A lot to learn...

[Jay]

Looking at Haynes manuals, etc.. I realize I had a LOT to learn about the RX7 engines. I'm sure it'll all make sense once I start tearing it apart.

The car I'm dealing w/ is a bone stock 1979 RX7 w/ a 12a. Where's a good place to start to boost performance on these things, or would I be better just dumping the engine in favor of a 13b?

Are any parts interchangable between the two engines?

[2ROTORMOTOR]

Ok the 12a engines are good, but a 13b is better. A 13b swap isnt that hard at all and its a noticeable gain. But the best way to learn, is to open your engine up, once its open and you see whats inside with your own eyes you could maybe have a better understanding of it. Now Im not necessarily telling you to open up your engine if you dont know what you're doing, but if you buy a 13b, and swap out your 12a, open it up. Now there are some videos out there that show you how to rebuild the engine, go to ebay and type rotary rebuild video and see if you find it. The haynes manual is good but it leaves alot of stuff out.

[Jay]

Well, I'm pretty competent when it comes to cars. I did the V8 swap on my Malibu. I also have a nitroused Neon. I've been fabricating parts for a few years now, and been rebuilding engines for about 10. I understand the Wankel as a concept. It's all the little things like ignition timing and a/f ratio that I need to get a feel for.

[2ROTORMOTOR]

o ok then. But remember when rebuilding the engine, its easy to misplace things and put thing where they do not belong. But other than the engine itself every thing else is pretty str8 forward. Timing is still corrected by putting it on the leading Which is equal to #1 plug. I mean everything else is pretty much str8 forward except for the actual workings of the engine.

[Jay]

What are the usual bottlenecks/problems w/ these engines?

[2ROTORMOTOR]

ok, first of the one main problem that you'll of people complaining on, is the reliability issue. But I for one will tell you that any engine that is abused and not treated right will die unexpectedly. These engines are very reliable as long as you take care of them. Now, one way to keep this engine runing w.o problems, is to control fuel that it receives. Now u wont need to worry about it in stock for, or with mild upgrades. But once you start going with boost and all of that, it becomes a problem. Nitrous is good if you put a wet shot. You could even go into a 75shot using wet injection.

[Jay]

I plan on sticking w/ NA for the time being, to get a feel for the car. I might toss on a 50 shot for the hell of it, but this car is mainly for drift. As light as it is, I don't need much power.

The reliability doesn't scare me. I owned a Jaguar. :)

[DongeR]

there was a video some place of a fb doing 9k parked for 9 mins. then the exhaust caught on fire. great vid and great engineering. i believe if the radiator had an overflow of water i doubt it would have blown within 20 mins.

[84gslse]

i will be swapping in a t2 engine and all of the associated components pretty soon, would you be interested in buying these, car has 160000 miles. but i doubt the engine and tranny do. i got to drive my friends 85 gsl-se (with the 13b) and it didnt feel nearly as fast as mine did. it would be a solid engine and tranny to start from. let me know if you are interested

[Jay]

Buying the NA 13b? What kinda figure did you have in mind? Where are you located?

[84gslse]

im not sure, i was thinking 450-500 would be a decent price for everything, because im not gonna need it anymore but im not sure when it will be out of my car. im in great falls, montana. nw montana about an hour south of canada

[2ROTORMOTOR]

You know a local junk yard may have what you want. There are 13b engines readily available. And if you want to run n/a power, and maybe spit out a lil money just do this. Get a TII engine and have it ported, depend on the emmesiion laws in your state, there are a couple different ports you could do. P-P is one of the best ports ever for effective n/a engine build. It puts the intake ports on the rotor housing instead of the plate. But for alot less money, you could get the Bridgeported engine, along with high comp. rotors, running a carburator. Thats one of the best setups for fb's. I say you look into it if you want to run nitrous or just plain ol n/a

[Jay]

Lemme ask a stupid question here. T2 = twin turbo engine?

I know high boost piston engines are lower compression... are the rotaries?

[2ROTORMOTOR]

no and yes. The t2 is the turbo engine found on 2nd gen rx7's. and Yes they are of lower compression compared to the non turbo.

[Jay]

I'm assuming different rotors give you different compression, similar to the piston. Is there anything in the rotary that took the place of the cam? What I mean is... upgrading the cam on a piston engine can net some decent gains. Is there something similar to be done on the rotary?

No not at all. Intake Timming is done by the rotor it self

[2ROTORMOTOR]

I'm assuming different rotors give you different compression, similar to the piston. Is there anything in the rotary that took the place of the cam? What I mean is... upgrading the cam on a piston engine can net some decent gains. Is there something similar to be done on the rotary?

Nope. And thats the beauty of it. porting and polishing are a rotors best friend. You could get some nice high comp rotors though and that along with some other upgrades will give you the upgrades your looking for.

[Jay]

Okay, so "duration" and "lift" are set. No cam timing (duh.) I'm sure there's spark timing, right? Would running an MSD or similar digital ignition help at all? I know RX7s have problems w/ spark at low RPM.

I've done my share of porting/polishing in conventional engines. I'm sure the same theories apply? Smoothing, enlarging, reshaping?

[2ROTORMOTOR]

Okay, so "duration" and "lift" are set. No cam timing (duh.) I'm sure there's spark timing, right? Would running an MSD or similar digital ignition help at all? I know RX7s have problems w/ spark at low RPM.

I've done my share of porting/polishing in conventional engines. I'm sure the same theories apply? Smoothing, enlarging, reshaping?


Yea you could set spark timming up to a certain point( not very much). But if you have a distributer then one of the best upgrades to ignition is a blaster coil from msd. But on 13b FI, Theres nothing better than the stock ignition. When you go F/I then is when spark amplification comes handy.Also spark is not a problem at all on rx7's. If you are talking about how they run rich, its a totaly different story but has nothing to do with spark.

[Jay]

As I understood what i was reading, they run rich at low RPM to compensate for the exhaust gases that sneak into the combustion chamber.

[Quakefire]

Well for reliability. (Sensitive people and young children should not read this)


I saw a video of a guy draining all the oil, and all the coolant out of his 12a and putting a brick on the accelerator. They had bets of a couple minutes for the thing would fail. After 10 minutes the engine was on fire and still running, untill of course it threw a rotor out of the side of the car.

I havent heard of any piston engines running for 10 minutes without oil at full throttle

[silverspeeder]

my friend told me to replace the stcok diff. if i do a 13b swap on my 1981 RX7.?? do i really need to im just looking for a little extra power for my car???