Fantastic! Thanks. What is the size of that t fitting?
Using the PAIR valves as a crankcase evacuation system
Lots of questions came up after a post I made about plumbing the PAIR valves into the crankscase vent to evacuate and create a vacuum internal to the engine.
Why do some thing like this? Well, on a 90 degree V twin as the crank spins, the internal volume of the engine changes significantly. The engine is also pumping air under the pistons back and forth to each other, and in and out of the engine. There are also basic aerodynamic principal at work too. The crank and rods and tranny are all spinning around in the engine pushing air around with it. This is drag added to the engine which takes power.
Conventional crank I4s do not change crank case volume during an engine revolution, but they still pump the air from under the piston back and forth and cause internal losses. We used to actually make cut outs between cylinders when we using ZX11 engines long ago for the F1 sidecars. It made a difference. This is why also many manufactures are cutting out the cylinder sleeves between adjacent cylinder, they want to get rid of internal pumping losses. I included a picture of a set of OEM GENII Hayabusa cylinders to show what I am talking about.
Next thing to talk about is the PAIR valves. How do they work? Well simply put, Bernoulli's priciple of high velocity air creates a low pressure region. The PAIR valves do exactly this. As the high speed exhaust gas goes by the hole in the exhaust port it creates low pressure that gets channeled through the reed valves in the head and up to PAIR valve control solenoid. When the solenoid opens, it draws cool air form the air box and mixes it with the out going exhaust to burn unspent hydro carbons on the way out of the exhaust.
So why not use the vac created by the PAIR ports to pump out the crank cases to take advantage of the benefits described above. Here is how I have been doing it on the SV1000. Quick and easy. Pull the air box out and pull the PAIR control solenoid out, but leave the hoses that go to the front and rear cylinders. Bridge the electrical on the harness side of the bike that was plugged into the solenoid with a 1Kohm 1/2 watt resistor. I take the old plug, and use a couple of connector s and such and make a nice little plug unit to keep the FI light from coming on. Now scrounge up a T fitting such as the one shown in the image below. Now connect the upper part of the crank case vent hose you disconnected to remove the air box, to the T fitting. Now just plug in the front and rear PAIR hoses into the T. Remember to plug the port in the airbox when it goes back together. The bike will now pump on the crankcases as soon as the bike starts. As the exhaust gas speed goes up, the lower pressure seen in the crankcases.
I would pull out the reed valves under the plastic PAIR caps bolted to the valve covers, and clean them very well and make sure they are sealing well. A poorly sealing valve will not allow the bike to hold best possible vacuum.
I have set up many SV1000 and a whole bunch others. In my experience with the SV1000 oil consumption will not be an issue because the vents are well baffled, and if it were pumping oil through the vent, it would have originally been pushing it into the air box to get consumed anyway.
I do not have any direct dyno data for the SV1000, but I can assure you it will help. Lots of info out there on SV650s, Ducatis and tons of other race engines and vehicles. All of our race bikes I set up have been pumping on the crankcases for many years.
I did collect some data a couple of times to see what the pressure level was actually getting to in the crank cases, but I am not sure if I can find it any more.
You also have to remember to pull the oil fill cap before draining out our oil, or it just wont drain, because the cases are not vented due to the reeds being closed.
-MS
Why do some thing like this? Well, on a 90 degree V twin as the crank spins, the internal volume of the engine changes significantly. The engine is also pumping air under the pistons back and forth to each other, and in and out of the engine. There are also basic aerodynamic principal at work too. The crank and rods and tranny are all spinning around in the engine pushing air around with it. This is drag added to the engine which takes power.
Conventional crank I4s do not change crank case volume during an engine revolution, but they still pump the air from under the piston back and forth and cause internal losses. We used to actually make cut outs between cylinders when we using ZX11 engines long ago for the F1 sidecars. It made a difference. This is why also many manufactures are cutting out the cylinder sleeves between adjacent cylinder, they want to get rid of internal pumping losses. I included a picture of a set of OEM GENII Hayabusa cylinders to show what I am talking about.
Next thing to talk about is the PAIR valves. How do they work? Well simply put, Bernoulli's priciple of high velocity air creates a low pressure region. The PAIR valves do exactly this. As the high speed exhaust gas goes by the hole in the exhaust port it creates low pressure that gets channeled through the reed valves in the head and up to PAIR valve control solenoid. When the solenoid opens, it draws cool air form the air box and mixes it with the out going exhaust to burn unspent hydro carbons on the way out of the exhaust.
So why not use the vac created by the PAIR ports to pump out the crank cases to take advantage of the benefits described above. Here is how I have been doing it on the SV1000. Quick and easy. Pull the air box out and pull the PAIR control solenoid out, but leave the hoses that go to the front and rear cylinders. Bridge the electrical on the harness side of the bike that was plugged into the solenoid with a 1Kohm 1/2 watt resistor. I take the old plug, and use a couple of connector s and such and make a nice little plug unit to keep the FI light from coming on. Now scrounge up a T fitting such as the one shown in the image below. Now connect the upper part of the crank case vent hose you disconnected to remove the air box, to the T fitting. Now just plug in the front and rear PAIR hoses into the T. Remember to plug the port in the airbox when it goes back together. The bike will now pump on the crankcases as soon as the bike starts. As the exhaust gas speed goes up, the lower pressure seen in the crankcases.
I would pull out the reed valves under the plastic PAIR caps bolted to the valve covers, and clean them very well and make sure they are sealing well. A poorly sealing valve will not allow the bike to hold best possible vacuum.
I have set up many SV1000 and a whole bunch others. In my experience with the SV1000 oil consumption will not be an issue because the vents are well baffled, and if it were pumping oil through the vent, it would have originally been pushing it into the air box to get consumed anyway.
I do not have any direct dyno data for the SV1000, but I can assure you it will help. Lots of info out there on SV650s, Ducatis and tons of other race engines and vehicles. All of our race bikes I set up have been pumping on the crankcases for many years.
I did collect some data a couple of times to see what the pressure level was actually getting to in the crank cases, but I am not sure if I can find it any more.
You also have to remember to pull the oil fill cap before draining out our oil, or it just wont drain, because the cases are not vented due to the reeds being closed.
-MS
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The reed valves will open when the pistons are traveling downward and reducing the crankcase volume which will push air into the exhaust ports. Then when the pistons rise the next time the reeds will close and the expanding crankcase volume is what creates the negative pressure within. I've not given much thought to exactly when the exhaust pressures will go negative in the cycle as to where the pistons will be when this happens. The crankcase will experience negative pressures just from having the reed valves controlling the breathing thought the negative exhaust pressures could very well enhance the effect. Mine does the same thing with a one-way valve on the breather hose to the airbox...and it does make a difference in how the engine runs. The Ducati fellows were able to measure a several horsepower increase when they opened up the breathers on one of their race bikes...so it wouldn't surprise me if the SV gets a couple more too.
Thanks
Not too keen on cutting down the hose as some may wish to be able to put it back as it was. I will try to locate some rubber hose and larger blanks to blank the hole as this one is bigger than the pair outlet and what I have won't fit.
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