Not sure if that is a blow off valve to help with drivability, or a waste gate mechanism for controlling boost. My guess is it is a BOV, as Kawasaki probably engineered the boost limits in with the supercharger drive.
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The blow off valve is controlled by the ecu. They could easily stop the positive pressure going to the bov, that would allow the valve to open and bleed off as much boost as they want.
I love that the BOV vents to the air cleaner so that I can reroute it to vent into the atmosphere. In fact, I may 3D print a little BOV horn to make sure it can still be heard over the exhaust. I think that might be my first mod while I'm waiting for my exhaust system to come back from the fabricator...
They didn't.Kawasaki probably engineered the boost limits in with the supercharger drive.
The only thing they could have done was put different sized sprockets on the bike the H2 has a 22T drive sprocket and a 25T drive sprocket which is a 0.88 ratio. which is a reduction in final speed.They didn't.
I had read that since this a centrifugal sc and is directly linked to engine speed and not say exhaust which is controlled more by hitting the gas well the h2 sc will continue making boost even with a closed throttle and this isn't good so Kawi put that wastegate to vent boost during non throttle times.
Thats exactly why they have to run a BOV/Wastegate (they do the same thing btw)
A normal blow off valve has a spring that keeps the valve closed just enough. The vacuum line that runs to the top of it, when under boost will add psi to the spring side of the bov, that is what keeps the valve closed. As soon as the spring side sees vacuum it will allow the valve to open from the pressure on the plenum side of the bov and the pressure is relieved.
All kawasaki would have to do is close that valve off when they want to and that valve will open right up if there is any pressure inside the plenum.
You could actually just bypass that valve but the problem will lie in how much boost your going to get. With the supercharger able to possibly make 35psi you can get in trouble in a heartbeat. but you could also just run a aftermarket boost controller.
But then there will be the problem of loosing other features like maybe launch control traction control etc.
Guhl will have a flash sooner than we know it and I'm sure he can adjust the boost levels with that and everyone will be happy.
If you want to run crazy boost just add a nice thick head gasket to the mix and you can probably be pretty safe.... possibly lol
A normal blow off valve has a spring that keeps the valve closed just enough. The vacuum line that runs to the top of it, when under boost will add psi to the spring side of the bov, that is what keeps the valve closed. As soon as the spring side sees vacuum it will allow the valve to open from the pressure on the plenum side of the bov and the pressure is relieved.
All kawasaki would have to do is close that valve off when they want to and that valve will open right up if there is any pressure inside the plenum.
You could actually just bypass that valve but the problem will lie in how much boost your going to get. With the supercharger able to possibly make 35psi you can get in trouble in a heartbeat. but you could also just run a aftermarket boost controller.
But then there will be the problem of loosing other features like maybe launch control traction control etc.
Guhl will have a flash sooner than we know it and I'm sure he can adjust the boost levels with that and everyone will be happy.
If you want to run crazy boost just add a nice thick head gasket to the mix and you can probably be pretty safe.... possibly lol
Thats exactly why they have to run a BOV/Wastegate (they do the same thing btw)
This is sorta right as both release boost. The BOV is to release boost when the throttle is closed and the vacuum in the intake release excess boost. This is to prevent blower damage. A BOV does not control the boost from the standpoint of trying to lower boost from 12 to 10 pounds. A waste gate is designed to release boost at a certain boost level. This might be as low as four or six pounds boost on a lightly built motor, to 30+ pounds on a specially tuned motor. The waste gate is usually adjusted by a spring inside the actuator, or by using some sort of boost control device that is linked between the turbo and the actuator. Most cars with factory superchargers have their boost limited by the drive sprockets on the supercharger drive and I am assuming from what we have seen that the Kawasaki will be similar. Unless you have a way to change that drive ratio, you cannot adjust the boost as the supercharger is putting out max boost already. As you modify the motor more and move more air through it you will find that your boost drops with the added efficiency. I just had the heads redone on my turbo Honda and the boost dropped two pounds when it was started up, this required stronger springs in the actuator to raise the boost levels back up.
This is sorta right as both release boost. The BOV is to release boost when the throttle is closed and the vacuum in the intake release excess boost. This is to prevent blower damage. A BOV does not control the boost from the standpoint of trying to lower boost from 12 to 10 pounds. A waste gate is designed to release boost at a certain boost level. This might be as low as four or six pounds boost on a lightly built motor, to 30+ pounds on a specially tuned motor. The waste gate is usually adjusted by a spring inside the actuator, or by using some sort of boost control device that is linked between the turbo and the actuator. Most cars with factory superchargers have their boost limited by the drive sprockets on the supercharger drive and I am assuming from what we have seen that the Kawasaki will be similar. Unless you have a way to change that drive ratio, you cannot adjust the boost as the supercharger is putting out max boost already. As you modify the motor more and move more air through it you will find that your boost drops with the added efficiency. I just had the heads redone on my turbo Honda and the boost dropped two pounds when it was started up, this required stronger springs in the actuator to raise the boost levels back up.
