How Exactly Do You Blow A Rotary?
 

I mean, there's no rods to sling, but there's obviously lots of seals that can go out.

So what happens when you over-rev a wankel? Do the apex seals just sh!t themselves creating massive blow-by? Or does something else happen?

I was just wondering....the question just popped into my head...

Major issue with the standard configuration rotary ( 12a 13b ) . Is the apex seals are the weakest link in the compression phase.

Abrupt Detonation/knock will put all the pressure on these 2mm or 3mm seals, which can cause them to crack, break.

Where as piston motors. The biggest part of the blow, is at the piston dome ( hopefully ).

So when tuning, running a rotary , the fuel ratios and ignition have to be dead on.

The above is mainly , why do boosted rotaries blow.

As to non turbos, they are inmortal... okay maybe not. But much harder to kill them, unless doing dumb stuff like over revving for long periods of time. ( here you'll spin a bearing, like a piston motor )

Here's a video

http://www.youtube.com/watch?v=Z7kj9...feature=relmfu

If you can stand the voice,

Here is a video of the engine failures

http://www.youtube.com/watch?v=jDwln...feature=relmfu

I believe that the video posted mis-diagnosed why that engine failed... Just saying.

I Believe the video just read out , what the blog stated why those motors failed.

I believe its pineapple or mazdatrixes fail motor section pictures.

Most rotaries die because of pre-detonation, causing the apex seal(s) to shatter and break. Pre-detonation can occur for any number of reasons. You can have a bad tank of gas and pop your engine that way, your tune can be off and it leans out too much, you can hit a massive boost spike and pre-det that way, super cold winter weather can cause your boost pressure to climb, causing pre-det, etc., etc., etc.

If you spend all day cruising at the redline then you're going to damage the motor. However, unlike pistons, rotaries aren't as prone to damage when you take the revs high.

Your biggest killers are going to be predetonation, overheating, and carbon buildup. This is the main reason why Auxilary Injection (Water Injection/Meth Injection) is so pupular with this community. A/I effectively combats the biggest killers of our engines. Using A/I is not a promise that you'll never blow your engine, but it's going to take a lot more abuse to get there.


Long story short...

The "best" way to blow a rotary would fall under either:

Bad tunes (pre-detonation)

Bad gas (pre-detonation)

Too much boost/Lean conditions

Overheating

What would you say killed 'em? I mean cracking the housing on the combustion side makes sense.. Not entirely sure what causes the heat to go up, but yeah. Also don't get why that keyed shaft was worn? Lack of lube?

So in other words, the same exact things that kill piston engines, lol. Where does the auxiliary injection get injected? Directly into the combustion chamber? Or into the mani?

So if predetonation is typically a problem, what typically causes overheating (I'm assuming constant overrevving?)? I'm assuming with carbon build-up there's not much to be said...just happens over time?

Not sure why the vid said they're not vulnerable to pre-detonation, seem they're perfectly vulnerable to it if you're boosting...any motor that uses compression is vulnerable to it.

Yeah, figured those poor apex seals take a beating :(. Knock can destroy anything, IMO, that's why it's so important to tune if you're boosting. You said the ignitions have to be dead on..does that mean you don't retard ignition as much for boosted rotary apps as you do piston apps? I mean I assume you have to retard it none-the-less...what's the timing in stock form from TDC (or what is the equivalent of a rotary of TDC?).

Sorry about so many questions guys, it's a completely new world to me, haha.

EDIT:
Thx for the vids btw, I kinda already knew the stuff in the first vid, but the failures vid was a great help!

DUDE that was OUR engine, it failed due to the stationary gear letting go @the rev limiter (8250), it did NOT crack because it was hot.

http://fc3spro.com/TECH/HOF/K2RD/k2rdhof01.html

the stationary gear broke, so the rotors stopped orbiting, and started spinning, which turned them round and broke the housings, when all that seized up, it broke the flywheel key, because the car was still going 100mph....

its not a typical failure at all

So in other words if the stationary gear breaks, the whole engine is typically completely hosed?

