Ohhhh, I got you.

Why would you pump all that extra air into the engine if you weren't going to use it? Also, this would cause it to run super lean and possibly burn the sparkplugs. At least if you allowed the fuel to fatten up when you hit the gas pedal because your ignition wouldn't be able to do both well without changing physical parts. It seems like it'd be easier to try that cylinder shutdown thing that they have now for the pistons. Just have the computer not inject for said rotor or produce spark on it's pass. Balance this with the other rotor so the eccentric shaft doesn't go all wobbly.

 

That super lean mode would be useful for idle and very low load operation. It's basically one of the ways in which direct injection reduces fuel consumption (ultra lean operation at low loads).
The spark plugs would be in the fuel rich area, so I don't see a great problem with them getting damaged.

The problem, as you say, is the piggy rich mixture with a normal injection volume. But that can be avoided if the fuel is injecter directly into the engine just before the spark plugs. This way, it does not have the time to collect in one spot and will remain well distributed. This solution would call for (at least) two injectors per rotor, but the new 16x appears to already have this number of fuel injectors (the only difference is that, with the 16x, one is in the intake manifold); the only problem remaining is getting enough fuel pressure to be able to fire a fuel injection right at the highest pressure position in the engine (near the spark plugs).

Rotor deactivation would be another thing to consider. Just disable the fuel injectors for one rotor (the ignition system can remain active or be switched off, it doesn't matter) for a certain amount of time. After that, reactivate the rotor and, when it's running steadily, deactivate the other rotor. This way both rotors get their "rest" time and their "working" time, and wear should be well balanced.
Then, if during single rotor operation you press the gas pedal a little more, the inactive rotor comes back on line and the engine is immediately able to provide full power.

 

Leave it to us Italians to come up with the craziest, most complex engine possible *cough*Desmodromic*cough*

 

Naaahhhh...

I prefer rotaries

Both simpler and more complex than a desmodromic engine at the same time...

 

Rotaries are quite fascinating, though I wish another company would take a swing at making one. Mazda is a good company, but it seems like more expensive production methods of some componentry in the engine would not hurt profit margins and would make these engines go faster and longer.

We all agree that piston engines have thousands more moving parts than rotaries and are alot bigger (more metal). Motors like the 3.5L V-6 out of the TL Type-S (J35A3) and the 3.0L Twin Turbo BMW (N52B30) are loaded out with sweet magnesium components and variable timing systems. You can get both of these engines in cars that are less than $10000 US dollars more than a 40th edition RX-8. My question is, what's holding Mazda back from spending more on material and production costs for an engine that's half the size of most Otto cycle engines?

 

Simple answer: low production volumes.

Were the rotary used by more models, development costs could be spread much more. High development costs for a low volume item mean much higher final price; thus lower sales.

If you can't increase production volumes, the only other alternative is to limit development costs. Otherwise you need to get something serious to sell for that price (think Nissan GT-R, BMW M3 and up toward Ferrari, Lamborghini and the like).

 

I was just saying that all of the housings are probably about 1/2 the volume of metal that a standard V-6 engine would use for head and blocks. That trend continues throughout the drivetrain.

I suppose you're right though. Maybe they could just offer two engines like most car companies do it. Make 90%-95% the standard rotary and make a limited run super trick motor with the magnesium parts, engine coatings, billet eccentric shaft, ceramic apex seals, Moly coated side seals. I'd pay for a $40000-$45000 RX equipped out like that for sure.

 

it's threads like these that keep me loving this site..

 

Just wait until the book comes out!

 

Bump this one.

The RX8 has three fuel injectors and two fuel rails. The Secondaries fire in the intake manifold which has been shown to improve mixing of the air/fuel and more complete atomization at high loads (in addition to cooling benefits) in piston motors. The downside being that in low load situations the fuel can actually create an intake backfire (in extreme examples on piston race motors; sudden deceleration has lit air boxes on fire).

The primaries fire much closer to the ignition event (P1's are more responsible for low load and idle; then the Secondaries come on in order to provide better fueling in the torque peak; and then the P2's come on in order to (and here is my question):

1 - Cover fueling shortfall by the P1,Secondary combo (despite its less stellar location).

2 - Cover fueling shortfall and needs less time to fully atomize at the super high load point of the engine.

I am curious as to how the physical location and the stock fueling maps are interrelated.

Caveat - I may 100% wrong in which case I anxiously await correction.

 

On a related note; it looks as though the stock PCM is set to push all the fuel on the P1; and then once the Secondary come online; then it ramps them equal; and at high RPM it actually gives the Secondary more fueling than the P1.

So it would seem that the PCM has a small preference toward the Secondary; but doesn't actually push more fuel onto that injector - even though it could.

Thoughts?

 

They *probably* have their reason to do what you said above, but I still think Mazda is having a hard time trying to perfect the timing of the engine.

What we're seeing is probably the *closest* to perfection.

The newest flash actually advanced the timing a bit isnt it ?

 

Yeah timing is a whole nother ball of wax - I am just trying to understand what they are doing fuel wise; but it appears that they are kinda working something like this.

http://www.usrallyteam.com/content/t...ng_article.pdf

 

they mention Cosworth in the article, hmm, too bad they dont do any Rotary stuff

I like their MZR parts ...

 

LOL - FOCUS MAN!

JK, it would be nice to have a lot more smart people on all of this; but every bit we learn helps. I have a plan to emulate Mazda's stuff as close as possible; I'll uplod it soon.

 

Well, who knows what Mazda is thinking. After all this is their engine, and they've been working 40 years on it. Maybe they're working on something like that. Who knows

it seems that with every flash they just *feel like* to try something new.

 

HAHA; you may be right - we are beta testing. I am in the Army; so Im used to it.

Guinea Pigs FTW!

 

I hate to say it but ... yeah I think we're all Guinea Pigs ...

I am still on Last recall's flash(RB version) and I premix so Im ok for now ... I kinda want to do MSP16 cuz people's result are pretty positive.

thinking ...

 

I 100% agree. I don't even care for the jump between 5th and 6th. All the other upshifts pretty much drop my revs exactly where I want, except for 6th. I'm all for close ratios; but why does 5-6 have to be even closer than 1-2, 2-3, 3-4, or 4-5?

 

I'd love to see rotor deactivation as you described, along with a stop-start system in the 16X. If Mazda included both of those features, that might actually be compelling enough for me to consider trading my 2004 RX-8.

 

"The side exhaust ports ... allowed the closing point to occur later earlier, right around exhaust TDC."

"The second thing is that the 13B exhaust ports had a much longer shorter expansion stroke. The exhaust ports opened much earlier on the old engines."

"A long short expansion stroke is unfavorable in terms of thermal efficiency."

"By raising the compression ratio, they made this area slightly smaller. This does a better job at minimizing the containment volume of the exhaust gasses at closing timing and reduces the need for internal exhaust gas recirculation."