Originally Posted by edinlr View Post Kawasaki probably engineered the boost limits in with the supercharger drive.
They didn't.
I have read something about possibly a two speed drive to the supercharger, but in any case, the boost will be "fixed" by whatever gearing ratio Kawasaki engineered on the drive between the engine and the supercharger. I think we have heard something around an 8:1 ratio so when the engine is turning 10,000 rpm the supercharger will be spinning 80,000 rpm. This is a fixed ratio and the only way to change this is by altering the drive gears, sprockets, etc. that go to the supercharger.
They didn't.
I have read something about possibly a two speed drive to the supercharger, but in any case, the boost will be "fixed" by whatever gearing ratio Kawasaki engineered on the drive between the engine and the supercharger. I think we have heard something around an 8:1 ratio so when the engine is turning 10,000 rpm the supercharger will be spinning 80,000 rpm. This is a fixed ratio and the only way to change this is by altering the drive gears, sprockets, etc. that go to the supercharger.
The two-speed drive to the supercharger was in the patent documents, but not in the production vehicle.
The bypass valve is for bypassing a small portion of the airflow under shut-throttle conditions so that the compressor is not operating near dead-headed in an operating region that is called "surge" (too much pressure ratio and not enough flow). "Surge" to a turbocompressor is akin to "stall" in an aircraft - too much load with not enough speed, leading to abnormal airflow conditions. The bypass valve is not meant for boost pressure regulation under load. The flow rate through the bypass valve has to be just enough so that the compressor blades are not stalled.
The old skool mechanical blow-off valves worked using intake manifold vacuum to detect shut-throttle, this one uses a solenoid valve under ECU control.
A properly designed mechanically driven turbo compressor does not need overspeed or overpressure protection ... that is simply set by its mechanical drive ratio and the compressor's flow-versus-pressure characteristics (the "compressor map"). It has no need for anything like the wastegate or variable-vane mechanism that a turbocharger has.
The bypass valve is for bypassing a small portion of the airflow under shut-throttle conditions so that the compressor is not operating near dead-headed in an operating region that is called "surge" (too much pressure ratio and not enough flow). "Surge" to a turbocompressor is akin to "stall" in an aircraft - too much load with not enough speed, leading to abnormal airflow conditions. The bypass valve is not meant for boost pressure regulation under load. The flow rate through the bypass valve has to be just enough so that the compressor blades are not stalled.
The old skool mechanical blow-off valves worked using intake manifold vacuum to detect shut-throttle, this one uses a solenoid valve under ECU control.
A properly designed mechanically driven turbo compressor does not need overspeed or overpressure protection ... that is simply set by its mechanical drive ratio and the compressor's flow-versus-pressure characteristics (the "compressor map"). It has no need for anything like the wastegate or variable-vane mechanism that a turbocharger has.
It is possible to deduce the operation of this system from the hose routing in the schematic and the way the bypass valve looks.
The solenoid valve is connected to a pressure source (airbox) and a vacuum source (throttle body). It selects either the pressure source or the vacuum source to apply to the bypass valve control port. Note that if the throttles are nearly open, there will be no vacuum source (there is boost throughout the throttle bodies anyhow), and the state of the solenoid valve won't matter. If the throttles are shut then the solenoid valve can apply either airbox pressure or vacuum to the bypass valve.
If the hose leading to the bypass valve has boost pressure applied to its diaphragm, that forces the valve shut, and the boost pressure inside the airbox won't open it. If the hose leading to the bypass valve has vacuum applied to its diaphragm, that pulls the valve open.
The solenoid valve is connected to a pressure source (airbox) and a vacuum source (throttle body). It selects either the pressure source or the vacuum source to apply to the bypass valve control port. Note that if the throttles are nearly open, there will be no vacuum source (there is boost throughout the throttle bodies anyhow), and the state of the solenoid valve won't matter. If the throttles are shut then the solenoid valve can apply either airbox pressure or vacuum to the bypass valve.
If the hose leading to the bypass valve has boost pressure applied to its diaphragm, that forces the valve shut, and the boost pressure inside the airbox won't open it. If the hose leading to the bypass valve has vacuum applied to its diaphragm, that pulls the valve open.
