2012 Mazda 3i Skyactiv, Castrol OE 0W-20, 7k

[OVERKILL]

Originally Posted By: badtlc

Of course it isn't the most accurate. I think I quite clearly said it wasn't, unless you still can't read.


Oh, I can read just fine. And I've read all your posts. You are just getting rude now because you have no REAL data and people are taking issue with that fact. Which brings me to:

Quote:
Speaking of can't read, I can't read your previous post. Too long and you make assumptions based on previous designs w/out considering Mazda might be different.


So I write a detailed post on how the traditional system works, AND take the time to theorize how you THINK the Mazda system works, and because it is so long and detailed, you won't take the time to read it. Bravo! Speaks volumes as to the quality of your posts and your ability to participate in educated discourse. Of course the fact you stated that I make assumptions based on previous designs is proof of the fact that you did not read it, as I spent a great deal of time theorizing how the system you are envisioning might in fact work.

Quote:
If you can't admit that the premium fuel is doing SOMETHING, then you have obviously made up your mind on the subject and should really just stay out of this thread, please. If you think something else is improving my results, provide that.


I gave you a VERY clear way to CONFIRM whether what you are claiming is ACTUALLY happening. There are a plethora of different ways for your car not to be diluting and none of them involve the fact you are running high test.

However, now you are asking me to leave your thread so you can continue to theorize over something you are completely unwilling to actually take the time to prove? Seriously? You actually desire to wallow in ignorance instead of exercising your brain cells and spending some time that might actually make you a more knowledgeable person and verifying what you claim? I find that very disheartening.

To be clear: I'm not saying you are "dead wrong" or that the Mazda engineers haven't done something different here. What I'm saying is that what you claim is happening is NOT traditional, and I spent some time in that "too long" post both listing how the traditional system operates and how the system you are envisioning here actually WOULD operate, and we could be having an intelligent discussion about that right now if you hadn't blown me off because you don't like to be questioned.

 

[OVERKILL]

Originally Posted By: badtlc
Originally Posted By: Ben99GT
Originally Posted By: badtlc
The skyactiv engine runs rich in "closed" loop mode to cool temps in order to prevent knock while running lower octane during higher compression. Running a higher octane doesn't require the combustion chamber to be cooled as much to prevent detonation or knocking.


So the skyactive engine doesn't run stoich in closed loop, seems like that would defeat the efficiency gains of the high compression. That doesn't sound right.


Unless something has changed recently, very few, if any cars run stoich from what I understand. That is around 12.6:1 and EPA has set the lower limit to around 14.7:1 for emissions from what I can figure out. Is there something about current fuel that raises the stoichiometric ratio?


Stoich for gasoline is 13:1, but as you've noted, the EPA changed that to 14.7:1 for Catalytic converters.

There's actually a pretty good Wiki on it:
http://en.wikipedia.org/wiki/Air%E2%80%93fuel_ratio

Quote:
In reality, most fuels consist of a combination of heptane, octane, a handful of other alkanes, plus additives including detergents, and possibly oxygenators such as MTBE (methyl tert-butyl ether) or ethanol/methanol. These compounds all alter the stoichiometric ratio, with most of the additives pushing the ratio downward (oxygenators bring extra oxygen to the combustion event in liquid form that is released at time of combustions; for MTBE-laden fuel, a stoichiometric ratio can be as low as 14.1:1).

 

[SteveSRT8]

The only person who has made up their mind is the OP who imagines his assumptions to be facts.

It would be nice to see some more facts and perhaps some Mazda info.

 

[Trav]

Originally Posted By: SteveSRT8
If Mazda varies the closed loop mixture significantly it is the first engine ever made that does so. The whole purpose of the feedback loop is to maintain efficiency and an exact mixture to feed the cats what they want. Lean burn makes too much NOX.

Under heavy throttle/open loop enrichment is a standard feature, and many mfgrs use fuel as cylinder coolant.

I would like to see a link or some real evidence that would back up your assertions, please. This (if proven) would be the first real substantive piece of the much over-hyped 'Skyactiv' technology.


Thats pretty much it. From what i have read about it it appears Mazda opted for a 2 phase DI injector with 6 ports, basically a new diesel style injection type with diesel spray pattern.
One injection late in the intake stroke and the second injection on the compression stroke.

This is what cools the charge and lowers the chance of detonation. Lots of valve overlap and a special piston head are also used.
From what i can tell Sky Active looks a lot like some sort of a hybrid. An ignition fired gasoline engine with some diesel injection technology. Pretty cool actually.

