I dont know what to say

[yetterben]

Anyone looking into serious rotary power let me know i am waiting on my e-shaft from a kiwi to build my 4 rotor. 7's are my first love. gonna shove a 4 rotor in a 79 sa

[MAG58]

I've always thought the sound of a 4 rotor was just this side of heaven.

The power to weight ratio is crazy... To see a normally aspirated 4 rotor in a Z would be.. I'm not sure if words could describe it.

 

Here's a video of a Kiwi with his 4 rotor FD3S. It's N/A on pump gas with an 8500rpm redline. I think the last place I read he was somewhere north of 600hp on pump gas.

 

[yetterben]

 

 

turn up your speakers for this one.

 

[dan5138]

Hmmm they build these by using 2 20B rotaries and having a custom crank made right? I dont think think the 13b sandwich plates would stack quite right...

 

*Adds 4 rotor Z to my someday when i'm rich project list*

[yetterben]

there is no difference between 13b housings and 20b housings. The extra displacement was from adding another rotor and so on. The thing needed for a 20b is the special 2nd intermediate housing. for the 4 rotor you need two bringing the total to 4 housings 2 irons and 2 intermediate plates. for more detaile dinfo go over to rx7club.com Ecentric shaft not crank buddy lol.

 

Tell yah the truth most 20b's where junk until the very last run with code d stamped on the block.

 

guys over in oz that are hard core are even taking 13b housings now and milling 10mm from them and relocating the coolant seals to get 12a housings.

 

Feel free to look me up over there i have done several 12a blowthrough turbos and a camden on my first gen 7.

[Careless]

not having been in a 2.6 litre rotary powered car... I am still anxious to see when the first 3.3 litre 5-rotor makes its debut.

 

i think martians will come to earth before that happens, but i dunno what's cooler, martians or a 5 rotor.

[MAG58]

I'm not sure if it would be practical to build a five rotor. By that time you'd end up having an eccentric shaft that's so long, it wouldn't be able to safely spin at the typical 'rotary like' rpm due to the shaft flexing too much.

 

Mazda is supposedly coming out with a new, Direct Injected, all aluminum 16B 2 rotor for their upcoming sports car. 3.2L 4 rotor anyone?

[m4xwellmurd3r]

I'm not sure if it would be practical to build a five rotor. By that time you'd end up having an eccentric shaft that's so long, it wouldn't be able to safely spin at the typical 'rotary like' rpm due to the shaft flexing too much.

 

Mazda is supposedly coming out with a new, Direct Injected, all aluminum 16B 2 rotor for their upcoming sports car. 3.2L 4 rotor anyone?

Hmmm 3.2L 4 rotor in a Z.

When you tell people you have a 3.2L Z, they'll expect the sound of a roaring stroker, but instead will be greated by the scream of a 4 rotor mimicking the sound of a high rev formula 1 car.

[Bart Hoedemaker]

Rotary's are nice, but they do have wear problems.

[MAG58]

Only when you treat them like piston engines.

 

Rotaries are a special breed, but if treated correctly, a 1000+ 4 rotor should last just as long in race use as, say, a 1000hp 2-3l piston engine.

 

When Mazda raced their 787B, they kept the shift point at 7500 IIRC, because they thought that a 9k shift point would wear out the motor. (by 9k the motor was making 300hp more than it was at 7k) But when they tore it down after the LeMans, the motor had yet to polish off the machine marks on the irons. They can be stout.

[Gritz]

These motor caught a bad name because people don't unstand them and don't know the first thing about them..so just like anything people jump on the "Rotaries suck" bandwagon..My brother owns a 88 turbo II and have be pushing around 300hp for years..

 

I love Rotaries!!!

[Ferrariferg]

/ I agree. / I have a couple friends with FC's and I love the way they sound. I learned to drive stick in my friends first FC. It died a short time later but thats another story. lol. You just have to know how to treat them. Besides. How often do you see a car that you can rev nearly as high as a street bike?

[MAG58]

Racing Beat had a few 13B's spin 12K before. Let's see a 1300cc motor do that for long.

[Gollum]

How'd this thread get so invloved in rotor talk? Oh well.

 

Lets not forget that it's extremely hard to ever compare a rotary engine to a piston engine. Even RPM's are completely different. The eccentric shaft is internally geared, so the rotor is never moving as fast as people imagine, but it's still putting out as many fires per 720 degrees as a 4 cylinder in a 2 rotor configuration. Bizarre? Ya bet.

 

And the durability, ability, longevity, etc of a piston engine at any RPM comes down to design. Motorcycle engines are made to hit well over 10k all day long, and last reasonable lengths of time considering the RPM, by using very oversquare designs. I was actually reading a paper by ducati the other day talking about how as the years have progressed their bore has gotten larger and larger while their stroke shorter and shorter in order to accommodate higher and higher RPM, and subsequently more HP.

 

Motorcycles have more wear issues in the head, valve timing system, pumps etc, than they do in the pistons and rings themselves (depending on what engine we're talking about here). Some say that even ducati's factory crank balancing is far from perfect, thus there is even more wear longevity to be had by have the crank rebalanced.

 

I guess my point is that any engine can reach insane RPM if built for it and any engine will have wear problems when you exceed it's physical limits.

