whitey

Hey, thanks for coming into this thread even though these aer all probably questions you have answered a milion times before.

Were any first gens equiped with the 13b from the factory, and if so is there a link I could go to the explains what years and trim levels came with what?

Are any OEM carburetors on first gens preferable for performance (or other) purposes then others?

What should I look for if I am interested in buying a first gen for a restoration project. This project would have a goal of low fourteen second timeslips and a fresh, stock looking car.

TheTwinTurboRX-7

13b came in the GSL-SE in 84 and 85

All stock carbs are the same Nikki as far as I know, which isn't far.

Any first gen can hit the fourteens with a port job, aftermarket carb, weight reduction, and free exhast.

Hope that helps some.

brison

The 13b engine was standard in the '84 & '85 GSL-SE models only. The SE was the symbol for the 13b engine, fuel injection and larger brakes & wheels. Most 1st geners will tell you that this is the car that you want if stock speed is what you are after.

The '79 is also popular because it didn't come with alot of extras to weigh it down.

Alot of guys put weber carbs (45 interior diameter, I think) sidedraft with a modified intake manifold on the 12a's.

All OEM carbs were Nikki 4bbl. There are a few mods that will increase performance to this carb. I am trying one of them right now.

Hope that this helps.

RotorMotorDriver

iTrader: (1)

1984 and 1985 GSL-SEs have 13Bs, as well as all RX-7s 1986-1995.
Not that I know of. I have heard that the 1979 intake manifold flows better than the others, but according to Paul Yaw, the carburetors are all the same for flow.
Watch out for rust. Mosty under the storage bins behind the seats, and in the rear wheel wells. Make sure the frame is stright, and just in general in good condition.

~T.J.

whitey

Assuming I can get my hands on a reasonably priced 84-85 gsl-se, how easy would it be to put a carburetor on those 13b's? What all is involved?

Manntis

the 13B in the Special Edition (SE) is fuel injected and as such is a fairly reliable engine - some say the MOST reliable Mazda ever made. It's easy to wring performance out of it through intake and exhaust mods - going carb'd wouldn't necessarily do much for you.

They start at 135 HP from the factory with a broad torque band starting in the low RPMs. Change the intake filter to a free-flowing K&N, bolt on a Racing Beat header and exhaust system (eliminating the cats) and you're up in the 165 - 180 HP range before you've even touched the engine itself. Then there's street porting, etc.

whitey

And how might that effect gas mileage?

Manntis

Fuel Injection almost always gives you better gas mileage than carburation

whitey

OKay, thank you for all your help.

Roughly how much horsepower can the stock injectors support? And the ECU?

whitey

BUMP................

jonfc3s

iTrader: (3)

the stock injectors on a gsl-se are actually better than the injectors on turbo II's, many turbo guys actually upgrade their 550cc injectors, to the gsl-se's 680cc injectors. they will support enough power for the na rotary, but, if going turbo, upgrading might be necessary due to the motors 9.4-1 compression,......

whitey

Are you saying that an upgrade would be necasary to avoid detonation by running rich? Couldn't other means be used to avoid detonation?

At any rate, I plan to keep the car naturally aspirated, So from what you tell me the injectors will support all the power I will need. I would like to make a little over 210 whp, and preferablyhave the injectors running less then an 80% duty cycle (it was recommended I not exceed this). So roughly how much power would you expect the stock injectors and ECU to support before I might have to upgrade and have the ECu reprogrammed or chipped?

Wankelguy

I'd just put a Dellorto on it, myself. Then you wouldn't be faced with the limitations imposed by the stock FI setup. 210 whp is unrealistic for a stock-ported 13B, you'd need to do some healthy street-porting to get that much horsepower, and run a long-primary exhaust system which doesn't collect until right before the muffler.

whitey

See, thats what I was thinking. Once you have your fuel injection set up, thats it, there is no adjusting or tuning with out considerable difficulty. I figured a carburetor would be preferable. Right? Still, swapping to a carburetor is not exactly a peice of cake either, so if I got a GSL-SE I might keep it F/I and just modify the existing system according to my needs.

I am aware that the stock 13b ports would not allow for 210 horsepower, at least not N/A. I was thinking a pretty agressive street porting would be in the cards. I might be happy with less then 210whp though. That much power should put me in high thirteens with some radials and and LSD?

Wankelguy

The Dellorto swap is a piece of cake. The upper manifold bolts to the stock lower manifold. Couldn't be simpler. And the Dellorto has a choke, which the Webers do not generally have. Then, when you do some porting work, you can change venturies and rejet and the same carb will work. As for 1/4 mile times, I'm not a drag racer, but I suppose that a low ET depends on more than just horsepower.

whitey

OK, thank you for all the info you have all taken time to give me.


I hear a lot of people talking about 4 port side housings and 6 port side housings, and which is preferable to which...any links or info I should know about this?

Manntis

The 6 port is preferable. It brings in more air around 3000 RPM, which allows a broad torque band.

whitey

Some people have said that swapping in some 12a side housings would be preferable to the 6 ports.....why?

And no one has really given me any type of gues as to the amount of power stock gsl-se injectors can support.........is this cause no one is sure, or cause it varies, or just cause no one posted it?

1984special

I think people want the 12A 4-port side housings because there is much more hp to gain from porting. The 13B 6-port side housings do not gain much from porting because their size is limited by the aux. ports.
Mazdatrix has a good article here


I suppose if you are going to get the engine rebuit it wouldn't hurt to look closer into the matter. Unless of course you live with the emission *****, in which case, you would not be able to pass emissions with a port job.

Hope this helps!

whitey

Thanks very much for the link, very informative. How difficult is it to aquire a set of side housings from a 12a? And If I was tearing down an old motor to get ported and rebuilt it wouldn't be much more difficult to swap to the different side housings once I had them right?

rotor vs. piston

You should just go ahead and put that in you sig. That's all I ever hear you say BUT it is never the less true and the best way to start.

Rotor13B

Hey, He answered the question didn't he?