Questions About Rotary Engine

[thteh86]

Question About Rotary Engine

1stly i would like to thank all the sifus here for willing to spend some time for an RE noob like me and sorry to all those i've offended b4 here, but ur help is being appreciated

I heard that once the engine's rotor seal is broken, the whole engine has to be replaced, no chance of replacing it? Or is it something else, I'm not sure

I'm really interested in getting an RX7 but it's just a matter of time and money, just like some forummers here, while waiting....learn about it

sorry if my questions are noobish

 

[joe13]

depends... its likely the engine, or parts of it (housings, rotors), can be re-used in a rebuild...

 

[thteh86]

nope, wat i heard is, if one of the parts broke, we'll need to shop for a new set of engine, which i forgot which part is that...hehehehe

 

[13btt]

Rebuild or replace?

Before I answer your Q about whether the engine needs replacing, I would like to say that it is a fantastic idea to learn as much about rotary ownership before getting one - this will save you time and money due to incorrect advice from supposed "rotary mechanics"

Your question has been answered before in this forum.

When an apex seal breaks/cracks it most often, if not always, damages the aluminium rotor housing surface. The small piece(s) of apex seals fall out of the rotor and are "run-over" by the rotor itself causing scoring of the housing sealing surface. Hence, the rotor housing MUST be replaced. Your cheap rebuilders will sometimes reuse these "damaged" housings to give you well, "a cheap rebuild" - BUT the compression of the engine will be low and not last long. High quality rebuilders in the USA never reuse rotor housing as they can afford RM2,000 per piece for a new one, which is only $500 in their currency.

If you're unforunate the extent of the damage may extend to damage of the rotor itself. That is, the apex seal groove of the rotor may be damaged if the apex seal breakage is severe and/or the breakage occured at high revs etc etc.

Most often (once they have been correctly measured for max wear limit) the iron housings that make up the rest of the engine "sandwich" can be reused very successfully. There are 3 iron housings namely front, rear and centre.

 

[reartyre]

related question - i think

like for engine oils ... you know when to change .... how about the apex seals ... does it needs to change regularly like oil ...

correct me if i'am wrong ... basically when during compression test you can detect whether the apex seals out of order or not ... but like 13 btt was saying if the rotor is forced to work under high rev ... then it cause damage on the housing ... what other ways to detect whether the apex seals are broken or not ....


will it be best to tune the timing of an fd at a proper shop or just D.I.Y ... if D.I.Y any particular person on the prawl at the moment ... hehehe ... looking for a nice looking fd to tune it .. hehehe

 

[saru-kun]

Is it still possible to get new powerplants direct from Mazda? Meaning, a complete brand new 13B-REW with all its accompanying ancilliaries. If yes, the ballpark figure would touch... (waits in anticipation)

cheers

 

[phat7]

approximately 3k usd. still available.

 

[13btt]

For oem ecu the timing is not adjustable.

You can suspect apex seal(s) are busted or slightly damaged through poor idling, poor/difficult cold starting, difficulty starting when engine is hot etc etc (assuming the other causes to some of the above have been eliminated). Also as the engine gets clogged up with carbon or just tired from mileage, the compression will be lower which is sometimes also due to worn side seals and/or less springy apex seals in their rotor grooves.

If you one wants to make a comparison (though still quite different) the apex seals are the equivalent of piston rings in a piston engine - that is you don't can't change them during regular maintenance but only at overhaul/rebuild.

I think I'd better take some pics of the various components of the engine so to better explain the whole thingee and workings?

like for engine oils ... you know when to change .... how about the apex seals ... does it needs to change regularly like oil ...

correct me if i'am wrong ... basically when during compression test you can detect whether the apex seals out of order or not ... but like 13 btt was saying if the rotor is forced to work under high rev ... then it cause damage on the housing ... what other ways to detect whether the apex seals are broken or not ....


will it be best to tune the timing of an fd at a proper shop or just D.I.Y ... if D.I.Y any particular person on the prawl at the moment ... hehehe ... looking for a nice looking fd to tune it .. hehehe

 

[13btt]

Better 'bang for your buck' would be to buy brand new aluminium rotor housings from mazda and new side seals - this would then make an excellent rebuild.

