brianw

Man, I need $1200 bucks what could I expect from that 12a turbo?

fitzwarryne

The 12AT is a factory spec with low compression rotors and efi. In stock form it produces about 136fwhp. Ita 1/4 time was about 15.6 seconds.

Numerous aftermarket turbo set-ups have been added to the carb 12A usually by changing to a Weber. With its hiher compressionrotors boist is lower. Gearbox and drive train become the week link but around 250hp is reliably obtainable. With porting, intercooling, and transmission upgrades then a 300hp streetable 12A should be the target. Putting it in perspective, this is about the same level of output as the factory full race NA 12A PP engine achieved.

DriveFast7

iTrader: (1)

the turbo only added 36 horsepower? that's not too exciting. what boost levels does it run at? what kind of torque numbers?

can it be improved upon?

fitzwarryne

The 12AT as stock has limitations, its use primarily was a marketing exercise when RX-7 sales were sagging in Japan. It ran at about 6 boost.

Yes you can improve on them with porting, a bigger turbo, new ecu and intercooling.

I suggest the best option is to turbocharge a 12A or go for a 13BT.

cosmicbang

I suggest a street port 13B 4 port with a good carburettor and exhaust. Very simple, lots of power, good fuel economy.

brianw

RWHP? $'s?

fitzwarryne

A moderate streetport on a 13B-4p should produce around 145-155rwhp. A 'streetport' is enlarged ports which can vary according to need from the stock porting up to where its nearly necessary to cut a bridge [almost 50% of the seal unsupported]. How far you go depends on your compromise between race and street characteristics. Thus you can get a 20% variation both in power and idle speed.

The problem is getting the engine, most likely you will be up for a full rebuild plus the porting cost. add in a good carb and exhaust system and a US$3,000 level budget starts looking realistic. It really depends on how much of the work you can do yourself.

If there are no 4p engines around some people are going for a late version 6p and adding Pineapple convertors to bring it back to 4p. Experience on this is mixed but it is worth investigating.

REVHED

What the hell are you talking about? Most of those things apply to any engine not just bridgeports.

A properly built bridgy will give a lot of turbo's a run for their money. Also, injection helps alot with the driveability.

fitzwarryne

REVHED- I fully agree the difference in cost between street and bridge porting is small in comparison with the total cost of the rebuild. A bridgy can be used on the street but is it a good daily driver, I think that was one of the points raised.

If injection improves driveability, does that mean a 13B efi is better than a 12A carb as the better candidate for a bridgeport?

brianw

Mine will be a daily driver, I paln on useing a carb, and I can do anything that does not require a machine of some sort myself. I really whant to hit the 1hp to to lb ratio.

REVHED

If I was to build a quick na car again I'd definately do an injected 13B. I've driven a friends 13Bpp with efi and it's very streetable... except for the noise. lol It will happily cruise around at 2000rpm whereas with the Weber it would buck around like crazy. And it's an 11sec car no less.

cosmicbang

That is kind of conservative.

BrianW: go search in the forums and talk to some engine builders you will get a better idea. You can get 200 rwhp with a NA 13B 4 pt streetport. Your actual result will depend on the type/extent of porting and your choice of induction. Some carburettors may not have the highest power output but are more practical for everyday driving. If you want EFI, I would suggest a stand alone. You will need a good free flowing exhaust at any rate.

deeman111

yeah you would need the stationaries, carbon seals, the "oil stuff"... probably worth getting everything balanced too.. oh and dont forget the shatter shield for the transmission/clutch.... coz if something goes at 10k u really want to try and save your legs.

oh and also make sure everything is red... coz red always goes faster

-James

fitzwarryne

If someone claims they get 200rwhp from a streetable streetport then they must have rotors driven by hot air. I have been to several dyno days where streetported cars were well down on this even taking account of dyno differences.

200rwhp is some 250hp at the flywheel which is really pushing most bridgeport NA 13B-4p to obtain. The top PP race engines were putting out 280-300fwhp at 11,000rpm, registering around 225-230rwhp.

Thus I still think 200-210fwhp is to be expected from a streetport not at the wheels. However if someone comes up with an accurate dyno sheet i am willing to change my mind.

12abridgeport

To any engine?

If i would've put all of those $$ in a 5.0, i would've been producing around 350 hp and god knows how much tourque. Eat less gas then a bridgeportski, make way less noise, not having any trouble coming out the hall at a stop light, and last waaay longer than 20k miles, and also not sound like a honda. Ok, maybe that last one doesn't apply to bridgeports but you guys got to admit that some rotors with some cheap *** exhasts do sound a lot like a honda. Bzzzzzzz

Yes, bridgeports can be a lot of fun sometimes, i'm not denying that myself...my point is just that they are impractical in every way.

However, even if you look at it from the street port perspective, you don't need to pop open street port every 20k or less, the motor idles at 1k, you don't have to balance the motor, clearance rotors, oil mods, hardened stationary gears and bearings. Basically in order to have a properly built brigey you would need to spend some serious money on it, as you can see i left out a bunch of stuff from my previous post. So if you put it all together you are going to be way better off just getting a turbo motor.

