Quick_lude

This is interesting.. How often should you do this? Do you think this will be applicabble to the Renesis?
I really hope Mazda does promote this car better.. once it gets off the ground. I like the rotary concept and wish this car a huge success.

MyT13B

Pouring the teaspoon of oil in the intake is a logical step to starting ANY engine that has been washed by fuel.

I well tuned engine would rarely need this sort of treatment.

There have been occasions for me where a hard run of the engine would roast the sparkplugs. This promotes hard starting and pouring alot of fuel through the engine while trying to get it to fire. This escalates poor compression and things get worse. The oil metering pump will not put enough oil around the seals to make up for the lack of oil due to this washing.

It is OK to add oil this way if you know the seals have been washed. you could also add premix oil to the tank for assurance at tune-up time. Don't add too much however. 50 to 1 mix is fine if you are still using the oil meter in this case.

wakeech

you made +275 bhp on a 13B turbo?? HOLY CRAP!! what was the redline on that mother??

** oops!! you SAID 13B!! oh, and btw, what's the diff between the '74 13B's and the post '86 or whatever 13B's?? those old ones didn't have 6 port induction systems, did they??

MyT13B

In 1974 the 13B had the largest intake porting with 4 intake ports, not 6. A turbo version did not exist in production for that year. It was also pre RX7.

Building this engine took extensive porting with full Street porting on the primaries and what I call 'baby' bridgeports on the secondaries. Carbon apex seals and six grooves in all the water jacket passages around the combustion side make it cooler and higher revving to a 7500 redline, 8500 max. Though it has seen higher revs, I am not that insane to hold it there, the next gear is much more fun!

The Holley TBI is a two barrel set up. so each barrel feeds one rotor. All intake ports are open to the fuel. Idle is 1500, Boost comes on strong at 2500. The turbo is oil cooled and it was a trick to find the right place to tap oil from the engine to keep it lubricated without losing oil pressure.

Seeing that the Reneisis does nearly this without a turbo is very exciting to me. 450hp sounds like a reasonable goal using one of these!

wakeech

450bhp?? woah... how much boost to you figure you'd need to pump that?? assuming that becuase of the materials used (there ceramic stuff in the exhaust ports or something... can't remember who said that on this forum, but obviously it'd crack if hit with a dremel or die-grinder) would limit the amount of porting you could do (which isn't such a big deal 'cause the ports are already enormous), and we'll just hope that the 9k redline wouldn't induce any knock at full-on boost...
can't do that math right now, just got up... :P
hmmm... i read in a magazine that an old 13BT (all the turbos only had 4 port, even the 13BREW i think) ported like crazy with 20 psi (that's 1.4 bar,) made something in the order of +500 hp... (redline at 8k)
that boost number sound about right to you??

MyT13B

I doubt that engine lasted very long.

In the 13B series your combustion was 180º before the exhaust opened. When you examine how the rotor pushes on the eccentric shaft you begin to see that you need to make the burn and expand extremely fast between say 20º ATDC and 160º ATDC.

In reality the highest mechanical advantage comes around 45º ATDC to around 235º ATDC. The Renesis design of exhaust porting takes full advantage of this fact. I would think that by retarding the ignition timing by 5º - 10º from the old school 20º BTDC MAX you could get the BANG to occur at the right time to get the most out of the engine. This is ideal for any kind of boosted engine.

My stated estimations are based on my own experience and are probably conservative since I would use a premium pump grade fuel (90 octane). Racing fuels like 105 octane would require more ignition advance than pump gas and then you push the fine lines of devastaion.

If a turbo renesis was produced, I suspect it would also have a similar 4 port intake unless they could control ports 5 and 6 electronically.
But, as I have seen, the 4 port arrangement is plenty for a boosted engine. Another thing I have observed is the larger the intake ports, the less boost you need. I only use 5-6 psi of boost for my race engine. If I had used 1982 housings (some of the smallest intake ports)from the factory , I am sure the boost required for the same effect would be around 10 - 12 psi.

