Thinking about doing a large streetport on my 12a and then putting a turbo on it.

How would I go about sizing the turbo and would I be able to setup a blow-through using my PHH44 or would I need to go bigger?

 

PHH 44? i'm guessing the Mikuni???

anyway, you'd need to set some goals when you go about sizing the turbo. spool ease? overall power? etc.

one of the beauties of turbocharging is the fact that you are FORCING air into the engine, so throttle size doesn't matter so much. your Mikuni may actually be an asset for off-boost driving. could you find a bigger or better carburetor? sure, but (at least in MY opinion) you can make that decision after you have everything else sorted.

 

Needs to be reliable most of all. This car will never be on the street so it will be driven pretty hard on the track so I need something that will hold up to that. I am just looking for a little kick. Basically trying to almost get the same power as a stock 13bT. Nothing too extreme. Needs to make power at around 4K and up to 7k. I am basically trying to see if I can push out more power while being more cost effective than a 13bTII swap.

 

you remember that game as a child where you're given side by side photos and then you're asked if they match? well, at least to me, those statements don't match. doubling the original output is pretty extreme from any vantage point.

that said, if that's all you want, then you should be able to build around the 13B's Hitachi (maybe get it modified a bit), but i don't see why you'd NEED more than that if you're being serious about what you want.

as for reliability, i also don't see any reason why you'd expect any less reliability than any other turbo rotary Mazda offered if you stick to the basic principle of satisfying the engine - fuel, ignition, intercooling, temperature control, etc.

 

As I understand the S4 turbo is around 185, I want to be somewhere around 160-170 at the crank (if I can get to 185 safely then I'm cool with that too), not quite double, more like a 55-75% increase (12a's have 110 stock don't they?). I've lightened the car so much already that just having the Mikuni makes a huge difference at 3.5k and above. I've got a Holley fuel pump and I am running it on the low side right now so I think I'll have enough fuel input, I'll have to figure out a mounting situation for the intercooler though because I have an oil cooler installed. I am also running the stock coils, would I need to upgrade ignition?

 

The 12A had more like 100 or 101 stock. Some say it was 105. Maybe the ones from the 70s had 105?

 

Doing a t2 swap would be way cheaper than having a 12a ported and fabbing all kinds of other things.

 

well, Jeff20B already touched on the 12A horsepower numbers, so no need to belabor the details. my original point was really that 80 to 100 HP over stock is not "just a little kick." bolting on a header is just a little kick.

there are (and have been) quite a few guys that have really well-put-together blow-through 12As. my advice would be to seek out some of those threads and start putting a plan together for yourself. i feel you can achieve your goals. i can't speak to costs, but i can't imagine it being MORE than a 13B-T (considering you'd probably have to build it, too).

 

Work in a fab shop, benders, cnc plasma, waterjet, lathe/mill, tig/mig welders. Can probably fab whatever I need.

Yeah I am using just a little kick too nonchalantly. I am just thinking in terms of modern cars, a turbo that adds 80-100 hp is typically a smaller turbo, it's just not a little kick on an engine that only has 100hp to begin with. Hrmm maybe I should start with a s4/s5 then. Decisions decisions.

 

So what's the going rate of a 12a w/ manual tranny in good condition? It runs with my Mikuni PHH44 and I have a modded Nikki to throw in.