Dolmar 7900 Photos ???

[Kneejerk Bombas]

If you say it works, that's good enough for me, I never ran one.
It just looks like those cheap fiters on the small homeowner saws I've seen.

 

[Kneejerk Bombas]

Just curious, what's a PP 7900 go for delivered to WI?

 

[Saw Man]

Been wanting to reply with pix that show how the AIR MASTER SYSTEM works, but am still so far behind will do later.

This is the ONLY SELF PURGING Air Filtration System on the market. Quite frankly, it's simply the best.

You must look at DOLMAR's air filtration design as a "SYSTEM".
Just like the Turbo Charged SYSTEM that Jonsereds invented, that Husqvarna borrows from a sister company.
Tearing apart one componet will not give a correct view of how it all works together!

Here's a quick description. Pix will follow.


All edges are 'sealed' so no air 'leaks' into the SYSTEM.

Carb Air Hood: Rounded for increased air flow, and quieter.

Air Intake: Located high on the left rear.
Cleanest spot on a cutter for air induction.

Aysymetrical slots (different size) reduce air intake noise, and help keep from pulling in larger sized particles. Dirtier air.

First Chamber in Hood: Seperate divider panel with 7 angled holes, having rounded/smooth edges placed in the upper corner.
Dirtier air comes in thru slots. Heavier particles-chips fall/stay down, cleaner air flows UP thru the 7 holes into the Second Chamber.

Second Chamber is the Carb "Box": Air is drawn into the carb creating a 'Low Pressure Area' or Chamber as long as the throttle plate is cracked open. The wider it's open the higher the air flow, the lower the pressure becomes to a certain point, just like every other saw.

Here's the AIR MASTER difference:.......PURGE HOLES !!!!

In the bottom of the carb box-second chamber, there are two holes on either side of the carb. On the bottom of the holes are two synthetic rubber flaps that OPEN & ClOSE as the air pressure changes.

Basically their simple Reed Valves. As the throttle plate is opened air is sucked into the engine thru the carb,...reducing air pressure.
That keeps the simple valve flaps (holes) closed.

As the throttle is closed, the air pressure increases, allowing the
valve flaps to Open.
Letting dirt,...chips,......FALL OUT of the carb box.

Not all the dirt falls out right away. As the saw idles, it is still letting dirt fall out thru the two holes.

In effect it is "self cleaning' much more efficient,........
than....ANY....other air filtration system on the saw market

There was a web site that did show the air flow, but was hard to view the purging.
Had it on a CD, but can't quickly find it.
I'll try to find it, and post it. I'll translate into English.

 

[rbtree]

And for that matter, air can't get in either, eh Mike?

Thanks for that info, Saw Man! A PS 7900 PP is definitely in my future!

 

[cuttinscott]

Go to the link below to view a video on the filtration system.

"Air Master" Air Filtration System video link

 

[cuttinscott]

 

[bwalker]

Russ, Waht I am saying is that although husky filters appear cleaner upon inspection in reality they are not. Air injection only removes small particles and not the fine bug dust that clogs filters. Awhile back Walt Galer had a simular comment about air injection and it mostly being a marketing issue.

 

[jokers]

Mike Maas,
I clearly understand the filtering concept that you are describing and in filtering terms it is known as precoat where it is know or expected that a certain percentage of the particulate in the filter stream, whether it be air or water, is of a given size which will coat and closely interlock forming an outer shell "filter" with much smaller openings thus improving the filtering efficiency. The problem is that too much precoat increases the differential pressure (∆p or delta p) which causes a flow restriction. Stihl knows this, that is why they try to compensate for the quick change in ∆p in their non-cyclonic filtering method with the Intellicarb on certain "pro" saws which would be likely to see a higher duty cycle. In common terms too much precoat can also be considered as too much fine particulate in the filter stream. The cyclonic action imparted by systems like Air Injection or Turbo filtration work on particulate of all sizes but the energy imparted is relative to the mass of the particle, ie; large particles having a higher mass also end up with more energy imparted to overcome the orbit breaking vacuum present at the throat of the carb, and are thus ejected in an orbit that bypasses the filter. Air, with it`s lightweight constituent atoms does not have the energy to overcome this low pressure at the throat and is drawn in. The lighter solid particles in the filter stream are subjected to varying amounts of centrifugal force and vacuum based on their mass and shape, this is mostly the stuff that hits the filter. I don`t think that this is what Ben was saying anyway. I think he was stating that both filters end up with similar amounts of bug dust after a given period of run time.

It sounds to me Mike like you haven`t got much, or maybe any, experience using a saw with Jonsered style filtration vs the traditional style found on Stihl for example. Try it sometime because it really will make you think twice about using a saw without it afterward.

Ben,
As much as I like Walt and miss his posting here, I don`t agree with everything he has said. In fact he was proven wrong a couple of times if memory serves me. He`s human just like the rest of us and subject to the same prejudice or misconception that anyone else may be. I will say this, it`s a real shame that he felt that he could not continue to post here after having a flaw in his voluminous knowledge exposed. Noone is 100% right but he is closer than many of us and his vast experience, even when filtered through the eyes of a human, was both enlightening and entertaining. I`m not ashamed to say that I miss Walt.

