Well, isn't this intriguing as F*ck.

"If only EssExTee could be so grossly incandescent" (essextee) 05/07/2014 at 13:56 • Filed to: alternative fuel

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Back before Saturn was given the axe by GM, they were experimenting with something called HCCI* fuel technology. Essentially, the ignition was via compression like a diesel, but the engine ran on a super lean mixture of gasoline or E85. Details after the jump.

*Homogenous Charge Compression Ignition

Instead of glow plugs, the engine relied on spark plugs when cold or when under load, but the rest of the time would switch to compression ignition, leading to a cleaner burn and something like 15% better fuel economy. Because it burns gasoline rather than diesel it requires conventional exhaust treatments, rather than the expensive and extensive catalyst systems that diesel engines need.

In 2008 Saturn applied this technology to an Aura, converting a 2.2L Ecotec engine to the new system. Thanks to direct injection and VVT/VVL on both cams, it provided a very respectable 180hp and 170ft-lbs. The crossover from spark to compression ignition was managed by a sophisticated engine controller that relied on input from cylinder pressure sensors.

This technology is highly impressive, and Saturn nearly had it refined to the point of being production ready but unfortunately the brand was killed off before that could happen. You can read more about it !!!error: Indecipherable SUB-paragraph formatting!!! and !!!error: Indecipherable SUB-paragraph formatting!!! .

BugEyedBimmer - back in the Saddle Dakota Leather > If only EssExTee could be so grossly incandescent 05/07/2014 at 14:02

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Why did GM not carry this over to any other brands or keep testing it? An E-Assist setup with this engine in it would get astonishing mileage for a gasoline engine and still be able to scoot pretty well.

If only EssExTee could be so grossly incandescent > BugEyedBimmer - back in the Saddle Dakota Leather 05/07/2014 at 14:04

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From what I understand of the brand, Saturn was given extensive autonomy from the rest of GM. It's possible that this was purely a Saturn skunkworks-type project that was not endorsed by their overlords.

RamblinRover Luxury-Yacht > If only EssExTee could be so grossly incandescent 05/07/2014 at 14:07

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Saturn aren't the only ones that have experimented with CI gas engines, just the ones who've gotten the furthest. I did a whole lot of reading on this stuff about 7 years ago when it was current, but I've forgotten most of it.

Stupidru > If only EssExTee could be so grossly incandescent 05/07/2014 at 14:19

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Not exactly "new" stuff for the automotive industry but it's not old either. I work for a small engine company and we've been trying this for a few years already

Logansteno: Bought a VW? > If only EssExTee could be so grossly incandescent 05/07/2014 at 14:57

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Saturn was doing Plug-In hybrids before it was popular. The Vue Greenline Plug-In was supposed to release but then Saturn was killed. I really think they were going to be changed from a "cheap" brand to a green brand before they got the axe.

It's a shame, because this would've been an intriguing CUV.

BugEyedBimmer - back in the Saddle Dakota Leather > If only EssExTee could be so grossly incandescent 05/07/2014 at 14:58

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Damn, that's a shame. Because think about it. Saturn was discontinued in 2009, which means that this had to have been in testing by 2008 or before. If they had followed through with it, they might have been able to rebuild GM and keep the other brands. Saturn might still be around and considered "America's Toyota" as far as FE goes.

heywood220 > If only EssExTee could be so grossly incandescent 05/07/2014 at 19:45

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I remember reading a while ago that Hyundai is working with the University of Wisconsin on a setup that sounded like this. Havent heard anything in a while about it tho so I don't know what the status of that is currently.

Bandit > If only EssExTee could be so grossly incandescent 07/19/2014 at 12:52

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that's really freaking cool! It's a shame the idea was killed when Saturn was killed.

gmporschenut also a fan of hondas > If only EssExTee could be so grossly incandescent 07/20/2014 at 04:31

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Problem was trying to balance the engine temperature, fuel air mixture, compression ration, during all three phases, HCCI, the transition and under normal spark mode. there is a very narrow temperature band the engine would have to be kept in. Drive faster, well that would increase cooling, over the radiator so that would have to be adjusted while factoring in outside temperature. With all those variables you start getting into a crazy matrix that would have to be carefully controlled, without advancing the timing too much and creating knock.

If only EssExTee could be so grossly incandescent > gmporschenut also a fan of hondas 07/20/2014 at 13:58

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That would be the "sophisticated engine controller" I mentioned.