Turbo Retrofit Poll

Ekh said:

Considering the entire engine costs $800 or a bit less, $3K seems like a real stretch to me.

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Brainmatter said:

Please read the following in the most simplistic of mindsets and disregard many of the ticky tacky technicalities I've failed to mention. If you've picked up on them you already know that to cover it in depth would require pages and pages no one would read... so here goes! in layman terms.

So, I keep hearing this 12:1 compression ratio being thrown around as a limiting factor, but just remember, that is the static compression ratio only. There is a lot more that comes into play, especially when adding variable cam timing. Just how aggressive the cam is and what they are doing with cam timing makes a big difference in the cylinder pressures developed. When you throw in variable valve or cam timing, then you can change the dynamic compression as well as cylinder pressures. Think Otto cycle vs. Atkinson cycle vs. Miller cycle. The Mazda skyactive engines, for example, allow enough camshaft timing change that the engines sometimes run on an Otto cycle and other times an Atkinson cycle. The static compression ratio never changes in these engines yet the cylinder pressures are extremely variable. In cruise conditions you have an engine that is like an 8:1 with a 50% volumetric efficiency, but when you need power.... more like an engine with 12:1CR and 95% V.E! (examples for illustration only... I have no idea what the actual figures are).
Which gets us back to the turbo in question: In super simplistic terms: The only thing a turbo or supercharger is really doing is raising the power density of the engine. The end result is higher dynamic cylinder pressures under boost conditions. If the Elio engine is a modified Atkinson cycle engine already (to meet economy targets), then it may be running cylinder pressures that are more in line with an Otto cycle engine running a 9:1 static compression. In that case, assuming the rest of the components are fit for task, turbo away!
Or maybe every rod, bolt, seal, crank, gasket, and all imaginable parts were designed specifically to tolerate designed engine output +10%. In that case, we are stuck with the power we've got. Think Cosworth Vega engines: capable of 250 NA horsepower, but the engine blocks would split in two.... WITHOUT turbos!

Just like almost everyone here, I have no clue what the actual engine design is other than it is a somewhat conventional ICE engine, so I'm just blowing a lot of smoke. It does look likethe engine has the built in capability to breathe very well: Big, long intake runners and nice exhaust manifold. Maybe too well?Who knows about the head design? Basically, I'm just trying to remind everyone that there are a whole lot of variables, and what we don't know makes a huge difference. At the same time, what we do know does not really matter. It's basically the worst situation to be in.

If someone does have more info on the actual design parameters of the engine and the capabilities of the VVT system, I would be interested in hearing that. Looking at what I can see I think there is an easy 25% increase in this engine without a turbo: It really looks like it was designed to have a really good V.E. overall. They probably killed it in the head/cam/valve design.

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TCBronson said:

With 12 :1 compression, I would think that you could only do a 3 to 4 lb boost. To get a higher boost I would think you would have to change the head and lower the compression ratio. That would be expensive and not easily done to the first Gen Elio's. But even a modest 3 or 4 lb boost on a light weight car should help make it more peppy than a non turbo Elio.

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