But then again, for the money you would spend on a cheap turbo setup, after all the work and trouble because you know there is always some kind of trouble with turbos, one is going to realize, wait a minute, for a around $3k you could've had a stock car that is making as much power without any hussle.

I'm just very irritated that i've flushed so much money down the toilet. I've had a 13b radical street port, turbo, NOS, and a bridgeport, so i'm not just making all this stuff up. I guess at some point you got to realize something, do you just want to go fast and spend as less money as possible or go fast in style with more problems and more money spent on your setup?

Right now, i just want to go fast. The most i got for my money up to this day, is a $1k i've just spent on an '85 Honda VF700C. Oh yeah, a 12s vehicle for just a grand, can't beat that!

DriveFast7

iTrader: (1)

I think streetable is the key word in this post. Streetable meaning it has mufflers and is at or near street legal sound limit.

I personally saw a winning regional SCCA 2nd gen E Production car with a 13b 6streetport and a 48 DCOE put 182 to the ground. I do doubt with mufflers and 4 ports instead of 6 it would get up to 200rwhp.

Bridgeport NA 13B-4ports put 280-300 at the fly. In Australia they have taken bridgeport engineering to the next level and put out much higher numbers. I saw a 13b PP with small endurance intake sleeves put 318 @ the fly and that is an endurance motor made to last and not made to max hp. A sprint race 13b PP with a 58mm Gene Berg IDA copy with 48mm chokes put 360 @ flywheel. And MY GOD did it sound good.

Bill Auberleen's race shop is down the street from me and his IMSA GTS-2 2nd gen tube frame had a 13b PP with Motec and had 351 @ the flywheel. The most power from any n/a 2 rotor in the early ninties......

All said and done, I think the person who started this thread should buy a 13b 4 port streetport with all the usual hop up parts and if he wants more power you can always turbocharge it.

fitzwarryne

Drivefast7- I agree with your advice on theoriginal thread question.

A 12A bridgeport is not suitable for a daily driver. The way to go is have a streetport.

Ideally a 13B-4P with a Weber carb and a good exhaust system. If the budget is limited, stop with a 12A streetport and modified Nikki carb with a good header.

People may argue about power output, but what matters is you will have great performance on the road and impress any date and not attract the police.

brianw

Okay if I start from scratch why use a 12a? are the parts going to be cheaper? When I built my big block everybody said "big block,big bucks" but I found that the larger displacemnt allowed made the HP's that much eaiser to get. It this the same kinda thing? I'll be doing most the work myself. I have heard of mixing the two for a really good combo. Just trying to figure out which one to start looking for.If not both

DriveFast7

iTrader: (1)

The bigger displacement of a 13b also means bigger horsepower and has more potential. Yes you're correct. 12a engine and rebuilt parts are somewhat cheaper.

4 ports make more power and you don't have to mess with the auxialary ports as with a 6 port

A 4 port 13b can be made with 12a 4 port side and intermediate plates. 13b rotor housings, rotors, e-shaft, counterweights.

13b rotors:
89-91 rotors are lighter, make more power, and more sought after.
86-88 more pleantiful.
74-77 Rx-4/REPU & 84-85 GSL-SE heaviest.

Good info here: http://mazdatrix.com/eng13bsp.htm

DriveFast7

iTrader: (1)

And here:

http://mazdatrix.com/engsp4p.htm

brianw

That's the one DriveFast7, what kinda HP could i expect out of that combo? I didn't see that there.

fitzwarryne

The original thread question was whether to bridgeport his 12A.

While there is much hp merit in building up a hybred 13B-4p, isn't suggesting going down that track a gold plated concept? What sort of all up cost will it be? The engine package from Mazdatrix costs up to $6200!

A 12A rebuild kit, porting and modifying the Nikki is a very economical way of adding power.

brianw

fitzwarryne, I realize that I have kinda hijacked this thread so I'm sorry if we are off topic. I am trying to find a way to acheic=ve 1hp to 10lb in a streetable motor. I am thinking that althought I wil need three core motors this still will not be that expensive as I could do the port and assembly work myself. Am I missing some vital step/parts that will be specific to this engine. In other words other than the three cores won't the cost be realitive despite the parts used?

DriveFast7

iTrader: (1)

It can be done a lot cheaper than that.

No gold plated 13b housings . . . .

Cheapest way would be to buy a used Rx4/REPU/Cosmo 13b; they do show up on thepartstrader.com every once in a while.

Otherwise the cost really isn't a lot more assuming you have used parts in usable condition.

You'd be best off buying NEW 13b rotor housings than playing with cored ones. Getting good 12a iron plates that haven't been lapped already is getting tougher to find but certainly doable.

13b 4-streetport won't make 100/1 ratio but you should be happy with it. Otherwise blow-thru turbocharge!

cosmicbang

I had one of these hot air cars several years ago It was excellent in extended high speed driving and very dependable not having a turbo.

Here is a link for porting information on 13B 4-port engines, with pictures. Click on the word "Porting" on the left side
http://www.rotary13b.com/rotary13b/porting.html
And another one
http://www.mazdarotary.net/porting.htm