DR. Victor Wankel

you refering to the sky active 3 as far as hybrids go? thought that only got 40mpg max?

RIWWP

iTrader: (2)

The 40mpg SkyActive 3 currently for sale in the US only has part of the SkyActive technologies. Expect an increase into the mid to high 40s once everything can be brought over. Chassis changes needed for several components would have meant a new round of federal licensing that Mazda couldn't take the time and/or money to address, so they dropped the compression slightly for now.

I was more referring to the CX-5, an SUV that can get 35mpg in the gas version, 52mpg in the diesel version. The new 6 should be about 40mpg (gas, or ~58-60mpg diesel) as a mid-size sedan. If they applied the SkyActive to the subcompact 2, it would top 50mpg easily, possibly 60mpg.



I entirely believe that they are taking the learnings and tech from the SkyActive piston engines and applying that to the 16x prototype learnings and will not have trouble hitting acceptable mileage and emissions goals.

comebackqid

iTrader: (13)

RIWWP I was hoping they would incorporate it into the next rotary design I think with it being a 1.6L will help a lot for power concerns and with the skyactive they can possibly make decent power and pass emissions.

I really hope they work something out because the world needs at least one rotary car in production or something bad will happen LOL.

Mazmart

iTrader: (12)

The skyactiv Mazda 2 with 1.3 and CVT makes 70 mpg on the Japanese cycle and has accomplished better than 50 mpg through the mountains.

I agree with your statement regarding Skyactiv tech being studied and applied to the RE. I know they are doing it.

Paul.

DR. Victor Wankel

how do you they incorporate skyactive tech into a rotary? the 3 is a piston driven engine.

bse50

be it piston or wankel they both work thanks to the same principles.

RIWWP

iTrader: (2)

Both use low pressure from volumetric expansion to draw in air, injects the fuel, compresses the mixture, and ignites it to produce power.

SkyActive plays with intake port shape, exhaust port shape, compression cavity shape, exhaust header, timing, fuel pressures, etc... To shed compression heat to achieve higher compression than traditionally possible, getting more energy from each combustion, increasing thermal efficiency, torque, and overall economy.

All of these concepts can apply to rotaries as well. Just have to have the creativity and ingenuity to design without blinders on.

craiggger

Well done. checkmate

cliffkemp

Saw a video about the guy that said the sparkplug hole is causing compression loss and the 'bathtub' should be offset on the rotor itself. I have not seen any real discussion on this and maybe, I just overlooked it on here.

The sparkplug hole concept seems legit from what little I know about the engine. As the apex seal passes over the hole, the compression and exhaust cycles have some overlap due to the size of the hole for the plugs.

Since there is some overlap due to the hole size, some compression is lost to the exhaust side, so to speak, and some power is lost due to this....How much is debateable.

It would stand to reason that, at lower rpm's, this would contribute to lower mpg due to the apex seal passing over the hole slower and, therefore, losing a little more compression to the exhaust phase side.

According to the video, the guy tried a modified version and was able to see some results of this modification. The exhaust went down but as much as 600 degrees in the supposed test.

Any views or thoughts out there from people who have either tried this as well or any engineers? I was not too keen on moving the actual 'tub' to near the top to help out much of anything but, I do not fully understand the dynamics of this motor either.

Bladecutter

Already discussed.
There's a thread or two on the forum about it already, one from just a month or two back.

BC.

j9fd3s

its true the trailing spark plug hole causes a small compression leak, however a small leak is still better than a single plug ignition.

plan B would be to put the plugs in the rotors, but that means a rebuild every time you need plugs, too german, even for the germans.

Mazda has tried a bunch of different chamber shapes, and there are tradeoffs with each one, try the rotary engine book https://docs.google.com/file/d/0Bzy-.../edit?hl=en_US

actually i would expect the 16x to have something fancier as a chamber shape, as they can computer model things now, the 70's used a high speed camera, or multiple temp sensors.

Wankel04

2017 the return of an icon. Mazda RX7 | Rotary Power Crew

I know it's kind of old news, but I'm all giddy about this!

