Atkinson cycle engine

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Atkinson cycle engine

Post by Wildcat445 on Fri Feb 12, 2016 7:29 pm

It does not take much to entertain me.  We get "Car and Driver" magazine at work.  It's not much of a magazine, really, and I think the writers in that magazine are all snoots who worry about things the average slob just wanting to get to work would never think of.  They get their panties in a wad about "uncommunicative steering", "blatant understeer", "waggy backside" and other terminology that they probably make up as they go along, and that only they understand or give two hoots about.  There are a couple worthwhile terms that have been used lately that got me to thinking.  Atkinson cycle and Miller cycle engines.  I'm an old auto mechanic.  I have no idea what these are.  

We are mostly familiar with the four cycle Otto cycle engine.  Atkinson cycle and Atkinson cycle compatible refer, nowadays to engines with variable valve timing camshafts.  This technology basically fools the engine into thinking that it has more or less compression, and more or less displacement than it actually has.  This technology, combined with pressure aspiration, direct fuel injection and computerized engine management is what enables a little 122 cid four cylinder to build more power than a 327 Chevy did back in the day.  I read where Ford has a version of the 2.0 Liter Mustang 4 banger that makes 350 horses!  That is almost approaching 454 Chevy territory.

I Googled "Atkinson Cycle" engine:

https://en.wikipedia.org/wiki/Atkinson_cycle

Then Miller Cycle:

https://en.wikipedia.org/wiki/Miller_cycle

The most common usage of Miller cycle engines is in Mazda cars.  

Back in the day, when you wanted to wring more power out of the old buggy, you would add a "3/4 cam" or a "track grind" or an "RV grind" or a "full race" camshaft to basically do the same thing.  It would change valve lift and duration and fool the engine into thinking it was more than it really was.  Now that same operation is accomplished by a computer and a couple doodads in the engine.  I'm amazed how much power a little four banger has nowadays.  In my time, a four cylinder engine was only used on farm equipment.  Now a turbocharged, intercooled, direct injected four banger is a real engine.  Wonder how much power a Chevy 454 or a Ford 460 would have with this technology.

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Re: Atkinson cycle engine

Post by Conelrad on Sat Feb 13, 2016 1:31 am

Sort of the way you can make high hundreds HP from an electronic Cummins 5.9L Diesel.

D

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Re: Atkinson cycle engine

Post by Wildcat445 on Sun Feb 14, 2016 4:05 pm

That is another amazing engine that has been developed ad nauseum in the past few years. That engine appears in about any type of equipment that can be pulled by an engine and that it will fit in. Anytime they can wring more than one horsepower per cubic inch out of a diesel is a good day. Does the Cummins 5.9 have variable cam timing?

I am reminded of the Novi racing engine, extant from 1939 to 1966. Designed and built by Bud and Ed Winfield, of Winfield carburetor fame. and financed by Lew Welsh of the Novi Mechanical Governor Company of Novi, MI. Leo Goosen and Louis Meyer are said to have had a hand in development as well. Built to utilize the 3 liter engine formula then current for Indy 500 racing cars, it was a 90 degree V-8, cast in iron, displacing 183 cubic inches. It has 16 valve heads with twin overhead, gear driven camshafts. One cam ran the intake valves, one ran the exhaust valves. It had hemispherical combustion chambers and was fired by a Mallory magneto. It was fueled by three Winfield 97 carburetors and a front mounted centrifugal supercharger, gear driven by a shaft from the rear of the engine. At 8000 engine rpm, the blower ran at 42,000 rpm and supplied 30 psi of boost. This combination was good for 450 horsepower at a time when the current engine to beat, the four-cylinder Offy, put out 300. The unique cam drive setup and the gear driven engine components gave the Novi and wail and exhaust note unmistakable in the day.

The Novi V-8 was simply more engine that the cars and tires of the period could support. The Novi never won the Indy 500, although it nearly always led the race at one point, many times nearly the whole race, and then sometimes by several laps. Typically, something little would fail and put the Novi on the sidelines. I don't remember a time when a Novi engine per se would fail. It suffered magneto failure, clutch failure, driveshaft failure, an accident, tire failure, rear end failure, thing like that. Usually occurring late in the race. The highest a Novi ever finished was third, in 1948, driven by the great Duke Nalon. Two drivers were killed at the wheel of a Novi. Ralph Hepburn in 1948 and Chet Miller in 1953. The last driver to drive a Novi in the 500 was Bobby Unser, in 1966. The Novi was front wheel drive or four wheel drive and was heavy, thirsty and hard on tires. I remember Jim Hurtubise and Art Malone burning rubber down the backstretch shifting gears after a pit stop. By the time 1966 rolled around, the Novi was developing 800 horsepower with carburetion and magneto ignition.

Fast forward to today. What if an enterprising soul would take the old 80 year old Novi and reproduce it. Use exactly the same long block design. Cast the engine in light alloy. Use hemi heads with 16 valves. Chain driven dual overhead camshafts with variable intake and exhaust valve timing. Direct and port fuel injection with computer engine management. Coil over plug ignition. And then use intercooled twin turbochargers replacing the antique supercharger. Tweak the exhaust and head porting a tad. Run the engine at 8000 rpm like the original, governed electronically to 8200 rpm. Then back this powerplant with an 8- or 9-speed dual clutch automatic transmission. If they were getting 800 out of a Novi with carbureton, one should realize at least 1000 horsepower from a modern version with fuel injection, better ignition, and computer engine management. Modern racing car chassis can better handle the horsepower of the Novi. Better tires, better track, better drivers. It would be fun to watch at least.

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Re: Atkinson cycle engine

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