require a lot of money and time to do it right. Maybe in a year or two.

So, I have now decided to do a turbo setup instead. The goals are:

1. Reliable
2. Fast
3. Cheap

In that order. It has to be reliable because it's my daily driver and my only vehicle right now in college. However, it will be fast. Stock this car makes 110whp. It's pretty common to make 250whp on stock miata engines, and some have pushed it further with success. My goal is with this turbo setup is 300whp with the headroom for 400whp with a built bottom end. 300whp on a stock motor will be pushing it, but it's been done. These motors don't simply fail at these power levels. Knock kills them. Tuning will be key at these power levels. Right now I'm around 130-140 whp, and 220whp or so on the bottle.

So the last item is cheap. At this point, most of you were probably pondering posting pick 2 of those 3. Well, it will be a DIY setup to save cost. When I say cheap, I'd rather not waste money more so than anything. For example I have a bypass valve from the millenia SC I'm going to try to use as my recirculating BOV. I have 6 bucks in it, so if it will do the job, that would be great. Still, I will need a good wastegate and I'd rather not spend 200+ on it.

Right now the short block is stock with 141K on it. The head has A LOT of custom head work done to it, around 35 hours of work modifying it. Extensive bowl work, blending, HEAVILY unshrouded, back cut valves, turned down stems, etc. After the head work it ran so lean on the stock ecu it would buck and hickup after 5K RPMs. ;D The car makes a lot more power than stock now that MS is going and fuel and spark are under control.

Right now the plan is to build my own manifold. Probably will be a log manifold with 1.5" sch 40 SS pipes. JGS makes a kit manifold using these parts for 190. I could source the parts for 100, but after shipping and all their offer seems somewhat appealing. Exhaust, IC piping, etc will all be custom made.

My biggest question right now is what turbo to use. Again, I want to make 300 whp now and have headroom for more. I"m considering a t3/t4 setup. Either a 50, 57, or 60 trim compressor. Probably a .63 A/R turbine. I'm leaning toward the larger compressor. Does this sound like a good turbo for this application?

FWIW, I will have the nitrous so I can spool the turbo a lot sooner. Lag isn't really a problem. I already have a 20x12x3 core intercooler, ACT Extreme clutch, and a few other bits. I pretty much know how I'm going to build this setup, but what turbo to use is my last piece of the puzzle. Any opinions are appreciated.

Also, there is one underlying goal for my build. When finished, the car will appear 100% stock. It will look stock and sound stock. The intercooler will be the only thing that gives it away, and it will be painted either silver (to match the car) or satin black. The exhaust will be 3" to the rear and have a turndown. The stock tip will be welded on for the stock appearance. I'll post pics in a few.

Patrick.

EDIT: Pics!

Direct Port:
Attachment 18213

Hotside SC pic
Attachment 18214

SC bracket
Attachment 18215

Relocated proportioning valve.
Attachment 18216