C Del

Interesting-looking book!

Better scan:
http://foxed.ca/rx7manual/manuals/RE...amoto-1981.pdf

fyrstormer

Yes and no. Part of the compressed fuel charge *does* leak from one chamber into the other by passing over the apex seal through the hollow gap in the sparkplug, but that compressed fuel charge isn't actually *lost*, it's just transferred into the next combustion chamber where it will get compressed all over again. Nothing actually leaks out of the engine through the sparkplug holes, unlike leakdown around piston rings which then escapes out of the crankcase through the PCV vent.

Mazdaspeed RX8 ver2

Hm, thread revival, awesome.

C Del

If you look at pages 47-49 of Yamamoto's book on the rotary engine, there's some explanation of the concept of Leading Deep Recess, which I believe is what the guy in the video was proposing in addition to modification of the spark plug holes. The data Yamamoto presents seems to indicate that an LDR rotor does increase fuel efficiency by increasing the burn rate of the fuel/air mixture, but it also increases the rate of NOx emissions, which could be an environmental impact problem. It would also seem that LDR rotors increase idling stability. His data also suggests that increasing the compression ratio offers similar benefits and drawbacks, and that a ratio as high as 10.5:1 might be possible on high grade premium gas, though that seems to be right on the edge.

Of course, all this information was collected more than three decades ago and Yamamoto doesn't even suggest or imply anywhere that side exhaust ports were even under consideration at the time.

Edit:
Also, the spark plug hole probably causes some EGR within the engine, which should be good for HC emissions. Sealing it better might improve MEP in the combustion chamber, but it could also give the rotary even more trouble with the regulators.

j9fd3s

i thought there was a section or sentence on side exhaust ports?

the data they collected 30 years ago is still totally valid, but in the last few years there have been some neat improvements in flow analysis and this lets the engineers try a bunch of different piston and port shapes in the computer before they try em in real life.

so i would expect they are spending a lot of time on the new engine on the chamber and port shape, i would also expect a special combustion recess, although it might not be fancy like the skyaktiv.

cliffkemp

The next combustion chamber is the exhaust and out the tail pipe. It does get 'lost'. It may be minimal but, it is lost due to the overlap at the leading plug holes size. It is not going to get compressed again compared to what it lost. Bad piston rings will lose compression into the crank and the head and cause a loss in power, too.

How to fix the overlap problem without creating other problems, long term, has yet to be determined for mainstream rotary engines.

I believe that a larger yet, narrower rotor will prevail in the end to fix the tq issue at lower speeds along with better gear selection in top gear will prevail and keep the rotary viable. Fixing the apex seal issues with better technology may come in time as well. Time will always tell.

RIWWP

iTrader: (2)

What about pressure differentials?

If the exhaust face has a higher pressure than the intake face (likely), then the air/fuel charge isn't going to the exhaust face when the apex seal crosses the plug hole, the exhaust is going to the fresh intake charge face. EGR effect?

C Del

That's what I had thought. Just now I went into Yamamoto's book to find the graph that I thought would support that notion, but now that I'm looking at it, it actually seems like the leading plug is placed strategically where the pressure differential is very low. It does look like some leakage should occur from the compressed charge into the uncompressed charge through the trailing plug hole, but that shouldn't be too much of a concern since it will simply be compressed again.

Reference page 23, figure 3.12.

I'm skeptical that changing the plug holes would help any, but changing the rotor recess shape seems at least somewhat promising.

reddozen

iTrader: (1)

The old 12a rotors had shaped combustion pockets (like a tear drop). It's supposed to help with fuel economy like you've mentioned.

sweatr

There is one on the horizon. The 16x (rx9) to come out in 2014.

WTBRotary!

iTrader: (6)

Don't you start on the next RX , if the next RX comes out next year we would obviously have more info on it...

This is the Gas/Oil premix thread... Lets keep it this that way...

maxchao

iTrader: (2)

lol ok I just wanted to confirm my thought. Interesting stuffs. Thanks for the info.

gwilliams6

Mazda has the next RX7 with the 16X engine slated for 2017 arrival, not 2014