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Update on the ACCESS fuel efficient engine project; simulations find up to 48.9% improvement in fuel economy over baseline

Robert Bosch LLC, AVL Powertrain Engineering and partners including the University of Michigan are working on a four-year, $24-million US Department of Energy (DOE)-supported project— Advanced Combustion Concepts—Enabling Systems and Solutions (ACCESS)—to achieve a 30% fuel economy improvement in a gasoline-fueled light-duty vehicle without compromising performance while also meeting SULEV emission standards. (Earlier post.)

At the recent 2013 SAE World Congress, engineers from Bosch and AVL presented papers on progress in the ACCESS project, describing the design, combustion development and controls development for a resulting 4-cylinder gasoline turbocharged direct injection (GTDI) engine with part-load HCCI capability.

Especially with increased production volume of renewable fuels and optimized powertrain solutions for flexible fuel vehicles, there is a chance for combustion engines to not only remain in the market but also be sustainable for future vehicle. Future advanced engine and powertrain configurations must address emission and fuel economy requirements for worldwide applications, transition to bio-fuels, and synergies with future powertrain trends.

—Wheeler et al.

The ACCESS project focuses on:

  • Coordinating multi-mode combustion events to optimize engine performance with improved thermal efficiency and reduced emissions over the entire drive-cycle operating conditions.

  • Developing robust and flexible control algorithms, on the basis of a universal modular platform, to coordinate various actuators, especially during combustion mode transitions.

  • Designing a powertrain system to enable the proposed advanced combustion and control strategies, which include air-fuel path, combustion system, after-treatment system, and vehicle platform.

  • Implementing the proposed approach and demonstrating its associated fuel efficiency benefits on engine dynamometer and on full-scale vehicles.

Design. The project team is replacing a 3.6L high-feature V6 in the Cadillac CTS with a modified 2.0L I4 Ecotec engine. To achieve the target fuel economy improvement over the baseline V6 configuration, the team used GTDI technology for downsizing in combination with part-load lean homogeneous charge compression ignition (HCCI) operation for further fuel economy gains. A number of engine design changes and controls enhancements enable part-load HCCI capability.

Among the design changes for the engine are the use of a dual direct and port fuel injection strategy (to be explored using both single and dual fuel concepts during the project); Delphi two-step cam-switching hardware; Denso electric VCT phasers; an Eaton R410 supercharger; HPL-cooled EGR; and an increased compression ratio of 11:1.

The team redesigned the cylinder heads to accomodate cam profile switching (CPS) and electrically actuated cam phasers to enable transient operation between HCCI and spark ignition (SI) operating modes. The cylinder head was also modified for centrally-mounted direct injectors.

The intake manifold was modified for high pressure EGR feed and port fuel injection (PFI).

The two-stage boosting system (turbo- and super-chargers) was designed to accommodate part-load HCCI range extension as well as full-load performance. Pistons were redesigned to achieve the target compression ratio and to accommodate optimized injector targeting.

Combustion studies. The team compared several combustion modes—Spark Ignited (SI); Homogeneous Charge Compression Ignition (HCCI); Spark-Assisted Compression Ignition (SACI)—under various conditions (naturally aspirated, boosted, lean, and stoichiometric) to compare the methods of controlled auto-ignition on the downsized, boosted multi-cylinder engine with an advanced valvetrain system capable of operating under wide negative valve overlap (NVO) conditions.

The engine was operated under steady state conditions at a constant engine speed of 1500rpm and various loads (2.0 - 6.0 bar BMEP) to investigate the impact of extending the HCCI/SACI operating range and compare the results to traditional SI combustion modes.

HCCI operating mode was tested under lean conditions both naturally aspirated and with mechanically supercharged operation to increase the load range. SACI combustion was examined at both lean and stoichiometric operating conditions, with the use of external cooled Exhaust Gas Recirculation (EGR) for mitigation of combustion noise at high loads.

They found that the effective load range of naturally aspirated lean HCCI is limited but provides good combustion stability with significant improvements in BSFC compared to the optimized SI combustion mode. Extending the lean HCCI range via forced induction improves the lean capability at higher loads but exacerbates loss mechanisms that reduce overall brake thermal efficiency. Extending the operating range through stoichiometric SACI combustion modes resulted in BSFC improvements at the mid- and high-load points tested.

Vehicle simulation. The team used AVL CRUISE to conduct vehicle simulations using engine maps producing via 1D simulation. The CRUISE model was validated using published data for the baseline 3.6L naturally aspirated, port fuel injected V6. They found that using the 2.0L I4 GTDI with HCCI alone resulted in a 42.4% improvement in fuel economy over the baseline engine for the Metro-Highway (M-H) cycle.

When thermal management and start-stop control technologies are added, the result is an estimated 48.9% improvement in fuel economy over the baseline.