If they were successful for a test run using 20 psi, I suspect also that the ports were rather mild. My power is limited by the TBI fuel delivery. It was designed to produce up to 300 hp when applied to a particular 350 cu.in. Chevrolet V-8. So I didn't expect to get any more from the race engine.

banzairx7

Reading through this post you'd think that no rotary in the last 20 years has had reliability problems. The 3rd gen RX-7 was one of the most unreliable cars I have ever seen. I doubt more than 10% made it to 100k miles without a new motor. Between the cracking vacuum lines, cracked exhuast manifolds, splitting turbo outlet pipes, exploding AST's, broken sway bar mounts, melting pre-cats it's amazing any are still around. Mazda needs to be very careful to not repeat what they did with the third gen. That is why we are waiting so long for this car. they are going to run it through the mill and then some. If mazda ends up with another problem ridden rotary it will take a long, long time to recover if ever.

The normally aspirated RX-7's were bullet proof in stock form, as long as they weren't overheated. In anything other than stock it's all up to how well the engine was tuned. A rotary is not as tolerant of tuning mistakes when modified. Many mistakes that people get away with all day long on a piston engine will kill a rotary in short order.

This is what I say when people ask me about the reliability of the rotary-

"If you leave it stock you can beat it relentlessly and not worry about it, If you modify it all bets are off"

rxtreme

iTrader: (1)

Are you talking about modded 13B turbos or the NA models? I have heard rotaries are totally intolerant to detonation as well as the overheating issues plagued by most turbo'ed models. However, I would think simple bolt on's wouldn't be too risky for a NA rotary, would it? If I added a CAI, exhaust and maybe a quality ECU chip, how much risk/gain could I expect? If I gained 20-30HP from those mods I would probably be pretty happy. Anyone have experience with the older NA rotaries with those kinds of bolt ons?

MyT13B, you seem to have alot of experience with the older rotaries with heavy porting and more extreme mods, how about something a little less extreme?

Donny Boy

I owned a 1984 13B RX-7 and put 155,000 miles on it without even a minor hitch. The car worked as well in the end when I sold it to when I first got it. One of the best cars I ever had in terms of reliability, not to mention the other benefits.
Reliability is not an issue, unless you work for the fearful competition!

banzairx7

NA is pretty hard to blow up but it can be done. None of the previous NA rotaries had any problems with Just exhaust and intakes. My 84 SE is on its fifth motor in six years :-( But all can be attributed to something else besides poor design.

Motor #1- hit a large puddle and ingested many gallons of water- blown motor
motor #2- Mechanic dropped a pebble into #2 injector hole blocking the injector. two months later blown motor
Motor #3- Blew a heater hose and motor overheated. Two months later the coolant o-rings went
Motor #4- I was very tired and stupid late one night before a race and shot nitrous into the motor when it wasn't running. Went to start it and BOOOOM.. blown motor
Motor #5- Getting it up and running right now

I hope mazda puts a mass air fuel injection system on this car. One of the reasons that the 3rd gens died with very small mods was that the ECU didn't measure actual air flow. It used a speed density system. All the previous years had used an air meter. So when you increased air flow through the motor the ECU idn't know. Things got lean and boom... blown motor. Well actually not boom. The death of a rotary is not very dramatic, it just runs really rough and has no power. It would be way cooler if flames shot out or something.

The other reliability problem I just thought of was all the damn rubber vacuum hoses on the rotaries in the past. They ALWAYS cracked and would give you nightmares trying to track down idling problems. I did notice in pictures of the renesis there are lots of steel lines. Hopefully these replaced the rubber lines on previous generations.

wakeech

true banzairx7, the 13BREW wasn't really reliable, and that's 'cause of the fancy-pants sequential twin turbo system Mazda incorperated with that sucker.

i think that most of the people on this forum, however, aren't joe anybody "don't know nothing 'bout no rotaries", and take very good or at least very adequate care of their engines, and too most are NA (or at least were at one point )

and rextreme, i know that those are the three most typical and first mods any new school import tuner will do, but i really REALLY don't think you'll pick up 20 hp over stock with that. remember: the engineers at these aftermarket places are the guys who didn't make the grade to get into the factories...
the engineers at the factory, however, are obviously going to be the best and brightest. now, depending on application, these fellows will design the engine (and associated bits, like the exhaust, engine management computer, and intake system) for a certain application. look at the cars the new schoolers are modifying: economic grocery getters (like Civics... <<shudder>>) which've been engineered for a quiet, comfortable ride at a low cost of fuel and highly effective emissions control systems. the RX-8 isn't even close to that; mazda's not going to dick around with this thing, and produce it with 15 hp less than it could have to improve gas milage by 2 mpg, or to save cost to build by a few hundred dollars.
so the way this thing is coming from the factory will already be in a very high state of tune, and i really couldn't see you gaining anything noticable with those sorts of aftermarket mods, unless you were planning something MUCH bigger, like a big blower or turbo which would completely outstrip the OE in capacity to breathe (or in the case of engine management, be unable to relieve it of knock or keep it from drowning the engine)

