Pinnacle Engine pre-production prototype opposed piston engine shows about 27% fuel consumption improvement across different scooter cycles compared to conventional engine

Fuel mass flow comparison shows Pinnacle engine ahead at just about all points in the map. Click to enlarge.

A 110cc pre-production prototype of a Pinnace Engine 4-stroke opposed piston scooter engine (earlier post) showed approximately a 27% improvement in fuel consumption across different scooter cycles compared to a conventional benchmark engine in dynamometer and simulation testing by FEV.

FEV performed engine mappings in a dynamometer test cell to evaluate the fuel economy of Pinnacle’s TP90 scooter engine compared to a benchmark engine (N15) from Pinnacle’s Asian OEM partner. The obtained data was used as an input to analyze the fuel economy during three different motorcycle cycles: IDC (Indian Driving Cycle); CDC (Customer Driving Cycle); and WMTC (World Motorcycle Test Cycle).

FEV found that throughout the complete engine map, the fuel mass consumed during the performed mapping was lower for the TP90 engine compared to the N15 benchmark engine—the difference is substantial at higher speeds and loads, dur to the significant difference in enrichment at which the engines can operate.

The simulation data showed similar results, with the TP90 engine showing lower fuel consumption throughout the tested area of the engine map. The higher the weight factor of high speed and load areas in the engine map, the bigger is the benefit in regards of fuel consumption. The simulative cycle-specific reductions are:

• Improvement during IDC: 27.4%
• Improvement during CDC: 28.7%
• Improvement during WMDC: 26.2%

Pinnacle Engines, initially targeting lower power applications (such as tuk tuks and scooters) in developing markets in its commercialization strategy, has signed a licensing and joint development agreement with a major, as yet unnamed, Asian vehicle OEM, with products now expected to be available in early 2014. The work on the TP90 is for that partner.

We are very excited that we were targeting at least 20% [improvement in fuel consumption] and came out at 27% is pretty good. We’ll work on reducing cost and noise, but this is a very significant step forward.

—Monty Cleeves, Pinnacle founder, President and CTO

The Pinnacle T90 is a 1-cylinder, 4-stroke, spark-ignited (SI), opposed-piston, sleeve-valve architecture engine; the N15 benchmark engine is a production 1-cylinder, four-stroke engine. Both engines are intended for scooter applications.

Test engine specs
	N15	TP90
Bore [mm]	53.5	39.0
Stroke [mm]	48.8	46.0
Compression ratio	9.35	15.0

Due to the characteristics of the driving cycles, most operating points are at the targeted 4000 rpm; only during starting, heavy acceleration and idle phases (idle speed: 1500 rpm) do other engine speeds become relevant. For this reason, said FEV in its report, the engine mapping focuses especially on 3800 rpm, 4000 rpm and 4200 rpm. Many measurements were taken with small load increments at these speeds; less important areas of the engine map were covered with fewer measurement points. Testing performed consisted of load sweeps at different engine speeds.

FEV adjusted settings for air fuel ratio according to the base calibrations for both engines. Due to the major differences in engine design, these settings differ significantly. Spark timing was adjusted to MBT (maximum brake torque) when possible. MBT spark timing was considered when peak pressure location was around 13° CA after TDC. The production engine was operated with production spark timing.

Engine efficiency, Pinnacle TP90. Click to enlarge.		Engine efficiency, N15. Click to enlarge.

Cleeves told Green Car Congress that the smaller 110 cc engine (Pinnalce had earlier been working on a larger 250cc proof of concept) exhibits a bit more friction, with more of an impact at lighter load, due to some design choices the company made partly due to geometry issues in trying to pack the engine into the constrained scooter space. He expects those to be addressed in another month or so.

By changing the geometry by 10mm or so in the location, we can minimize the sliding element and save considerably on friction. Because the combustion chamber is much smaller than in the 250cc engine, it is hard to fit everything in. We made our piston crowns much differently than in the first generation. In piston design, there is a whole science involved in where to put the center of gravity of the piston. Because we anticipated quite a number of changes to optimize the combustion process, right now, according to FEV, there is almost as much available friction improvement at drive cycle loads for just changing the center of gravity of the piston as there is for the sliding friction.

—Monty Cleeves

On the emissions side, noted Cleeves, Pinnacle can run its engine efficiently enough at at a low enough temperature to avoid the need for a three-way catalyst to meet Euro 6. Right now, the emissions standard in the target market is Euro 4.

They [the partner] are already running two-way catalysts to deal with CO and hydrocarbons. We look in good shape to meet emissions requirements. That said, we’re not satisfied with the hydrocarbon emissions. A catalyst could take care of it, but we’ll get a little more efficiency if we get the HCs cleaned up. We’re looking at piston crown development and flame speed optimization.

—Monty Cleeves

While Pinnacle is first looking to the lower power applications, Cleeves suggests that there is a major opportunity for the engine as propulsion for the bottom half of three-quarters of the expanding automotive market in Asia—those customers who can’t afford a hybrid or a PHEV.

This combination of variable compression ratio and our operating mode gets us huge fuel economy wins. We did another study with FEV, projecting our data onto a turbo downsized application; we get nearly 50% improvements in common automobiles. This is light load fuel economy, so its largely impacted by our ability to downsize, and VCR allows us to put out tremendous power density. We end up being a real natural for the basic automobile. That’s what needed all over Asia.

—Monty Cleeves

Source: Green Car Congress