Next Generation Ford EcoBoost to Offer Cooled EGR; Exploring More Advanced Turbocharging, Ethanol Options
14 April 2010
The next generation of Ford’s EcoBoost turbocharged, direct-injection gasoline engines will introduce cooled EGR (exhaust gas recirculation), enabling higher compression ratios, according to Ford executives speaking at the SAE 2010 World Congress in Detroit. Cooled EGR as applied to an EcoBoost engine can improve efficiency, reduce the tendency for an engine to knock, and reduce PM emissions (which can be an issue with gasoline direct injection engines).
Applying cooled EGR to an EcoBoost engine results in a cleaner-running engine that develops more power and delivers as much as a 5% gain in fuel economy over current EcoBoost engines, Ford says. Other technologies being studied to further expand the potential of EcoBoost include more advanced forms of turbocharging as well as different approaches to leveraging ethanol blends.
While PM emissions have long been the concern of the diesel industry, the advent of direct injection (GDI) engines raises the PM issue for the gasoline engine sector as well. In general, GDI engines have elevated PM emissions due to the presence of liquid fuel in the combustion chamber; these deposits lead to higher HC and PM emissions, as they create locally rich areas within the combustion chamber, even when the global equivalence ratio is lean.
In a paper on the role of EGR in PM emissions from gasoline engines being presented at the SAE 2010 World Congress in Detroit this week, researchers from SwRI note that:
As modern gasoline engines move to higher specific power levels, the size of the enrichment region, in terms of percent of the total engine performance map, increases significantly. By using EGR to reduce combustion temperatures and eliminate the need for enrichment, the PM mass and number emissions were reduced substantially.
Comparisons in the enrichment regime indicated the primary benefit of EGR was from eliminating enrichment, but a significant benefit was found from using EGR even at rich conditions. EGR also reduced PM emissions at part load conditions, particularly those above 50% load.
—Alger et al., SAE 2010-01-0353
Separately, a team from AVL Powertrain Engineering, AVL List GmbH, and Ford are presenting a paper this week at the World Congress on the development of a combustion system for a flexible fuel turbocharged direct injection engine.
A logical and synergistic extension of the EcoBoost strategy is the use of E85 (approximately 85% ethanol and 15% gasoline) for knock mitigation. Direct injection of E85 is very effective in suppressing knock due to ethanol’s high heat of vaporization—which increases the charge cooling benefit of direct injection —and inherently high octane rating. As a result, higher boost levels can be archived while maintaining optimal combustion phasing giving high thermal efficiency. However, due to their different properties, optimization of a combustion system for both regular grade (91 RON) gasoline and E85 is non-trivial.
—Whitaker et al., SAE 2010-01-0585
Resources
Terrence Alger, Jess Gingrich, Imad A. Khalek, Barrett Mangold (2010) The Role of EGR in PM Emissions from Gasoline Engines. (SAE 2010-01-0353)
Paul Whitaker, Apoorv Agarwal, Christian Spanner, Kevin Byrd, Yuan Shen, Heribert Fuchs (2010) Development of the Combustion System for a Flexible Fuel Turbocharged Direct Injection Engine (SAE 2010-01-0585)
I am still waiting for the first manufacturer to approach the issue of optimizing for gasoline and E85 by specifying a turbocharged engine that requires premium unleaded gasoline or E85, with no regular unleaded gasoline allowed. It's at least a first step toward narrowing the window of possible octane ratings and allows a step away from the lower compression ratios required for regular unleaded. The user would have an incentive to use E85 over premium to get maximum power output, but could operate with premium unleaded when E85 wasn't available.
Posted by: Wes | 15 April 2010 at 05:40 AM
That is what Ford's Ecoboosting does but it's still possible to safely run Regular. Engine control units are pretty impressive in that they can usually make up for not only octane differences but turbochargers mean there is even more room for adjustment. It's been said in a couple publications, I believe, that the Ecoboost Engines were built to run better on E85 but still run albeit with reduced output and power on Regular. Although I do believe the advertised HP ratings are on Regular grade gasoline.
It is my understanding that quite a few newer engines are built so that they run better with Premium fuel but the ignition timing is retarded a little bit which is more effective for better fuel economy than decreasing compression ratio or enrichment of the fuel:air mixture. So when these "Normal" gasoline engines are ran with Premium or in some cases E85 they "suddenly" gain more power. Ecoboost just takes this a couple steps farther and builds an engine that makes the most power on E85 but still runs acceptable on Regular or Premium. So technically a purely E85 Ecoboost engine could be smaller still than the Gasoline Ecoboost and make up for the fuel density differences between the two fuels. But Ecoboost is really the first of it's kind specifically because the main difference between the other Motor Companies applications is the E85 Design emphasis. It's hard to complain, Ford is the only Motor Company trying to give us so many options in regards to E85.
Posted by: Allch Chcar | 15 April 2010 at 10:41 AM