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Ilmor Engineering Builds a Five-Stroke Motor

130hp and 122lb-ft. That means peak torque is achieved at ~5600RPM, then? I'd like to see the power and torque curves... Pretty damn cool. Sciency, but cool.
 
I don't get it. What's the advantage of this motor? 130hp out of a 700cc turbo-charged motor doesn't sound like much at all.
 
Dr. Evil said:
Fuel efficiency, ostensibly. I don't get it, either, tbh.
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Yeah, but you should be able to get similar fuel savings by just using a smaller motor, right? A turbo-charged 500cc motor should be able to put out 130hp, right?
 
wannabe said:
Yeah, but you should be able to get similar fuel savings by just using a smaller motor, right? A turbo-charged 500cc motor should be able to put out 130hp, right?
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It's also about durability, too. You can turbo anything to the moon, but how reliable will it be, even during a race?

Me, I'd start looking into two-smokes again...
 
If it's anything like the 5-stroke motor developed by Mazda for their Millenia S (a.k.a. "Miller cycle engine"), then it's a way to extend the timeframe for which the intake valve can stay open, while also allowing higher output with less friction-wall losses from the piston. Where the Millenia S employed a straight supercharger to perform, the Ilmor looks like it is using a piston-pump to move the air to reach the same effect.
 
There is no 5th stroke in a miller cycle engine. There are two big differences:

* A Miller-cycle engine depends on a supercharger.
* A Miller-cycle engine leaves the intake valve open during part of the compression stroke, so that the engine is compressing against the pressure of the supercharger rather than the pressure of the cylinder walls. The effect is increased efficiency, at a level of about 15 percent.
 
"The high pressure shaft powers the two outside cylinders, which operate like a normal four-stroke motor, while the low pressure shaft powers the larger center cylinder, which gathers exhaust flow from the other two cylinders."

I don't get it. How does a glorified EGR valve make it a 5 stroke?
 
cycle61 said:
I'm still confused about what the center cylinder does.
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It seems like it's part of the turbocharger, or at least that's what I gather.

For a similar setup, check out this converted Ducati. This guy converted his V-twin into a single + an air-pump (supercharger).

After looking at the camshaft arrangement, I think I have an idea of what may be happening...
ilmor-5-stroke_2.jpg


Notice that there is only one set of lobes per firing cylinder; the center cylinder has two sets of lobes, but we'll get to that later. Also, keep in mind that it is forced induction.

What i think is happening is that there is no separate intake or exhaust valves for the firing cylinders. The valves do double-time, operating as both intake and exhaust valves. What dictates where the air goes is both the turbocharger and the air-pump/vac in the center (with its own set of valves, which operate as exhaust-only valves).

On the intake stroke, the turbocharger is forcing air in, and the center cylinder is closed off. Fresh mix comes in, and when the motor hits BDC, the valves close (could be past BDC through compression stroke, depending on the turbo arrangement). Then the firing cylinder goes through compression/explosion strokes as per a normal four stroke. As the firing cylinder goes from BDC to TDC on the exhaust stroke, the valves open, and the air-pump center cylinder acts as a vacuum and helps draw the exhaust gases out. Once TDC is reached, the air-pump is no longer used as the turbocharger is now back in charge of getting the fresh charge in. The whole time this happens the valves remain open.

Of course, this is all conjecture, speculation, and probably waaay off base on how it is really done.
 
From Ilmor's site it looks like an alternate description would be

A parallel twin coupled with a synchronised thumper which uses exhaust from the twin as its mixture. The second burning in the thumper allows greater overall efficiency and lower emissions.​

I think each small cylinder has one intake valve and one exhaust valve which dumps directly into the center cylinder's intake. I'm kinda iffy about the choice of '5-stroke' terminology but I think they come up with it like this: one outside cylinder cycle (4 strokes) also has an associated half cycle of the center cylinder ('equivalent' of 2 strokes), but there are two primary cylinders, so divide 2 by 2. So 4 strokes + 1 stroke = 5 strokes. I wonder how often they're firing the center cylinder.

http://www.ilmor.co.uk/concept_5-stroke_2.php

Yeah, I wanna know what this thing sounds like. *Grinn*
 
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I would think they're firing the center cylinder like a two-stroke, every time the piston is TDC, bang. and I don't think the "5-stroke" term is meant literally (e.g., "six-stroke" was already being used elsewhere).
 
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Ahh. Yeah, that makes it make more sense. Fires once per rev 'cause it has new intake every rev *and* a four-stroke plus half a two-stroke equals a five stroke. Cool.
 
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