MyT13B

My 1982 12A now has full street ports clear to the absolute limits on all 4 intakes. The exhaust ports were slightly enlarged.

The rotors have been chamfered near the side seals in the locations where the intake opening is controlled as the rotor passes by. The crank time you gain from street porting is about 30º. You then gain another 25º by chamfering the rotor. When you see how much larger the ports are using this method you raise a few eyebrows.
I always use the factory's special carbon apex seals, the don't last as long but they do far less damage if they fail. Cast iron apex seals do too much damage to the engines in my opinion in many ways, especially at high rpm.

I installed the engine with the factory accessories (carb, exhaust, smog stuff) and only made the primary carb jets one step bigger.

I also added a lightweight flywheel for quickness.

My fuel mileage went from 20 mpg to 27 mpg on the highway. The car now rockets to 5000 rpm and runs out of carburetor. The carb makes a good restrictor plate now.

An aftermarket intake and exhaust would make this engine capable of 200+ hp within the stock redline.

I have 40,000 miles on this one so far and it is sweet to drive. I would guess the stock 110 hp is now around 150 with a remarkable change in the torque output

rxtreme

iTrader: (1)

Well, CAI/H/E with a good chip/fuel management sys. MAY get you 20HP at the wheels in an Integra GS-R, which came more tuned from the factory than, let's say, a Civic. Good tuners could even squeeze 20+ more HP in NA form from a 195HP type r with more radical treatments, but nothing too extensive.

Some of these guys working the aftermarket are actually very smart and they produce parts with the engineering knowledge of the motors they're building them for. I'm not talking about joke aftermarket parts from, let's say, APC or Tucan, but the folks at AEM, DC, Hondata, and I'm sure MAZDASPEED are intelligent people who research and apply they're products using good sound engineering sense.

In addition, I honestly believe that if Mazda can offer the RX-8 for a price we all hope for, they must have cut corners somewhere. Especially considering the amount probably spent in the engineering of this thing. This car is supposedly being mass produced to appeal to a large number people belonging to different markets. What's to say it's not going to be a little softer, quieter, or calmer than us hard core enthusiasts would like?

I'm not saying it's not going to be a great car, because I know it will be. What I'm saying is I have faith that they will leave a little room for the aftermarket to take advantage of.

banzairx7

On a race only exhaust I can see an easy 20hp on this car. The earlier NA cars gained 25-35 wheel hp with the RB header and dual exhausts.

My friends 83 12A had the stock exhaust manifold no cats and a magna flow muffler. He switched to the RB header and dual exhuast setup and went from 89hp to 116hp with no loss in torque anywhere. Rotaries love a free flowing exhaust!!!!

BTW- no honda every gained more than 7-8 HP with an exhaust. The typical intake/exhaust combo at most nets 10hp.

rxtreme

iTrader: (1)

I've heard the RSX type s can gain close to 10 HP with a good intake alone. The ECU is being messed with by Hondata right now and they have unofficially mentioned substantial gains can be made in that department. Now, an exhaust by itself won't gain hardly $hit, but combo'd with a good CAI, header, and ECU you should be able to see 20 HP, easy.

73JPS

I have never had a problem with any rotaries I have ever owned, BUT

When I have looked in my local autotrader over the years, I can't find an issue that doesn't have at least one post 1985 RX-7 being sold with a "new engine". This has always cast doubt in my mind about what Mazda did to hurt the reliability of the 13B after the first generation sevens; and then I have to give my head a shake and remind myself that many cars would have been abused or modified, or run by less than knowledgable owners.

But if somebody was just doing research on their own, and did not know rotaries, I would have to say that seeing so many used vehicles of a type advertising "new engine" would cast doubt in their mind about the reliability of something as unique as a rotary.