first things first, congratulations. rotary engines are fun, but they are also more maintenance than a piston engine. i will go through that in this post along with some other things. i hope that this post can inform and educate you without adding a lot of excess. a lot of things are also covered in the FAQ thread that is also pinned to the top of the board, but this is just kind of the bare bones of what you need to know.
oil consumption; the rotary engine is designed to burn oil as a part of the lubrication process. the rotors cannot seal the combustion chamber like the piston engine can, so the engine meters a little bit of oil into each combustion cycle in order to lubricate the parts inside of the chamber. because of this, there is some debate on what oil to use, but i will go into that a little later. since the engine burns oil, you either need to top off the oil occasionally or just do more frequent oil changes like i do. i change the oil at 1000 mile increments rather than the 3000 mile recommended increments. this means that i never have to top off the oil in normal driving conditions, but i have to add about a half a quart between changes under harder conditions. just keep an eye on the oil level for the first few months until you can get into a pattern of changes and top-offs.
fuel consumption; if you have been through your first tank of gas already, then you know that the rotary engine isn't fuel efficient. it hasn't been built for efficiency nor has it had the kind of research and development that the piston engine has had. these two factors combined, means that the rotary is expensive to operate per mile. the engine is, however, extremely efficient in power per liter. the rotary engine can easily produce 100 hp per liter naturally aspirated, where a modern piston engine has to have serious tuning and valve timing to produce that without forced induction. turbo rotaries tend to consume more fuel, but produce more power (which brings me to my next point).
forced induction; with a rotary engine, there is really only one type of forced induction to consider; turbo. the rotary engine is pretty small, so if you supercharged the engine, you would be almost doubling the size of the engine. the engine also lacks the torque to efficiently power the compressor. turbo, on the other hand, does not tax the engine the same way that a supercharger would. it basically operates on wasted energy of the motor, in that it uses exhaust pressure to turn a compressor which forces air into the intake. rotary engines can handle larger turbochargers than piston engines of comparable sizes, so that is a good thing to consider when choosing a compressor size.
i have a few more things to post, but i will post those later.
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RE: GOT/LOOKING FOR MY FIRST ROTARY. WHAT TO EXPECT.
here are a few more things to look at for the daily operation of your rotary.
oil; i have talked about oil already, but this is a little more specific. as i said above, the rotary engine is designed to burn oil. this means that the engine is a little more restricted on what types and weights you can use. i will say that you need to stay between 10w-30 and 10w-40 for moderate weather conditions and step a little higher or a little lower for more extreme conditions. now, here comes the constant struggle and debate. synthetic or conventional. i will say that i know a few synthetics that are fine to use with a rotary, but i don't trust that many of them. royal purple, castrol syntec, and total (elf) are all three just fine. any others, you are kind of on your own. other synthetics may not burn correctly in the combustion chamber and may clog up the ports to the point where the peripheral ports will just no longer work. i, personally, use conventional (castrol gtx) and i have good luck with it. there is no lack in performance and the ports all open from what i can hear. you can pull the oil metering pump and premix gas and oil in the tank if you prefer, but you always have to remember to mix when you pump gas. i will put formulas up for this in a later post.
gas; this is also kind of an area of debate. do you use premium, do you use regular? all that i can say is that you need a gas that will keep your ports clean. this is why i recommend premium. if you don't want to foot the bill on premium every tank, i recommend either running a clean burning additive every third tank or premium every third tank. this will help to keep your ports clean and run the motor more efficiently. all that i can really say is don't be a cheapskate when it comes to gas. this is what could make or break your motor in the long run. some people are doing E85 conversions, which are pretty simple to do on a rotary since there are no valves to burn up and the motor benefits from higher octane. i will go into methods for that in a later post also.
idling; this is a very important issue with rotary engines. the engine has aluminum and steel components which tend to shrink and expand at different rates when heated. if you don't let the engine idle for a few minutes before driving, you will be forcing the aluminum parts to expand much faster than the steel parts which will cause the seals between these parts to be stressed to the point of breaking. this is one of the things that will make the difference between going 100k miles between rebuilds or going 300k plus without a rebuild. you might notice in your rx7 that the engine idles really high for a few seconds when it first starts up. this is designed to warm the pre-cat before operation, but really isn't the best thing for your engine. if you don't want the engine to idle high, tap the gas pedal right after ignition to stop it or just start the car in gear with the clutch pushed in.
that is all for now, but there is still more to come, so stay tuned.
