Its a single throat carb that feeds both the stratos and the charge ports, not your usual set up but does create an exception.What about it?
Its a single throat carb that feeds both the stratos and the charge ports, not your usual set up but does create an exception.What about it?
They use 2 stroke mix for their strato function, not fresh air.What about it?
If your feeding the "stratos" with fuel/air mix it would seem to me its not a strato. I haven't seen an 881 so I can't say for certain. Maybe someone who has can chime in.Its a single throat carb that feeds both the stratos and the charge ports, not your usual set up but does create an exception.
I just looked at some pics of the 881 intake tract and carb. It appears to me that what Stihl did was use the fact that fuel leaving the carb nozzle will tend to hang on the bottom side of the carb. The intake boot is split so the fuel rich side at the bottom goes into the crank case and the fuel lean top side goes to the strato ports.If your feeding the "stratos" with fuel/air mix it would seem to me its not a strato. I haven't seen an 881 so I can't say for certain. Maybe someone who has can chime in.
Here is what Stihl says about the 2-Mix engine.They use 2 stroke mix for their strato function, not fresh air.
On my makita 6000, that is how it works. Strato charge is pulled in through the top of the transfers and stacks on top of the fuel/air charge. So that way it goes into the cylinder first when the ports open. The rest of the charge has to carry enough fuel for air only charge.That's not how a strato charged engine works. The fresh air side is only used to push exhaust out.
The carb settings are larger because the signal is to the carb is diluted.
Thank of it from a differential pressure standpoint and then what stratified charge actually means. You will get what I'm saying.On my makita 6000, that is how it works. Strato charge is pulled in through the top of the transfers and stacks on top of the fuel/air charge. So that way it goes into the cylinder first when the ports open. The rest of the charge has to carry enough fuel for air only charge.
That doesn’t change how it works, on the strato saw I have the strato port runs from the air cleaner to the intake port. It has a throttle blade and a reed valve. The throttle blade is so it doesn’t work at all throttle openings. during the intake stroke fresh air is pulled into the transfers while air/fuel is pulled into the bottom end. The regular intake port closes earlier and the strato port being reed valved continues to flow loading the transfers with fresh air. Then as case compression starts the charge is compressed as normal. Then when transfers open the fresh air which is in the transfers goes into the cylinder first, then it’s followed by the air/fuel. Since the first charge forcing the exhaust out is fresh air, less unburned fuel will end up in the muffler. Once the exhaust closes it’s all mixed up and burned as normal.Thank of it from a differential pressure standpoint and then what stratified charge actually means. You will get what I'm saying.
Fresh air via stratos purges the cylinder of exhaust, transfers open and fuel air mix purges the cylinder of fresh air. Spark plug fires, repeat.That doesn’t change how it works, on the strato saw I have the strato port runs from the air cleaner to the intake port. It has a throttle blade and a reed valve. The throttle blade is so it doesn’t work at all throttle openings. during the intake stroke fresh air is pulled into the transfers while air/fuel is pulled into the bottom end. The regular intake port closes earlier and the strato port being reed valved continues to flow loading the transfers with fresh air. Then as case compression starts the charge is compressed as normal. Then when transfers open the fresh air which is in the transfers goes into the cylinder first, then it’s followed by the air/fuel. Since the first charge forcing the exhaust out is fresh air, less unburned fuel will end up in the muffler. Once the exhaust closes it’s all mixed up and burned as normal.
I expect you could make the saw run quite well by taking advantage of the strato port and its reed valve. Extra fuel can be added as needed to match the extra fresh air. No need to get crazy on the piston port intake and suffer the issues with long intake timing.
now I have not researched how other saws achieve strato ports, but the makita design seems to work quite well.
How do the strato purge the cylinder when the transfers are closed? the strato port only goes to the transfers and there are no ports in the piston. When the transfers open, the cylinder pressure has dropped due to the exhaust being open, then the compressed air and air/fuel go from case to the cylinder. Flows from high pressure to low. Other designs might be different, but that’s how my 6100 works. Simple design imho.Fresh air via stratos purges the cylinder of exhaust, transfers open and fuel air mix purges the cylinder of fresh air. Spark plug fires, repeat.
They don't start purging until the transfer open if the motor you are speaking of doesn't have dedicated strato ducts into the cylinder. That doesn't change what's going on. That is a cushion of air separates the fresh charge from the exhaust port until most of the fresh air cushion is expelled into the exhaust port and the port closes. This layering of exhaust, fresh air and fuel/air charge is why the design is called stratified charge.How do the strato purge the cylinder when the transfers are closed? the strato port only goes to the transfers and there are no ports in the piston. When the transfers open, the cylinder pressure has dropped due to the exhaust being open, then the compressed air and air/fuel go from case to the cylinder. Flows from high pressure to low. Other designs might be different, but that’s how my 6100 works. Simple design imho.
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