I meant wastegate.
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Kawasaki Ninja H2...750 cc supercharged.
- Thread starter CafeRay
- Start date
I meant wastegate.
I mean a low pressure valve that bled while holding boost constant at say 10psi. Imagine a perfectly flat boost curve
After the turbo spools up, max pressure is reached and the wastgate lets off excess, you cannot build pressure beyond a certain amount or blammo. This is getting far more sophisticated, in modern F1 engines, the turbo does not spool up by pressure, but by an electric motor (zero lag), and excess pressure and off-gas spinning on deceleration generates electricity to the batteries. Net result: same power as normally aspirated bigger engines, 30% less fuel used.
Still, power adders on bikes makes little sense when typical litre bike engines are already too powerful.
Man, I wish GTAM would set up an "Ask Brian P/JohnnyP636/Reciprocity" subforum. No more sifting though sand dunes to get a few grains of information. Seriously.
Yeah, but that's hardly typical. The VW system is very efficient, because no energy is just blown off, as the vanes turn to reduce pressure, the turbo makes less drag.
Ah ok. So what I saw was a supercharger (centrifugal) with a waste gate to bleed pressure so it wouldn't keep building boost at high rpm.
I'm starting to want this bike lol
Uhhhh... every turbo 'boost curve' eventually reaches a peak and stays flat. That's what a wastegate does. Production turbo cars get to maximum boost very quickly and the wastegate bleeds excess exhaust gases away from the turbine, which is far more economical than bleeding off pressure from the cold side.
The reason this makes sense specifically in a centrifugal supercharger application is because those blowers only produce maximum boost at redline, since they're spun by a pulley connected to the crank. The theory is that you can spin it faster, earlier, and then bleed off whatever pressure you're not using after a certain rpm. Its a case of math and flow characteristics to get this one right though.
well...okay, it's different, but given that an I-4 can give us 193hp normally aspirated, exactly why would we do this?
Makes sense on turbodiesels, makes sense on cars to improve economy, but has hp really been a problem on bikes since the Hayabusa, ZXr1400, Tuono, HP4, etc. etc.?
Do we care about fuel economy?
What's the advantage?
love4speed
Member
Damn Kawasaki, stop teasing us. If the spy pics are correct, it will be my next bike.
I hope they also comes with all the electronic controls stuff like HP4
I hope they also comes with all the electronic controls stuff like HP4
There is no "wastegate" on a supercharger.
I'm thinking that this will be a 750cc bike with the power of a litre bike. The smaller bore lets the engine be physically narrower, which is a good thing. More power is not "needed" but it sells in that market segment. It's quite possible that the real reason involves EU CO2 emission limits, which currently aren't regulated for motorcycles, but could be, when the regulators figure out that the larger-displacement motorcycles use more fuel (i.e. emit more CO2) than a good many mid-size cars.
I'm thinking that this will be a 750cc bike with the power of a litre bike. The smaller bore lets the engine be physically narrower, which is a good thing. More power is not "needed" but it sells in that market segment. It's quite possible that the real reason involves EU CO2 emission limits, which currently aren't regulated for motorcycles, but could be, when the regulators figure out that the larger-displacement motorcycles use more fuel (i.e. emit more CO2) than a good many mid-size cars.
Not in the traditional sense, but there was a performance shop a little while back that started integrating wastegates into centrifugal blower installations to get them to peak pressure before redline, and it worked with moderate success. Obviously this is almost completely opposite of what a wastegate was made to do (vent exhaust gases, not compressed intake air) and I can't remember the name off the top of my head, but the idea was as I described above. They used a relatively large wastegate on big V8 centrifugal blower installations to get maximum boost before redline and then maintain that pressure as revs climbed. The results were a massive improvement in midrange torque with very little loss in peak horsepower. Again, this is a very specific way to negate the inherent disadvantages of a centrifugal blower... they just happened to use an already available aftermarket wastegate instead of engineering their own device for the purpose.
I'm pretty sure that an OEM like Kawasaki is smart enough to size the supercharger so that the delivery volume and pressure are matched to the engine accurately enough that it won't need to blow off pressure constantly when the engine is running (which wastes energy), only when engine load changes abruptly.
