Wankel Rotary w/base/Atkinson/Miller cycle modes.

You seem to be getting many things wrong. The peak efficiency of a turbo engine is higher than a similar normally asperated engine. Peak efficiency is 50% for some real world tdi engines. It doesn't matter what native compression is, only effective compression, friction, pumping losses. If you drop a 42% peak efficiency 1L cycl di turbo into a prius, it will be replacing 38% 1.8L atkinson. Its efficiency range may drop off more than the prius, but over a wide range of load the smaller turbo will be more efficient.

There is a reason that the 1.8l gen III engine is more efficient than the 1.5L gen II even at low power levels. Compression and Expansion are the same, but the stroke/bore ratio is better mixing of fuel air. The bigger gain is reduced friction from lower rpm operation for the same power. The bsfc of the gen III is much better because of little things that violate the rules of thumb of smaller engines are more efficient.

This is quenching, required under high rpm and high load. You can simply cut off the power and not go into this inefficient range. Ford has a techique of using e85 and gasoline, putting the e85 in at higher loads to prevent problems. EGR can be used, but this reduces power. BMW also in their newer engines moves more to a miller cycle with valve timing. But the region is available for inefficient power. Water injection also has been used. Atkinson removes the ability to use this power for an engine. The native compression is lower than maximum atkinson, but the effective compression even at 2000 rpm can be higher.

On passenger cars this method is not used.

But the big point is rotaries in the real world are not as efficient as di turbo state of the art piston engines. People speculate about them, but haven't been able to successfully build them.

 

Yes as long as it doesn't unduly increase friction loses. Saab has some patents for variable compression that gm owns now. I think expense and reliability are a problem. I don't think it would greatly increase efficiency, and would not increase power. To do a simpler model you could use a hybrid turbo charger which is a generator on exhaust gas plus a super charger. That way you can build your engine at 11:1, super charge it to 14:1 (raised because of inter cooler) and capture the exhaust energy. This does require a buffer battery, but if you are making it very efficient this is a hybrid. At appropriate power levels it can run the miller cycle. The cheaper parts/ higher reliability are why we use turbos now. BMW and ford seem to be making these for highway efficiency, but they get inefficient at high power levels. BMW has a eco mode on its upcoming 328i that keeps it out of inefficient range and trains the driver on what makes the engine efficient. The tech is all relatively new in the consumer automotive market, which is slow to adapt new tech. Hyundai has shown it can inexpensively make a twin scroll turbo and di. Only aftermarket and racing have hybrid turbos.

It has a dual injection system so it can't get up to the compression of pure di, it doesn't have the pistons shaped right, I don't think it has full control of the valves. The toyota technology for this is called valvematic, and I don't think its on that engine. Also you can get higher effective compression without detonation with an intercooler. BMW, mazda, and fiat on some of their engines have the valve control. I think the bmw 2L turbo controls air intake through the valves and waste gate after it warms up its at wot. This means in eco mode it tries to leave the waste gate closed, and does a miller cycle through valve control to control power level when its most efficient.

 

I highly regret commenting on this thread. I wished only to point out that the power/weight and power/size advantages of rotaries came at the expense of efficiency with current implementations, and turbo charged piston engines could have good measure here but with higher efficiency. I'll try to reply one last time, but I don't think you will understand, and I'll let you have the last word after this.

Call it monkey for all I care. The bmw twinpower turbo 2L does indeed use forced induction with late valve closing with WOT to set power levels, when WOT otto timing is not required. I was calling this technique miller cycle. All piston engines do pump air gasses and some of this energy can be captured with a turbine. If this is hard to understand think of a supercharger and a generator, which is a hybrid trubo. If you still don't think the generator will be able to have any power, try plugging your tail pipe and see how the car runs Please do this as a mental not physical experiment as its bad for the car and/or the object you plugged the tail pipe with.

Conceptually you have downsize the turbo engine to have the same power as the engine you are comparing it. So in the case of bmw in the 328i they replaced a 3L 6 cylinder with a 2L 4 cylinder turbo. They did add a little extra hp and torque to the small engine, but it is much more efficient. The smaller engine reduces frictional and pumping losses. If you are replacing a 4L V8 with a 2L I4 turbo, then the turbo simply gets too big to maintain efficiency in many modes with today's technology.