AVL CRUISE fuel economy results (Wheeler et al.)
Engine configuration FTP75
% improvement
3.6L high-feature V6 19.7 31.7 23.7 base
2.0L I4 GTDI 23.4 37.8 28.3 19.2%
2.0L I4 GTDI w/ HCCI 28.2 44.7 33.8 42.4%
2.0L I4 GTDI w/ HCCI & extra controls 30.8 44.8 35.9 48.9%

Performance in the simulations took a bit of a hit. While the baseline 3.6L V6 accelerates from 0-60 mph in 5.5 seconds, the 2.0L I4 GTDI with HCCI (both with and without the extra control technologies), takes 6.2 seconds to go from 0-60.

Base engines have been rebuilt according to the new design and are now running at AVL, Bosch and the University of Michigan.


  • Wheeler, J., Polovina, D., Frasinel, V., Miersch-Wiemers, O. et al., “Design of a 4-Cylinder GTDI Engine with Part-Load HCCI Capability,” SAE Int. J. Engines 6(1)doi: 10.4271/2013-01-0287

  • Polovina, D., McKenna, D., Wheeler, J., Sterniak, J. et al., “Steady-State Combustion Development of a Downsized Multi-Cylinder Engine with Range Extended HCCI/SACI Capability,” SAE Int. J. Engines 6(1) doi: 10.4271/2013-01-1655



Why did it take $24M of rare public $$ to select and configure improved sub-units to get 46% reduction in fuel consumption?

Why this wasn't done by our glorious private enterprises 10+ years ago?



you don't seem to understand this requires the most advanced technologies in term of sensor, real time computation, integration, complexity management

wake up my friend

HarveyD the 1960s: NASA sent people to the moon and Boeing flew the first B-747 with four power complex Jet engines. Powerful computers have been around for 3 to 4 decades and 1001 other technical accomplishments took place.

That being said, it is difficult to understand, why rather simple up-to-date automobile ICEs were not developed much sooner.

It seems obvious that the responsible manufacturers waited for the arrival of much more efficient HEVs, PHEVs and BEVs to wake up and run to the authorities to get hand outs ($$$M) to do the R & D they should have done many years ago, when they made huge profits selling inefficient gas guzzling boats on wheels.

To wake up would be to stop buying their inefficient ICEVs and restrict our future purchases to HEVs, PHEVs, BEVs and/or FCEVs. That's what 5,000,000+ have already done and many more to come.

Wake up my friend.


no in the 60s we didn't have piezo injectors, turbos, cheap and small computer that we could put on a cars, you are wrong on this.

HHCI regime is extremely difficult to control, tried before but impossible without today technology

as for efficiency clearly their simulation show that their solution would be better than a HEV and cheaper

5000 000 EV S come on Nisson sold 40 000 leaf at best same for GM and its volts, are you dreaming awake ?


I done doubt the potential higher performance but I maintain that it could have bee done 10++ years ago. Car manufacturers were too satisfied with the profits they were making with the huge gas guzzlers they were pushing on us to dare changing the status quo?.


Correction: first words should be....I don't.......could have been....


Correction: - you do not understand the basics of scientific/engineering advances.

You should have learned this 10 years ago.


These $24M for engine research are some of the best spent taxpayers funds I can think of. I cannot see how anyone can possibly complain about it.

Jeez, we are talking about a 30% reduction on oil consumption. It is worth 100s of billions, literally.


Nobody wants to admit it, but our glorious Big-3 stalled or stood still and produced 200+M lemons during four+ decades or so, starting in 1960 to 2000+.

My wife and I were victims of the Big-3 and had to buy a new car every second or third year or so, at least until 1990 when we switched to long lasting better built Maximas and Camrys.

We haven't bought a Big-3 vehicle in the last 23+ years and do not intend to visit their places soon.

If you don't believe me, look at who has mass produced 90% of the excellent electrified vehicles in the last 12+ years.

The Big-3 are trying to catch up and continue to fool their customers with their usual PR and/or copying mechanical-electronic gadgets from Japan, South Korea and EU or by having their small cars produced in Asia, Mexico, Brazil etc.


These $24M spent on engine research represent some of the best spent public funds I can think of.

It is beyond me how anyone can be against this expenditure. A 30% reduction in oil consumption is literally worth 100s of billions of dollars a year, not to speak of the benefits for future generations.



Why didn't you do it yourself 10++ years ago since you are so sure it could have been done ? you would be tremendously rich now... Anyway I don't know what you are trying to prove but your insinuation that we will all drive EV in 2020 is silly and unfounded. The technology won't be ready, and ICE have still margin for progress that will delay the point of economic viability of EV even if at the end EV will replace ICE unless H2 kills EV in the egg...



You can't possibly use logic to argue with a nitwit like Harvey D. He believes in his very bones that the world operates on Conspiracies of all sorts, simply to prevent his distorted Utopia of he and his friends from arriving.