Same as any other bike lol that looks like one of those high speed test tracks in europe
Wastegate is in the exhaust tract, allowing exhaust gasses to escape thru the tailpipe without passing thru the turbine side of the turbocharger, as the wastegate only opens when max pre-determined boost is already reached. Any more exhaust would simply drive boost levels too high, theus the use of a wastegate to bleed off excess exhaust.
Blowoff Valve is used to bleed off intake pressure between the compressor side of the turbo or supercharger, and a closed throttle plate (closed throttle between shifts, or sudden letting off of the throttle for sudden deceleration). The closed throttle will not allow the boosted intake charge to be ingested by the engine, so it piles up in the intercooler tubing and intercooler, and once those are full, the boost will run back thru the turbo/supercharger's compressor wheel that could be spinning at upwards of 150,000 rpm or more, potentially stalling it, and causing thrust bearing damage. The cool PSSSSHHHT sound of the blowoff valve that people are hearing has simply been vented to atmoshpere for fun and noise, whereas in OEM applications, the blowoff valve's venting is run back into the airbox or intake plumbing before the turbocharger/supercharger's compressor inlet.
VAriable vane turbochargers like VW's and Porsche's design were first successfully implemented in a production car way back in 1989 by Garrett, Caroll Shelby and Chrysler in the Shelby CSX.........taking the normally aspirated 80 hp 2.2 Dodge 4 cyl, 8 valve, non-cross flow headed K-car engine into the 200hp, and well over 200 ft lbs of torque territory with zero discernible turbo lag. It was an awesome feat back in 89, and that car is still one of my favourites of all time, with it's fibreglass Shelby engineered wheels and Koni full suspension, it was a fantastic little sleeper.
For simplicity's sake, picture the round tunnel doorways on Star Trek type spacecraft that have triangular plates that swirl and converge into the middle to close the door, and swirl out and away from the centre into the walls to open-this is similar to the way the vanes inside the turbine work in this system, constantly changing the volume inside the turbine housing allowing less or more exhaust thru, as well as helping the turbine wheel quickly spool up by staying closed until desired boost is reached.
Blowoff Valve is used to bleed off intake pressure between the compressor side of the turbo or supercharger, and a closed throttle plate (closed throttle between shifts, or sudden letting off of the throttle for sudden deceleration). The closed throttle will not allow the boosted intake charge to be ingested by the engine, so it piles up in the intercooler tubing and intercooler, and once those are full, the boost will run back thru the turbo/supercharger's compressor wheel that could be spinning at upwards of 150,000 rpm or more, potentially stalling it, and causing thrust bearing damage. The cool PSSSSHHHT sound of the blowoff valve that people are hearing has simply been vented to atmoshpere for fun and noise, whereas in OEM applications, the blowoff valve's venting is run back into the airbox or intake plumbing before the turbocharger/supercharger's compressor inlet.
VAriable vane turbochargers like VW's and Porsche's design were first successfully implemented in a production car way back in 1989 by Garrett, Caroll Shelby and Chrysler in the Shelby CSX.........taking the normally aspirated 80 hp 2.2 Dodge 4 cyl, 8 valve, non-cross flow headed K-car engine into the 200hp, and well over 200 ft lbs of torque territory with zero discernible turbo lag. It was an awesome feat back in 89, and that car is still one of my favourites of all time, with it's fibreglass Shelby engineered wheels and Koni full suspension, it was a fantastic little sleeper.
For simplicity's sake, picture the round tunnel doorways on Star Trek type spacecraft that have triangular plates that swirl and converge into the middle to close the door, and swirl out and away from the centre into the walls to open-this is similar to the way the vanes inside the turbine work in this system, constantly changing the volume inside the turbine housing allowing less or more exhaust thru, as well as helping the turbine wheel quickly spool up by staying closed until desired boost is reached.
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My point was about the inherent inefficiency of a centrifugal supercharger being aided by a bypass (in that particular case, a repurposed turbo wastegate) in order to move more air earlier in the revs. I doubt Kawasaki would be using a centrifugal blower anyway, I think a roots-type would be easier to integrate into a small package while providing more low-end and midrange grunt as opposed to a peaky centrifugal unit.
It's centrifugal ... look at the patent drawings ...
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