Rotary vs. Piston rebuild
 

Is it true rotary engine is harder to rebuild? or piston? My friend said piston is way easier to rebuild and less complicated.

The rotary is easier to rebuild by far. You have less things to measure and fewer parts to deal with. The only time consuming thing is cleaning everything.

I think so too, i post this thread up bcuz my friend thinks i am retarded and inexperienced to engine knowledge for thinking rebuilding and working on rotary is easier. Well this basically opinion base and there is no right or wrong. But my friend got flare up over this convo.

The only thing that makes it hard is not having the right tools.

rotary is much easier. I agree that the cleaning sucks, but once you do one or two, even that isn't that bad.

Depends on the engine, lol. 32 valve DOHC v8 vs a SOHC 4banger? Riiiiiiiight :P

The real thing is with a lot of piston engines you can do quite a lot with the engine still in the car.

Very true.

I think it is because they think that it is hard to work on a rotary and not have it jump from the car and beat their piston lovin ass.

After rebuilding a few 4 cylinder, and 6 cylinder and 8 cylinder motors (I do it at work, so I'm forced too) A rotary is 1000 times easier to rebuild. A piston engine to be fully rebuilt, and done right, will need lots of machining to the engine block, heads, and crank. Then the Valve seals, springs, lifters is a complete nightmare. A rotary can be rebuilt in your own home, and at most the sideplates will need a re-grind at most, and is rare. In fact this is why I am forcing my girl to get a Rx-4 and sell the Mx-6, after two V-6's dying slowly, I dont even want to start to rebuild that damn V-6, would cost a fortune to do it right.

Come to think of it I cant think of anything that can potentially hurt you inside of a wankel, In my aviation maintance class we learned that (in airplanse at least) that the exaust valves have something (dont remember what) in them that melts and moves (in a sloshing movement to help keep cooler, and if this core touches oxygen such as grinding to far or cutting witha band saw it could explode, injure, or blind you or something like that.

I think it is sulfur. not sure though, and dont know why sulfur does such a thing, but I will take my teachers word for it and not find out for myself.

wow, i guess i kinda prove my friend wrong about rotary engine.

Ive helped rebuild a couple and I was very worried at first. After I saw how easy it was I was amazed. If the parts were cleaned you could rebuild a rotary in an couple hours. Im sure some of the more experienced builders could do it in less than that.

yes we can pull my engine, tear it down, clean it, assemble it, and reinstall it in a weekend.

your friend must not know how a rotary works

to rebuild an A-series piston engine for a mini requires the following to be done:

rebore by 20 thou (minimum)
suitable replacement pistons
new piston rings + oil control rings fitted
crankshaft re-ground to next size
cylinder head total stripdown, light skim to clean
valve guides replaced and reamed to suit
valve seats re-cut (if bad)
valves re-seated
8 springs to be compressed, then valve caps and collets fitted
new main bearings an big-end bearings to be fitted (5 total)
new timing chain fitted
new oil pump
new clutch
a billion new gaskets


and thats not including the gearbox which is also the sump!



and to rebuild a rotary, it's just a general bit of measuring to make sure things are within their limits, some new apex seals, some new side seals, and a new oil pump if needed



mini's are my passion, but I'd rather rebuild a rotary any day!

Ask your friend what's going to be so hard about a rotary and what is so easy about a piston engine? You don't need piston ring compressors as a start. You don't need to bolt anything onto the crankshaft (eccentric shaft). It just slides through the rotors. Our bearings are pressed into the stationary gears as one piece. We don't need to install each half in the bearing journals. Valve lash adjustments? I don't think so. Valve springs to install? Nope. Trying to line up a camshaft? Nope. We've got 5 housings that stack up like a sandwhich. 2 rotors that need their seals installed which isn't hard to do and requires no special tools other than a little vaseline and an eccentric shaft. What's the problem? We have no valvetrain components to deal with and the only bolts are the ones holding on the stationary gears and the 18 main engine bolts. If your housings need resurfacing, you just take it to a place with a lapping machine. They aren't hard to find. You don't need to find an automotive based machine shop to do valve jobs or rehone your cylinders. Lapping is about $25 a side here if needed. It's easy. If someone suggests that a rotary is harder to build than a piston engine, I'm not sure that I'd even want that person touching a piston engine. Doesn't sound like they know what they are doing.

MazdaTed there sodium filled valves and yes cars can Have them too, As an automotive tech I can say a Rotary is easier to rebuild than any piston engine. people are just afraid of Rotarys beacuse must people don't even know how they work!!!!! even in my feild of work!!!!

:pat: AHH sodium, I knew it was smething with an "S"

Thanks for clearing that up, that will probably be on my FAA powerplant test in a couple of months.

I'd have to say a rotary is easier to rebuild, since there's really not much to do comparibly, and it's reasonably simple to put back together apart from the seals.
Definetely rotary easier than piston

a piston rebuild makes it run like a new engine...
i.e. reuse blocks, but bored up, new pistons, turned crank, oversized bearings, resized rods, etc etc

a rotary rebuild is more like an engine refreshen up...
i.e. reuse irons/housings, you can lap irons.... but new seals...

Uhh.... What?

You dont need to do a rebore, new pistons, or any of that crap, unless you ACTUALLY need to. Most people do a small bore for better breathing anyway, plus more displacement never hurts... but you dont HAVE to.

Longer rods mean you need shorter pistons, and you dont always need bigger bearings - but obviously, new bearings/rings cant ever be a bad thing. But you dont need to go to a damn machine shop to clean it up and put in new bearings and re-ring.

Hell, you can re-ring from below and leave the heads on, if youve recently done topend work and CBF'd to remove the heads, lol.

I see your point but why go through the trouble of just re-ringing the engine from underneith and not do a full inspection of the engine? There's more to a piston engines compression than just new rings. Youv'e got valve seats and head gaskets to worry about so the heads will need to come off and things taken apart to do the job right. I mean something else could go wrong that you could have fixed in the first place.

You dont need a teardown to inspect it, and generally if nothing is acting up the valve seats and head gaskets are just fine.

You tend to know when one or the other is screwing up :bigthumb:

small bore for better breathing?
do you know how a piston engine works?


rering while leaving head on? i want to see YOU do that. have you ever tried pulling a piston out from the bottom?

not really, both engines can be "like new"

on a rotary to make it like new, you would use new housings, or very lightly used housings..... and lap or get barly used irons ......

so both engines can be fully rebuild to like new, or reuse alot of parts....

rebuilding my motor was easy, although i failed in one part, and that was a coolant seal i didnt put enough of that hylomar stuff on so it got stuck between the motor when i slapped it together =(

Flame if you want, i figured i didnt do that bad considering that pulling out hte motor, dissasembling and reassemble, etc, was the first biggest thing i have ever done on a car other then install my intake! The car did run, i drove it for about 4 miles. but it ate coolant etc. Almost had it down my first time tho. I was 17 at the time. Im 19 now and im sure i could rebuild it again and just be more careful at the coolant seals and have a good running motor.