conatus

so i plan to transplant a rotary engine from a car into another vehicle where space and weight is a concern so i have a few questions. what model car can i find a naturally aspirated rotary engine? how much horsepower/torque will this engine have? how big and heavy would it be if you striped it to its essential operating components?

Aaron Cake

iTrader: (1)

NA rotary engines were available in all of Mazda's rotary cars from the beginning until '93. With the 3rd gen RX-7, all rotary engines made were twin turbo. Then in 2004, the RX-8 was released with a NA 13B Renesis.

You will likely want to use the engine from an '86-'92 FC RX-7. These came both turbo and NA. The NA engines are very common. 86'-88' makes 146HP and about as much torque. 89-92 is 165 with about as much torque.

Stripped to just an alternator, the 13B from those generations is about 300 LBS.

Now it's time for you to do some searching and basic research, as I've given you a place to start.

conatus

i think i misspoke when i said naturally aspirated. it also has to be non fuel injected.

farberio

iTrader: (7)

You can make any 13B non-fuel injection. I think the 12A's were non FI.

diabolical1

iTrader: (3)

welcome to the board.

you probably need to give us some idea of what you're trying to do just so that the info you receive is most relevant.

as far as fuel injection is concerned, USDM Mazda rotary cars were all carbureted pre-'86.

Crit

iTrader: (6)

Except for the GSL-SE, which used a simple 2-injector EFI setup, similar to the early 2nd Gen.

JoeyMazda

What kind of car are you putting the rotary engine in?

Aaron Cake

iTrader: (1)

GSL-SE being the exception.

All 2nd gens have 4 injectors. Two primary, two secondary.

conatus

i am not putting it in a car. much smaller than that. that is why size and weight are critical. the whole thing can only weigh 1250 pounds including my 290 pound self. it can have a 53 inch wheelbase and about a 4 foot maximum with. i plan to use a gm 7.5 inch rear end (or similar) cut down the the with i need. i'm still looking for a transmission short enough to still have a short drive shaft (flex is a concern). i would like to keep the weight as close to the back as i can as rear wheel traction is critical.

Crit

iTrader: (6)

Yeah Aaron, but outside of the 4 injectors, the S4 system. Same AFM setup, no VDI, etc.

diabolical1

iTrader: (3)

nice catch, guys. yes, i totally overlooked the SE in my previous statement. my bad.

RotaryRocket88

iTrader: (7)

So it's a small 1 person vehicle? If you need a compact driveline, why not use a VW trans-axle? It's what just about everyone uses in dune buggies, and that includes cars with V8s & turbo engines. The transmission gears are beefed up on high hp applications, but an NA 13b will be fairly easy on it (~140 ft. lbs. torque stock).

They're fairly light too. Somewhere around 70lbs., and you'd be able to get rid of a separate rear-end and driveshaft. The only catch is you would need to rear-mount the engine.

FusedKNIVES

Okay i have a 89 rx7!! and recently the check engine light came on. The thing is that when it comes on i can't accelerate when i push the petal to the floor the car sstarts bouncing as if its trying to breath or catch its breath in a way! it wont go fast at all. and when i turn off the car and turn it back on the check engine light is gone! but then it comes on again after awhile of driving.. this happened to me last week, then for the weekend it didn't do it, now it started today again.. anyone know what may be the problem?

thanks!

conatus

rear mounted engine is a no go. it also needs to be a solid rear axle not that, that could not be accomplished with the vw but why not just start that way.

Aaron Cake

iTrader: (1)

Not quite...

The AFM in the 2nd gen is a 5V unit, 1st gen is 12V.

The 2nd gen uses a variable reluctor crank sensor with a trigger and home wheel, as opposed to triggering from the distributor like the 1st gen.

Crit

iTrader: (6)

Which is why I said similar in my original post. For God's sake, there will be differences, and I know them as well as you do. In the grand scheme of things, the SE motor was a preproduction trial for the S4, with unused center iron engine mounts, thermowax high-idle, abandoning the then-current beehive oil cooler and returning to the front-mount, etc.

conatus

i am looking at a 12a engine. is it possible to strip this engine down simple like engines were in the 60's.

Crit

iTrader: (6)

Well, the 60s would be a stretch, but yeah you can tear a 12A down to nothing but an alternator, water pump, and a few wires. It's pretty off-topic, so start a new thread and we'll talk you through it.

conatus

ok first i need to acquire the engine. another question: is the bell housing proprietary to this engine/transmission or is it fairly easy to bolt a different transmission to a 12a

Crit

iTrader: (6)

The turbo cars have a larger flywheel and clutch, and different tranny, but the NA stuff can be swapped without any trouble. The only caveat is to realize that the flywheels are all sized to counterbalance the internals of the engine they're mated to, and should never be swapped. If you have a good 12A with a bad flywheel, then it needs a replacement from a 12A of the same setup. Keep the flywheels on the blocks, and you should be able to swap away.

Aaron Cake

iTrader: (1)

I really don't want to make this into a big deal, but you claimed that the 2nd gen used 2 injectors and that it had the same AFM as the 1st gen. That's just untrue.

Also it is only S5 2nd gens that have VDI.

I don't want to go splitting hairs here, but as you posted, the information is not correct. It could just be because of the way you said it vs. the way it can be interpreted. Someone just jumping into the thread without prior knowledge could be confused.