Gforce 8

Hope this is not a repost:
Mazda continuing with rotary engine development | Autocar
I'm glad they haven't given up on it.
But the wait is gonna suck!!

77mjd

It is a new article, but nothing we don't already know.

monchie

Only time will tell...

simonmd

Mazda won't give up on the rotary, its too much a part of what they stand for and they've had over 40 years perfecting it. Whether we'll see a proper sports car like the RX7-8 again is up for debate but I'm sure it will been seen again in hybrid form at least.

Harlan

iTrader: (3)

I've heard good things about the 16X regarding direct injection and fuel economy. Not just good economy "for a rotary" but real good economy. I don't think Mazda is done yet.

j9fd3s

i actually would not mind if the US market got held back a year or two. it would be nice to let them make the new car for 12-18 months before we get it, that way they can iron out any bugs.

it just seems like with the FD and then the Rx8, they showed up with stuff that needed to be corrected, and it just gave them a bad rap right from the start.

simonmd

And to compensate you and try to keep confidence in the market, they gave all you guys a rediculous 100,000 mile, 8 year warranty! We can only dream of such a safety net over here.

olddragger

iTrader: (3)

i am not sure about DI used in the rotary engine.

reddozen

iTrader: (1)

I would rather not miss out on the 50th anniversary car here in the states... Just don't buy the first one if you're not willing to risk it. I honestly don't think they will make the same mistake twice though.

Harlan

iTrader: (3)

Get all the fuel in the direct center of the bathtub and ignite it. Lean burn without the consequences. It's not DI only, during higher loads it has regular injectors.

DI timing is so precise now they can have multiple fuel air pockets in the same chamber!

77mjd

If they want to stay in peoples good graces and possibly attract new customers to the rotary, they'd best offer another 8 year 100k warranty right out of the gate. If they manage to solve the issues the Renesis has it shouldn't even be an issue.

MattMPS

after seen some bibliography about the injection system of SKYACTIV-G (multiple injections, 8-hole injectors, higher pressure..etc..) i'm betting about DI also in SKYACTIV-R

and i'm expecting big news also in ignition system...

olddragger

iTrader: (3)

Oh I agree--just cant say I am going to like it. I forsee a problem with intake carbon/gunk buildup.

Are to thinking the laser ignition? That is not going to happen anytime soon.

Bladecutter

The biggest problem with DI is directly related to oil mist vapor from the crankcase ventilation system that builds up on the intake valves of piston engines, and over time (a short period at that) builds up enough carbon on the intake valves to actually reduce the amount of air that can enter the combustion chamber, which then reduces power.

In the entire intake system of a rotary engine, there is only one valve system that can build up deposits like this, the SSV valve. This has been a problem in the past, but they managed to figure out a way to resolve the problem during the RX-8's production run. And the build up only occurred on cars that weren't exercised on a regular basis, had overly long oil changes, and were not driven like a sports car should be.

Not to mention, when the SSV opened (if the problem was intermittent) the actual amount of air passing it was not reduced, like it is on the intake valves of a piston engine.

So, with that being the only real valve that can get PCV build up on it, and we already know how to prevent it, or eliminate it, why are you nervous about DI on a rotary engine again? The benefits are way too great to pass up.

BC.

MattMPS

Yes. but 2017 is not "soon" IMHO...and the most important problem to solve is this one (ignition) IMHO

olddragger

iTrader: (3)

These are some of my concerns with DI in a rotary engine. These are just my opinions and what I know that has been dealt with in some recips that I am aware of:

1- DI combustion has the ability to produce far more soot than premixed combustion (port injection),
Manufacturers have added systems to capture these oil droplets and particulates, but no system is 100% effective. As a result, there are many disappointed early adopters that have to have costly repairs. Manufactors torture tests do not reveal this type of problem. Reason being these types of issues will only appear after years of short trips (preventing the engine from reaching operating temperature), bad batches of fuel, etc.

