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Discussion Starter #1
Nissan's VC-T engine essentially alters the compression ratio by changing piston stroke distance while you drive to go from high compression ratio while cruising under light load, to a very low compression ratio during full throttle acceleration to increase knock resistance as well as turbo boost performance.


On the other hand, Hyundai has introduced a rather complex camshaft design which alters valve timing depending on how you drive. It's sort of like an advanced variable valve timing system which delays valve timing on the intake side during light loads and speeds it up for better performance during heavier loads.

So my question is - is this technology worth it, both in terms of economic feasibility and long term reliability? The CVT on the Altima is a real bummer, but could any of you picture yourselves driving one of these? It's definitely a nice car with some very cool technology. I can't wait to see what Mazda comes up with in the next generation.
 

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In a word, no.

SkyActiv already accomplishes this with VVT on the intake specifically, with the phaser being electrically driven. That's how they manage to get their sort-of Miller/Atkinson cycle to work, and it also makes piped EGR unnecessary, which reduces complexity while basically eliminating the intake fouling that otherwise occurs with it.

Engine designs that change piston stroke distance have been experimented with before but the complexity it introduces is quite extreme and it's in a part of the engine that is under quite-severe conditions. Never mind that they're all trying to achieve what Mazda already has in terms of fuel efficiency and that's BEFORE the HX engine shows up over here -- it's already in Europe and here in test vehicles, and frankly THAT ONE is a game-changer in that it should return fuel economy very similar to that of a diesel but without the price tag and complexity of modern common-rail diesel engines and their exhaust after-treatment requirements.
 
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Discussion Starter #3
In a word, no.

SkyActiv already accomplishes this with VVT on the intake specifically, with the phaser being electrically driven. That's how they manage to get their sort-of Miller/Atkinson cycle to work, and it also makes piped EGR unnecessary, which reduces complexity while basically eliminating the intake fouling that otherwise occurs with it.

Engine designs that change piston stroke distance have been experimented with before but the complexity it introduces is quite extreme and it's in a part of the engine that is under quite-severe conditions. Never mind that they're all trying to achieve what Mazda already has in terms of fuel efficiency and that's BEFORE the HX engine shows up over here -- it's already in Europe and here in test vehicles, and frankly THAT ONE is a game-changer in that it should return fuel economy very similar to that of a diesel but without the price tag and complexity of modern common-rail diesel engines and their exhaust after-treatment requirements.
The only real benefit I see to Nissans application is a vast range of compression ratio variation (like 8. Something to 14) which is very useful for turbo application in my opinion, but Mazdas simpler more old school method seems to be optimal especially since they have managed to get rid of the EGR valve.

What about Hyundai's version of variable valve timing? Is that also too complex? Seems like a very smart feat of engineering.

On a side note, you've mentioned before you dont see a point in using 91 octane fuel for your Mazda. Would it be worth it just to reduce low rpm pre detonation? Especially if you can find ethanol free premium fuel for a similar price like we do here, i think is worth it. I've tried several different fuels in my bmw in the past, including 87 octane and found that the improved efficiency of ethanol free 91 octane almost completely negated the extra fuel cost.

Lastly - you said Mazdas VVT is electrical. I know BMW's do it based on oil pressure, and then theres hondas vtec. Which works best?
 

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No. There's no possible way in hell you're going to get ~20% more fuel economy. Not a snowball's chance in Hell and anyone claiming you will get anywhere close to the additional fuel cost back in better efficiency is flat-out lying.

Mazda's intake VVT is electrical (stepper motor); they also have an exhaust phaser but it's much more-limited in effect and that one is oil-driven. The electrical drive is a LOT more precise and, at least thus far, it appears to be dead-balls reliable too.
 

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Engine design is even harder than 21st century democracy because it requires even more compromise. Every design parameter "knob" that engineers can turn affects an engine's power, fuel efficiency, and emissions, and clever solutions to hack long-established trade-offs between them generally compromise cost, durability, and refinement.
I think the opening paragraph to the article is right on.... It's a bunch of hacks that will compromise long term durability.
The only real risk that the manufacturer takes in this compromise is if the warranty is still in place when things start to fall apart
I suppose it's not a bad thing if you are leasing the car or only keep a car for a few years, just expect big bills if you keep it for a decade or so.
 
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Discussion Starter #6
No. There's no possible way in hell you're going to get ~20% more fuel economy. Not a snowball's chance in Hell and anyone claiming you will get anywhere close to the additional fuel cost back in better efficiency is flat-out lying.

