During research into Atkinson engines, I thought of something I haven't seen anywhere else: A gasoline engine with no throttle. Here's the idea:

Atkinson cycle engines use late valve closure to trap less air and fuel in each cylinder, generally in conjunction with high compression heads (to be technically correct, high expansion heads). My idea is to carry this concept to an to extreme, and use variable valve timing to vary the amount of air and fuel trapped in each cylinder and thereby vary the power output.

At idle, the intake valve would close at ~5-15 degrees BTDC, but the throttle would be wide open. (For that matter, why even install a throttle?) Then, when more power is desired, advance the intake valve closure to take bigger gulps of air. Full power output would be with intake valve closure at about BDC. (For really high expansion ratios (<13:1) full throttle would have to be ~30 degrees ABDC (~150 degrees BTDC) to avoid ping.)

Drawing air in at essentially atmospheric pressure instead of the vacuum that the throttle creates would substantially reduce pumping loss. Since VVT has already been developed, little new tooling would be needed, only a change in cam actuator programming.

The only problem I see so far is that there would be no manifold vacuum to run power brakes, but that's not a big deal to fix, since diesels use vacuum pumps anyway.

Maybe I should patent this idea. Or send it to Toyota. Has anybody seen anything like this?

Honda has been using this for a few years in its i-VTEC engines.

Hmmm, extreme Atkinson eh? I don't see why this could be done, except for the percieved needs regarding acceleration? For instance the 1NZ-FXE suffers from less low end torque due to pushing some of the air back in the intake manifold, and wasn't deemed suitable for a stand alone drivetrain. This would be even more efficient by pushing out all but the air it needs, eliminating pumping losses, but it would have even less low end torque, so it wouldn't be suitable for most new cars, i.e. luxo-barges. If someone were to say, drop it in a smaller ~1600-1800lb echo, then that would make for one heck of a economy car. It'd probably have 3L lupo performance, with 3L lupo mpg. In terms of comparable tech, it sounds a lot like Toyota's Duel VVT-i, but with more of an economy angle. And it sounds kinda like BMW's throttleless valvetronic deal, which is naturally in a luxo barge, so probably isn't aimed at economy specifically. I think the difference is that BMW managed to have continuously variable valve lift, with variable valve timing.

edit- SVOboy, so i-VTEC expells air back out the manifold after BDC? The only engine I heard doing this was the one in the Prius, everyone else just uses the same variation on VVT-whatever to have the intake valves open early for more low end torque.

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<sigh> Leave it to Honda to do something so smart. What compression ratio does this engine have?

What the honda engine does is use the intake valve timing to eliminate the need for a variable throttle and just runs WOT but narrows down the VT accordingly.

You mean I've been driving around all over town at WOT in the TSX! JK

It is a great feature -- the Variable Cam Timing does a great job at idle to reduce emissions. The rest of the time it seems to do something to get good mileage...

RH77

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Yeah, if i-VTEC is running WOT all the time then it's probably a refined version of what every manufacturer's (VVT-whatevertheheckwellcallit) doing along with drive by wire. Since the engine can't operate at WOT when cruising at low load(the little thing needs at most, maybe 6-10hp@55mph?), the mileage could be much better if they were able to push some of the air out during low load to reduce pumping losses, which is what Sludgy's talking about. But... since they didn't, the civic, even though is has less reference area, less drag, less weight, and probably less rolling resistance, still gets ~7mpg (btu adjusted) less than a TDI.

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Sludgy: you're as smart as BMW!

http://en.wikipedia.org/wiki/Valvetronic

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FF
ForkenSwift cheap electric car conversion- Geo Metro fuel economy mpg modifications

The i-VTEC only runs WOT under low load, I'm assuming this has something to do with running the engine efficienty, but it's not all i-vtec, just that with the fancy drive by wire business. So yeah, fun stuff.

So how would you drive this car most efficiently? Put it in D and take it easy, or use the AutoStick to get it to the highest gear with little throttle input at cruise? (VCT and TBW)

RH77

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Its such a good idea it makes my head hurt... when i first read sludgys post before any of the other I just thought to myself, just buy a diesel then read his closer and he wants a gasoline one.

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Diesels could effectively use "Atkinson" VVT too. Diesels are frequently designed with high compression ratios (20-22:1) in order to help cold starting. High compression ratios increase bearing loads and frictional losses more than any energy derived from more expansion. Optimum diesel efficiency occurs at about 15-16:1.

Diesel VVT would allow high compression ratios at startup, after which the intake valves would be retarded to lower the compression ratio. The expansion ratio would stay the same, so this would lower both the frictional loads, and still keep the high expansion ratio, for a double benefit.