Is it still possible to get new powerplants direct from Mazda? Meaning, a complete brand new 13B-REW with all its accompanying ancilliaries. If yes, the ballpark figure would touch... (waits in anticipation)


cheers

 

[jasonlel]

Better 'bang for your buck' would be to buy brand new aluminium rotor housings from mazda and new side seals - this would then make an excellent rebuild.

Da Guru Has Spoken........

 

[saru-kun]

I think I'd better take some pics of the various components of the engine so to better explain the whole thingee and workings?

http://www.rotaryengineillustrated.com/

joe13 placed this in the useful sites section. Basics of the rotary can be found here, from its anatomy to its working cycles...

Better 'bang for your buck' would be to buy brand new aluminium rotor housings from mazda and new side seals - this would then make an excellent rebuild.

I wouldn't mind forking out about 10k for a rebuild...as long as I'm a major presence in its rebuild... hehehe

Cheers

 

[13btt]

No problem you can assist - I hope you have good mechanical skills though...?

At 10k your engine could be better and stronger than mine - you will most likely have the best rotary engine in Malaysia!!!!!!!!!!!!!

We could build an absolute ripper engine with that level of commitment, including custom fit tension bolts from Australia (really nice) so that you can boost above 1 bar without flexing the housings/engine assembly, new bearings throughout and new aluminium housings, new apex seals, new side seals, corner seals, new o-rings...the list goes on........yippeee bring it on.


I wouldn't mind forking out about 10k for a rebuild...as long as I'm a major presence in its rebuild... hehehe

Cheers[/QUOTE]

 

[thteh86]

yeap, agree with wat sarukun has said, me too will be willing to spend 10k for a rebuild to learn something, if only i haf the cash la...hehehehehe



thanks 13btt, another question...how often does the apex seal will be damaged? My friend was quite skeptical about rotary engines, and he always tell me that only rich fella will be able to maintain the fragile rotary engine, and with his driving way, he will have to change at least once in a year, which really made me doubt the rotary b4 I read this forum. Petrol consumption I believe it's reasonable enough for a powerful engine, but about the maintanence? Especially the apex seal itself, he always tell me that once the seal broke, ur whole engine needs to be replaced



But somehow, thanks to this forum, my view towards Rotary has changed, and it has become one of my most ideal car in mind

 

[13btt]

good feedback & me getting carried away...AGAIN

thteh86,

I am glad to hear that you have found this RE forum helpful - that is really good news for the persons involved in getting this forum off the ground despite many sceptics. I really do encourage others that also find benefit to speak up & tell us how it has helped u too!

So long as you look after fueling and don't overheat your engine (assuming you started with a good engine in the 1st place) you will not encounter any apex seal related problems whatsoever. Breakage only occurs through abuse of the engine & misunderstanding of its somewhat unique requirements. The engine will last you very well as it still does for me 3 years on from rebuild.

I confidently drive my RX almost every day and don't even think about breaking an apex seal because I know I have correct (adequate) fuel and therefore my apex seals will not break - they only break when you have lean burn and pre-ignition (knock / detonation) causing uncontrolled small combustions which crack the apex seal(s).

Also I never stress about overheating either because I have a more efficient radiator to dissipate more heat together with a PIVOT fan controller to make my fans cut in earlier at 90 degrees versus oem which is normally way above 100 degrees - way too late for our climate.

Once you have your RX-7 setup correctly in the areas that matter (and I am definitely not referring to external appearances including huge wing, bodykit etc etc) it is a very enjoyable experience owning, driving and looking good in this unique sportscar.

OK getting back to your comment about your mate - this is very common because there is so much misinformation floating around and of course some does come from those "mechanics" I often speak of that spread similar negative and misinformed comments too due to lack of correct & technical knowledge.

