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Optimizing the Saab BioPower 100 Concept Engine for E100

GM’s Saab BioPower 100 Concept, presented at the Geneva Motor Show (earlier post), showcases the first production-based turbo engine to be optimized for neat bioethanol (E100) fuel.

In combining Saab turbocharging expertise with the use of high octane E100 fuel, the optimized 2.0-liter engine from the 9-5 range develops 300 hp (221 kW) maximum power. The standard, unmodified 2.0-liter engine that is the basis for the BioPower 100 delivers peak power of 150 hp (110 kW).

Modifications to the engine management system and internal components enable the engine to exploit the high octane benefits of E100 fuel by using a higher compression ratio, together with more boost pressure. The outcome of this work is peak power of 300 hp and a remarkably high specific power output of 150 hp per liter.

This exciting concept shows the tremendous potential of bioethanol, in terms of both performance and future opportunities to ‘rightsize’ engines.

—Saab Automobile Managing Director Jan Åke Jonsson

Running on E100, the concept car’s engine also delivers 295 lb-ft (400 Nm) of torque between 3,000 and 5,100 rpm, with almost 85% available at just 2,000 rpm. This strong and flexible power delivery gives the Saab BioPower 100 Concept car zero to 62 mph acceleration in just 6.6 seconds and 50 – 75 mph (fifth gear) in 8.2 seconds. The standard 150 hp gasoline engine produces 177 lb-ft (240 Nm) of torque from 1,800-3,500 rpm, giving zero to 62 mph in 10.2 seconds and 50-75 mph (fifth gear) in 16.3 seconds.

Behind the enhanced performance is the ability of E100 fuel to resist harmful self-ignition, or ‘knocking’, as the fuel/air mixture is compressed in the cylinder. This attribute is denoted by E100’s high 106 RON octane rating. It permits the use of an engine compression ratio that is higher than normally possible with turbocharging, giving more power and greater combustion efficiency without risk of knocking.

The BioPower 100 Concept’s engine operates with a compression ratio of 11.0:1, compared to 8.8:1 for the standard gasoline engine. This has been achieved by modifying the shape of the piston crowns to reduce the volume of the combustion chamber, thereby raising the engine’s compression ratio.

New software for Saab’s Trionic engine management system, which controls the throttle setting, ignition timing, fuel injection and turbo boost pressure, looks after the different ignition timing and fuel/air mixture requirements of E100 fuel.

More durable valves and valve seats are fitted to the engine, together with bioethanol-compatible materials throughout the fuel system. The only other modification necessary is pre-heating of the fuel. This is required to achieve good cold-starting performance, which is the main reason why bioethanol is currently blended with gasoline and sold as E85 fuel.

In ambient temperatures below 60°F (15.6°C), the chemistry of E100 makes it resistant to vaporization and, as a result, it can be difficult to start the engine. To overcome this issue, the Saab BioPower 100 Concept has an experimental fuel heating system, using small heating elements in the inlet ports downstream of the injectors. When the engine is cold, these elements warm the incoming fuel sufficiently to allow it to vaporize. Shortly after start-up, the function is automatically deactivated.

The high compression ratio allows the engine to generate more torque more quickly, particularly from low engine speeds. On the road, the driver of the BioPower 100 Concept will immediately notice a sharper engine response, with a better low speed pick-up before the turbo is engaged.

On full throttle openings, the turbocharger packs up to 1.2 bar (17.4 psi) boost, without risk of knocking from the high octane fuel. It gives the BioPower 100 Concept driver access to the sort of in-gear performance typical of a modern, naturally-aspirated engine of four liters or more. Maximum boost pressure in the unmodified gasoline engine is 0.4 bar (5.8 psi).

That impressive 150 hp/liter specific power output also indicates considerable potential for engine rightsizing, giving the driver the performance characteristics of a larger engine without incurring its additional weight, greater complexity or higher fuel consumption. In this way, E100 offers significant potential to reduce the displacement of an engine—thereby reducing fuel consumption—while still achieving a desired power level.

