Turbo sv650, build information, video etc.

Hey that's good stuff. You tube for you:

Im a bit confused with this project, I have been told that the crank has issues at around 85bhp, fully speced race bikes without a turbo get to around this figure, anything more and things break, what power is it making?

[embee]

Crank issues are usually speed related. Stresses are more or less proportional to rpm squared, so increasing max used rpm from say 10k to 11k will increase stress by over 20% (rpm squared = 100 to 121) which is often more than enough to take it into the region of "when" rather than "if". You don't design 20% more strength in a crank than it needs, it's inefficient.

Tuning for power in a normally aspirated engine usually involves increasing rpm, it's the simplest way to increase mass airflow rate if there's still scope regarding the gas flow in the head. That's when cranks get touchy.

Pressure charging, turbo or supercharging, generally doesn't increase peak cylinder pressures achieved compared to a normally aspirated engine. In simple terms the peak cyl press achievable is dictated by the octane rating of the fuel, knock will occur when the fuel/air mix has been exposed to a certain temp and pressure for a certain length of time (simplified version anyway). Once you reach the knock limit you can still increase boost but you'll also retard ignition away from "best ignition" and also increase enrichment to cool the charge further, the net result tends to be pretty much the same peak pressure. Pressure charged engines generally don't need bigger bearings than N/A engines.

You may need to address heat rejection in order to avoid exceeding metal temp limits (e.g. between valve seats), but as often as not unless you're going to run for prolonged periods at high boost then you'll get away with it on a street engine, there's usually enough safety margin in a well developed production engine.

Good start embee! It can have a tendency to be complicated.
As to the crank:
1. I'm reducing my rotational mass by having reduced the stator and flywheel with the five bolts to a total of 3.032 lbs. I left all the magnets on as I need the power for my pig of a oil pump utilized to push oil from the turbo back into the crank case. I'm stillllll waiting for that to come back from being balanced. Was hoping it would have been here yesterday! Yes indeedy, increased RPM limits are a serious stress to these cranks.

2. The power from the boost is applied more linear from this application. Also applied at lower rpm as embee refers. The linear application is as apposed to a hit from nitrous or the massive shock of angular momentum force upon the crank (in that case may also be referred to as "moment of inertia) from executing a down shift from 5th to 3rd with sticky tires and a 185lb rider. That force with an almost 7lb rotational weight on the end of the crank with an oil feed hole passage removing some metal strength creates the break most common. They will also break at the rod connection point next to the crank counter weight on occasion as well.

3. I am installing an anti-detonate tank that will come on after 4psig. Almost finished with that. I live at 6200ft elevation I drive where just about everywhere in my state is 4800 to 8000 or higher. I need 3.83psig just to get to sea level 14.7 atmospheric. I try to keep my A/F ratio consistent and not use over enrichment for additional cooling. Over enrichment can cause detonation as I have proven a few times in my purposeful experiments on another bike. Water/blend will most always have a more efficient effect of cooling and if done correctly have an expansion rate that can provide some positive displacement and effect in the combustion chamber. Also eliminates the need for retardation of ignition timing which I don't want to do on this bike. This also addresses heat rejection/displacement>absorption as well. Anti-detonate is applied through the Crown method.

Once I have everything where I want it I will test for Bhp and get real some real data. I've been filming all of these things and will also the dyno testing as well. Should have a decent film if all goes well!

Also to note. I do use 91octane now as I boost currently to 5psig which the engine still maintains the stock stator. With the lighter stator and ADT I will feel comfortable at 10psig. The cranks metal materials observed for tension, shear, compression and also rated at "moment of inertia", can handle much more but I feel the cylinder head and head bolts would be compromised. I've had more issues with head bolts stretching than anything. This is a STOCK motor with 70+k(thousand) miles on it. To prove the point you can charge a higher mileage engine without much issue. 6 to 8 psig is quite conservative for my elevation.

[yorkie_chris]

Originally Posted by embee

Crank issues are usually speed related. Stresses are more or less proportional to rpm squared, so increasing max used rpm from say 10k to 11k will increase stress by over 20% (rpm squared = 100 to 121) which is often more than enough to take it into the region of "when" rather than "if". You don't design 20% more strength in a crank than it needs, it's inefficient.

The weak bit seems to be the drilling on the end of the crank which feeds the bushing for the starter gear. This is spinning a supposedly balanced lump so IMO it's not related to speed directly, but to the acceleration of the crank and/or shock loads.

Some people have said their reasoning for using slipper clutches on race bikes was to reduce stress on this bit when paggering it down through the gears on track.

[mikerj]

Originally Posted by yorkie_chris

The weak bit seems to be the drilling on the end of the crank which feeds the bushing for the starter gear. This is spinning a supposedly balanced lump so IMO it's not related to speed directly, but to the acceleration of the crank and/or shock loads.

It could be a torsional vibration issue, which would be RPM related.

So if I reduced the max RPM on the engine and added some forced induction I would get the same power by just a different delivery further down the powerband?

Crank issues on these poor devils have been beat to death on these forums, I've explained how I help get around their weakness's.
So M1tch1978, keeping with stock application includes it's established RPM limits by the factory. The linear apply of force is just easier on the crank as it doesn't create the shock force as also mentioned by Yourki-chris. As with everything there are limits and balance to this application.

Forced induction needs to be better understood from a physics and general science standpoint related to all the components in our ICE's. There is more misconception throughout the internet than truths or mostly half truths, pits and pieces relayed in the wrong order and "as I understand it" translations. Some of it gets down right into pseudoscience, which really drives me nuts. I sure will not profess to know much about anything as there is a crap load to learn in this world and with the things we have interests in. Most scratch the surface of information and some dig a bit deeper. In this day and information age sighting relevant and credible sources is a must.

As to the bike: replaced my copper boost line which had a small crack from the farrel which apparently I tightened down to much...oops. Much better now!

[yorkie_chris]

The thing is with engineering complex systems you could study a lifetime on each facet of the design of each component.

There's only so far this will go and unless you've got more resources and brains than toyota or honda then there's a lot to be said for welding a load of bits together and having a go!

I can't wait to see dyno runs

Well....as usual with me...I dumped it in a parking lot! Sum bitch. Turbo side down. Took off on cold tires turning in the parking lot of where I get coffee every day. 28degree F and on a surface that was resurfaced a couple months ago with oil. Only damage was the lower faring and broke the back peg and slider. Four week old paint job. So at least I can fix that soon. Bugs the crap out of me already. I blocked off the waste gate completely this morning, re-wrapped rear exhaust and turbine housing to notice a good 5oorpm gain in boost signal. I took off a bit "spirited" and did a dognut and before I knew it was looking at the clear blue sky! Crap I say! Ok used more explicit words to be truthful. After taking it home it drove fine. Today also was my first day taking her over 125mph also. Once maintaining speed it drops to 3psig. However kept it under 6lbpsig to get there...quickly. Turbo bushings holding up well. Lots of room at top end. I have 2 extra teeth at the drive gear as well. Licking my wounds and getting ready to repaint the fairing and re-make the inlet to the turbo. All else fared well (no pun intended). Oh well