I am new to the rotary engines that Mazda uses. I have read up on these engines and know exactly how they work. I have heard people say that although they theoretically should last longer they often don't. So my questions are: how long should I expect this engine to last? Are there modifications to the renesis engine that might make it last longer? Does minor maintenance neglect hurt this engine more than a traditional design? Is there any more maintenance required for a rotary?

I know there are a lot of people (especially on this board) that love the rotary design and have a huge bias toward it. So I am asking that you try to keep it honest and let me in on anything I should have a concern about. I am not buying an RX-8 for long-term lifetime usage, I would be buying it for performance. But I would like to know what I am up against.

Thanks!

 

All engines are built different, and rotaries do need more maitenence. They arent as bomb proof as some Piston motors are but NA rotaries do hold their own. You should NEVER EVER EVER EVER EVER EVER forget to do an oil change on a rotary and NEVER EVER EVER EVER EVER EVER EVER EVER EVER EVER EVER EVER EVER EVER EVER EVER EVER let it over heat. A modification you might want to look ino is a bigger radiator.

 

The biggest thing you need to pay attention to on the OLD rotaries is the oil level. The rotary was, and may still be, designed to have some oil consumption to keep the seals lubricated. The RENESIS may not be as oil thirsty but just make a habit of checking your oil at least every other gasoline fillup.

The 3rd generation rotaries were quite troublesome. They were basically the same as the 1st and 2nd gen engines, except that the turbos were very complicated and the car lacked adequate cooling, as Velo already pointed out. Overheating kills rotaries, although overheating a piston usually screws it pretty bad as well.

Besides the 3rd generation twin turbo I mentioned, the 1st and 2nd generation normally aspirated engines are absolutely amazing. There are tons and tons of 1st generation cars that are raced, and raced hard, and they are still on the original motors at well over 200,000 miles. Really, they are probably some of the most well built and reliable engines in the world.

As far as maintenance, it is always a good idea to keep a check on fluids for ANY car. With that being said, I already mentioned the oil level, which is probably the single biggest thing to watch if the RENESIS is anything like the 13B when it comes to oil consumption. I don't think a bigger radiator would be necessary if Mazda did its homework and gave the car adequate cooling. Other than that, the engine is pretty much the same. You treat it well and it should outlast just about engine on the road. Please remember though, that although the odds will be very low, there will always be some "bad" engines and that applies to both piston or rotary in any given car. Hopefully you do not end up with a car that just got a bad engine because of a fluke. So please don't think that if you may happen to buy a bad engine, that all rotaries are junk. A bad Honda engine doesn't mean that every engine from Honda will be the same, and please don't dismiss the rotary if you happen to be unfortunate enough to get a bad one. (<---gotta have the little disclaimer)

Welcome to the rotary club. Hopefully you'll see how great the rotary is after driving one. There is so much more to it than just performance.

 

My friend has an Rx-7 and he had to import engine parts from japan at 60k miles. Is this average? And what can be done to keep it going?

 

Hi,

Sorry for my naitivity, but I was just wondering if I was reading some of the articles correctly...it says that the 1300cc engine can produce 250bhp, now, I'm no mechanical expert, but this is surely some engineering feat!

...I did a little (emphasis on the "little") bit of research into rotary engines in general, and it says that they are generally slower and consume more fuel than most piston engines...so...?

...I appreciate the hype behind Mazda's heavy development into the new technology, but this surely too good to the true?

Please put me at my ease, and confirm or dismiss the 1.3 litre engine capacity spec...

Cheers,

1

 

The 1.3L is correct.

 

engineering feat, well yeah. but you also have to look at this way. HP is a number derived from the torque, which is an actually measurable force. Now its also has something to do with the RPM's so a high reving motor in NA use, like the S2000 motor and the RENESIS rotary have higher hp, 240 and 250 respectively but not much in the way of TQ. If you look at the chevy small block, such as a LT1 350 CI engine or a 5.7 liter motor, you see a lower RPM higher TQ to hp ratio. That is how they get the high HP by having a high revving motor.

 

It's 1308cc in swept volume, 654cc per chamber, but it is a two stroke not a four stroke like normal piston engines, so in actual fact it's working capacity is 2616cc.

 

auto piston motors are 4 stroke....

 

these things always turn out to be mis-information conventions.

Torque - while being measurable (as is power BTW) DOES NOT DETERMINE ACCELERATION. This is because to determine acceleration (and hence the *pull* you feel) you need to know the rate at which the tractive effort is being developed. There is a convenient name for it - POWER. You can have all the torque in the world but if it's only at low RPM levels then you need wide ratios to make the car driveable which compromises acceleration. EG a steam engine has much more torque than any SB chev ever made but because it's made at VERY low RPM it's next to useless in performance applications because it can't be spread with gearing.

In short torque is only useful in applications where time IS NOT IMPORTANT.