 

Just talking like this though sure makes me want to build a 9k+ rpm L24

[yetterben]

"The eccentric shaft is internally geared, so the rotor is never moving as fast as people imagine"

 

Nothing like more misconception to make it look worse. Damn dude....i don't have anything else to say to this thread lol.

 

I have had rotaries for over 15 years and have successfully raced them for 10.

 

Here is my beater turbo car all custom CARB!!!! !12A BIG NUMBERS.

 

http://s224.photobucket.com/albums/dd53/yetterben/?action=view&current=movie_01_01.flv

[blaze73]

Here's the Queen Street Racing BMW (regarding the OP's vid).

 

 

Just mental.....

[Gollum]

"The eccentric shaft is internally geared, so the rotor is never moving as fast as people imagine"

 

Nothing like more misconception to make it look worse. Damn dude....i don't have anything else to say to this thread lol.

 

I have had rotaries for over 15 years and have successfully raced them for 10.

 

Here is my beater turbo car all custom CARB!!!! !12A BIG NUMBERS.

 

http://s224.photobucket.com/albums/dd53/yetterben/?action=view&current=movie_01_01.flv

 

Then please tell me how I'm wrong. It takes 900 degrees for a rotary engine to complete a "cycle" but RPM's are still measured the same as a piston engine.

 

You can see it clearly in this animation that the eccentric shaft is moving FASTER than the rotorL

 

 

They even state in this video by car and driver magazine, that the eccentric shaft rotates three times for every rotation of the rotor.

 

http://www.youtube.com/watch?v=oGrD7FTFLJc

 

So please, tell me how I'm so wrong you just want to give up, or how this is some misconception that even big name magazines don't get it.

[MAG58]

I think they can be compared, eccentric shaft speed vs. crank speed, because pistons move at vastly different speed than the crankshaft, and equally rotor speed is different than the eccentric shaft. Just because a big name magazine says that the rotor spins once for every 3 eccentric shaft revolutions doesn't mean it's still not spinning that RPM. That's not what they're saying either. Would you have a piston speed gauge in your car as opposed to a tach? I doubt it, and if you do I'd like to see it. If you want to compare the two, compare rotor speed to apex seal tip speed and compare eccentric shaft speed to crankshaft speed. There's no need to get hostile.

 

 

I don't understand why when some engine or idea goes against accepted norms that have been around for a while they get all indignant and defensive. What makes everyone think they've been doing it right for all this time? If you quote wins, they've only been winning against themselves...

[Gollum]

I wasn't intending to look like I was getting hostile, just wanted proof as to why my comment was so "off base" that it wasn't even worth "correcting".

 

I wasn't trying to say a piston moves faster/slower than a rotor, just stating that many see rotary engines as "high rpm" and in one sense they are, their "crank" eccentric shaft moves very fast, I was just noting that the rotor itself isn't moving at those speeds like many out there think.

 

Though I for one, not a rotary expert, would be interested to hear the actual apex seal speed in ft. per sec. at 9,000rpm. I honestly don't know.

 

I never meant to be making a anti-rotary post, nor an anti-piston post. My post was much more about the wear factor mentioned, and how I find it relates to RPM, or the overall speed of moving parts. I was showing that in a piston engine seeing high RPM, you generally reduce the stroke to keep piston speed down, while to achieve high RPM in the rotary engine the rotor itself is "slowed down" much like running a lower stroke.

 

The main difference between the two, is that if you slow the rotor down more in relation to the eccentric shaft then you're also lowering your ignition events per rotation, whereas in a piston engine if you slow the piston down by reducing stroke, you still have the same number of ignition evens per rotation. Though in a piston engine no matter what increase in RPM means increased work for the valvetrain.

 

And as my previous post had started: The two are almost impossible to compare.

[MAG58]

I can totally agree with that. The needen't be compared. It's like comparing a turbine to a piston airplane. Completely different beast.

 

But I'd like to clarify a few common mis-conceptions:

 

They're not as un-reliable as many think. I've seen and driven rotaries with 200k+ and they still all post 130+ per face on both rotors. It's treating them like a rotary that makes them live. Treating them like a piston engine and they die fast. People think that it's louzy that a full bore, 13B, PP rotary that sees over 10K (I don't care how you want to compare engine speeds, that's truckin') wont last over 20,000 miles. Find me a comparable 2ish Liter 4 cyl (comparable power from NA and equal combustion events per revolution) that sees speeds over 8k regularly puts out 300hp on pump gas (rotaries either have 8.5 or 9:1 cr) with big ol' cams that does see that kind of engine life and I will be surprised.

 

Rotary power curves are different too. They're less parabolic, and tend to make all their power at the top end, where they like to sit. Remember, the factory quoted torque curves for the 1991 Prototype cars placed the 787B 4 rotor at the top of the list. It made more torque than all the 3.5L V12 cars and more power to boot. (600+ hp at 7500 with 10.0:1 CR aint bad for a 2.6L NA motor in my book)

 

The only thing rotaries fall short on is oil consumption. Again, treating this motor like a 4 stroke piston engine kills it. Allowing a bit of 2 stroke oil in the motor to keep the apex seals safe means a little worse emissions but a much longer lived rotary. Beyond that, it's all about preference, and if I had the money, I'd put a 3 or 4 rotor in a Z in a heart beat. The 2 rotor weighs just over 200lbs. That's a power-to-weight ratio I can get behind.