I don't know enough about the ecm and the system to get into the weeds with the technology but it does look interesting. It sure isn't rehashed lean burn technic.

 

[OVERKILL]

Originally Posted By: Trav
Originally Posted By: SteveSRT8
If Mazda varies the closed loop mixture significantly it is the first engine ever made that does so. The whole purpose of the feedback loop is to maintain efficiency and an exact mixture to feed the cats what they want. Lean burn makes too much NOX.

Under heavy throttle/open loop enrichment is a standard feature, and many mfgrs use fuel as cylinder coolant.

I would like to see a link or some real evidence that would back up your assertions, please. This (if proven) would be the first real substantive piece of the much over-hyped 'Skyactiv' technology.


Thats pretty much it. From what i have read about it it appears Mazda opted for a 2 phase DI injector with 6 ports, basically a new diesel style injection type with diesel spray pattern.
One injection late in the intake stroke and the second injection on the compression stroke.

This is what cools the charge and lowers the chance of detonation. Lots of valve overlap and a special piston head are also used.
From what i can tell Sky Active looks a lot like some sort of a hybrid. An ignition fired gasoline engine with some diesel injection technology. Pretty cool actually.

I don't know enough about the ecm and the system to get into the weeds with the technology but it does look interesting. It sure isn't rehashed lean burn technic.



I agree Trav, the system itself looks pretty neat. But if it does indeed vary A/F (and I can only imagine it doing so in the way I described a few posts back) relative to knock feedback, it would be the first system I've ever heard do it too. I'm not, nor have I said, it isn't happening, I'd just like some proof of it. And logging the O2's is a pretty easy way to get that info

 

[OVERKILL]

BTW, here's the sort of data I was hoping for (just logged this from my car as an example):

 

[Trav]

Originally Posted By: OVERKILL
But if it does indeed vary A/F (and I can only imagine it doing so in the way I described a few posts back) relative to knock feedback


Agreed i cant see any other way it could do it either.
Sure they are doing some neat tricks with technology but the are not reinventing the wheel.

 

[DBMaster]

I know automakers have botched things in the past and that there was an issue with oil dilution in the Skyactiv-D's sold overseas. (Mazda claims to have resolved that.) But, I still find it very difficult to believe that after touting the fact that this engine is DESIGNED around the use of regular unleaded that the engine would have issues related to oil that could cause damage to it.

I think it's time for me to stop reading threads like this in which armchair automotive engineers argue over whether or not the manufacturer of the car knows its own hardware. I am using Mazda's specific oil and filters, burning 87 octane, and going with the 7,500 mile OCI. End of story for me. I guess I'll wait for the engine to blow up on my way to work one day.

 

[badtlc]

Originally Posted By: DBMaster
I know automakers have botched things in the past and that there was an issue with oil dilution in the Skyactiv-D's sold overseas. (Mazda claims to have resolved that.) But, I still find it very difficult to believe that after touting the fact that this engine is DESIGNED around the use of regular unleaded that the engine would have issues related to oil that could cause damage to it.

I think it's time for me to stop reading threads like this in which armchair automotive engineers argue over whether or not the manufacturer of the car knows its own hardware. I am using Mazda's specific oil and filters, burning 87 octane, and going with the 7,500 mile OCI. End of story for me. I guess I'll wait for the engine to blow up on my way to work one day.


1) what makes you think there is a risk of damage? Nothing has indicated there are any issues or problems.
2) The engine doesn't run regular grade gas over seas.

 

[SteveSRT8]

Originally Posted By: Trav
Originally Posted By: OVERKILL
But if it does indeed vary A/F (and I can only imagine it doing so in the way I described a few posts back) relative to knock feedback


Agreed i cant see any other way it could do it either.
Sure they are doing some neat tricks with technology but the are not reinventing the wheel.


This is what we have all come to think of as far as Skyactiv goes. It's an Atkinson derived design that uses the power stroke a bit more efficiently.

From WIKI: "Recently Atkinson cycle has been used to describe a modified Otto cycle engine in which the intake valve is held open longer than normal to allow a reverse flow of intake air into the intake manifold. The effective compression ratio is reduced (for a time the air is escaping the cylinder freely rather than being compressed) but the expansion ratio is unchanged. This means the compression ratio is smaller than the expansion ratio. Heat gained from burning fuel increases the pressure, thereby forcing the piston to move, expanding the air volume beyond the volume when compression began. The goal of the modern Atkinson cycle is to allow the pressure in the combustion chamber at the end of the power stroke to be equal to atmospheric pressure; when this occurs, all the available energy has been obtained from the combustion process. For any given portion of air, the greater expansion ratio allows more energy to be converted from heat to useful mechanical energy meaning the engine is more efficient. The disadvantage of the four-stroke Atkinson cycle engine versus the more common Otto cycle engine is reduced power density. Due to a smaller portion of the compression stroke being devoted to compressing the intake air, an Atkinson cycle engine does not take in as much air as would a similarly designed and sized Otto cycle engine.
Four-stroke engines of this type with this same type of intake valve motion but with a supercharger to make up for the loss of power density are known as Miller cycle engines."