So I'm guessing this doesn't happen often?

well i've seen two, this one, which was on the rev limiter for a good 15 seconds at a time, every lap, and eventually it just said no, and came apart. the failure was blamed on the rev limiter BTW, hitting it is ok, but 15 seconds is too much.

the second one, also a road race car. had a missed shift, so instead of 4th it got second, which is like 12,000rpm or something. it damaged the gear, but it still ran, it just sounded like a piston engine that needed a valve adjustment.

its pretty rare, i've only seen the two in the 20 or so years that i've been playing with these things.

on STOCK cars, the biggest mode of failure is from a burst hose, or radiator, and thus overheating. the rotary is less tolerant of overheating than a piston engine. the 12A cars also have metering pump failures so they run around with no metering oil.

plus all the stupid crap people do like run without oil, or jack the car up with the fuel lines, or put the distributor in wrong, etc etc.

the apex seals don't really blow until you start modding the car. the stock ECU is tuned for a stock engine, so when you put the big exhaust on there, it might not be rich enough.

Yeah, I hear ya, I've def. driven Honda/Acura engines hard and they don't miss a beat. But I don't hold them there, either.

lol, Yeah, same exact thing happened to my friend in his type R - blew the motor sky high. Though I'm really surprised it couldn't take a 1/2 (if that) second rev to 12k :-\.

The valve noise, was that the trans gear that chipped or the stationary?

Fair enough, with my luck it'll happen on the first day, lol.

12A? That's the predecessor to the 13B? 1.2L 2x rotor?

Metering oil/pumps? What's that? Is that the bit that's injected into the chamber for ignition for the lubrication of the apex seals? Might be talking out my ass here but I read that somewhere.

Yeah, a well built motor can't fix stupidity. Though I ran into a dealership where the guy was telling me this woman ran her car 30-50 miles (civic) w/ no oil, dramatically shortened its life I'm sure, but it was okay after that. Not sure how much he was exaggerating, never ran a car w/o oil.

Can you elaborate on jacking up a car with fuel lines? huh? Completely lost me there.

I plan to mod it :).

I want to get into the rotary game a bit, I'm in the H/A game right now, been so for the last 6 years. Though I kind of want to change it up. I don't mind going the extra mile to learn about rotaries, nor do I mind going the extra mile to do the maintenance. I just don't want to dive into the rotary world and lose reliability, get what I mean? I'm generally nice to my car, but I like to have no reservations about pounding on it from time to time. Just want to make sure if I treat a rotary nice and <3 it, it'll <3 me back when I'm pounding on it, y'know?

I originally found an FD down in NC with the motor out - cheap. But somebody bought it before I did.

Now I'm thinking about getting an FC (with a motor), having it as my daily, but rebuilding a SEPARATE 13B for light/mid-range boost, then swapping it in come Spring. Not sure what goals are realistic, not sure what these motors can hold in terms of power in stock form. Certain goals are only realistic for certain motors.

we've road raced an integra since 2004, the rotary is better :) our current engine is at 50+ hours and its still together, but its down 15hp, its tired....


lol, we blew a type R up too. the engine AFTER the one in the pics put up with a season @9400rpm with no complaints, i still have it, it is tired, but it also came out of a junkyard!

the type R saw 9600, and um dropped a valve, and you know the rest, broke the block, head, piston....


yeah the 12A is the 1.2 liter version, they started with 60mm wide rotors for a 960cc 10A, widened it to 70mm for 1146cc 12A and then 80mm for the 13B.

the metering pump is the thing that lubricates the seals, the rotary doesn't have the oil spray that a piston engine does so it needs either the pump system, or you can mix oil with the gas



lol this is true! i've seen a couple cars run really low/out of oil and be ok, but usually not! so yeah the normal stuff applies...


[qoute]
I plan to mod it :).

I want to get into the rotary game a bit, I'm in the H/A game right now, been so for the last 6 years. Though I kind of want to change it up. I don't mind going the extra mile to learn about rotaries, nor do I mind going the extra mile to do the maintenance. I just don't want to dive into the rotary world and lose reliability, get what I mean? I'm generally nice to my car, but I like to have no reservations about pounding on it from time to time. Just want to make sure if I treat a rotary nice and <3 it, it'll <3 me back when I'm pounding on it, y'know?

I originally found an FD down in NC with the motor out - cheap. But somebody bought it before I did.