The overall fuel consumption of the current Saab 9-5 BioPower engine using E85 is about 30% higher than on gasoline and the optimized BioPower 100 engine is expected to yield a near 10% gain against this. Bioethanol burns at a lower temperature than gasoline, which reduces thermal stresses on the engine and benefits fuel consumption at higher cruising speeds. With the future addition of direct injection and lean-burn technology, E100 fuel consumption can move even closer to gasoline levels.

For optimum energy saving, E100 applications could also be combined with electric hybrid technology, reducing fuel consumption and CO2 emissions still further. This development has already been previewed in the Saab BioPower Hybrid Concept, the world’s first such vehicle to use pure bioethanol. (Earlier post.)

While the BioPower 100 Concept is focused on performance, it still retains a flex-fuel capability and the engine will also run on gasoline, or E85, although power levels are not so high. Trionic monitors fuel quality after every visit to the filling station and automatically makes any adjustments necessary for running on E100/E85 and/or gasoline in any combination.

To handle the increased performance, the BioPower 100 show car is fitted with a limited-slip differential and larger front brake discs (13.6 inches) and calipers, while using the sport chassis settings of Saab 9-5 Aero SportCombi. It also has a dual pipe rear exhaust system, with tailpipes similar to those of the Aero X Concept.

Bioethanol’s simple, fixed chemical composition opens up new possibilities in engine management and control. It consists of just one hydrocarbon molecule, whereas retail gasoline is a cocktail of several hundred different hydrocarbons as well as additives to prevent engine deposits which may not be necessary with bioethanol. It is also biodegradable and will dissolve in water.

As it is a single chemical compound, bioethanol allows engineers to exercise much greater precision in maximizing engine performance. For example, it is possible to maintain an ideal fuel/air mixture (Lambda 1) at all throttle openings without impairing the smooth running of the engine, according to GM.

Saab’s experimental variable compression (SVC) engine, revealed at Geneva in 2000, has played an important role as a test bed for BioPower development work. It has been used to help determine the optimum relationship between compression ratio and boost pressure for the BioPower 100 application.

Bioethanol is a potent, high quality fuel which opens up exciting possibilities in helping to meet the environmental challenges that face us. As the need to reduce energy consumption increases, we are exploring ways to run smaller engines that give relatively high power, with and without hybrid technology. Bioethanol can play a key role in this ‘rightsizing’ process, while also minimizing fossil fuel emissions.

—Kjell ac Bergström, GM Powertrain – Sweden president and CEO



If they can get 300HP from a 2L engine, it would be interesting to see what they could get from a 1L or a 600cc engine (for smaller cars(!)).

+ all the hybrid stuff if required.

Also, I would be cautious about E100 - desperate people might try drinking it.

My first car had 45 HP, so a factor of 7 greater is probably a bit excessive.

Mark A

At all appearances this seems like a feel good win story. But realistically, if vehicles like this were produced, what would the refueling infrastructure be? Keep in mind alcohols inheret ability to absorb water, if not in an entirely closed container. Or the pipeline corrosion problems with alcohol.

Would driving a vehicle like this perhaps would require a support team, such as with a top fuel car or an indy car, which run on E100 ethanol?? I am preparing to stand corrected, and to learn.


You can ship ethanol in pipelines, just not the ones currently used for shipping gasoline because they will rust out from the water absorbed in the ethanol.


E85 to E100 optimization for all exotic sports cars!

11.0 to 1 static CR on a turbocharged port injected engine is insane. I bet they could get somewhere around a 14.0 to 1 static CR on a naturally aspirated engine optimized for E100.

Is the 10% better to be read as a 20% fuel economy hit when optimized on E100 or should it be read as 10% better than 30% such that it is a 27% fuel economy hit? Of course, getting double the horsepower with only a 20 or 27% hit on fuel economy is quite impressive if the fuel economy driving test takes into account some wide open throttle use utilizing that excessive horsepower.


Mark A:

Butanol is a much better choice as far as fuel alcohols are concerned. Its energy density and combustion properties are much closer to gasoline, so can be burned in most of the cars already on the road. And importanly, it's not nearly as hydrophilic as ethanol so can be shipped through pipelines.


More GM Dog & Pony show.