Now lets look what happens in cruise. That properly sized engine will have the boost on at these power settings. The 328i is boosted to a flat torque curve at 1250rpm. So that smaller engine will have a right sized boost while supplying the energy for forced induction through pulling power from the exhaust gasses. This means reduced pumping losses. The intercooler allows compression at lower temperatures giving more efficient combustion. The normally aspirated engine looses power through the exhaust gasses. Get the revs up though, and the turbine loses efficiency. It dumps some of that power through the waste gate and may need to run rich to stay cool and not produce too much NOx. It is at the high power settings that efficiency drops, and most experience the boy racer turbos like the evo, and keep them in the inefficient range. Toyota says they can get to 42% efficiency using cylinder design, di, valve timing. They claim they can get to 45% efficiency if they add a tubo to the mix. IIRC the compression ratio of the Gen III engine is only 9.5:1 while expansion is 13:1. Replacing the gen III prius engine with a turbo 1L can't get the full efficiency because some power is wasted ballancing the engine. It also would have higher NVH and higher cost. If you are going to a more powerfull car though like the TCH turbo charging a small 4cylinder starts to make sense.

 

Egr was first massively implemented to reduce combustion temperatures and thus limit NOx formation.

The RX only has the VVT-i that's on other Toyota engines. The only 'E' valve control system they have available to the public is VVT-iE on the LS600h L. It refers the intake valves being control electrically instead of by hydraulics.

While I doubt it, I'm not saying it can't get to or approach full Otto cycle. Apparently it requires premium fuel, which is required for this to work with a non-DI engine. With regular fuel the ECM will disable this or dial it back to prevent knocking and engine damage. Engine efficiency and fuel economy will drop then.

Why the hate for ecoboost?

Yes, turbos can, and have traditionally, been used for increasing performance. So have hybrids. The aforementioned LS was designed to offer V12 performance for V8 fuel economy.

The Prius's main strategy for saving gas is to downsize the ICE to the point that the engine is operating at its most efficient load for the majority of the drive, when cruising. Such a sized engine alone would have unacceptable acceleration and hill climbing abilities. That's why standard ICE car have an oversized engine, to meet those less frequent demands, which means the engine isn't at its most efficient most of the time. To negate the drawbacks of using a right sized engine, the Prius uses an electric motor for boost.

A turbo can be used in the same way. To provide extra power to a properly sized engine as needed. It's not as effective as a hybrid, but it is less expensive in materials, weight, and space.

The V6 ecoboost came out first because, unfortunetly, it is easier to get people to pay extra for performance than economy, and Ford did need to start recouping the R&D costs for the engine line. It does deliver on the V8 power for V6 fuel economy, and V6 F-150s are now out selling V8 models

The 2L, 4 cylinder ecoboost is now available in the Edge and Explorer. Both of which only offered a V6 previously. The lack of of a 4 cyl. before didn't stop either model from being sold. The 1.0L 3 cyl. ecoboost is coming to the Fiesta. The new Fusion is getting the 1.6L ecoboost. An engine nearly a full liter smaller than the base 4 cyl., and may be part of the reason the Fusion might dethrone the new Camry as family sedan mileage champ.

As to a high compression, non-turbo, DI V8. I imagine it would as well as the V6 ecoboost, but why bother with it. The trend in most markets is towards smaller engines. Some markets even impose extra fees on more cylinders and larger displacements. Then there is diesel, which tends to be a better option for work trucks.

 

The example is right there under your comment. The 2012 328i. I don't think you can test drive one in N.A. yet you can in Europe. Test drive one if you get a chance. It is one of the few cars with twin scroll, di, and valve timing that can change to late closure. It is replacing a DI 3L otto engine, so its easy to evaluate if it is more efficient. It turns out it is, since this was the design goal. Isn't it wonderful how engineering happens.:rockon:

The 328i does not use egr so some efficiency might be gained there, but it does use wot after its warmed up in most cases. In wot valves control the amount of air goes into the cylinders, reducing throttling and pumping losses.

 

Between an Atkinson and Otto of same displacement and cylinders, how different can exhaust flow be? Temperature as an effect, but is it great enough to make turbo impossible one and not the other?

I was merely reinforcing austingreen's point about EGR being used for quenching.

If it's so readily available, why can't you supply the info or link? I have asked multiple times. It's your claim, back it up.

