I don't mind old threads coming back up because it means people are using the search, and it's working!

As for an N/A 12a over 200hp, even with FI it seems unlikely short of a J-Bridge or P-Port, which are both completely unstreetable engines. I'd love to be proven wrong though!

 

200hp out of a 12A? Easy; use two.

Much as I love the 12A, going to that much trouble & expense to try to squeeze 200hp out of 1.1 liters displacement is a misuse of technology. Trying to also claim longevity as a goal is straight up working at cross purposes.

Go to a 13B. Don't waste scarce 12A parts blowing up perfectly good engines for no good purpose when there are 13B's around that already have you closer to your goal before you turn a screw, & for which more stuff is available.

Just my 2c, of course.

 

We did pretty decent with a side fed p-port here lately. I think we only pushed it 8-8.5k? As for streetable... I use that term very very loosely. Lol.

 

I agree, but keep in mind that when this thread was initially posted in 2004, you could still get new 12a Rotor Housings from Mazdatrix/Mazda. They hadn't gone NLA yet, so back then even I was thinking of building a 12a for mine.

As it is I'm looking for a very streetable 160+ rwhp out of the FrankenEngine 13b I hope to build with S5 TII Irons, S5 N/A Rotors, Rx8 Rotating Assembly and Stat Gears and a nice sized street port with a Sterling strapped on top. We'll see how close I get to that number when I eventually build it. I figure that my old, tired 12a with 200,000km on it is pushing 104rwhp right now, and the stock S5 N/A did 160fwhp with all its emissions controls intact, so it doesn't seem out of the realm of possibility.

Jon

 

Hecubus84 recently dropped a 2nd gen engine (complete) into his fb. I've driven it. I need it. The difference in low end torque is amazing, as is the extra power throughout the power band. And don't even get me started on fuel efficiency! I hate him! Damn him for making me unhappy with my little 12a! lol.




.

 

Haha, well I don't plan on bringing over the EFI or the 6-port bits of the N/A FC engines, so I probably won't have that fuel efficiency and low-end torque. I'm building a 4-port 13b with high-comp rotors that I'm running a Sterling Carb on.

I still think it'll give me better power and fuel economy than my current rig, if only because the compression won't be in the borderline-rebuild zone and it's a larger displacement engine! But I couldn't really care less about the fuel economy, as long as it's not atrocious. Give me 12L/100km (20mpg) on the highway or better and I'm happy. My Mazda6 can be the "fuel efficient" car, lol.

Jon

 

I Don't give out this kinda info often but.... copy a 6 port rx8 ports on to the 13b primary and 3rd and 4th ports, clean up, street port the aux, aux port auctation is EASY if you keep the air pump.


I too have a 91 13b in my GSl-se, running the stock injectors/afm/ecu. and maxing out at ~5500 rpms. keeping the stock dizzy kills what would but a terrible beast. As is it will bark 3rd...
I have a customer that i'm putting in another 89 swap, with 89 ECU/efi, plus the Rx8Street port. going in an 84 gsl.

 

Thanks for the info, it's definitely worth considering! I've long since deleted my air pump, but I could add one back in or build something to sense RPM and actuate them with little electric motors. Then there's the issue of making a manifold to mate up my carb to a 6-port setup, because otherwise I'm bringing the whole EFI system over or building my own...

I'm mainly trying to keep things simple and mechanical though, hence the 4-port carb setup, at least on this one. Plus I want to see what a Sterling can do on that engine since I don't think anyone's done that and posted dyno results yet. The engine build's at least a year off so we'll see what happens when I get there.

 

hmm good idea. didn't they move the side seals in the Rx8 rotors to make the ports bigger without the seals falling in?

other than that, if you read the SAE paper the Rx8 makes its power by increasing the intake area quite a bit (65%), so you're on the right track

 

Right, though one of the reasons they were able to increase port area so much while still being emissions compliant is the peripheral exhaust ports. But that's no reason for us not to take advantage of their porting skills for our ports as long as they aren't going to eat our side seals or corner seals for breakfast.

 

people have used rx7 rotors in rx8 engines with NO mods to the rotors... so it works.

 

I don't have any doubt in my mind currently building an efi setup on my stock GSL motor. And a ported version on my rx2. Combined with other basic mods I see it being attainable. Just depends how its done. Ask people who have done it. Maybe not have broke 200 on efi alone but combined with other mods its more than "plausable. "

 

right, putting the Rx8 intake ports on a peripheral exhaust port engine adds overlap, which is bad, but you have no choice.

just checking its a great idea actually.

 

hmmmmm, a 12A-MSP Renesis...my gears are turning...esp as the Renesis had the coolant seal grooves moved back to the housings where they belong