Compensating Carburetors? What are they? Do they work?

[Atomic Hawg]

Hi. I have pasted some blurbs about models which feature compensating carburetors. I am curious as to what makes them different from regular carburetors. Do they work? Are they a good thing? Does this mean that they tune themselves? Can you enlighten me? Thanks.

This (2159) is Jonsered’s first saw that has a carburetor with built-in fuel compensation. This means that the fuel-air mixture is kept constant, so that the power remains unchanged over time. Together with turbo air cleaning, this keeps the power high while reducing filter wear, emissions and fuel consumption.

IntelliCarb™ Compensating Carburetor measures air on clean side of air filter and adjusts metering diaphragm in carburetor. Keeps RPM levels even when filter begins to clog.

 

[brages]

Rather than being open to the atmosphere, the "other side" of the metering diaphragm is open to the inside of the air filter. I guess the idea is that a clogged air filter will reduce fuel and air equally, keeping the mixture constant. It won't compensate for altitude, clogged fuel filter, gummed up carb passages, though.

I think most Stihls have this.

The MS280 has the IED carburetor - this is a more sophisticated electronically-controlled carb. Still, I think it's not a "closed-loop" system like an emissions-controlled automobiile motor.

 

[Saw Dr.]

Intellicarb works fine, but is of no real value to those who keep their air filters clean. I think this feature is more for the marketing folks. On many Stihls it is just a simple swap of the carb top, and air filter. Some of the air filters are the same, just with a knockout plug in the Intellicarb port if you're not using it on an intellicarb saw.

 

[a. palmer jr.]

I've had a few of these that wouldn't run right, put a regular carburetor on and it runs just fine. Just block the hole in the air filter.

 

[Chris-PA]

All the McCinderblocks had effectively the same thing, as did other McCullochs - the entire carb was mounted in a sealed housing below the air filter, so that's where the diaphragm vent was too. Of course, even cheap lawn mowers have had properly placed bowl vents for decades. Once again marketing makes a big deal over nothing.

What amazes me more is that apparently some of these manufacturers tried to implement it, somehow got it wrong and it didn't work right! (you had one job....)

 

[Duane(Pa)]

Wow! A thread from 09?

 

[Chris-PA]

Doh!

 

[a. palmer jr.]

Nah, I started it back up again when I got another Stihl that did what my last one did. I don't know whether to try to fix this thing or convert it over to the non-compensating carb like I did my last one. For the life of me I can't see the difference but I guess there's something that I'm missing. I wonder if I could just get a top plate from another carb and stick it on it and block the filter hole off? Oh, by the way, mine is a 390 and the last one was a 290, both had new p/c kits in them. Maybe I should give it some break-in time before I start making changes...

 

[Rx7man]

Chris, the old homelites had the same idea.. bonus was the whole carb was kept clean.. downside was they were sometimes a misery to get out, and the bigger an area you need to seal off, the more chances of dirt leaking in

 

[HuskStihl]

"Intellicarb" is a pure marketing gimmick, and when you read the propaganda, you'd think the saw had EFI. Makes it hard for me to believe their advertising claims about what M-tronic does. (Which is unnecessary, BTW, as m-tronic works very nicely)

 

[a. palmer jr.]

I was also wondering why the big scoop on top of the carburetor when the regular carburetors just have a small hole in the top cover? I know they're not pushing that much air through that thing..

 

[C George]

"Intellicarb" is a pure marketing gimmick, and when you read the propaganda, you'd think the saw had EFI. Makes it hard for me to believe their advertising claims about what M-tronic does. (Which is unnecessary, BTW, as m-tronic works very nicely)

The ones ive worked on always run better with the compensating system eliminated

 

[C George]

I was also wondering why the big scoop on top of the carburetor when the regular carburetors just have a small hole in the top cover? I know they're not pushing that much air through that thing..

plug that top snorkel with rtv silicone and drill a horizontal hole below it in the top cover assembly so fuel diaphram can move

 

[bwalker]

"Intellicarb" is a pure marketing gimmick, and when you read the propaganda, you'd think the saw had EFI. Makes it hard for me to believe their advertising claims about what M-tronic does. (Which is unnecessary, BTW, as m-tronic works very nicely)

Intellicarb worked ok for the purpose it was designed. IE to compensate for plugged air filters. Stihl didn't have an air injection until decades after Husky so it was sort of a band aid.
Mtronic is a whole different deal and is a great system.

 

[bwalker]

The ones ive worked on always run better with the compensating system eliminated

I've not noticed this at all with the MS260.

 

[C George]

I've not noticed this at all with the MS260.

I cant say Ive done an MS260 ,, those very rarely come back into the shop

 

[C George]

Intellicarb worked ok for the purpose it was designed. IE to compensate for plugged air filters. Stihl didn't have an air injection until decades after Husky so it was sort of a band aid.
Mtronic is a whole different deal and is a great system.

Guess Im old school and would rather keep a couple spare air filters

 

[bwalker]

Guess Im old school and would rather keep a couple spare air filters

The problem is with certain models like the 360 and 260 the filters plug up really fast. Especially if your cutting something like standing dead red oak.
And we all know that many people never clean their filters or adjust their carbs.

 

[C George]

The problem is with certain models like the 360 and 260 the filters plug up really fast. Especially if your cutting something like standing dead red oak.
And we all know that many people never clean their filters or adjust their carbs.

Im open to that statement , many just dont know what proper maintenance is