Toyota isn't dispelling the myth. There is no mention of regular fuel use for the hybrids on the Lexus site. The only mention of fuel grade is in a footnote stating performance and fuel economy numbers where reached using 91 octane.

Yes, modern engines can adjust for a lower octane, but at the expense of fuel economy. Enriching the mixture means burning more gas.

No.
When premium fueled cars run regular fuel economy drops. Only a little, but it still means burning more gas. Less is always greener, and the difference in economy usually works out to about the same cost per mile.

Sorry, I was thinking of the gen2. Either way the Prius has the engine power downsized to where efficient power output is at the load the engine will spend must of its time.

Higher octane allows higher compression, which as you have been pointing out is more efficient. DI just allows regular to be used at higher compression. Premium plus DI can go higher. We will be getting a detuned Skyactive-g in NA, because Mazda doesn't want to face the uphill battle of selling an economical, premium fueled car here.

The turbo does not need to be boosted to the point that CR needs to be lowered. Volve has been using low boost turbos for years on engines with CRs no different than a straight Otto.

It's just conjecture at this point. While the 6.0L V8 (the one the ecoboost compares to) peak horsepower is a little higher that the ecoboost 6, the V6's, slightly less, max power is available for nearly the engine's entire rpm range. That's do to the turbo.

It wasn't that long ago when the Camry dethroned the Taurus. The rumor is the 2013 ecoboost Fusion beats the 2012 Camry by 2mpg. The hybrid will best the Camry by 4 in the city and 2 or 3 on the highway. I suspect more will be leaked next week, but I think Ford's real challenge will be on matching or beating the Camry on price.

 

He can not supply a link, because one can not exist. The engine does not have the electronic valve modulating hardware or software to do what he is describing. I did ask a friend at bmw, toyota does have this technology, and has it on some 4cyl otto engines sold outside the us.

New Toyota Valvematic system goes beyond valve timing - Motor Trend Blog

Let's play pretend that the rx450h engine has this tech and compare it to the bmw 4cyl 2.0 turbo. These engines have roughly the same hp and minimum useful rpm. The bmw turbo is happy at 1250rpm. The toyota di+pfi 3.5L atkinson is also in the GS so this can be compared to the 528i o 328i application. Hopefully bmw will apply activehybrid to it, so we can see a real comparison. Both engines have a compression ratio of 10:1, the lexus has an expansion of 13. At full throttle, no boost, 1250 rpm, the turbo will have 2L of air, this is less than a full charge for the lexus,so there will be only 7.5 compression if this air is used (13* (2.0/3.5)), likely lexus either adds exhaust gas and/or uses lean burn. Its easy to see why this normally aspirated engine would be less efficient even before taking into account its higher mass and friction. Now if you look at a 2 litre atkinson 4cyl, it would simply run more efficiently at 1600 rpm. The difference is it can not provide the same torque and hp when needed.

 

Cool.
Outside the US likely means countries where higher octane is the norm. Toyota likely figures it won't sell here with a premium requirement. I guess it could work with regular if it went into lean burn while on an Atkinson cycle. Then it's a question of NOx emissions.

 

They are both made from the same base stock, naphtha, so differences in production have more to do with demand. Different crude types might make it more cost effective to make regular if not enough compounds for rising the octane are present. But we aren't limited to crude for them. Ethanol in E10 raises the octane from regular gasoline's 87 to nearly 89.

But it's not equivalent volume. The Fusion's base engine is 2.5l I4. The ecoboost going into it is 1.6L. I'm sure a 1.6l DI with proper compression is more fuel efficient than the ecoboost here. But will it return the mpgs pluged into the Fusion while still giving acceptable performance?

Are you spreading rumors now? As of right now, the most fuel efficient engine available in the Camry, in North America, is a 2.5l I4 with 10.5:1 compression and no direct injection. Unless Toyota plans to introduce another engine in the 2013MY, then this is the engine the ecoboost Fusion is competing against. As I said before, it's going to be a question of Ford meeting Toyota's price.

 

op2:

Is anyone taking book on this thread? What are the odds?

Tom

 

again? I am using the example of the bmw 328i engine which actually exists and is a turbo 2L I4 with max hp around the same level as your RX450h 3.5L atkinson. It is not an atkinson engine, but can control its valves to act like one.