When you ask him why he didn't do this R&D himself, on his own 10++ years ago, if it was so simple, as he says, he swiftly changes the subject. The sad answer is that with his warped brain, he couldn't even envision what is being done with hard effort and the background of the present evolving state of the technology.

Reality is that this combination of technologies is how the genuine Engineers of this World will improve our World. Engine efficiency and fuel economy has improved continuously for a century or more, but he doesn't know that or appreciate the progress.

The Polemicists of Harvey D's stripe will never do much except sit on the sidelines and criticize. Cyphers are cyphers and that is all they will ever be.

I have long ago given up trying to reason with Harvey D. Let him dwell in his mythical corrupted Paradise.

A Facebook User

it's all about profits and fat pay cheques over technology & real innovation. No company cares about innovating for the market, all they need is fat pay cheques & let the consumer / environment rot in hell. The point is, if the Govt. had not pushed this with it's money nobody would have cared to get it this far even for the next 10 years & we all would have been driving cheap plastic soap boxes. Look at the PHEV's & HEV's, nobody cared for them until public money was ploughed into them. On the other hand Prius came out a decade earlier even at a loss they wanted to change the market for good.


This stuff could not have been done 10 years ago.
The microcontrollers were not available then at the right price.
Nasa might have done it, but not Ford or GM or VW.

Also, it takes time for ideas to form and get developed - in people's minds and in metal/silicon.
+ 10 years ago, petrol was still cheap and people weren't so concerned about CO2 emissions.

The advantage of extra research like this is that guys can try other things, and take a longer view - the motor companies are probably more short term in their thinking.

Good to see that they have a heavyweight like Bosch in the mix and I wish them well.


The rising success of compact more efficient HEVs, PHEVs, BEVs and future FCEVs is what is forcing gas guzzling ICEVs manufacturers to do better.

It is a question of do or die. Fed. $$B may not be available the next time around.

Had the electrified units been marketed 10+ years sooner (and it could have been), ICEVs manufacturers would have done their homework 10+ years sooner.

Of course, higher oil price is one of the main driver, but that started in 1973, not in 2013. CAFE is another main driver, and that could have been more so many years ago.

I don't believe that we should find or make excuses for the Big-3 very slow innovation during 4+ decades. Adding high wings on rear fenders was not that smart but we bought it?

More and more buyers are going to wake up?


If the US automakers had served the customers, most of them:

wouldn't have crushed EVs

wouldn't have gone bankrupt

wouldn't have stolen bailout $billions

would have have marketed fuel cell vehicles(ten yo H2 Initiative) for years from their decades of $billions of taxpayer grants

would have marketed the hybrid(>50 mpg) first/best

etc, etc

'Wake up' indeed.


fyi - The Engine Control Unit(ECU) controls the engine.

"This stuff could not have been done 10 years ago." WRONG

"In 1988 Delco (GM's electronics division), had produced more than 28,000 ECUs per day, making it the world's largest producer of on-board digital control computers at the time.[4]" wiki

Even the honest, but then smaller, Toyota 1997 Prius sold 18,000 units and had the control technology on the road.


How many of the $70+B bailouts and handouts from USA & Canada did the Big three pay back so far?

What is the return on investment for the contributing taxpayers?

Will USA and Canada do it again?


Toyota sold over a million Prii a year and this will be the first full year Prius went from 1 to a family of 4 hybrid vehicles.

Already being the best selling car in Japan and California, expect 10 million Toyota hybrids sold before 2018 - barring tsunamis and nuclear radiation.

Nick Lyons

This is all win. I want this engine in my next car; I drive mostly highway miles these days, so 45mpg highway without hybrid compromises looks great to me. Add idle-stop and you've got an all-around winner.


"simulations find up to 48.9% improvement in fuel economy over baseline"

In other words - simulations - there is no such engine, might never be one, nor is this non-existent ICE engine in a car.


A virtual ICE in a virtual vehicle?


Also, the 'baseline' is a 9 yo, originally 17 mpg city GM V6 design.

Let's hope the computer(..& 'extra controls') can virtually do 48.9% better.


It is simple: USA does not go to the moon any more – Detroit big 3 do not lead the automotive development any more. How could anyone expect a fuel efficient car to come from Detroit? In this case, perhaps someone else have to show them how to do it. Or, maybe it is the customer’s fault. The US customer would, in any case, prefer an ancient and sluggish V6 over a high-tech responsive L4, regardless of the fuel consumption advantage of the latter. Perhaps the big 3 know this and just offer what the market is asking for…


It is not only about computer simulations. They will go all the way to real vehicle testing.

“Implementing the proposed approach and demonstrating its associated fuel efficiency benefits on engine dynamometer and on full-scale vehicles.”

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