Ilmor Engineering builds a five-stroke engine
English engineering firm Ilmor knows all about engine design, having produced powerplants for Formula One, IndyCar, and NASCAR. But its latest internal combustion creation, in contrast to those racing engines, is designed to burn fuel more frugally: a gas-powered five-stroke with diesel consumption.
It starts with a three-cylinder, 700cc, turbocharged engine with 130 hp and 122 lb-ft. There are two overhead camshafts: a high pressure shaft turning at half the crank speed working on the two high pressure cylinders, and a low pressure shaft running at crank speed for the third cylinder. The two outside, high-pressure cylinders work like a normal four-stroke, but alternate their exhaust flow into the third, central low-pressure chamber. That cylinder's expansion and compression strokes aren't fixed, so it can be selectively tuned for the best expansion ratio.
The principle is that extra work gets done for the same amount of gas, and Ilmor claims increased fuel efficiency over conventional gas engines. The five-stroke is made with current, in-use technology so there'd be no extra costs for exotic materials or processes, and it's said to be "relatively compact." Ilmor says the next step is to build another working prototype with targets of 10% better fuel efficiency and 20% less engine weight compared to an equivalent four-stroke engine.
[Source: Ilmor via Motor Authority]
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Reader Comments (Page 1 of 2)
Luis 9:41AM (8/11/2009)
suddenly BMW's 3-series with 3-cylinder engines don't sound so far-fetched.
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Alex 9:45AM (8/11/2009)
Engineers amaze me.
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letstakeawalk 9:56AM (8/11/2009)
All an engineer needs is a problem to solve. Their capacity for creative thought is a boon to all mankind.
Hey, if it keeps the ICE around that much longer, I'd be happy!
adrenalnjunky 10:27AM (8/11/2009)
@lets
"all they need is a problem to solve" - AND for everyone to stay out of their why while they solve it.
Rick C. 10:48AM (8/11/2009)
And that's exactly how I feel and why I tend to banish the pencil necks from my lab or the floor.
Assass1n 9:47AM (8/11/2009)
how is it possible to have an odd number of strokes? It would go D, U, D, U, D, Then the next series would switch U, D, U, D, U. How would it work and how would another stroke on top of a conventional four stroke be more efficient?
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Bryan Riddle 9:58AM (8/11/2009)
and how would reading the article before posting a question answered in said article help?
Assass1n 10:27AM (8/11/2009)
@ Bryan Riddle
Sorry, I can't read the article as my workplace has blocked the site. I would read it though as the autoblog post is a little vague.
adrenalnjunky 10:28AM (8/11/2009)
Or just look at the pictures under the post - either way - it's pretty well explained.
Nateb123 4:35PM (8/11/2009)
Excuse me commenters while I actually explain the question rather than insulting him to feel good about my miserable existence. Also, I'll explain why you all just jumped on the "we're smarter than you" bandwagon without thinking this through because the term is a misnomer.
The outer pistons just work like all 4 strokes. Intake, Compression, Expansion, Exhaust. The next stroke comes from the exhaust port of the smaller pistons because attached to the intake of the big piston. So it begins its cycle of intake/expansion and then goes straight to exhaust/compression. Since this is basically an extra 2 strokes which is alternated between two 4 stroke cylinders, it's been called a 5 stroke. But obviously that's total crap since each charge experiences 6 piston strokes so it's a 6 stroke engine
If someone else better understands this, please do go ahead and explain but I can't see any other way this would work. Also it's worth mentioning that this engine design has already been invented...twice. Once by the folks Moller has contracted to build an engine for that Skycar that will never happen and once in the 60s by Rolls-Royce. Only difference is they were both rotaries but the idea is exactly the same.
TigerMil 9:56AM (8/11/2009)
A question is whether the 700cc is based on the displacement of the two outside cylinders only since they're the primary gas handlers. OTOH, the inside cylinder does contribute directly to torque/hp so it could arguably be counted.
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audi_arena 10:09AM (8/11/2009)
Just 10% better fuel efficiency? That doesn't seem like a big enough increase to me... wouldn't it be simpler and more effective to just develop diesel engines further?
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sparrk 10:19AM (8/11/2009)
...and 20% less weight
Tourian 10:22AM (8/11/2009)
But look at the power, that's only 700cc and 3 cylinders. What if it were 2.0L/2.4L and (3)/4 cylinders like a typical small car engine?
652059 10:42AM (8/11/2009)
I'm a big diesel fan myself, but I'm thinking that the benefit of this would be a cheaper mfg. cost than a diesel engine. That's one of the biggest problems with diesels being adopted in America - there is a large premium up front for the diesel option.
Now Ilmore, get back to working on that MotoGP bike!
Nateb123 6:39PM (8/12/2009)
@Tourian
You can't make a 4 cyl design with this far as I can see unless you route 3 smaller pistons' exhaust all into one big cylinder. I don't think there's the valve space for it to work terribly well, plus all the heat energy lost during routing of the exhaust just leaves via the radiator. So that means less efficiency and probably a minimal power increase despite the extra piston. Basically, to make a super clean I4 equivalent would mean making a V6 which is a big issue since space is at a premium for small cars.
rooster 10:16AM (8/11/2009)
This is similar to what has been being done with turbines for quite some time - utilize the "waste heat" from the first expansion process in a lower pressure system.
The fifth "stroke" is effectively the introduction of the exhaust gas through the center piston.
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UCJR 10:22AM (8/11/2009)
The number of prototype ICEs never ceases to amaze me. It will just become a matter of making a large-scale business justification and you'll start seeing many more alternative-cycle engines on the market (quasi-turbine, etc.)
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Ian 10:44AM (8/11/2009)
I bet it's not a 20% weight savings over an OHV design like in the Corvette!
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Sanders 10:51AM (8/11/2009)
Do you people always have to come out when the rest of humanity is trying to move forward with technology?