FWICT, using a non-OEM-equivalent filter in an Atkinson cycle engine will net nothng except more dirt and wear (taken from somewhere on the web):


Pumping losses are caused by the way power output from a petrol "Otto" engine is regulated. It is regulated by controlling, or rather constricting airflow to the engine. This constriction of airflow creates partial vacuum (low pressure) in the inlet manifold. Maintaining this "low pressure" in the inlet manifold wastes energy.

One reason for diesel "Otto"-engines being more effective than the corresponding petrol engines is because there is no pumping loss in a diesel as power is regulated by injecting less fuel into the cylinders and not by choking the airflow to the cylinders.

The pumping losses in an Atkinson cycle engine are reduced by allowing, in the compression stroke, a small amount of the fuel/air mixture to flow back from the cylinder into the induction system, without being burned, thus reducing the effective displacement of the engine.
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I would imagine the Toyota engineers have everything under control, and have taken air-flow through OEM filters into account.

 

Atkinson Cycle engines also have pumping loss.

 

"thus reducing the effective displacement of the engine."

While absolutely true, a bit (unintentionally) deceptive.

The point of the Atkinson cycle engine is to effectively "ellongate" the power stroke in relation to the intake & compression strokes. Remember that "free" waste energy often used to run a turbocharger? The atkinson cycle, in effect, makes use of that "free" energy, converting a 2.3L engine to an effective 1.7L displacement insofar as intake and compression are concerned, but more in the effective range of 2.0L during the power stroke.

You're unlikely to EVER see a turbocharger on an Atkinson cycle engine and it also results in a little more difficulty in keeping the catalyst up to the ~800F operational temperature.

 

I believe that the TPS (Throttle Position Sensor) reading that ScanGaugeII gives is indeed just what it says — the position of the throttle butterfly valve in the intake air path, and has nothing directly to do with the accelerator's position. In my TCH the TPS reading ranges over 13 - 70 (normal constant-speed driving gives 15 - 35; wide open throttle is ~70). Certainly it doesn't cover a 0 - 100 range. And, yes, it varies all the time when I'm in cruise control and the accelerator is fully up, as the ICE's power requirements are varied by the ECU.

Stan

 

Isn't a Miller Cycle engine the same as an Atkinson but with forced induction?

 

These so-called Atkinson-cycle engines are really closer to Miller-cycle engines in my view. Atkinson's invention actually used a complex crankshaft arrangement that made the compression stroke physically shorter than the expansion stroke. This extracted more of the thermal energy in the hot burnt gases, and made for a more thermally-efficient engine, albeit less powerful. Miller achieved the same goal by delaying the closing of the intake valves, so that the first portion of the compression stroke was ineffective, and made up for the lost power by using forced induction. Our engines are Miller-cycle engines without the forced induction. The power lack is made up by electrical assistance courtesy of the motor-generators and NiMH battery. Strictly speaking, a 2.4 L "Atkinson-cycle" engine is really closer to a 1.7 L "effective displacement" engine, from the fuel-usage point of view. Its so-called 12.5:1 "compression ratio" is really effectively closer to 10:1 (one can't use a 12.5:1 compression ratio with regular gasoline!). It's the expansion ratio that's 12.5:1, and that's why there's a thermodynamic benefit — more of the heat energy is being extracted from the exhaust gases.

Stan

 

Both Atkinson & Miller cycles rely on a larger power stroke than compression stroke. And that is what causes the increased efficiency.

The first Atkinson engines used a unique eccentric crankshaft arrangement to produce the cycle. The Miller engine changed the intake valve timing of an Otto cycle engine to produce the cycle.

Atkinson engines have a narrow torque range. Miller solved this with a supercharger. Atkinson didn't solve the problem.

Hybrids solve the problem with an electric motor.
Maybe it should be called "The Hybrid Cycle"!

A nice Diesel Hybrid would be even better. No Pumping loss!

 

Back on topic.

My "other" Vehicle:
Dodge V6 3.9L DOHC Fuel Injected Engine
Recommended Air Filter Change Interval: 20,000 miles

Fram $9.99 each 20k miles
Purolator $14.99 each 20k miles
K&N $35.00 each 1000k miles ( will never get there )

My Dodge has close to 140,000 miles on it now. Runs perfectly. Have only replaced a power steering pump at 110,000 miles.

Replaced the stock paper filter at ~20,000 miles with K&N.
Literally, the only filter I have ever bought.
$35 spent on last 120,000 miles going with K&N.
Would have spent $59.94 on Fram Filters in the same period.
Would have spent $89.94 on Purolator filters in the same period.

Plus I saved gas going to the store to buy new filters, plus I saved time, plus I contributed less material to the local land fill. ( just 1 box, and one filter, for the lifetime of the car ).

100 million traditional engine air filters go into land fills every year.
K&N has been making these filters since 1969.
The reviews over the years are overwhelmingly positive.
If they were bad for engines, this would not be the case.

1 K&N filter will be the only filter I will ever have in my FEH.
I'll report back later on how much money I saved after 200,000 miles.

( Notice I didn't need to mention gas to save money? )

 

I just ordered the K&N so I will see what it does for my mpg (I will post the results either way).

I ordered it from Summit & it was on B.O. so it will be a few weeks before I actually get the thing. I could have ordered it somewhere else, but I know Summit is reliable & I am in no great hurry for it as my paper filter is fairly new.

~John

 

Yes, but since with the Atkinson cycle there is not enough energy left in the exhaust gasses to drive a TurboCharger the "forced induction" is accomplished via direct drive by the engine itself using an SC, Super-Charger. Most commonly the SC is used to only bring a 2.3L engine using the Atkinson Cycle back up to the HP/Torque level of a standard 2.3L.

The advantage of the SC vs standard Otto compression ratio of ~10:1 is that the "charge" can be cooled via an intercooler.