Could This Be the Volt’s Combustion Engine: GM Demonstrates HCCI Motor for 1st Time in Driveable Car
HCCI stands for Homogeneous Charge Compression Ignition, and is a new type of combustion engine paradigm. Traditional engines, with which we are all familiar, use spark ignition (SI). In that system, a spark plug fires and ignites the fuel in the combustion chamber forcing the piston to move. In HCCI engines, the fuel is compressed within the chamber and is able to ignite through compression at multiple ignition points (as opposed to the single one at the tip of the spark plug).
This is referred to as a lean combustion process, and occurs at a lower temperature. This leads to lower CO2 output and improved efficiency, allowing for a 15% increase in fuel efficiency. The process is said to nearly equal diesel engines in terms of fuel efficiency, but does not require the expensive processing needed to deal with noxious diesel emissions.
On August 24th, GM announced that two drivable cars using HCCI engines have been demonstrated, the first time that this type of engine has left the laboratory. The cars were a Saturn Aura and an Opel Vectra, both with a modified 2.2L Ecotec four-cylinder engine.
Apparently this particular type of engine is very good when confined to a single lower RPM. At high engine loads and fast speeds, these concepts have to be shifted to spark-ignition.
Based on these special properties, one might think that the HCCI engine represents the ideal agent to act as the Chevy Volt’s generator.
We think the initial Ecotec engine first announced with the concept could be out of the final plan, and ethanol remains in, but there does seem to be wrangling going on at GM to decide exactly what combustion engine the Volt will use. This may represent a logical choice. I am not aware, though, of HCCI being demonstrated with E85, although it is theoretically possible .
To learn more about this amazing new technology, read Sam Abuelsamid’s test drive experience here.
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9 Responses to “Could This Be the Volt’s Combustion Engine: GM Demonstrates HCCI Motor for 1st Time in Driveable Car”
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August 27th, 2007 at 12:09 am
I think it will depend on what the best speed for the engine is, and how much load is on it. I think direct injection will probably be the easiest advancement in internal combustion engines to incorporate in the generator.
August 27th, 2007 at 1:50 am
According to the ABG article, HCCI apparently requires sophisticated computer control mechanisms to get it to work properly, even at the low speeds and loads that a series hybrid gen-set would encounter. A more traditional ICE is more likely in the works - at least for the first generation Volt. Like I always say, keep in simple.
One option for the gen-set that hasn’t been touched upon, as far as I know, is the microturbines that GM used in its EV1 series hybrid prototype. As efficiency and low mass goes, that would be a great option, but GM’s existing manufacturing infrastructure is already well optimized for building piston engines.
August 27th, 2007 at 8:05 am
The engine won’t be running that much, so super high fuel efficiency is not critical. The most important considerations will be:
- cost
- reliability
- noise
Noise may actually be a big consideration. Given that the engine is usually off, the first few times it comes on may scare you. After that, it might just be really annoying, especially since you have no control over it.
Does anyone know which of these 3 engines has the least noise?
- 1.0L 3-piston turbo-charged with spark plugs
- HCCI
- small turbine
Also, since the engine runs at constant RPM, I’m assuming the exhust system would be highly tuned for this RPM. Does anyone know how much difference this will make?
August 27th, 2007 at 8:39 am
The HCCI engine has to be warmed up before it can operate in sparkless mode, an iffy proposition for the VOLT range extender, which will only run a few minutes before cutting off for awhile. Also, I’m not so sure the VOLT’s engine can be considered to be running under “light load.” I’d much rather the money be spent on batteries rather than the range extender. For some folks, like me, that range extender is going to get very little use. I can’t see GM looking for yet more unproven technologies to introduce into the VOLT. There are enough already to scare any
engineer.
August 27th, 2007 at 9:14 am
i’m concerned about the octane level of gas you use in this engine. wouldn’t it be a very specific requirement? in other words, if the engine was designed to burn regular gas, then premium may fail to ignite (because of its higher octane). likewise, if the engine was designed for premium, there would be devastating knock if regular gas was used.
also, i don’t see E85 as an option, unless the engine is designed for E85 only, and regular gasoline is never used (E85 has a very high octane number, even higher than premium gas).
August 27th, 2007 at 9:33 am
I’m sure the engine can adjust as needed to whatever fuel is used, since it will only have a constant RPM.
I like this idea, and it’ll be a nice surprise if they use it in the Volt.
August 27th, 2007 at 10:44 am
I tend to agree with Kent… let’s keep it simple. Too much invention means too much to go wrong. (That’s the engineer in me talking) GM can’t afford anymore unknowns. Bring the HCCI (which I must say is VERY cool) to other vehicles first, and once it is proven technology, cross it over to the Volt. (Same goes for the Volt… once it is proven technology, cross it over to other vehicles)
August 27th, 2007 at 2:13 pm
Another vote to not include a HCCI range extender in the Volt. It is to much of a unknown and already have enough new technology. Yes, focus on the electric powertrain and batteries. Just having ICE with turbocharge, like original proposal, will be fine for first release. Only better choice and proven is to offer diesel in US, but that could also add cost to item that will not be used that much. So agree keep it simple.
August 27th, 2007 at 2:30 pm
I must agree that now is not the time for HCCI. We have enough technical issues and will have enough service packs on the initial release of Volt 1.0 fine tuning battery mgmt etc. GM would be well advised to take the large gains in fleet fuel efficiency produced by the PEHV & not risk damage to the potential marketability by introducing too many unknowns with a planned implementation of 2011 model year production, which is only begging for trouble. Hopefully GM has heard of “milk before meat”. They have been working on this engine for several decades & still have significant issues. Not a good time to put a Piranha in the baby bath water.