Turbo SV650s better mileage and power

[renault_megane_dci]

Overlap associated to long duration cam is waste.
High rpm is waste.
Pumping loss is waste.

HYPOTHETICALLY, and bearing in mind we don't need high power when looking for all out FE, I would build a turboed SV with inlet cam phased for less overlap, and exhaust cam grinded shorter.
That would make a Miller cycle engine that would spin 3K @ 80mph in top gear.


That being said, I do like your particular bike in what she does provide : big fun factor (not really looking for that anymore myself, that is all)

[naturalextraction]

Agree cam has to much overlap for turbocharging for sure. Like any idea I always encourage one to at least make the attempt to give it ago. Real world living makes it difficult to have enough time much less money to do such things. There is also a mind set that has to be in order to see out goals to a fruition as well. Ain't easy. My other bike has taken 5 years to get it where it is and my ACVC hybrid hopefully won't take as long. That's part of R&D or experimenting. Seems like most on here arn't afraid to get their hands dirty or make a mistake or two. Its pretty cool to read what many or doing in this site. I appreciate the ideas and input, it's good to read and ponder on.

[Norm-SV650]

Very cool! Nothing wrong with increasing power and fuel economy. I thought about changing front sprocket since Ohio just up there speed limit to 70 mph. The worse I got this week in 90F heat sitting upright, opposed to laying on the tank, was 59 mpg. I usually average 68-72 mpg(2008 SV650F) but it is not allot of fun.

At cruise all my turbo-4 cars have positive pressure in the intake throttle body which the difference in fuel economy vs normally aspirated.

Good luck with the project!

[naturalextraction]

Although I'm not exactly sure why, but there is some indication as to a direct correlation to MPG stats from those that live in lower altitudes to higher. The F series SV here, Injected, rarely ever evens see 55 or so mpg. Even a well tuned Carb bike is usually in the mid 40's. As you know a lot has to do with how you drive. Here on Fuelly Suzuki SV650S MPG Reports | Fuelly you would be way above the average. Definitely keeping your cruse rpm within just below the peak of the cam profile helps the economy aspect. Going up a gear in the front is a good 500rpm drop. I will be taking a trip in a few weeks which will put me at about 2800ft so I'll be curious how I do. I suspect I wont do any better if in fact a bit worse and I have no means to re-tune without some difficulty.

[alvaro84]

Originally Posted by naturalextraction

I will be taking a trip in a few weeks which will put me at about 2800ft so I'll be curious how I do.

Our higher altitude trips usually give good FE, though it has nothing to do with the carb setting - one bike is carb'd with factory settings, the other is EFI. Less dense air probably helps, and gliding downhills is there too...

[cRiPpLe_rOoStEr]

Originally Posted by renault_megane_dci

HYPOTHETICALLY, and bearing in mind we don't need high power when looking for all out FE, I would build a turboed SV with inlet cam phased for less overlap, and exhaust cam grinded shorter.
That would make a Miller cycle engine that would spin 3K @ 80mph in top gear.

The original Miller cycle uses a supercharger. I might admit that I'd be quite worried about the discompression at the start of the expansion stroke decreasing the boost with a turbocharger...

[renault_megane_dci]

Originally Posted by cRiPpLe_rOoStEr

The original Miller cycle uses a supercharger. I might admit that I'd be quite worried about the discompression at the start of the expansion stroke decreasing the boost with a turbocharger...

Stop me if I am not using proper wording.

Induction
Compression
(Explosion)
Expansion
Exhaust

Miller (/Atkinson) is about lowering the duration of compression to maximise the effect of expansion.
It is oftenly done by increasing induction above what is required.
So, at the start of the compression stroke, there could be a gulp back of air that could stop the turbine from spinning resulting in fatigue failure of it just as what could be seen when closing the throttle.
There is a cure to this throttling issue, namely recirculation valve, but you are right, it could be not suitable at a high rate of use.

Maybe, the only way around it is to use a phaser on the inlet to run in atkinson up to a specific rpm and then normal phasing when power is requested.
Or maybe with low boosting and longer inlet tract ...

Anyway, sorry about the thread hijacking ...

[cRiPpLe_rOoStEr]

Originally Posted by renault_megane_dci

Maybe, the only way around it is to use a phaser on the inlet to run in atkinson up to a specific rpm and then normal phasing when power is requested.
Or maybe with low boosting and longer inlet tract ...

Or maybe going extreme with a twincharger (supercharger + turbo)

[mechman600]

I would leave it alone. After all, naturalextraction is getting middle weight/open class bike performance with entry level bike fuel economy, which is impressive already.

[renault_megane_dci]

Ho, sure, each to their own, I was just trying to use his knowledge to imagine a more FE friendly orientation of his setup.