Russ

 

[glens]

<b>Cuttinscott:</b>&nbsp; This is intended to be a friendly heads-up.&nbsp; That link contains an internal link <i>&lt;Ref href = "C:\Documents and Settings\The Cutting Edge\Desktop\Folders\Dolmar Turbo Type Air Filtration2"/&gt;</i> which would only work for the person who generated the link (unless some other user also happened to have that exact item in that exact pathway/filename on their computer) and if they're using a browser which follows links to non-served items from within a served page (some don't since it's really a security issue).&nbsp; I assume you're the person, so as a test, remove that file from that location on your computer (rename it or stash it somewhere else) and you'll see the nothing we're all seeing.&nbsp; I must disclaim that it's mostly an assumption on my part since I'd not be able to do the first thing with an "ASX" file anyway, but the way these things work I think you'll find I'm on to something. If not, then please accept my sincerest apology for even mentioning it.

<b>Ben:</b>&nbsp; I can see the value in the system so long as all it's parts are working correctly, but there really would have to be a slightly negative pressure (even the minutest amount) at the inlets to the ductwork surrounding the fan.&nbsp; If not, and there actually is a positive pressure in the system, then I'd tend to agree with you.&nbsp; I've used cyclonic separators in different kinds of industrial equipment and the idea is quite workable.

Glen

 

[glens]

I see that Russ had posted a typically good response to which I cannot much add.&nbsp; But I would like to say that if the fan blowing both air and particulates does so <i>into</i> the ductwork (thus pressurizing it) there would be no real benefit obtained.&nbsp; In order for it to work as a filter the air stream would have to travel at least <i>across</i> the inlet, maybe even some away from it, either way creating a draw of some amount.&nbsp;

Picture a couple of examples.&nbsp; Let's use a <b>!</b> and a <b>--&middot;</b> and a <b>?</b> to denote the ductwork, with the dot being the carb throat end.&nbsp; The air stream will be traveling downward.&nbsp; With the <b>!</b>, all manner of junk will be sent into the duct indiscriminately and it will pressurize the duct (as the term "turbo" would usually imply).&nbsp; With the <b>--&middot;</b> and the <b>?</b>, the particles will be moving past (and away from, with the second) the open end of the duct faster than the vacuum generated from the far end can overcome (much like Russ was saying).&nbsp; The result of the airstream moving past the end of the tube like that would in itself, however, create a slight vacuum within the tube thus canceling some (to whatever extent) of that which was being generated at the carb end.&nbsp; The more successful filtration would be derived from the <b>?</b> configuration, but the carb-opposing vacuum created would also be the greatest.

Hope this helps to convey my thoughts.

Glen

 

[jokers]

Hi Glen,

Thanks for what I take as a compliment. It means more coming from you because as you are well aware, I have often maintained that you are a smart guy! LOL.

We could sit here and conjecture back and forth all day about theoretical performance, both being right on certain points, but actual observation of the sysytems tells the true tale, filling in some of the blanks or dispelling incorrect assumptions. The Husky air filtration may be the biggest reason that I favor them over Stihl for the most part.

Russ

 

[glens]

Russ, it wasn't a compliment so much as stating the obvious.&nbsp; And why wouldn't I?&nbsp;

I don't think I intend to be saying there's a performance tradeoff beyond what's reasonable, with the system, just that there must be some even if it's not very significant.&nbsp; Probably along the lines of the heated handles on the sno-pros.

My biggest beef with it (beeves, actually) is that of the deceptive marketroid naming convention(s) used, but most importantly that Andreas' progeny didn't bring it to market first.&nbsp; Hahaha

Probably just like the way you feel about the "Intellicarb".&nbsp; The thing I think is funny is that on my old Homelites, where the entire carb is situated in the filtered-side of the airbox, the diaphragm gets it's pressure from there all the same as with the system you deprecate.

Glen

 

[Jacob J.]

Hey guys- The actual net performance gains from the air injection system alone are minimal. What it comes down is the difference in piston shape and weight, port timing and port shapes, and the whole intake system overall. These differences combined with air injection are what make Huskies and Jonsereds a different animal compared to Stihl.

 

[Kneejerk Bombas]

Russ, that was a wise crack about the air cleaner box being packed full of chips and working better. Sorry you missed that.

My Stihls do actually fill up with chips and need to be blown out, you can usually tell just by how it runs. We have a couple Huskys too and they don't fill up, but they do need to be blown out too. Like Glens says, the little fine stuff gets in there. Probably not as often, but it's hard to tell for sure.

 

[jokers]

Hi Mike, guess you had me there! I thought your remark about filling up the airbox was too comical to be for real but I guess I missed the sublety of the rest of your statement. Glad I didn`t call you any names or anything.

Russ

 

[Saw Man]

Trying to load a DOLMAR AirMaster video from my comphewter to the 'AS' forum.

Keeps telling me it's not formatted.
Any suggestions appreciated.

 

[jsikkema1]

Well my Blue Dolmar came in today...

Just arrived today is my Makita DCS7301... I took some pictures and took the covers off to get a little closer look see.


Attached are some pics

Jeff

 

[jsikkema1]

Left side

you can see the air intake slots on top left of air filter cover

 

[jsikkema1]

air filter

you can see the air filter with the cover removed

 

[jsikkema1]

air fliter size

I was a little surprised how small the air filter is. In addition, they send you a winter filter (silk type media) too bad the saw road all the way here on top of the filter putting two 1/2" long cuts in the media... I hope someone is reading this from Dolmar YOU CANT JUST THROW AN AIRFILTER LOOSE IN THE BOX AND EXPECT IT TO MAKE IT ON ONE PIECE !!!

For comparison I laid a brand new filter for a Husqvarna 356 next to the a/f for the Makita/Dolmar and the Husky has about twice the filter area. Perhaps that the largest filter that would fit in that stylish housing. The Husky filter almost fits in and the throat of the filters are identical.