RE: GOT/LOOKING FOR MY FIRST ROTARY. WHAT TO EXPECT.
going from naturally aspirated to forced induction:
there is a major achilles heel in our cars when it comes to going from naturally aspirated to forced induction. our cars are not the kinds of cars that can just have a kit bolted on and call it done. personally, the only kits that i have ever seen are upgrade kits, which means that you need to have all of the turbo framework before you can upgrade. the problem here is that you can't just buy the left-over parts from the next guys upgrade. you need the harness, ecu, sensors, etc. on top of that, the n/a model and the turbo model have different transmissions, driveshafts, and rear-ends. there are a couple more that have a LSD in the rear, and here is the list;
89-90 GTUs (not the 89-90 GTU, though)
some companies from time to time offer n/a to turbo swaps, but they come in and out of business so quickly that it is impossible to keep a permanent list of them. the best and most reliable way to go turbo is just to go ahead and buy a turbo II. the next best is to find a turbo II donor and swap them straight across. third best step to follow after that is to find an aftermarket company where you can find all of the parts. PM me and i will give you current info on where you can shop and what you need to do.
i have gotten a lot of questions lately about engine swaps, so i am going to go ahead and cover it in a FAQ post here. this should clear the air on a lot of swap questions.
first things first, the most common engine swap questions involve the second gen rx-7's (FC). that is what i will primarily cover, but i will also go into third gen (FD) and a little into first gen (SA/FB) swaps.
the first thing that you need to consider is the drive train of the car, rather than the motor. there are some options here and i will try to get all of them out. first option is to keep the stock drive train and swap a new motor. this is an economical option, but not the best. if you keep the stock trans and rear-end, i don't recommend putting a lot of power through it. the vehicles listed above are the only fc's that came from the factory with a limited slip; all others came with an open diff. this means that both tires won't spin off of the line. because of this, you will have traction issues here if you keep the stock rear-end. the stock trans is also a weak point on the naturally aspirated models. no FC transmissions were anywhere near as strong as the turbo II trans, so i recommend swapping the trans when you swap the motor. this will save you a little headache in the end.
if you do decide to keep the stock trans, you will need to keep the stock flywheel, clutch, and counterweight to adapt the new motor. if you swap the motor and trans, but not the rear-end, you will need a new drive shaft to adapt to the new trans. those are either custom built or ordered. www.mazdatrix.com has a drive shaft to help you here. if you swap the whole drive train, i recommend finding a donor car that has all of the parts there. you can go new on some parts, but you could find a donor to get parts like; drive shaft, rear-end, half-shafts, sway bar, etc. if you go this far, you may as well go ahead and replace the car. the only thing that you could gain from this would be turbo swapping a convertible, which never came turbo'ed. whether or not you use an FC trans, you can still swap another series motor. the bolts line up on all 1.3 and 2.0 motors. just remember that the trans decides what clutch, flywheel, and counterweight that you need to use.
the most common swap is naturally aspirated to turbo. most people keep it in the same series, but a few will swap FD motors into FC's. this is overkill, for the most part, unless you plan to build for ridiculous power. most people swap the twins for a single on the 13b-rew-tt motor anyways, mainly for the fact that the twins are extremely hard to tune for. the FC 13b-t is a solid motor that can be built for a lot of power and has plenty of after market support. there isn't really any reason to spend the extra money on the rew, except for really high output situations. even then, i recommend just going with the cosmo 13b-re motor anyways. not a whole lot more money, but easier to gain more power because of the configuration of the motor.
