Why is oil so important in a rotary engine?

[Glenn Butcher]

Oil is used for a number of purposes in a rotary engine:

1. To lubricate the Rotor Bearings along with the Eccentric Shaft
2. To cool the engine (specifically the Rotor's and Eccentric Shaft)
3. An oil metering pump supplies oil for injection onto the Apex Seals - to help the cooling, lubrication of the seals, also to help with compression.*
4. Cooling the turbos where applicable.


* On rotary racing engines, the Oil Metering Pump is often removed - and 2 stroke oil is mixed in with the petrol in the tank. It is then fed into the engine either by Fuel Injection or the Carburetor.

As per point 3 above, because the oil is used to inject onto the Apex Seals (for the reasons above) - the rotary engine tends to use more oil than a piston engine. This is one thing that is very important - ALWAYS CHECK YOUR OIL!

I will not go into the specifics of what type of oil you should run in your engine, as everyone has their own opinion. I personally think that what Mazda recommends it best (being Mineral Oils only). I do know however that there are a number of synthetic oils that are also suitable for use in a rotary engine - like Royal Purple for example, used by Racing Beat (http://www.racingbeat.com).

[MikeLMR]

Alegedly 1/3rd of the engines cooling is provided by the oil ... makes me want to upgrade that crap water/oil heat exchanger on my first gen :)

using two stroke oil is NOT advisable if you have catalitic coverters fitted to your car ... they will become rather expensive paper weights after a while :D

[WWW.EVIL7.COM]

Best to use synthetic oil in the engine and mineral two stroke oil in the tank as premix , block up the oil metering pump of course , dont worry about cat converters , they are cheaper to replace than an engine rebuild !

[FRENCH7]

Wich is the proportion between the two stroke oil and the fuel in the tank please ?

[Glenn Butcher]

Also, Allistair - what type of synthetic oil are they using in Oz?. Do they recommend to use it in a FD/Series 6 RX-7? I know that Mazda recommend Mineral Oil in all rotaries.

We need more info :-)

[WWW.EVIL7.COM]

Castrol do the best stuff , formula R i think it is , about 200 - 1 premix of mineral oil in the fuel tank . Only use mineral in the engine if it is running the oil injection setup .

[FRENCH7]

And what do you think about synthetic japanese oil for rotary engine like this one ?
http://membres.lycos.fr/rxmazda/oil.jpg

[Glenn Butcher]

I think that this oil would be fine, I know there are a lot of other Synthetic oils available in Japan. And around the world - (Royal Purple is one that Racing Beat strongly recommend).

For standard driving etc. (if at all possible in an RX-7) I would personally prefer to sticking with what Mazda recommends (mineral oils).

What oil do you run in yours Stephane?

[richrx]

hey has anyone ever heard of putting automatic transmition fluid into the engine then leaving it overnight before starting it in the morning?? I've heard that this can regain lost hp on an old engine.

[Glenn Butcher]

hmmmm - nope, sounds a bit weird to me? what would it do to the rubber oil control rings?

[MikeLMR]

Its alegedly a common thing to do in the US ... the detergents in the ATF clean the carbon deposits out of the seals in the engine and can restore compression on a carboned up engine

I've got a suspect engine in my spares car ... I might give it a try ... Its probably destined to become and desktop ornament anyway so I've not got much to loose :D

I wouldn't have thought it would eat the oil seals as its designed to for use in Auto boxes which must have millions of oil seals in them :confused:

look it up on www.mazspeed.com they have a few tips'n'tricks archived (how to adjust a 1st gen steering box is a god send :D )

[FRENCH7]

I run Shell Helix Standard "extreme" for high rev in my FD
Is it a good oil?
http://membres.lycos.fr/rxmazda/oil3.jpg

[Glenn Butcher]

Hi Stephane, yes should be ok - I think that one is a mineral based oil is it not?

[Glenn Butcher]

Originally posted by MikeLMR
Its alegedly a common thing to do in the US ... the detergents in the ATF clean the carbon deposits out of the seals in the engine and can restore compression on a carboned up engine

I've got a suspect engine in my spares car ... I might give it a try ... Its probably destined to become and desktop ornament anyway so I've not got much to loose :D

I wouldn't have thought it would eat the oil seals as its designed to for use in Auto boxes which must have millions of oil seals in them :confused:

look it up on www.mazspeed.com they have a few tips'n'tricks archived (how to adjust a 1st gen steering box is a god send :D )

Mike,

Yes - I can believe this would happen, and that ATF would help clear the carbon out (but where does it go?) i.e. when you turn the engine over all the bits of carbon may scrape through the engine?

Another suggestion for starting problems on cars that have been sitting around for a while:

Sometimes if a rotary has been sitting around for a while the apex seals and springs tend to "gunk" up - not giving you any compression (as the apex seals are stuck in place).

One way to correct this is to take the exhaust off, get some WD40 (with the fine nozzle attachment) and a screwdriver.

You will have to turn the engine over by hand so that you can see each apex seal through the exhaust port. Spray the WD40 onto the seal, then get the screwdriver and scrape away some of the gunk build up. The apex seal should actually spring in and out slightly - i.e. to help with compression on starting... I'll post another thread about this now, and carbon lock.

A friend of mine purchased an old RX-7 a long time ago, the guy he purchased it from thought that the engine was dead - but my friend did the above, and the car has been running fine since!

[MikeLMR]

i might have a bash at that, only trouble is I think this engine isn't worth saving, its been sat with water in it for 3 years at least so I bet the water seals are shot. I might have a crack at getting her to run, but i think i'll just pull the engine and strip it to check the condition of the housings etc. and see if its worth getting it rebuilt with a few "light" ;) modifications (see my other post in the porting section)