2-The percentage of ethanol in gasoline at the pumps is increasing. Ethanol has a tendency to increase the corrosion rate of the various metals used in an engine. Add this to the elevated fuel pressure and the fact the injector is directly exposed to in-cylinder combustion events, and you have a recipe for a problem. Furthermore, these injectors are very sensitive to fuel quality due to outrageously tight tolerances. It is very important to use high quality fuels and keep the filters clean. No one knows how pre mixing will affect the injectors either. Maybe we will not have to pre mix? I believe we will as..

3- DI will be hard on the ability of the apex/side seals to obtain proper lubrication.

4- there will be fuel pump recalls and if lean events occur during a FP failure--well you know what sometimes happens when a rotary engine goes lean
.
5-true DI cannot be done in the rotary engine because of the way the combustion chamber is used. DI cannot inject directly into the hottest part of the combustion chamber ( leading plug area) due to the rotary engines design. So DI cannot have as profound of effect in the rotary.

6- then there is the issue of fuel dilution in the oil--it does increase.

7- Part of DI ability to make more power is in using it the manufactors can up the compression ratio without any ill effects. However in the rotary engine increasing the compression past the current 10:1 does not do much.

I think DI can have some benefits--maybe they will use a di for the primary and then port injectors for the secondary's, but in the rotary it will not have as big of an effect as in the recips. It would be a bigger help if they would put forced induction on the engine.


the laser sparkplug is fun to think about--but I see a nightmare in trying to put it in the market. I have heard some good things about a "pulse" type of ignition that may make sense. Presently it requires too much power to be practical.

In 2017 the rotary engine is already outdated man---some MAJOR developments will have to be done before it will be competitive. I do cross my fingers--but I dont know.

Bladecutter

I believe you have combustion exhaust soot mixed up with oil mist, that is in the engine crankcase, and ingested by the PCV system.

I don't really remember too many pictures of rotary engines that were taken apart that showed any signs of ethanol damage. Lots of failed ignition damage, or low oil pressure damage, but mot much that can be directly attributed to ethanol damage.

Actually, I believe it would be the exact opposite.
With the fuel entering the combustion chamber between the apex seals, and being ignited quicker, and the fuel metering being way more precise, I believe you will see that the apex and side seals will require less oil to keep properly lubricated, and it won't get washed away and diluted by the fuel mixture anymore.

I believe the biggest danger of DI in a rotary engine is the increased combustion temps in an isolated area of the engine. They will need to truly beef up the cooling system on the ignition through the exhaust side of the engine.

HPFP's have become much more robust in the Japanese and Korean companies that build them. You have to remember that the German cars all use Bosch components, and we know they aren't being built for longevity, or cost savings.

The one thing that is truly eliminated in the rotary engine is spraying raw fuel on the exhaust stroke in order to heat up the catalytic convertor quickly. Increasing the pressure of the DI spray can get the fuel further into the bathtub of the rotor to atomize the fuel closer to the spark plugs, or a short burst of DI spray right before the trailing apex seal passes means that they can still have multiple DI spray events during an intake pass.

With how fast and accurate DI is with getting fuel into a combustion chamber, we really should see huge increases in just about every fuel related category.

Actually, with the rotary engine, I see this decreasing.
In a recip engine, the fuel is spraying into a round object, including on the exhaust stroke while the engine is cold. Directly below those round objects is the oil sump. The extra fuel that washes off the cylinder walls and past the low tension piston rings in recip engines goes directly into the oil sump, increasing fuel dilution.

In a rotary engine, there is no direct path for unburned fuel to get into the oil system. Since they can't do the extra fuel to light off the convertor during warm up exhaust strokes, I can't say that there will be any additional increase in fuel dilution in rotary engines. As if currently stands, the only entry way for fuel to get into the oil system is through the side seals on the rotors, and around the crankshaft. Since the fuel injected will be less now, and the whole rotor and intake of the combustion chamber will no longer be awash in gasoline, the dilution should decrease.

Again, way less of a problem for people who get their cars hot all the time, to burn off the extra fuel.

I can't say much about that.
It's entirely possible with the rotary engine, they can increase the ratio because they can eliminate knock right at the source, since they now have full control of the mixture directly in the combustion chamber, which is the same reason why they are able to increase the ratio in piston engines. I think you might be able to see rediculous cr in the rotary engine instead.

