runny_yolk

Does anyone have any information about scheduled maintenance for the RX-8? For example, I've heard that at a certain point, the apex seals need to be replaced. For owners of previous rotaries, does normal maintenance of such cars cost more/less than a typical piston car?

KKMmaniac

I forgot where I read it, (but I think it was some official document) I believe said the seals were designed with a service life of 150,000 miles. How this translates into real life, we'll have to wait and see. If we knew the mileage Mazda designed the 1st and 2nd gen. RX-7 seals for, we'd have a pretty good idea.

Other than that, no valves or timing belt to be concerned with, spark plugs (iridium center electrode) have long life; perhaps you'll want to change oil/filter and coolant a little more frequently than on piston engines. Maintenance in the RX-8's lifespan should be about the same, if not cheaper than on a typical piston engined car.

Red Devil

In my experience, if you need to replace the apex seals it is a preventative measure or you've blown your engine.

Either way, replacing apex seals is a rebuild, not a scheduled maintenance service. Treat the engine with respect and the seals will be fine.

runny_yolk

Ouch, if the above is true (plus the previous post stating that apex seals might be good for about 150K miles) that seems to imply that the typical lifespan of an RX-8 is 150K miles before repairs on the scale of an engine rebuild is necessary? That sounds rather horrible to me but I'm sure I'm misunderstanding something. I thought part of the allure of rotary engines was the greatly increased reliability and longevity?

B-Nez

150K is a very conservative estimate (if that is even official). This takes into account the number of owners who will not run-in properly, never change the oil, never check and fill the oil, and God knows what else. With the same amount of proper care and feeding you'd give any car, I'm sure your apex seals would still be fine after 150K. They'd be well worn, but shouldn't cause any more of a problem than 150K-mile piston rings (under the same conditions). The typical lifespan of a normally aspirated rotary engine (that is treated well) is definitely more than 150K. Of course, past performance is no guarantee of future results.

KKMmaniac

150,000 miles? My dad used to consider turning 100k in his Pontiacs a major triumph. Anyway, the general consensus among non-turbo RX-7 owners seems to be:

Break-in properly.
Warm up engine (coolant and oil) before driving hard.
Don't overheat.
Maintain carefully! Change oil every 3000 or fewer miles (exact interval open for debate) Some recommend changing coolant annually.
Don't push past redline!
Do let 'er rev some of the time! (keeping the above in mind)

I've heard many people claim over 200k before needing a rebuild. And no valve jobs up until that time. I haven't been so lucky (but crossing fingers for current '85) because I've bought cars that were abused and neglected in the first place. I only had my '79 for about the last 44k of 120k miles, and had to dump it due to emission legalities. (header, etc.) It wasn't exactly in full health, but it had a few more 10,000's left in it. Yes, maintenance and warm-up are probably a little more critical with the rotary. My advice is, look elsewhere if you don't want to do it yourself, or if you can't stay on top of bringing the car to a mechanic who understands the rotary.

Red Devil

There was an article on here months ago when I came to the forum more often. Anyway, the guy had a first generation 12A rotary engine that had over 250K miles on the original block. All he did was basic upkeep, and of course, he treated the engine well.

NA rotarys will last forever. Turbo rotarys can last over 150K as long as they are kept in proper balance, fuel mixtures etc..., and the heat is kept to a minimal.

My mention of preventative maintenance was more in terms for an FD with the sequential turbo configuration. They were often pushed past their limits, for the owner that was aware of this,
rebuilding the block before the apex seals broke was sometimes a practical step as it saved on buying more parts and using most of your oe parts.

I had to learn that the hard way, as like an idiot, I trashed several engines before learning my lesson.

RotorGeek

Would in intercooler help the Turbo heat issues??

daedelgt

An upgraded IC and rad is a must for maintaining turbo rotarys.

Red Devil

Yes, you have to have an intercooler for your turbo. And the larger the intercooler doesn't necessarily mean the better.

The real question with the Renesis will regard compression, which I believe is 10:1. The 13B-REW compression was 9:1 - as I recall. So I'm not sure how much boost could be run through a Renesis in comparison to the REW.

I also have heard rumors about the intake ports not being capable of handling boost. But that was months ago and I don't know what has evolved since in that aspect. Someone else should be much more qualified to answer that question.

There really are several factors that must come into consideration before slapping a turbo on any type of car. Finding the correct balance (compression, fuel mixtures, cooling system, ignition timing, boost levels, intercooler placement/size, etc...) and being realistic with power expectations is the best way to go.

I think my next rotary car will be supercharged instead.

Maximus

could you please explain this in a bit more detail?

runny_yolk

This is a little off the original topic but isn't supercharging still a form of forced-induction? How is it less stressful for an engine to be supercharged vs turbocharged? I ask this b/c I've only owned NA cars up to this point.

Smoker

http://www.rx8forum.com/showthread.p...5&pagenumber=1

babylou

The rest of the car will be ready for the crusher at 150k miles so who cares if the engine is a 200k mile unit. I only know one person who has ever owned a car with more than 150k miles. That guy puts about 500k miles on his pick up trucks in only about 5 years use. He is a hot shot parcel delivery driver. Must have some serious hemorroids!

runny_yolk

I must respectfully disagree with you. I know plenty of people who have well over 150K on their cars (though I also have a friend who has a 1997 with only 70K that he's replacing, partly because he hasn't changed the oil in over a year...) Anyway, the point being that not everyone replaces their cars every few years. At an average of 25K miles per year, 150K works out to just six years and I definitely plan to keep my next car for longer than that!