if you own a naturally aspirated FC and swap an FC turbo motor into it, you don't need to modify the motor mounts. the mounts will line up from FC to FC. if you are swapping in an FD or Cosmo motor, the motor mounts will need to be modified. www.banzai-racing.com has the mounts to do that. their mounts are the same to drop the FD, RE, and 20B motors into the FC. i will talk more later about the 20b, so let's not get ahead.
even though that information seemed in-depth, it was just the basics. now, we will get into the specifics.
onward to motors; as stated before, the simplest swap is the FC n/a to FC turbo. here is a bill of material for just the motor;
long block (rotating assembly, housings, irons, intake manifolds, turbo & manifold, all sensors, fuel system, etc.)
proper emissions equipment or block-off plates for it (block-offs found here www.banzai-racing.com )
power equipment, if applicable (p/s pump, a/c compressor, alternator)
management (stock ecu or custom stand-alone ecu)
wiring harness (stock or custom is fine. all depends on the management. donor would help here too.)
you will also have to decide on cooling. you need an intercooler and you need to decide on cooling for the radiator. if you get a turbo II hood, you can use the intercooler from the turbo II. if you use any other hood, you need to go with a different intercooler (front-mount, v-mount, air to water). then, for the radiator, you need to decide on a fan. the stock fan is surprisingly good. it flows plenty of air and basically has a failure rate of nearly 0%. the tax on the motor isn't really that bad either. you won't gain a whole lot from an electric fan and you will have to get something that is extremely powerful.
alright, back again. so much covered, but so far to go.
now, i covered FC to FC, but what about cross-series? getting there. the reason that i did that first is because of the fact that all of it is the basically the same. here are the differences;
1. if you swap an FD or cosmo motor, you cannot easily reuse the stock intercooler. it is impractical, so you will just want to explore other options.
2. you also will need new motor mounts. plugging again here, www.banzai-racing.com as always. like i have said before, they have great products and customer service.
3. you cannot even remotely use the stock harness out of your car. you need to either use the harness out of the donor or build a custom one.
4. you need to do an electric fan swap.
you will still need all of the same parts (motor, sensors, emissions, etc.) to do the swap, but it will just be a little different over all. the main advice that i have is that you will want to do a single swap. the twins don't tune very well and just turn into a headache in the end. i read a post once titled "rich man's non-sequential" that was all about reconfiguring the stock twins to run parallel instead of in sequence. it was the only good way to do it, and looked extremely complicated. in the end, the hp numbers weren't any better than a single swap. moral is, save time and money with a single.
the final message with this swap; you could do just as well dropping this extra money into modifying the turbo II motor. it costs considerably more over all and the extra power doesn't translate dollar for dollar. basically, for the money, you could rebuild the turbo II motor with a street port, throw in a hybrid from bnr, build a front mount intercooler, and throw in some new injectors with an rtek ecu. with the same money, you could buy the REW, put together a front mount, swap for a single turbo and manifold, get an electric fan, and buy the motor mounts to tie it all together. you would still need to deal with management, a harness, and adapt the stock radiator to the new motor. basically, it boils down to you settling for what you are actually going to use. sure, it is cool to have expansion space, but you don't really need all of it in the end. are you really going to build a 700 hp beast? probably not. most people will put together something that pushes 250-350 at the wheels and just enjoy it.
The stock fan flows a lot of air, so you need to get something that will flow a lot. Most people just get a fan from a ford taurus and wire it up. The shroud fits the radiator perfect. In all honesty, there are a lot of better options for mods. An electric fan swap doesn't do a whole lot of good.
just picked up a 88 convertible n/a 5 spd. First thing i want to do is ditch the mechanical fan and use an electric unit.. anyone had any experience with this... black dragon has one for 129 or whatever, just curious. pusher puller that kind of thing? ne one in vegas?
berzina123, If you want to do that I would HIGHLY suggest you build a fan shroud. It can be done. But you lose cooling when it is done. The e-fan out of a Taurus might be cheaper. No real gain doing an E-Fan swap unless you are running Turbo with a lot of upgrades and a good cooling system.