I already have a diesel F350, and I hate it. It gets worse mileage than either of my GM half tons, and it rides, well, like a truck. I can't wait to trade it for a new GMC or Chevy. Two more years of payments..... argghhh

Ford ought to rename it the "Powerjoke".

As long as we're daydreaming in this thread, how about this for a wacky idea? First add lean burn to the car, then change the A/F ratio as a function of engine air consumption. In other words, as air consumption decreases (light throttle) set the A/F ratio really lean, like 20:1, so power is reduced not only by the ammount of air going into the engine, but also by the weak A/F ratio. Then as airflow increases bump up the A/F ratio for more power. Power would be reduced at light throttle without closing the throttle too much, reducing pumping losses. It's similar to coasting in gear with the fuel off and throttle wide open, but not quite. As more power is needed, it's supplied by a larger percentage of fuel, so airflow through the engine stays more even. It's not quite like a diesel, but closer than the way gas engines are currently run.


Then meter some EGR gasses to act as a type of WAI to help promote atomization of the fuel, as well as the usuall EGR benefits.
I think it could work.

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Dave W.
http://www.gassavers.org/gaslog/sig.php?id=207

The problem with any lean burn system is NOx, just like diesels.

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Yeah , I agree.
While it is possible to reduce to mixture to gain FE in extremely light load conditions I belive that the engine is dirty.

An excessively lean mix doesnt burn well causing rises in bad gasses.

http://www.ae-plus.com/Technology%20...une%202006.htm

Fiat apparently though of the idea too, but BMW beat them to production.

Fiat tends to focus on the cheap compact car market whereas BMW doesn't.
They probably could justify the complexity and cost for most of their range.
Perhaps they will use it on the sports cars , and the extra costs involved would be charged for accordingly on those models.

Lean-burn? Another way to spell "burned exhaust valves"! The temp. rise will be high(er?)! Just a thought....
Then, there are emissions to consider ...with higher combustion temps, all this lean burn stuff screams higher NOx formation! If it won't pass emission specs...it ain't legal!

Ah, you're being realistic. I thought this thread was about 'Crackpot Ideas'?

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Dave W.
http://www.gassavers.org/gaslog/sig.php?id=207

DRW and Ted -

Is the 1992-1995 Honda Hatchback VX highway speed "lean burn" mode running dirty? Granted, if emissions standards were less stringent, it might just be "conforming to it's time", but I keep thinking that there are lots of "lean burn lurkers" out there that are emissions compliant and running fine.



CarloSW2

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Good points. I wonder if the auto manufacturers have to certify their cars using a more comprehensive test than the typical smog check that we see every year or two? In other words, are there different levels of compliance? OEM certification might be stricter, and consumer level smog checks are more lax?

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Dave W.
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Combine lean-burn, turbulence via grooves, organic-based fuels (or blends of same), politics, industry shufflings(wait! I said politics, yes?)...mix 'em all up , and... who knows what happens? Or, what you got? Me? I think I'll get another beer! -Ted Hart

Hi! I never said / implied that Honda's lean-burn set-up wasn't emissions compliant! Of course it is! The tailpipe numbers may be down...but the exhaust gases going into the catalytic converter(s) are high(er) in NOx . 'Tis the converters which burn off the fumes.
Incidentally, Road & Track magazine called the converter technology... when they first reared their smelly heads... "catalytic perverters"...'cause they gave off (still?) hydrogen sulphide gas(the "rotten egg" smell) and sulphurous acid !
H2S ...hydrogen sulphide... is also lethal! It is chemically related to hydrogen cyanide! Put that in your gas chamber and smoke it!

H2S is entirely unlike hydrogen cyanide (HCN). H2S toxicity is curious: low levels are non-toxic because the body metabolizes it. But abouv 1-2000 ppm, H2S is toxic enough to kill in a few breaths. On the other hand, HCN is cumulatively toxic, as the body doesn't metabolize it quickly. Smaller conituous doses can kill.

I see.... Perhaps the chemical encyclopedia from which I gleaned this info needs to be admonished...I did not make this up! H2S is a poison! Period! If one can smell it (the"rotten egg" gas) , the PPM ratios are into the red flag zone! We sha'n't even think about H2SO3...which readily goes to H2SO4 (sulphuric acid) when mixed with the water-ladden exhaust gases.
The source I used (years ago!) called H2S similar in toxicity behavior to the gas (HCN) used to execute Carl Chessman. HCN? Hmmm....

You must be rite !
90 year old men often smell like rotten eggs , and sure enough , a few years later , DEAD. !