Next: the rotary used by Mazda et al is a FOUR stroke motor. It has four totally seperatle events that make up it's combustion cycle. How many 2 strokes have a 270 degree power stroke? It does have a displacement of 1308cc yes, but it does ALL FOUR events during 1 engine cycle as opposed to 2 for the otto cycle.

Sorry for the rant but this same **** keeps coming up on the rx-7 forum from time to time.

 

I hate to be the bearer of bad news rpm-pwr but you are wrong.

Do you know what defines a two stroke and a four stroke? If you did you would not have said what you did.

The rotary engine is a four CYCLE engine, which goes through the normal cycles of induction, compression, expansion and exhaust, or suck squeeze bang blow if you like.

However, the difinition of a four stroke engine is one having one power pulse per two revolutions of the crankshaft, where the piston goes 1. down (induction), up 2. (compression) down 3. (expansion) and 4. up (exhaust). Thats four cycles per two revolutions of the crank.

A rotary engine has one power pulse, per rotor, per eccentric shaft revolution. That is on every rotation of the eccentric shaft there is one power pulse per rotor. This makes it a 4 CYCLE TWO STROKE.

So even though it's swept volume is only 654cc per chamber, it inhales this volume every rotation of the eccentric shaft, as opposed to every second rotation of a crankshaft in a 4 stroke piston engine. Therefor, for the same crank or eccentric shaft revolutions, the rotary engine inhales twice, so it's effective working capacity is double it's swept volume.

Simple maths tells us that 654cc (one chamber) x 2 is 1308cc. Multiply this by two chambers and you get 2616cc. Simple.

 

No problem
This makes absolutely no sense. Your definition ONLY applies to conventional piston engines. Did you notice the word 'stroke' ? The term 4 stroke refers to the number of piston 'strokes' required to complete the combustion cycle. So if you wanted to be anally retentive you could say the rotary is a 0 stroke motor since a rotor's movements aren't a stroke. The point I was trying to make was that saying the rotary is a 2 stroke motor is going to mislead the average reader. When someone thinks two-stroke they think of 2 cycle operation = very unreliable and very poor fuel and oil consumption. It gives the rotary a bad name.

You multiplied x2 twice because of the 2 rotors. It displaces 1308cc in 1 revolution. During that revolution all four cycles are completed. Pistion engine displacements are measured over 2 revoulutions because they requre 2 to complete a cycle and therefore all cylinders have inducted air after 2 revs. For comaparason purposes only, you double the rotary capacity to compare equivalent amounts of air/fuel combusted over the same 2 revs.

-pete

 

actually it IS a 4 stroke...there is an intake stroke, compression stroke, combustion stroke, and exhaust stroke. Although yes, it isnt exactly a stroke, but it is still considered such.

 

Lets do this the easy way. ITS A ROATARY so why are you comparing it to a piston engine? Its apples and oranges. If you really want to get in to it a rotary is more effiecnt at making power because of physics. In a piston engine and piston first travel down to allow air/fuel into the compustion chanber. Then the piston stops going down and travel up. Then it is shot back down by the explosive force, then turning around again to push the exhaust out. Now in a roatary the rotor rotates the same way all the time. The 3 sides of a rotor are alll doing something at the same time, one side is taking in the air-fuel, and another is compresing and igniting the mixture, while the third is pushing the exhaust out. And as the rotor turns each side does all 3 jobs.

To put this in more easy to understand way :
say you run from point A to point B and back to A.

If you were a piston you would run like this A,B,A,B, and back to A to start over

But if you were a rotory
Run in a cirlce from A to B and around to A agian.......Which whould take less energy?

 

You guys are getting confused between what is a cycle and what is a stroke. The Rotary engine is a 4-Cycle Two Stroke engine, like it or not.

If any of you had actually built your own motors you would have noticed the eccentric shaft's rotor journal is offset, and during it's 360 degree opperation, that journal goes in an anticlockwise direction from right to left (1 stroke) and the left to right (2 stroke). During this 360 degree rotation there will be one power stroke, as the rotor turns at 1/3 eccentric shaft speed.

It doesn't matter that the Rotary engine is not exactly the same as a piston engine in it's opperation or design, as the method of measuring capacity does not change. And as the humble 4-Cycle 4-Stroke piston engine is the in the majority, all other engines will be compared to it.

It cannot be argured that for the same swept capacity, a Rotary engine will inhale double that of a 4-Stroke piston engine at the same rpm. What I don't understand is why people get so bent out of shape having to admit this??????

The biggest problem the Rotary engine has is that people are happy to tell stories about whatever suits their argument at the time, not the facts. This is the cause of most of the confusion and some of you so called Rotary experts bring this apon yourselfves because you don't totally understand how it all works yourself.

 

they do the same thing and have the same name....they suck squeeze bang and blow. NUFF SAID! Thread closed. go to http://www.howstuffworks.com