Turbo SV650s better mileage and power

[cRiPpLe_rOoStEr]

We don't see so many folks turbocharging motorcycles, but it seems to be a nice project. BTW have you never considered to retrofit some aftermarket programmable EFI?

[naturalextraction]

Yes, as I use Micro Squirt products or build my own electronic control units. However I had never built a blow through system on a bike and was just curious which was rather a learning experience for sure. But I'm getting the mileage that I was aiming for and better actually. I know I could fine tune that like I have on my other EFI bike using the Micro squirt module. It gets between 75 and 85mpg and is faster than this one. You can see it here:
https://vimeo.com/26947432

[renault_megane_dci]

Clever stuff.

I have always thought a detuned bike engine boosted back to previous power level would do nicely better as far as FE is concerned but maybe I am considering a setup that would never pay for itself ...

[naturalextraction]

It can be less expensive than you would think. Although I can do my own machine work and fabrication, I've found many who can be plenty resourceful to get it done. This cost me less than $800 in parts only cause I bought fancy fittings which cost dang near $200. Not really necessary. The turbo I found for $75 and older IHI's from the 1.7L Scoobies are a dime a dozen plus there are other smaller turbos for less. It's just not about cost recovery as it is having a better efficient bike with more power on tap. I can keep it in the 60+mpg were I to drive like a sane person, but I don't, so it doesn't, but it can. Things do have to be done very right to have reliability. The other bike I mentioned is faster (over all quicker acceleration and top end) and just as reliable. Both bikes still need a couple fail safes installed and working on that when I have time. This is my daily driver and I have over 80k miles on it. I bought it for 1k and have seen my money back many times over in use. I expect the same now turbo charged. I don't even think of the time and money I put into it now. Like Reggie Jackson said after his warehouse of classic cars burned down in the 80's, " I don't build them for the investment or return on my money, I love these things" said with a tear in his eye.

[renault_megane_dci]

I fear I didn't make myself too clear.

I was wondering if (for example) I take a SV, bring it's power down to 50 hp through shorter cams (mainly) then boost it back to 76, wouldn't that make a more efficient engine than either the stock engine or your own boosted version of it ?

Then even if it is the case, having cams grinded on top of the turbo conversion could be something that could never pay for itself.

Or I could Miller it and only have the exhaust cams grinded ...

[naturalextraction]

Part of the efficiency of and engine is it'a ability to move air with fuel of course as the accelerant. The engine is not much more than an air pump with a lot of parasitic losses. Taking advantage of the volume in the chamber with more air and fuel to combust is volumetric efficiency. Changing the cam profile to move less air to de-tune or changing the cam profile, does not make it more efficient and then to just bring in more air, is still less efficient. The I.V.E. on the side of my bike stands for "Increased Volumetric Efficiency" just to state the obvious technically.

So you detune and bring up volumetric efficiency now from a lower starting point. Also the cam grinds provide max efficiency at different load and rpm ranges usually for a specific or intended use. I wont even begin to get into the many factors and variables that change efficiency regarding extraction of the internal chemical energy to provide the chemical leverage/energy in these SICE engines. They are by design not very efficient to begin with. The numbers seem to change depending on the source for typical four valve high swirl port combustion chambers, efi, engines. Some were from 35 to 38% with diesels approaching 45%. With DPI systems, variable cam timing, ignition systems and timing etc, efficiencies creep up some. There are many good books out there regarding a massive amount of research related to Spark Ignition Compression Engines and what brings up their "efficiencies" which also have multiple definitions related to certain aspects of it's operations and intended uses.

Here is one of my favorites related to your question in many areas of the book and is well written The Romance of Engines [R-188]: Takashi Suzuki: 9781560919117: Amazon.com: Books

This book by Dr. John Heywood from MIT and the Sloan School of Automotive Engineering, will very specifically in much technical detail answer every bit of your questions. I suggest looking for a used version or renting it on line as it's a bit pricey. Internal Combustion Engine Fundamentals: John Heywood: 9780070286375: Amazon.com: Books

Pretty much any question you can come up with there is an answer and there are reasons related to the intended use and build that most, especially motorcycle engines, already maintain a pretty high efficiency for it's intended use. Understand why high compression in itself increases efficiencies. Good basic thinking thought process though.

[cRiPpLe_rOoStEr]

Originally Posted by renault_megane_dci

I was wondering if (for example) I take a SV, bring it's power down to 50 hp through shorter cams (mainly) then boost it back to 76, wouldn't that make a more efficient engine than either the stock engine or your own boosted version of it ?

Considering that the shorter cams can eventually favor the low-end torque, it makes sense.

Or I could Miller it and only have the exhaust cams grinded ...

In the Miller cycle the intake cams are the ones grinded, not the exhaust. And it uses a supercharger instead of a turbo, or you could eventually use both

Well, in a V-Twin you can make a compact setup placing the supercharger in the middle of the cylinders.

[naturalextraction]

You would be using more fuel to make the same hp from stock application that ultimately will use less fuel to do the same amount of work, depending on where your using the most power in relation to the efficiency of the cam. Boosting air means more fuel. There would be no fuel consumption benefit and again, use specific "short cams" shorter duration specifically to gain with boosting. Lots of torque is added anyway with a turbo, and a supercharger takes energy as apposed to wasted heat energy used to spool a turbo.

Looking at it from overall efficiencies effectiveness. Lots of variables and unless you want all torque and little rpm range to flat line and different gearing, can you make that sort of work, again what is the application and build it for that. That's the diversity of the engines capabilities. Try and match apples for apples in performance of a stock engine and make the comparables is the point of getting the same but better. I have the same bike, better power, better economy, more torque. Gives me all around use for my needs. Again built specifically for my desires and what I wanted. I liked it the way it was stock, I just wanted to bring up overall efficiencies. Some area's higher than others with minimal loss. You will never gain across the board. You sacrifice something for gain in something else in these engines. Another reason I don't care for the SICE design.

[cRiPpLe_rOoStEr]

I'm more favorable to turbochargers because of their higher efficiency, but it doesn't mean I'm unfavorable to superchargers in some applications.

[naturalextraction]

Yes, when fuel consumption and efficiencies are not an issue or concern, like drag racing with a big mill, nothing still sounds awesome like an 871 or more!