Rafael Seidl

Mahonj -

I believe the Chevy Volt architecture called for a 1000cc three-cylinder motor (Opel has offered one in its entry-level Corsa for many years) driving a series hybrid with a beefy battery and drive motor. The plug-in element is that this battery can be recharged off the grid at night or by the little engine that could.

Since the Volt is intended as a PHEV technology carrier in the same way that the Prius actually is for HEVs, a successful launch would permit other GM brands to leverage the innards. Saab may well be one of them.

The alternative to the E-flex architecture would be a regular parallel hybrid, featuring an inline two with an inertial compensation mechanism (cp. BMW F800) and a honking starter-generator (cp. Honda IMA) that acts as an additional flywheel on the transmission side of the clutch. Having more flywheel mass compensates for the major drawback of an inline two, i.e. that torque is only generated 50% of the time. The electric motor provides the extra power needed for acceleration at any speed and for hill climbing. It also helps the engine rev up quickly, something it would otherwise not be able to do.

For customers who drive almost exclusively in nearly flat terrain, the concept would work best with an ultracap bank of perhaps 100Whr capacity (cp. Maxwell modules). These can deliver high power, efficient recuperation, good cold weather performance and long life. The primary downside is the low capacity, so hill climbs of more than ~50 vertical feet require downshifting into a low gear and crawling up. That sounds like a huge limitation, but if you live near the coast or in the Great Plains and this is not your primary car, it probably isn't.

Another issue is the relatively high self-discharge rate of ultracaps, so you will still need a regular 12V battery to make sure the car will start after a couple of weeks in long-term parking at the airport.

To serve customers who insist on more oomph and those wh need to drive in hilly/mountainous areas, designers would have three upgrade options:

a - double the displacement by using an inline 4. Cheap but you take a hit on fuel economy. As with any NA engine, rated power declines with altitude.

b - add a supercharger with a one-way reed valve plus an intercooler to the inline 2. You get high torque at low RPM so your gearing can be long plus high power at high RPM so you can maintain high speed. An elegant, compact and lightweight solution. However, you only get fast response, high fuel economy plus high power at altitude if you use a small turbo or better yet, a pressure wave supercharger (cp. Swissauto Wenko's Hyprex). These exotic beasts are not cheap and require sophisticated control strategies but they can boost specific torque and power to very high levels.

c - add a traction battery to the ultracaps module. Plug-in option with all the benefits that entails, but only some battery types work well in cold weather. Heavy and by far the most expensive alternative.

So why isn't anyone working on such an architecture given that batteries are not quite there yet?

One issue is that two cylinders just sounds awfully itty-bitty for a car, especially one big and luxurious enough to make such a high-tech drivetrain profitable. Engine revs would have to be kept low when cruising at any speed or the whole thing would indeed sound and feel cheap. Marketing departments would have their work cut out for them, especially as long as other models by the same brand/manufacturer feature high-displacement ICE engines.

That leads to the second issue: keeping the revs fairly low on an inline 2 would mean artificially limiting top speed to somewhere in the 75-90 mph range and really optimizing the aerodynamics. The fun-to-drive factor would have to come from the electrically assisted acceleration, agile cornering and low fuel consumption.

The third issue is that California's ZEV mandate is heavily skewed in favor of vehicles with high all-electric range, i.e. those with traction batteries and/or fuel cells. Fortunately, unless CARB changes the fine print, the bias will be much less severe as of MY2009, which is really just around the corner. Ultracap hybrids with small ICEs are perfectly doable with existing technology and fuel infrastructure, unlike FCVs.


The EPA has tested a ethanol & methanol fueled engine with a compression ratio of 19.5:1, which runs at peak efficiency of 43% on methanol and 40% on ethanol. It is a port injected spark ignition turbocharged modification of a TDI diesel engine. Meets Tier II NLEV requirements.


Seems like we should be selling E100 & M100 or a mixture of both for much more efficient green vehicles.

Also, I think it is inappropriate to compare different fuels in terms of miles per gal. Emissions and cost per mile are the proper comparisons.

Seems like we should be selling E100 & M100 or a mixture of both for much more efficient green vehicles.

Also, I think it is inappropriate to compare different fuels in terms of miles per gal. Emissions and cost per mile are the proper comparisons.