I have read something about possibly a two speed drive to the supercharger, but in any case, the boost will be "fixed" by whatever gearing ratio Kawasaki engineered on the drive between the engine and the supercharger. I think we have heard something around an 8:1 ratio so when the engine is turning 10,000 rpm the supercharger will be spinning 80,000 rpm. This is a fixed ratio and the only way to change this is by altering the drive gears, sprockets, etc. that go to the supercharger.[/QUOTE]
Yeah it is nuts. Think it spins at 9.2 times engine rpm, tops out at some 130000 rpms!!
Yeah it is nuts. Think it spins at 9.2 times engine rpm, tops out at some 130000 rpms!!
Worse. Mechanical engineer who works with the automotive industry.Nerds.
>
I'm not in powertrain engineering myself, but I have a friend who is ...
Sounds like we have enough brainpower here to reverse engineer what Kawasaki did to slow the H2. Hopefully someone like Kevin Cameron will do a more in-depth story where they explain the restrictions on the H2 among other things. Both bikes rev to 14,000, so the camshaft and head gaskets shouldn't make that much difference. If the H2R has more lift, you have to wonder how much thinner the head gasket might be. Head gaskets are usually around .050" thick, so I can't imagine them going a whole lot thinner on the R. I suppose the cams could have more duration and lift, but 100 hp worth? The earlier discussions about the ECU and some boost controls sound more likely. Changes to fueling, timing, boost, or the BOV seem like they will have more impact on performance. I know people are not too fond of the looks of the Akra exhaust, but that will probably help the H2 some also.
The no-brainer way to do it is to simply map the requested throttle position such that the (drive-by-wire) throttles don't open all the way at higher revs, even though the rider is requesting it.
The "slow" 2009 - 2014 Yamaha R1 was slow because that's exactly what Yamaha did. The restriction in the 2011-on North-American-spec ZX10R wasn't as obnoxious, but it was done similarly.
The internal details of ECU programming is not something I know about, but I'm sure someone will figure it out!
I'm afraid that changing the exhaust system is unlikely to make an appreciable difference in power, although weight is quite another matter ...
The "slow" 2009 - 2014 Yamaha R1 was slow because that's exactly what Yamaha did. The restriction in the 2011-on North-American-spec ZX10R wasn't as obnoxious, but it was done similarly.
The internal details of ECU programming is not something I know about, but I'm sure someone will figure it out!
I'm afraid that changing the exhaust system is unlikely to make an appreciable difference in power, although weight is quite another matter ...
Supercharger uses planetary gears, spins at up to 130,000rpm and develops up to
20.5psi boost pressure
Quote:
The impeller’s pumping capacity is more than 200 liters/second (measured at
atmospheric pressure), with intake air reaching speeds of up to 100m/s. After passing
through the supercharger, air pressure is increased to as much as 2.4x atmospheric
pressure (35psi).
Quote:
The rigid structure helps to ensure an airtight seal for the pressurized air at
approximately 2-bar (29.4psi)
That is the writing that are in BOTH H2 and H2R press release document found on the kawasaki web site. So both bike produce the same boost
20.5psi boost pressure
Quote:
The impeller’s pumping capacity is more than 200 liters/second (measured at
atmospheric pressure), with intake air reaching speeds of up to 100m/s. After passing
through the supercharger, air pressure is increased to as much as 2.4x atmospheric
pressure (35psi).
Quote:
The rigid structure helps to ensure an airtight seal for the pressurized air at
approximately 2-bar (29.4psi)
That is the writing that are in BOTH H2 and H2R press release document found on the kawasaki web site. So both bike produce the same boost
It is interesting when you read Kawasaki's website regarding the R. They suggest an inspection after 8 hours at over 8,000 rpm and a bottom end job after 15 hours. Who are you going to trust for this work, the lawnmower guy at your local dealer????? This should be an easy $2000 to $3000 bill. I am still curious why the R needs much more maintenance than the H2? The exhaust and clutch don't cause this wear? The ECU and cam timing must have pretty aggressive specs to require this kind of attention. Can't wait to unravel all of these mysteries.
True yes, but I'm willing to bet the street H2 would require the same look over after substantial amount of time spent under high stress application.It is interesting when you read Kawasaki's website regarding the R. They suggest an inspection after 8 hours at over 8,000 rpm and a bottom end job after 15 hours. Who are you going to trust for this work, the lawnmower guy at your local dealer????? This should be an easy $2000 to $3000 bill. I am still curious why the R needs much more maintenance than the H2? The exhaust and clutch don't cause this wear? The ECU and cam timing must have pretty aggressive specs to require this kind of attention. Can't wait to unravel all of these mysteries.
They're likely covering their ass on the R expecting it to under go a thorough ass kicking (or administer one, either way...)
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