Mazda's intake VVT is electrical (stepper motor); they also have an exhaust phaser but it's much more-limited in effect and that one is oil-driven. The electrical drive is a LOT more precise and, at least thus far, it appears to be dead-balls reliable too.
True - I'm not sure what i was thinking when I said that. According to my calculations, there is a roughly 5, maybe 10% variation between the two fuels which can very likely be chalked up to negated performance due to a presence of 10% ethanol in one of the fuels vs. The other.

So, in my opinion, regardless whether your car requires 87 or 91, use the recommended octane rating, but try to source ethanol free fuel if you can. Even if the variation in price is more than 10% where you live I still think its worth sourcing out ethanol-free for a number of reasons.

Judging by my seat of the pants evaluation comparing ethanol blended 91or 87 octane in comparison to Shell's 91 V-Power, I felt like I was really getting my money worth based on a fairly moderate performance increased alone. I felt an easy 1-2HP gain and the engine undoubtedly ran better. It also gave the engine a deeper tone while running through the RPM's. My friend made the same switch with his 2012 Acura TL and was under a very similar impression. Obviously your not going to see 20% savings at the pump but I see it as more than just a few dollars per pump - its important to consider what your engine is burning both for it's own health and at the expensive of environmental concern.

Also, dont forget that in the US fuel is much cheaper. I dont think its worth pinching pennies to use ethanol blended 87 if you have ethanol free 87 where you live whatsoever, regardless of price variation.
 

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US fuel may be much cheaper but the difference between 87 and 93 isn't in percentage terms. The last time I was in Canada I nearly crapped my pants when it was CAD $60 to fill my "6" up, but that's your "usual expectation" so.... yeah. Even so the difference here is dramatic -- $2.30 for 87 .vs. over $3, typically, for 93, so.... no. And ethanol free is even worse; it is typically either 89 or 92/93 and is nearly always a buck a gallon over or even MORE than straight RUG (with ethanol.) Up north it can be even worse in that they love their E-85 pumps there and if you can find ethanol-free it's not uncommon for it to be $5/gal. Now if you have an old diaphram-pump-style carb'd 2-stroke snowthrower you have no choice -- you run the ethanol free or you'll be buying carb diaphrams at least every year and maybe more often, as the ethanol eats them for breakfast. But otherwise? Forget it.
 
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Discussion Starter #8
US fuel may be much cheaper but the difference between 87 and 93 isn't in percentage terms. The last time I was in Canada I nearly crapped my pants when it was CAD $60 to fill my "6" up, but that's your "usual expectation" so.... yeah. Even so the difference here is dramatic -- $2.30 for 87 .vs. over $3, typically, for 93, so.... no. And ethanol free is even worse; it is typically either 89 or 92/93 and is nearly always a buck a gallon over or even MORE than straight RUG (with ethanol.) Up north it can be even worse in that they love their E-85 pumps there and if you can find ethanol-free it's not uncommon for it to be $5/gal. Now if you have an old diaphram-pump-style carb'd 2-stroke snowthrower you have no choice -- you run the ethanol free or you'll be buying carb diaphrams at least every year and maybe more often, as the ethanol eats them for breakfast. But otherwise? Forget it.
Seems like they are just coaxing buyers into going for the cheapest possible option full of ethanol...
 

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For on-road fuel there is an actual mandate for ethanol in the US (called RFS), and it is heavily-subsidized as well. Technically-speaking the non-ethanol fuel is for "off road" purposes but using it in a road car is not the same situation as untaxed off-road (dyed) diesel where you can get busted and fined (big!) for running it, since non-ethanol laced fuel in the US still has the taxes on it. The energy content loss means that a 2-3% decrease in fuel economy is expected when running E-10 over straight gasoline, but I've NEVER seen non-ethanol fuel that was anywhere CLOSE to only 2-3% more expensive so simply on economics it makes exactly zero sense to buy it.
 

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The Renewable Fuel Standard mandates that the refiners and suppliers must use an increasing amount of renewable fuels.
There are some key things to know about this:

1. It expires in 2022. After that we roll back to the Energy Independence and Security Act, which is more focused on better fuel economy then ethanol usage.
After the rollback to the EISA, it will be up to the EPA to decide on how to get achieve the higher CAFE standards. While I don't want to bring politics into this, next year's presidential election has the potential to greatly effect what we feed out cars in a few years.

2. The mandate is at the refiner/supplier levels; relatively high up the food change, and assigns a quota on how much ethanol is to be used. If a particular supplier can dump their entire quota into E85 then they can produce 100% gas. Other biofuel (eg biodiesel) production also counts towards this quota. Smaller producers are also eligible to get waivers of varying degrees.

