Dolmar 4 stroke saw in the makes?

[Cut4fun]

http://www.all4engineers.com/downlo...ir=mtzww/key=f7ab895d23a829cf16027361edd52b4d

 

[TonyM]

I'm glad to see Dolmar making some big investments. I knew there was a reason I jumped on the Dolmar bandwagon!

 

[Marco]

Sounds interesting, has anybody found any schematics or pictures of this thing?

 

[166]

Here is what the Dolmar PS-500V looks like!
They have been in prototype stages for about 5 years

 

[Dolmar_Tech_Mgr]

We had a running demonstation model at the Lousiville show running in the outside booth. Many came by and gave it a test.

 

[RES]

With the Dolmar design you still mix the oil in the gas. Is that correct? What is the advantage of a 4-stroke?

 

[Dolmar_Tech_Mgr]

You are correct that the saw uses a mixed fuel. The advantage to this is you can run the tool in multiple positions and it reduces the weight. If you did not mix the fuel you would have to have three tanks - one for fuel, one for bar oil and one for motor oil. This would make the tool useless in the woods with the added weight. The four stroke tool reduces the emissions from a normal two stroke.

 

[BlueRidgeMark]

The four stroke tool reduces the emissions from a normal two stroke.

Which just about guarantees that this is the future, whether it's good OR bad.

 

[Dolmar_Tech_Mgr]

Not 100% the future as there are constant developments for 2-cycle that Keep Hope Alive!

 

[JeffHK454]

Dolmar Tech , are there any preliminary weight or HP estimates ?


Some of my other loves are 2 stroke atvs and motocross bikes , two things that where killed by the government force feeding us 4 strokes.

I know that it's the future but.......... :taped:

Jeff

 

[Dolmar_Tech_Mgr]

No weights yet as all we have are hand made prototypes. It will be a 50cc saw and i think i heard 2.2kW but not totally sure of both numbers.

 

[rmihalek]

Isn't the crankcase the "tank" for the motor oil, or are you refering to a "third tank" as separate compartment from the crankcase?

 

[aokpops]

if they kept this up I,am going to put a two stroke on a harley . lets kept engines were they belong . I don,t need to see a another mottocross where it sounds like a long fart

 

[Dolmar_Tech_Mgr]

The question was what about using a two stroke mix oil instead of straight gas. The new Dolmar saw PS-500 V will be a four stroke and run on 50:1 gas to oil mixture. If it did not run on this mix fuel you would then have to have a Gas Tank, a Bar Oil Tank and a Motor Oil Tank making this bulky and heavy. The Dolmar four stroke sting trimmer MS-2514 and four stroke hand held blower PB-250.4 Use a four stroke engine that uses straight gas. This is benefical because you dont use bar oil for a string trimmer as does a chain saw.

The EPA and and California regulations are getting harder and harder to meet with scavenging two stroke technology. But changes and new models are getting cleaner.

 

[Marco]

I think you need a dry sump setup to run an all position 4 stroke, requiring an extra tank. I can't picture a puddle of oil on the piston if you ran the thing upside down.

 

[canguy21]

I think you need a dry sump setup to run an all position 4 stroke, requiring an extra tank. I can't picture a puddle of oil on the piston if you ran the thing upside down.

The fuel/oil mix goes through the crankcase same as a 2 stroke. The difference is that valves, not the piston, control the intake and exhaust. The advantage is that the intake and exhaust are tightly sealed and timed allowing for a more complete burn, hence fewer emissions. I have run Stihl's 4-MIX and Shindaiwa's C-4 and the torque and throttle response are outstanding. I really want to try a saw with this technology

 

[Fordblue_oval]

Soooooo.....It's a 4 stroke 2 stroke!!!

Neat idea...How does the intake charge meet up with the valve after passing through the crankcase??? Internal port??

I have a cheapy 4 stroke Troy-bilt(yea right...) string trimmer that has a sump on the engine..holds about 6oz. if I remember right. Little sucker runs extremely well as I was skeptical at first. Not sure if multiangle operation is advised though.

 

[sedanman]

THe cranckcase on a hybrid 2-4 cycle engine is sealed. There is a hole in the top of the intake port. When the piston moves up, there is a vacuum created in the crankcase whick draws air/fuel/oil into the cranckcase. As the piston is moving down, there is a vacuum created in the cylinder nad some positive pressure in the crankcase, this forces the mixture back through the hole in the top of the intake posrt where it cam be metered by the intake valve.

 

[Fordblue_oval]

Correct me if I'm wrong.....this is cornfusing

What happens to the intake charge that is drawn into the crankcase when the piston is in it's compression/power stroke?? Technically you would only need a charge drawn in when the piston is expelling exhaust and and drawing in the next air/fuel charge.

Dave

 

[sedanman]

Imagine taking a regular OHV 4 cycle engine and sealing off all of the crankcase vents. Drill a large hole in the top of the intake runner, under the valve cover. Since the crank is now sealed, pressure and vacuum in the crankcase act on the intake charge. When the piston moves up a vacuum is drawn on the crankcase and air/fuel/oil rush in to fill the void. When the piston moves down positive pressure moves the charge out of the crankcase back through the hole on the intake runner for the engine to use. Just as in a regular 4 stroke engine the valve cover and crankcase are vented to each other, just not to the atmosphere in the case of a pre-mix 4 cycle.