Mazdas focus on the entire car is what is unique here. But I feel certain that OBD2 and patents, etc., prevent them from reinventing the wheel with regards to mixture enrichment.

 

[badtlc]

Originally Posted By: SteveSRT8

Mazdas focus on the entire car is what is unique here. But I feel certain that OBD2 and patents, etc., prevent them from reinventing the wheel with regards to mixture enrichment.


I don't think they are. I think other automotive manufacturers using the wide band lambda probes (I think VW, BMW, etc) are doing similar things.

 

[OVERKILL]

Originally Posted By: badtlc
Originally Posted By: SteveSRT8

Mazdas focus on the entire car is what is unique here. But I feel certain that OBD2 and patents, etc., prevent them from reinventing the wheel with regards to mixture enrichment.


I don't think they are. I think other automotive manufacturers using the wide band lambda probes (I think VW, BMW, etc) are doing similar things.


Most of those marques (and any BMW I've ever seen) require premium fuel period, so there'd be no need for an adaptive strategy with respect to octane; it is a known quantity.

BMW's use of wideband O2's is for more granular control of A/F and subsequent emissions performance. Which is likely relevant to the fact that they don't use PCV valves or EGR valves, instead using air/oil separators for crankcase ventilation and using cam timing to accomplish EGR.

The main difference between the PZEV and non-PZEV 330i for the '03 MY (my sister's car) was the wideband O2's.

 

[DBMaster]

Do I really need to state this again? The overseas cars require premium because they have 13:1 compression. The U.S. version had it reduced to 12:1 because Mazda realized that we seem to be more price sensitive on gas.

 

[SteveSRT8]

Originally Posted By: badtlc
Originally Posted By: SteveSRT8

Mazdas focus on the entire car is what is unique here. But I feel certain that OBD2 and patents, etc., prevent them from reinventing the wheel with regards to mixture enrichment.


I don't think they are. I think other automotive manufacturers using the wide band lambda probes (I think VW, BMW, etc) are doing similar things.


Yes they are. All OBDII setups simply must share a lot due to govt regs. And while engines can adjust mixture based on O2 sensor input they simply do NOT react that way to detonation/preignition. All they do is retard the spark and listen again, repeating until it stops.

Personally I love Mazda's focus on improving many small things and thus yielding a nice car that drives well and still delivers the goods as far as economy goes. But I really think their engine is simply a modified Atkinson, even Car and Driver calls it that in their testing specs. This would explain the high comp ratio as well since AC engines lose compression to the atmosphere during a portion of the cycle.

Multiple injection pulses are like multiple ignition strikes, they're really not unusual.

 

[badtlc]

Originally Posted By: DBMaster
Do I really need to state this again? The overseas cars require premium because they have 13:1 compression. The U.S. version had it reduced to 12:1 because Mazda realized that we seem to be more price sensitive on gas.


And the reduction of compression didn't solve it on its own. Mazda engineers specifcally talked about enriching the tune for "87 octane".

Also, you avoided the question again. What makes you think there is anything wrong with Mazda's design? There have bee no indications of a design flaw.

 

[DBMaster]

Didn't realize you asked me a question, sorry. I don't know one way or the other if there are design issues. The gist I got from this thread, which actually became too technical for me, was that I should expect issues like oil dilution and valve deposits if I continue to use regular fuel - exactly what Mazda recommends in the owner's manual.

I didn't mean to come across as angry. One of the biggest draws of this car, for me, was its performance/cost ratio. If I have to use premium fuel in it part of the favorable cost-to-own is compromised. I do not intend to use premium fuel in it.

 

[badtlc]

It looks like the octane/leaning out might be tied to the stratification mode and "ultra lean mode" of DI engines. Here is layman's excerpt from a UK VW site:
Quote:

The higher the octane rating of the fuel the longer the FSI engine will run in FSI mode.