Boozehound

The car I just sold (91 Park Ave Ultra) had around 185K, and the body, interior, and engine were all still going strong. It never burned oil, destroyed plugs, overheated, etc. It had the occasional quirk or problem that had to be fixed (motor mounts, wheel hub, leaking brake cylinders), but nothing major. And all of this reliablity in a domestic that was the first model year for a new platform/body style.

Our 83 RX7 has done alright, but it needed a new engine at 77K - when they say don't overheat a rotary, there's a damn good reason. Long story short - don't let the water temp sensor go bad.

Long story short - take care of the car, and it should live for a long time.

Red Devil

In response to the turbo vs. supercharger question.

Yes, they are both forms of forced induction. The difference is that a turbo builds psi by feeding off exhaust gases. Thus the heat from a turbo is great, necessitating the need for an intercooler. And as we all should know...heat kills rotarys.

Conversely, a supercharger is belt driven, and doesn't generate any heat in comparison because the exhaust is not in the picture at all. If big hp numbers are what you want, a turbo is the way to go. But if you just want a bit more power, and to keep the reliability, then a supercharger is the answer.

To get a better idea about supercharging you should go to the Atkins Rotary website. They own Camden Superchargers and can supply much information on the subject.

RotorMotor

My dad and I put 230k miles on his (before it was mine) first gen. before needing a rebuild. The car wound up making it to 360k before we were finally through with it. It was 21 years old....

Smoker

RotorMotor,
you had the First Gen RX-7 right ?

RotorMotor

Yup. 1980. Pops took impecible care of that car, but man did it run and run and run....

wakeech

uh, a couple of points:
- turbos heat the charge gasses more because they generally compress the charge gasses a whole lot more (higher pressure) than your average blower, not because of the exhaust gasses (conduction through the turbo unit is low, and the air is in-and-out in a flash)

- too much heat is bad for any motor, just as not enough is also bad.

- superchargers obey exactly the same thermodynamic laws as a turbocharger, and heat the air in the same proportion as a turbo would: it's from the compression.

- turbos, with some forethought and planning, can just as easily be made a part of a durable engine system as a supercharger, and some may say more easily too (controllable boost, for one thing)

- getting information about a product from the manufacturer/distributor is kind of like asking a used car salesperson which car you ought to buy... do you really think any of the Big 3 are going to give you any concious forewarning as to how many recalls your vehicle will need??

as you can tell, i'm now a vehement turbo guy. SC's will never cut it, and are a silly idea IMO.

neit_jnf

It also depends on the type of compressor, there are some supercharges that actualy heat the air more than a turbo because of lower efficiencies and the way they move the air causing shearing and heating. A very good reading is Turbo Magazine...

Boozehound

Slow down the turbo bandwagon guys. There are plenty of good reasons to use either system (I like forced induction just as much as the next guy), but don't you think there's a reason that 'fuelers and 'funnys (both running well in excess of 300mph in the 1/4) have huge SCs? Neither one is inheriently worse than the other across the board.

Red Devil

Wakeech,

I follow much of what you say. Though I have never seen a case where a supercharger's compressed air is as hot as a turbo's. But I'm open to any clarification on the subject.

I agree that a turbo can be made just as reliable as a SC. The difference I see is that if the owner plans on running 8psi or less, than a supercharger is the way to go. Simply because there will be virtually no lag and better low end torque. I realize a ball bearing turbo would be very responsive, but not quite to the extent of an SC. I think any time 10+psi is the goal, than a turbo is the obvious choice.

Going to the manufacturer is not a bad place to get information. It requires the reader to take everything into context and interpret the information for themselves. No one should be naive enough to believe that any form of communication or news medium is unbiased - because everything is.

Just my thoughts.

wakeech

the reason that the degree of heating isn't as high is because the pressurization isn't as great: the more you compress a gas, the hotter it gets in a very predicable way (negating the pumping inefficiencies which neit_jnf was talking about).

as far as what's better for which application, the SC would be more at home on an engine with an operating range of fewer rpms (ie: lower redline, or a narrow band in which the engine is utilized) than one with a large operating band (ie: the high-power 6 port RENESIS). the claim that torque will be better at low rpm is one that is conditional: it depends on how much air you're pumping into the motor at whatever "low" is defined as. if we say the SC acn generate a nice 5psi of boost at 2200 rpm, then you'd be making tons of torque down low, but at that pulley ratio, the engine would be choked to death with very hot air as the SC began seriously over-spinning (even to the point of failure) around 6k rpm, which isn't even close to the 6p's 9k redline. if you have the ratios so you can make a peak boost level of 8psi at 8400 rpm, then you're going to be facing the same "lack" (:p) of torque at the bottom end, which gradually building boost up to the top end: this would create a motor which is super-peaky, and pretty tough to drive at 10/10ths.

with a turbo, you can size it so that it hits 65% efficiency around 4-5k rpm with any amount of boost you want (that's where sizing really becomes important), which then would level off with the waste gate all the way to redline and then some... this is still a fairly peaky motor, but has some more guts that you can dip into going lower to half-way down the tach, and still have a streetable, quiet, and polite motor below 3k.
... heh heh... bias, as you said, is in everything, and i really like turbos.

NEVAR!!