I bought my RX firstly coz i really loved the shape when i first saw it at the Aussie motorshow in 1991 and secondly I had seen many rotaries in Perth easily out-drag many hotted up V8s and turbo fours on the street, at illegal drags, car events and Barbagallo (those that know Perth well) raceway! I just had to get me one!!!!! Only after buying it here in KL did I later find out about all the bad talk of rotary engines - I was shocked to say the least, especially since there was only good talk & 100% praise back in Australia.

 

[saru-kun]

No problem you can assist - I hope you have good mechanical skills though...?

Erm...still learning hehehe. Currently helping out with team G-1 Symphony and apprenticing under a master. Rebuilding a 993 Porsche engine at the mo...

Me being and young and penniless....this is the only way to get close to metal...hahaha

Cheers

 

[thteh86]

Erm...still learning hehehe. Currently helping out with team G-1 Symphony and apprenticing under a master. Rebuilding a 993 Porsche engine at the mo...

Me being and young and penniless....this is the only way to get close to metal...hahaha

Cheers

never considered buying a porsche? hahahahaha

 

[saru-kun]

Hmm...I would, if it doesn't set me back 18 000 MYR for a new clutch set and flywheel. And thats road spec only.

Cheers

 

[saru-kun]

Hmm...I would, if it doesn't set me back 18 000 MYR for a new clutch set and flywheel. And thats road spec only.

Cheers

I'm sorry...let me correct myself. 15 000 MYR

 

[kuroneko]

13btt has really gone indepth about the apex seals.
Typically, through normal wear and tear, 2mm (factory spec) seals will last around 110,000km for turbo rotaries, and around 160,000km non turbo (although both cases I have heard much higher). Basically, if you look after your RE, it will look after you.

And about this common misconception about the RE being "fragile", it is the biggest pile of horse shit I've ever hear. A rotor can take the thrashing, any time, any day.

So long as you
1) Give it sufficient warm up time from a cold start (1-2 mins should be good)
2) Have reliabilty mods (straight through exhaust, air filter, possibly a good aluminium radiator if it really gets hot, and obviously boost gage and aftermarket water temp)
3) MAINTAINENCE. Do your oil change, coolant top up, check spark plugs etc REGULARLY. Signs of rough running, etc, will be easier to solve early on (before it turns into a big/expensive problem)

There are 3 common things that could end in an engine failure:
1) Blown apex seal
2) Leaking O-rings/water rings
3) Leaking oil rings

Symptoms:
1) as described by 13btt
2) Clouds of white smoke when pushing your engine hard, or at idle/startup. This means your rubber o-rings are leaking and coolant and water is leaking into the combustion chamber. Burnt coolant willl give a sweet smell.
3) Clouds of blueish smoke. Could even be the turbo seals.

Ways to avoid these problems:
1) as 13btt said, don't run lean basically
2) Keep your eye on water temperature. If it starts to climb rapidly, pull over STRAIGHT AWAY. I don't care if you're on the motorway, just do it! (lol) You really need an aftermarket water temp sensor, as the factory one is bad, only has 3 basic readings: 1)Cold 2)Normal 3)You just fried your engine
The Front, Intermediate, and End housings are cast iron, whilst the rotor housings are alloy. If a great source of heat is present(e.g. your radiator has a leak and all the water/coolant leaks out, running your cooling system empty), this will result in the housings expanding/contracting at different rates, which can cause warping of the housings. The o-rings are very close the the combustion chamber, and are suceptible (s.p?) to high temps of heat, causing faster wear. They are pretty thin peices of rubber you know...

oh man... so much typing again... sorry guys : (

if i made any mistakes or left anything out, feel free to let me know, it's 2.32am ,so don't blame me eh?

 

[kuroneko]

oops.

just realised there was a sticky called "Essential Rotary Maintenance"

maybe i'll just shut my yap for a bit :albertein