You see, when the FSI is running in 'Fuel Stratified Injection' mode it creates a lot of NoX (NoX - Very bad as far as emisions go) due to it being such a lean burn, so it has a NoX Cat which abrorbs the NoX, once its full the Nox probe (fancy lambda probe) senses this and the engine switches back to normal running and can safely clear the NoX out with the other gases through the main Cat so it can switch back into in FSI mode again.

The problem with octane levels is, and this is just an example depending on driving styles.

Out of 100 miles average :-

95RON - 90 miles normal, 10 miles FSI (lots of NoX made in FSI mode)

97+RON - 60 miles normal, 40 miles FSI (some NoX made in FSI mode)

Now regardless of what anyone says this is how the engine is built and as its more efficient in FSI mode VW always recommend the highest octane rating for this reason, they did introduce a 1.4FSI for the uk market that is made to run on 95RON fuel for longer but you want to see the size of the NoX Cat, more like a tanker. lol

And after all that, you will get better miles to the gallon running 97+RON regardless of it being an FSI, its they way they are made these days, the ecu recognises when the fuel mixture combusts and will adjust it accordingly, the cheaper the fuel the more retarded the timing, the more retarded the timing the less power, the less power the more you 'need' to put the foot down.


Going along this route it would appear that higher octane -> longer ultra lean burn mode runtimes, which is running leaner by definition. I'm almost positive this is very similar to what Mazda does.

 

[OVERKILL]

Originally Posted By: badtlc
It looks like the octane/leaning out might be tied to the stratification mode and "ultra lean mode" of DI engines. Here is layman's excerpt from a UK VW site:
Quote:

The higher the octane rating of the fuel the longer the FSI engine will run in FSI mode.

You see, when the FSI is running in 'Fuel Stratified Injection' mode it creates a lot of NoX (NoX - Very bad as far as emisions go) due to it being such a lean burn, so it has a NoX Cat which abrorbs the NoX, once its full the Nox probe (fancy lambda probe) senses this and the engine switches back to normal running and can safely clear the NoX out with the other gases through the main Cat so it can switch back into in FSI mode again.

The problem with octane levels is, and this is just an example depending on driving styles.

Out of 100 miles average :-

95RON - 90 miles normal, 10 miles FSI (lots of NoX made in FSI mode)

97+RON - 60 miles normal, 40 miles FSI (some NoX made in FSI mode)

Now regardless of what anyone says this is how the engine is built and as its more efficient in FSI mode VW always recommend the highest octane rating for this reason, they did introduce a 1.4FSI for the uk market that is made to run on 95RON fuel for longer but you want to see the size of the NoX Cat, more like a tanker. lol

And after all that, you will get better miles to the gallon running 97+RON regardless of it being an FSI, its they way they are made these days, the ecu recognises when the fuel mixture combusts and will adjust it accordingly, the cheaper the fuel the more retarded the timing, the more retarded the timing the less power, the less power the more you 'need' to put the foot down.


Going along this route it would appear that higher octane -> longer ultra lean burn mode runtimes, which is running leaner by definition. I'm almost positive this is very similar to what Mazda does.


Now that is an interesting piece of information. So while the (FSI) system doesn't actually measure the octane of the fuel, or modify the A/F relative to octane rating, this particular system stops running in FSI mode when its NOX cat is saturated, causing it to revert to the "normal" (non lean-burn) mode to reduce NOX and clear this catalyst out.

In this case, the byproduct of running higher octane fuel is lower NOX, which results in more FSI run-time and subsequently could potentially lead to less fuel dilution.

So then the question here is whether Mazda is utilizing a NOX catalyst like the FSI system?

And as I noted earlier, you could readily verify the system operating in this manner by datalogging the wideband O2's. They would show significantly longer periods of "lean burn" under the higher octane fuel.

This is quite interesting as it leverages the conventional feedback mechanisms I detailed in my earlier post with parameters set for lean-burn operation that are excepted once a certain flag is set (in this case a full NOX cat).

 

[DBMaster]

I see that Mazda has won some design awards related to its cats. Specifically, it relates to nano-particle sizes reducing the quantities of precious metals required as well as reduction of NOx in diesel emissions without urea required. I haven't found anything indicating whether or not my Mazda3 Skyactiv-G includes a "full NOx cat,"

 

[SteveSRT8]

Originally Posted By: OVERKILL

So then the question here is whether Mazda is utilizing a NOX catalyst like the FSI system?

And as I noted earlier, you could readily verify the system operating in this manner by datalogging the wideband O2's. They would show significantly longer periods of "lean burn" under the higher octane fuel.


ANY proof would be nice. Perhaps a simple data log?