supercharged nc30

[Maelstrom]

The main reason I am thinking of using a Rotrex supercharger is because I have read the information on the
G-Force site.

Researching this topic is a work in progress for me. Most of the key points with regard to load and stress seem to be similar to the following extract. Of course this comes from a source that has a vested interest and must be considered in that light.

An extract from http://www.keystoneturbollc.com/id78.html
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"So let's analyze peak cylinder pressure. If an engine is turbo-supercharged to the extent required to deliver double the charge mixture in the combustion chamber, the cylinder pressure from compression will certainly be higher than an equivalent normal-charged engine, as will the component from boosted combustion. But how much higher? Less than you might think. Suppose normal charged cranking compression yields 185 psi, and a turbo compressor adds an additional 15 psi of boost pressure. The total compression component of cylinder pressure would be 200 psi exerted against a 4-inch piston of 12.57 square inch crown area. Multiplying the 200 psi by 12.57 indicates a total compression loading on the connecting rod of 2,514 pounds at top dead center CTDC) for the supercharged engine. But this is only 8 percent higher than the 2,324 pound loading of a similar normal-charged powerplant.

Obviously, this is small compared to combustion loading, which could easily quadruple pressure in the combustion chamber to 740 psi in the normal-charged engine and 800 psi in the boosted engine, resulting in total loading of 9,301 and 10;056 pounds for the two powerplants. Think of it: atmosphere of boost will double the horsepower but the supercharged engine's pressure is nonetheless only 8 percent higher. And 100 percent of the added load is compressive through the connecting rod against the crankshaft."
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I am familiar with building racing engines that must run at high rpm and I have always used Carrillo rods in those engines. If the standard rods are close to their limit, then I would expect that failure should be quite common when these engines are used for road racing, particularly at venues like the Isle of Man with its long straights. The only crank failures that I have seen thus far, are the modified stroker cranks that are referred to on the G-Force site. If anyone has any links to broken rod/crank stories I would like to hear them. Load squares at the speed, so keeping rpm as low as possible is critical to this concept. If redline is lowered from 14500 to 12500 (peak standard power) then the load is reduced by 25%
Cheers

[CMSMJ1]

G-force have also been breaking dogs in the gearbox and this would be my concern - gearboxes are a touch rarer to find in decent condition and I expect a bespoke set of gears would be pretty expensive.

I do like the idea of a blown V4 - I'd be happy with a sensible, unstressed (lower revs) motor that produced a flat curve with 80bhp.

[amorti]

I do like the idea of a blown V4 - I'd be happy with a sensible, unstressed (lower revs) motor that produced a flat curve with 80bhp.

That sounds to me a lot like a VFR750

[dom-tune]

Would the carbs work ?or just turn into a massive leaking mess also will thay open under pressure?head down for the reply

[kevprojex]

you will need to make a air tight plennum for the top of the carbs and the carbs would need to be modified to run boost if using a blow through system , you have to modify them so you have slightly more air pressure above the fuel in the float bowl than in the venturi or the fuel will not flow up emulsion tube into the air flow . you also will need a boost activated rising rate fuel pressure regulator and you will need to run a electric fuel pump (eg)of 10psi max if funning 7psi of boost, turbo engines also have boost sensitive ignition timing , you will need to retard the ignition timing as the boost rises, you can buy retard controllers to do this , you can run fixed retarded ignition timing but it makes the engine feel flat when off boost . many turbo systems have been done with carburettors you dont need to run fuel injection go get the engine to fuel properly it just takes more work as it cant be altered with a computer. its not just bhp you gain with a turbo its the increase in tourqe that gives you the punch,i wouldnt like to run more than 5 to 6 psi on a stock motor without lowering the compression ratio but it would be a interesting project, and i bet a nc30 with 85bhp and 40flb would be very interesting ride not to mention different hummmmmmmmmmm ? .any one can go and buy a r6 .

[Neosophist]

.any one can go and buy a r6 .

Indeed.

Although this one is an 86 my ideal bike would be a 92 (best handling)

But it just goes to show you can even turbo a 25 year old beast with good effect



* Granted it is a lot simpler on the GSXR1100.. engines are strong as an ox and dont' usually need strengthening, it's been done many times and the exhaust layout makes it easier.

** My favourite part of that video is at 3m25s.. roll on from 100mph - 186mph :O

Hardly takes any time at all