3. While the main impact is that the gas going into our cars is ethanol laced; less than half of the quota fulfillment is to be simple corn based ethanol, advanced biofuels are to be the bulk of it in the end. And the advancements of these advanced fuels is not anywhere near what they want from it.

4. The increase in corn prices due to RFS is expected to be cost the average American $10
 

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True - I'm not sure what i was thinking when I said that. Honest question - Do you ever?



Judging by my seat of the pants evaluation comparing ethanol blended 91or 87 octane in comparison to Shell's 91 V-Power, I felt like I was really getting my money worth based on a fairly moderate performance increased alone. I felt an easy 1-2HP gain and the engine undoubtedly ran better. It also gave the engine a deeper tone while running through the RPM's. My friend made the same switch with his 2012 Acura TL and was under a very similar impression


Would you consider shipping some of that stuff you guys are smoking down here to the States? You can easily feel 1-2 HP gain? LMFAO 🛴
 

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No. There's no possible way in hell you're going to get ~20% more fuel economy. Not a snowball's chance in Hell and anyone claiming you will get anywhere close to the additional fuel cost back in better efficiency is flat-out lying.

Mazda's intake VVT is electrical (stepper motor); they also have an exhaust phaser but it's much more-limited in effect and that one is oil-driven. The electrical drive is a LOT more precise and, at least thus far, it appears to be dead-balls reliable too.
Not sure I could agree with anything more than this.
 

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Doing research for my wordy rant above.... but unrelated to the rant... I learned that ethanol not only gives us less power, but that the gasoline that is blended in is roughly 1 grade lower than the equivalent real gas grade.
10% ethanol + 84 octane gas = 87 octane. Likewise 87 becomes 89, 89 becomes 91 and 91 becomes 93
That same 84 octane gas mixed into a E15 blend bumps you up to 88- that's the only E15 grade I've seen at the pump so far.

I'm a little curious on how the "hE15" fuels in the Netherlands are working out
 

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Thanks for your totally useless input.

Again.
You mean like yours? Again? Still? At least I haven't been banned (yet) from multiple forums like yourself for worthless, stupid, dangerous comments and recommendations

Go get em Get-in-line You da man.
 
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Discussion Starter #16
You mean like yours? Again? Still? At least I haven't been banned (yet) from multiple forums like yourself for worthless, stupid, dangerous comments and recommendations

Go get em Get-in-line You da man.
How many times are you going to keep mentioning the same thing? You sound so delusional and disconnected from reality I'm inclined to start feeling sorry for you by this point.

Absolutely I am doing me, but I dont see why you cant take your own advice. (Again.) You can make this forum a better place, if you wish to.
 

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Doing research for my wordy rant above.... but unrelated to the rant... I learned that ethanol not only gives us less power, but that the gasoline that is blended in is roughly 1 grade lower than the equivalent real gas grade.
10% ethanol + 84 octane gas = 87 octane. Likewise 87 becomes 89, 89 becomes 91 and 91 becomes 93
That same 84 octane gas mixed into a E15 blend bumps you up to 88- that's the only E15 grade I've seen at the pump so far.

I'm a little curious on how the "hE15" fuels in the Netherlands are working out
Well that's because the ethanol really IS very knock-resistant, so the blend gives you the "octane" boost.

But the real reason for it originally wasn't corn subsidization -- it was from the days of carbs and early TBI engines before we had true closed-loop operation. There it really did matter in terms of hydrocarbon emissions, since MTBE (what used to be used before it was tossed due to groundwater pollution concerns from spills) and ethanol both contain "extra" oxygen and that reduced (by quite a bit) hydrocarbon emissions.

Modern closed-loop engines get exactly zippo in terms of hydrocarbon emission reduction from these oxygenates. The scolds like to try to claim otherwise but it's a lie; modern closed-loop engines pass emission standards easily without ethanol (or other oxygenates) in the gas. Indeed, the CO emissions are now so low that it's actually hard to kill oneself by inhaling car exhaust -- it used to be very easy to do and in fact it happened by accident all the time when people got stuck in snowbanks and such in the winter and then tried to keep warm with the engine. Now, other than in the first minute or two before the cat lights off, your engine produces so little CO that you might actually fail in committing suicide by this method.

But over the years ethanol has become insanely-entrenched in our farm belt and so lack of necessity of it in terms of actually controlling emissions (there are darn few carb'd and TBI engines on the road these days) no longer matters. Without the subsidies and mandates exactly zero oil companies would use it because it's more expensive than the gasoline is, and so not only are you damaging fuel economy you're also increasing cost which, of course, means higher prices. Nobody would do that voluntarily, but since the government mandates it and of course the first stop for all Presidential Candidates in the US is IOWA.....

I'll just leave it there.
 
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