1970's "30mpg" V8 cams, big car, w/14:1 CR on 87oct

[Beau]

Yes, I believe that is what Toyota is doing. I am sure others know more than I.

[Ecky]

Originally Posted by Big Dave

It this not exactly how Toyota puts an Atkinson cycle engine in the Prius? Its a Yaris engine with a different cam and the hybrid motor masks the poor low-end torque of the engine.

Holding the intake valve open beyond TDC vents off pressure, effectively reducing the compression ratio making it possible for high ratio engines to run low octane fuel.

Honda does something similar with the R18 motor in the modern Civic, some info on it here:

Technical Overview of Honda's new R18 i-VTEC Implementation

[Nevyn]

That's what I thought too, Big Dave. It sounded Atkinson to me; leave valves open longer to removed A/F mix and lower the amount of mix in the chamber to be compressed.

[oil pan 4]

You want something that runs real high compression, can run on real cheap fuel then you want a diesel.
Why bother trying to hunt down what may or may not have ever been when we have a proven platform?

[Beau]

For me, I am simply interested - it isn't something I am likely to pursue.

[stillsearching]

Originally Posted by Frank Lee

I don't think the non-Yunick cams were Miller cycle.

They were probably just like any of the "RV" or torque cams, intended to move the torque band down low.

I had one of those in a 283 in my '74 Nova; IIRC I usually got 23-24mpg with it when I behaved myself.

25mpg is a hella long way from 30 though.

Definately not. That's one thing i'm sure of. They dont run 14:1 compression on 87 octane.

The Miller/Atkinson cycle data sounds about right. What i'm wondering is whether that technology, for a given amount of fuel and air, is more efficient than a small engine without it though. (if it isn't then it's kind of silly...)

The Yunick stuff is completely different, that was just another "lost to history" story to share.


As to the Vicky axle ratio it was somewhere in the 3's I think, cruise RPM on highway was like 2400 maybe, somewhere in the mid 2xxx. There was no overdrive or lockup. Definately no 2 speed axle in it or other tricks. The only trick was a switch pitch converter that I remember - stalling at either 1800rpm or 3200rpm, the latter would get out of the sub-2500rpm 'hole' giving more torque to get off the line decently. The former used once you were at cruising speed.

As to why hunt it down vs a diesel... why not? Other good mileage enhancing ideas have been lost by the wayside (does anyone remember the "6 cycle" engine described in Mother Earth News in the 1970's that almost doubled power or mileage, your choice, by having two power strokes? No? Thats why I bring up these topics. Nobody is using that either that I know of.) and some for pretty poor reasons. It's either worth bringing back to life or worth verifying as researched and disregarded for the right reasons.

[mcrews]

Beau,
I had a 66 mustang w/ a straight 6 200 while in college. I have a stack of articles for when I finally biuld my dream stang. 200 block w/ auzzie crossflow head....or the offinhouser 3 bbl adaptor and clifford headers. All to a automatic w/ overdrive and a 3.xx rear end.
I use to drive my 66 for mileage back in 77-81 going back and forth to college. Only had the stock set up w/ clifford headers. use to get 28mpg back and forth to Texas A&M from Dallas

[Neen]

Can they really call the engine a 14:1 ratio engine if they are allowing intake bleed during the compression stroke?

[oil pan 4]

C/R is calculated by BDC cylinder volume over TDC cylinder volume.
It doesn't take throtteling or valve timing into account.

[thomason2wheels]

Originally Posted by stillsearching

The Yunick articles I remember more specifically - about 250hp, built on an Iron Duke 2.5L in a Fiero, the "homogenizer" made the intake charge VERY hot (over 400 degrees) which... doesn't make sense to me, since the difference in heat seems to be what creates the power difference. (how much more it expands when ignited, etc) Thats why we have intercoolers.

Have you seen the Yunick design discussed anywhere else either?

Which ford inline six forum? I'm curious?

That said back to original topic, hoping someone else will chime in with knowledge or testimonial or something...

The homogenizer design operated outside the normal ice parameters if i remember, i think it ran way hot and way lean compared to anything else. I can only imagine how hard the high temps would be on engine components, lubrication, and anything sharing space under the hood.