Now I'm thinking about getting an FC (with a motor), having it as my daily, but rebuilding a SEPARATE 13B for light/mid-range boost, then swapping it in come Spring. Not sure what goals are realistic, not sure what these motors can hold in terms of power in stock form. Certain goals are only realistic for certain motors.[/QUOTE]

i like the idea of buying a running car and then building a motor. at least you get to drive it and sort out everything else before you go nuts with the engine.

the engines are pretty simple, and most of the piston engine things apply. chamber (cylinder) sealing is KEY, so the housings need to be new or really nice, all new seals etc etc.

on the forum people are doing 400-450 hp and then adding water injection or race gas before trying for more, in japan they skip the water injection and i've heard of 700 on PUMP GAS, which is almost unbelievable. in japan they just use OEM parts too, and a GOOD ecu (they like the power FC or motec) and tune it.... i'm not sure why they can do that and we think we can't.

http://www.youtube.com/watch?v=rw0LFhJFxSs


you ask to much from it....that's when it will blow.




but it sure can be fun.

http://www.youtube.com/watch?v=0BGGB...eature=related


Things to keep in mind Goopy apex seals, ALS apex seals....They can help avoid alot of problems.

everybody has their own opinion of what is "best" when it comes to aux injection. some go for the "pre turbo" approach where it shoots directly into your inlet of the turbo to atomize the liquid through the intercooler and piping.

some say that it wasnt meant for that and that it works "best" closest to the rotor housings (or as close as you can get them on the manifold)

others go fo the after turbine, pre manifold approach where it is right before the intake mani .


either way you decide to go is your decision bc its going to be you who is fixing it is something goes wrong, but whatever you do decide to do , auxilary injection is a nice option to have . not only does it reduce pre detonation from over heating and ect... but it acts as a steam cleaner for your engine internals if im not mistaken :nod:

The 350-500hp range is achievable on a 13B even without a comp tune.
I'm running 420hp on a T|| motor, street port, t3/t4 hybrid turbo@ 20psi, front mount intercooler, and only a threshold gain controller. And it's been at 15psi (380hp) for 65K and it's been driven hard and so far no problems at all.
So along as the motors are taken care of they will last long even taking abuse the whole way.

And the 700hp margin is easier to achieve in japan cause they have pump gas at 110octaine, hence why imports engines (typically skylines without re-tunes) develop engine "ticking" after a short while.

To OP: if you want into the rotary scene and want reliablility get a computer tunable ecu, that way when your just daily driving you can't use a more conservative tune, than when you want to tear it up on the streets or the track just take 2 min and change the tune (some programs have save slots for easy tuning instead of tinkering every time).

I have a question on this particular subject. It's about 30*F here in Indiana and I tried firing up the FC. It's decently modded. ~300HP with after market turbo intercooler and ecm for the broad stuff. This is my first rx-7 and when I tried to start it ran at 1500rpm and quit. then restarted and tried to hold 1500 rpm to 2000rpm and it started popping loudly. Awful explanation, but I'm worried that it's detonating I quit trying to get it started and I thought I'd ask here before I do something I will regret later. Is it just the cold weather starting or is my car's setup? It's kinda got me worried...Sorry for noob questions...just put my mind at rest or not.

popping, i would rater think there is somethig wrong with igition or fuel delivery then.

knock/predet sounds like marbles in your intake and believe me once you have heard it once, you wont forget that sound again.
here, watch this:

http://www.youtube.com/watch?v=WuCUGcqO5SE

Immediate failure happens by spinning/siezing bearings, or breaking a stationary gear, or walking a rotor gear, or having a rotor hit the side housing or sometimes smack the pinch in the rotor housing.

Apex seal failure from overrev can be a five point palm exploding heart kind of thing. The engine runs fine because the seal is only cracked. The next time you rev the engine over a critical point, it lets go.

yea it was not knocking. more like a firecracker pop it was coming from the exhaust. maybe detonation? i haven't heard anything like it before.

detonation, ping, knock... same thing, just different words ;)

As i said, my money is on your fuel delivery system and ignition system, start there ;)

To OP.

The main reason Rotaries are thought of as "weak and not reliable" and breaks down, is:

1. Bad owner tuning the rotary as if it was a piston engine.
2. poor or no maintanance and no proactive ownership reguarly checking small things like scanning oil for metal residue when changing oil, cleaning their injectors every second year when owning a tuned car, regularly inspecting and changing coolant liquid.. those things that goes above and beyond regular mantanance for the everyday owner.
3. little knowledge of how the rotary engine works and old technology leading to engines dieing on you for reasons we now know how to prevent( pre/post AI enlightenment for ex)

Thanks oyvindjs for the advice,

Sorry if this is thread jacking, but I felt it was applicable to the original post. I've never heard a 13B with detonation, so i don't have that to compare to. From the way it sounded, it was coming from the exhaust. That was making me think of ignition or fuel delivery. A guy told me to let it warm up 5 minutes (or a quarter of the way up on water temp) before driving, which has worked well for me.

I honestly think it sounds like it was running rich and flooding, then burning post combustion. I might start a new thread, just to keep this thread on topic, if it's keeping this thread off topic.