Marlon Nerling

Mark A asks:
"Would driving a vehicle like this perhaps would require a support team, such as with a top fuel car or an indy car, which run on E100 ethanol??"

Mark: The Brazilian cars are running in E100 (Better said E93 ) since 30 years!

And to the message poster:
"This development has already been previewed in the Saab BioPower Hybrid Concept, the world’s first such vehicle to use pure bioethanol"

Please, see above!

I don't know how many studies may be needed, before the carmakers go to Petrobras and licence the allways existing Ethanol tecnology.

Mark A

Marlon, I understand that Brazil has been running ethanol at much higher concentrations than us here in the USA. But how many gas stations do Brazil have, compared to the USA? In theory, each and every station, or a majority of them, would need to have the capacity to sell E100 or E93 before the vast majority of people would even consider buying an optimised E100 vehicle.

And yes Cervus, I have always thought that butanol is a much better alternative than gasohol (ethanol).

But I am also severely worried about our nations farmland being used to grow corn for ethanol, or soybeans for biodiesel, instead of FOOD! Subsidies currently favor ethanol over food. The pork industry in this country is already starting to feel the pinch of the limited corn supplies, in higher grain prices, and in not being able to compete with ethanol plants, due to the subsidy, for the corn supplies. (This according to Small Farm Magazine.)

So in short, be happy in driving your turbocharged ethanol powered green car, when driving to the store to buy high priced bacon and pork chops, or corn chips. I fear it is only just beginning.....


I agree that growing corn or even switchgrass for ethanol fermentation is a bad idea, and an inefficient way to produce fuel.

I believe methanol / ethanol and electric energy for BEVs or PHEVs are the best prospects to replace fossil fuels for vehicle energy requirements at present.

I figure the best way to produce fuel is by using waste CO2 or biomass carbon, and surplus green energy. The Fischer Tropsch process can convert the biomass to Syngas, which can then be converted most cheaply to methanol (also ethanol but more expensive) with added energy. The idea is that, unlike with alcohols produced by fermentation, 100% of the biomass carbon is converted into liquid fuel carbon, which makes maximum use of the plants best capability, that is to fix carbon out of the atmosphere. This method makes alcohol fuel which is CO2 neutral. As a solar energy conversion process, crops to fermented alcohol has less than 1% of the efficiency of solar panels.

The added energy needed to convert CO2 or Biomass to alcohols could be obtained from remote coastal automated hydro/tidal power installations, with Plants that receive liquid waste CO2 by tanker, and return with alcohol in the same tanker. Also locations such as Iceland which has huge geothermal power resources. And transporting alcohol or CO2 by tanker is safe & environmentally low risk, unlike the dangerous transport of LNG or Petroleum.

Another example would be Wind Farms like Western Alberta, which cannot deliver peak energy to the grid, so why not convert surplus energy plus waste CO2 to methanol or ethanol.


A good analysis of the terrible energy efficiency of plant solar energy conversion is found at:

Mark A

Food vs fuel heres an article:

Tim L

The reason for higher grain prices, food prices is not from non-edible corn that is being used, but the gasoline and diesel used to transport it. Its funny we are all of sudden running out of corn feed for pork producers.. since there is over 17lbs of feed left over per bushel used for ethanol. Ever noticed how UPS and the US Post Office keeps raising prices? Its not because of corn, its the oil companies keep inflating prices and making millions of dollars a minute on us.. Please do more research on it before you post.

Tim L

Mark. Remember these figures in your research..... To make fuels, it is a very black and white comparison. It takes 1 btu to make 0.6btu's of gasoline, plus you have burn off impurities that pollutes the air even more. Ethanol from non-edible corn is 1btu to 1.7btu output. Switchgrass is nearly than 6 times that of corn. I also like to remind people that Ethanol may absorb water, but gasoline varnishes. If stored for long periods of time.. say 1 year, it is easier to drain water and start over than to remove varnish from wherever gas is present, not just in the tank. Since most newer automotive systems are plastic, nickel and stainless, there is minimal chances of rusting out are minimal. Piping it, will not corrode the lines like is stated above. Its not like ethanol absorbs huge amounts of water as soon as it leaves the distillery. The chances are about as likely as the pipeline gumming up from varnish.

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