The Chrysler Neon and Two-Stroke Engines
In the mid-1940s, Chrysler had developed an EBDI (external-breathing, direct injection) two-stroke concept engine when the Texaco Combustion Process was applied to a uniflow, opposed piston ported engine. This engine was operated for several years with a variety of fuels on the Texaco, Diesel and Otto cycles. Although it never went beyond the experimental stage, an intriguing outgrowth of this program was a two-stroke diesel engine that offered outstanding fuel efficiency.
When the Neon was first being designed, Chrysler said it would have a two-stroke engine with direct injection; the engine was to have no head gasket (few Neon owners could object to that!), with the head and cylinder block cast in a single piece.
Joe Goulart directed the 20-person engine team (a joint venture with Mercury Marine) from its creation in 1989 until he died in early 1995. “We investigated new two-stroke engine designs from other manufacturers,” said Dr. Benjamin Sheaffer, Mercury Marine Advanced Engineering Manager, at that time. “However, after working with Chrysler engineers and seeing first-hand their current two-stroke design and emissions control technology, we concluded that an alliance with Chrysler would serve both parties well.”
Both companies agreed to independently fund their own development activities, with the work coordinated by a program committee. If they had concluded that production was viable and cost effective, further discussions would determine production plans.
Chrysler tested its 1.17 liter Phase 2 engines for 100,000 miles, then started to test Phase 3 engines (with 1.5 liters). In addition to being larger, the Phase 3 engines had a balance shaft rotating at the speed of the crankshaft (unlike the 2.5 liter 4s, which rotate at twice the speed). The engine had external exhaust gas recirculation (EGR) and two spark plugs per cylinder. The direct fuel injection system worked at 1,000 psi.
The direct injection engine would have been revolutionary at the time, long before Mitsubishi started to spread its own direct injection engines. The final 1.5 liter three-cylinder would have produced 95 horsepower and 128 lb-ft (174 Nm) of torque at a low 2,400 rpm, and be about 80 pounds lighter than the 132 horsepower 2.0; it would have been more powerful overall and probably more responsive than the 1.8 and 1.6 liter engines used in many export Neons; gas mileage was estimated at 10% higher than a conventional engine of similar power. Like the new Hemi, it had two spark plugs per cylinder; it also used a supercharger.
That was the design to end up in the 1997 Neon - but it clearly did not! The goal of selling 25,000 North American 2-stroke Neons per year never resulted in a single sale. Neither reliability nor performance were problems: Automotive Industries' test drive showed the 1.5-liter-equipped Dodge Shadow to have strong performance and smooth, quiet running, and internal tests verified the engine’s durability. The main problem with the engine was the oxides of nitrogen - NOx - which were fairly high due to the extremely lean-burning nature of the engine. Chrysler needed to be able to process those emissions, currently not a feasible option. The EPA also demanded on-board diagnostics which were not relevant to this engine, and oxygen sensors which were also not needed, but these demands could almost certainly have been overcome through negotiation or executive order. In the end, the main problem might have been that the largest advantage of two-stroke engines was increased gas mileage, and that other technologies, applied to four-stroke engines, had much the same effect; and that customers were not generally asking for higher gas mileage at that time. Chrysler’s limited resources, customers’ priorities, Bob Eaton’s penny-pinching, and the takeover by Daimler may all have doomed the program as much as NOx emissions and regulatory issues.
On the brighter side, the advances made by Chrysler and Mercury have been used on both automotive and boating sides. For conventional car engines, these advances include better fuel injectors, a high pressure fuel pump, and a direct injection system (which Chrysler has yet to use).
After seven years of researching two-stroke engine technology used in motorcycles, small boats and lawn mowers, Chrysler engineers have gained valuable experience in technologies associated with injecting fuel directly into the combustion chamber, according to Floyd Allen, executive engineer, core powertrain.
"We think we've shaved 18 months, maybe two years, off the development time for four-stroke direct injection engines," Allen said. "We've learned a lot about stratified charge, lean burn combustion, direct injection, highly-efficient, high-pressure injectors and high-pressure gasoline fuel pumps."
Four-stroke DI gas engines are believed to have the potential of one day achieving more than 45 miles per gallon, which is comparable to advanced, small displacement direct injected diesel engines of the future.
"We've also taken two-stroke technology as far as it can go without a lean burn catalyst, a device that might enable the two-stroke engine to meet the strictest, future emission standards in the United States," Allen said. "When that development comes, and I wouldn't be surprised if that happens in the next five years, Chrysler now has the potential to be ready with a marketable, two-stroke engine."
Two-stroke engines have long been promising because of better fuel economy, fewer parts, better efficiency and a smaller engine package (about two-thirds the size and weight of conventional engines) that would allow for more design flexibility and lower hood lines.
Chrysler first began looking at two-stroke engines in the 1940s when it applied a process developed by Texaco -- a uniflow, opposed-piston, ported engine. Chrysler revisited the subject more earnestly in 1989.
"We purposely kept it small, about 20 young engineers, working in a focused, frenzied environment of creativity, much as a racing team operates," Allen said. "In fact, the culture created here was, in many ways, a forerunner of the platform approach to building cars that Chrysler has instituted."
Many people, including some within the company, thought the technology didn't have a chance. Tom Lawrence, engine development supervisor, was aware of those skeptics from the time he signed up for the two-stroke team in 1989.
"As good as the technology sounded, there were potholes along the way," Lawrence said. "People within and outside the company were saying it couldn't be done.
"For example, it was said we couldn't make the engine idle because it would violate the second law of thermodynamics. We couldn't come close to the Tier 1 NOx standards because the invention of a lean burn catalyst didn't seem possible. Some people thought we were wasting company funds at a time when they were scarce. I don't recall if we took those statements as challenges, just ignored them or really didn't know any better. We just carried on."
On the contrary, it may turn out to be one of the best research investments Chrysler has ever made.
"It was a great investment," Allen said. "Seven years ago, two-strokes were an unknown quantity to us. Now, it's one more piece of the technology puzzle we understand. Would we do it again? In a New York minute!
"This is very similar to the infusion our Patriot program gave the hybrid electric vehicle development team. We took both technologies as far as we could and are now concentrating our efforts on those areas that appear to be most promising in the very near future."
The results from the two-stroke program include:
- a direct injection fuel system that has promise for four-stroke applications.
- a high-pressure fuel pump (capable of producing 2,000 pounds per square inch) that could survive the demanding environment of an automobile engine.
- a mechanically-driven, centrifugal compressor, capable of spinning a compressor wheel at speeds of up to 1,400 revolutions per second, that could be used as a super-charger in four-stroke applications.
- a roughly 10 percent improvement in city fuel economy over comparable four-stroke engines that delivers performance (128 lb-ft of torque).