I see no benefit of having a fuel injector in the air stream at all.
An oil injector, yes.


I think the rotary engine will come into its own in the future.
It just depends on how financially healthy Mazda becomes between now and 2017.

BC.

alnielsen

iTrader: (4)

It is a repost.
https://www.rx8club.com/general-auto...utocar-243305/
This is a article about rotary engines, not the RX8. So, if you looked in General Automotive, you would have found it.

Moving to General Automotive

alnielsen

iTrader: (4)

A laser ignition would work well with the design of the rotor housing. There is a thread here about the shape, size and depth of the spark plug holes. A laser ignitor would only require a small hole and eliminate any compression loss.

olddragger

iTrader: (3)

1-- no mix up--soot is a end product of combustion--the systems added to help with this are the pvc systems etc.
This pvc system actually promotes intake port carbon deposits due to the siphoning these oil vapors/soot back thru the intake port where they can be deposited. Much like the intake valve guides in the recip engine. If you also think we dont have blow by in this engine then you are mistaken. Look at some owners SSV deposits even now. DI has the potential to make that much worse.

2- the ethanol damage is to the direct injector themselves--not the engine. Please read more carefully or perhaps I wasnt clear enough about my opinion.

3- the omp holes now are located where? The direct injector is located where? The intake charge will not carried as far but that also means no premixing benefit. Rotary engines need premix IMHO--even the s2 engines have failed compression testing and they have the better omp's. You cant premix with DI. Plus the gas being directly injected into the combustion chamber will have a more profound washing affect.
4- FP /system problems with DI exist--just go to a dealership and ask.
5- increasing the compression ratio past 10:1 does not gain anymore power like it does on the recip engine. If you want to make a diesel rotary--yep then that may work.

Its good to have discussions like this. I agree that mazda hasnt given up on the rotary. I love this engine but with the power/economy metrics that are being set now a days I dont see how it will be able to compete. 400 hp is now almost the norm in a performance car. Even grand Touring cars have over 300. Plus they have good gas mileage for their power levels.
Now if Mazda will go the way of the Lotus and can produce a a 3 rotary engine that can put out 325 hp or so and give over 20 mpg then they may have a chance. Or if they can reliably put forced induction on it then that may be the ticket.
Dont get me wrong--I hope they can.

j9fd3s

i've seen a couple of SAE papers, and soot is a problem, i forget what the other variable is, i want to say AFR vs soot, but its something like that.

we've had ethanol in CA for a couple of decades and i've never seen anything damaged that could actually be blamed on ethanol. it just isn't a problem. if you left an injector in ethanol for months will it rust? yes. if its a problem in the real world we would have seen it in CA.

well, we actually don't know where any of the injectors are located, we can speculate, but they may have moved since we saw it last.

and speaking of speculation, if there is less fuel to wash down all the walls, in theory this improves things. i will grant you we don't really know

sure, people have problems with tires too... but really go to ANY dealership, preferably Audi, and ask about DI problems. Audi tear those engines apart every 20k, because they clog with junk. the first one is under warranty, the second is on you!

with the present geometry this is correct, however if they change the K ratio with the new engine, it changes the compression ratio.

since the Skyactive pistons are so odd, i expect the new rotary to have a special chamber shape, weather that is a really precise bathtub, or something else, we don't know.

yep me too. well i had a 3 rotor, there are a few good reasons why you'll never see one! mileage and heat are two biggies, if you think a twin turbo FD is hot when you open the hood, you're unprepared for the 20B!

20mpg freeway is possible with the 3 rotor, but when the gas pedal moves, mileage drops FAST.

olddragger

iTrader: (3)

Lol-- I bet it does, but the grin gets bigger!

I agree there are a lot of unknowns and who knows what they may come up with. Mazda does need more Zoom-Zoom- now.
By the way--in Ga the BMW's are having a lot of carbon buildup in some of their di engines---they have to walnut shell (sandblast) the valve guide's port clean at times. Those short trips etc are killers. Plus in Ga we have dirty gas.

Concerning the compression ratio-- i had forgotten the new geometry in the 16X---hmmmm??