Stihl MS500i

[RI Chevy]

Hopefully they have developed better rubber that is impervious to Ethanol.

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[Adamski]

The best saws are all over 15 years old anyway

I hope so... Else I have been buying the wrong saws lately..

 

[MarcS]

I'm cautiously optimistic and the only Stihl I've got is an 041.

Does anyone have experience with the cutoff saw to say if it revs as high as a carbed version? Does the case injection change the torque curve at all?

Not apples to apples obviously but when diesels went to electronic controls where they could alter the timing and duration of the injection event the horsepower more or less stayed the same but the torque curve got a lot broader and torque went up by 30-40%.

 

[Deets066]

I'm cautiously optimistic and the only Stihl I've got is an 041.

Does anyone have experience with the cutoff saw to say if it revs as high as a carbed version? Does the case injection change the torque curve at all?

Not apples to apples obviously but when diesels went to electronic controls where they could alter the timing and duration of the injection event the horsepower more or less stayed the same but the torque curve got a lot broader and torque went up by 30-40%.

All cutoff saws are rev limited at a low rpm because of the wheels/blades they use.

 

[MarcS]

All cutoff saws are rev limited at a low rpm because of the wheels/blades they use.

Gotcha, I wonder if there is a noticeable difference in torque though between the injected and carb version of cutoff saws. Maybe they are so rev limited it wouldn't be possible to tell though.

 

[RI Chevy]

You need a saw that is a little more current. Like a Stihl 026, 036, 046, 066. Then have it ported. Then you can gauge the power a bit better. [emoji106]

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[paragonbuilder]

I think it should. After hearing stories of A/T and M tronic correcting air leaks it should be able to feed some mods. I still want to know where the fuel pump will be and what the tiny high pressure lines will look like.

It could be an electric pump, the Saw needs a generator for the controls anyhow, and it wouldn't need super high pressure.

 

[RI Chevy]

I am still for the KISS principle. Nothing wrong with the good ported carbed saws we all have now.


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[astnmacgto]

Being part of the generation that can make crazy, usable, reliable power with ls engines versus the original sbc makes me say bring on the new technology

 

[MarcS]

You need a saw that is a little more current. Like a Stihl 026, 036, 046, 066. Then have it ported. Then you can gauge the power a bit better. [emoji106]

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Lol, the 041 is from an old friend that I won't ever give up. I run newer ported stuff mainly...2153, 2260, 2171. With that said a properly tuned 041 is a very smooth torque monster and fun to run. Hey, here's a thought...maybe this new system will give us the torque back of the old 041, 045, 056 etc just with a bunch less weight and higher revs?

 

[blsnelling]

I'm confused with this talk about MTronic being slow to respond to changes. My experience is that a ported saw corrects immediately for the changes. What am I missing?

 

[blsnelling]

I've only recently acquired autotune saws so never paid much attention to how it works to adjust with such limited info as it must get. Seems it doesn't change in real time though, takes a bit to learn new conditions.

It operates solely by monitoring RPMs. It monitors how small adjustments, several times per second, affects RPMs, and adjusts accordingly. It happens immediately.

 

[wcorey]

It operates solely by monitoring RPMs. It monitors how small adjustments, several times per second, affects RPMs, and adjusts accordingly. It happens immediately.

Wow, I can't imagine how they pull that off with just RPMs, I'd think it would at least need throttle position info.
I had even figured it to somehow use the metering diaphragm position as a crude sort of mass air flow sensor.

So it must only adjust the jet size to RPM and then of course the varying vacuum at different throttle openings/RPMs inherently pulls in x amount of fuel like any carb.

But then how does it differenentiate between increased throttle opening and an air leak if it has no idea where the throttle plate is? RPM goes up in either case...
Seems too good/simple to be true but I guess...

What took so long for them to figure this out? Coulda' pulled off that technology back in the 70's...

As far adjusting to changes, supposedly the new AT on the 572xp has a much faster response time and they sort of emphasize that as a significant feature.
So I assumed the old system had some sort of limitations in that regard.
Marketing...

 

[blsnelling]

My experience and comments are based on how Stihl MTronic works.

 

[Willard]

Expect to see carbon fibre components on this MS500i to keep this 80cc saw at 13.669lbs.
Also from what I can see it's SDI (semi direct injection) into the crankcase similar to what Polaris sleds have been running for years.
SDI advantage is low pressure is only needed to deliver and the injector nozzle is not exposed to the combustion process.

 

[Jimmy in NC]

I'm cautiously optimistic and the only Stihl I've got is an 041.

Does anyone have experience with the cutoff saw to say if it revs as high as a carbed version? Does the case injection change the torque curve at all?

Not apples to apples obviously but when diesels went to electronic controls where they could alter the timing and duration of the injection event the horsepower more or less stayed the same but the torque curve got a lot broader and torque went up by 30-40%.

My crews fought over that saw. Everyone I have recommended them to LOVES them. If it doesn't start in two pulls, it isn't going to start. Pulls great, fuel economy is awesome... yeah it lives up to the hype.

 

[Jimmy in NC]

I think it should. After hearing stories of A/T and M tronic correcting air leaks it should be able to feed some mods. I still want to know where the fuel pump will be and what the tiny high pressure lines will look like.

Pulse driven pump like most small equipment uses. Simple and reliable. Priming one of these is a must though to generate fuel pressure to start first time of the day.

 

[Jimmy in NC]

Behind the flywheel?

Under the primer bulb... it's a small pump with 3 or 4 lines on it.

I wonder if the injection unit / fuel pump will sit where the carb does. No high pressure line from the tank or pump in the tank (we all know how fun that is).
Gas /oil mix would have to be injected into the case at a point with lots of air flow and turbulence to remain atomized, what better place would there be? Transfer tunnels would be too late to lube the bottom end.

How is it done on the fuel injected cut-off saw I've heard mentioned?

Right at the bottom rod bearing in the crank case.

Wow, I can't imagine how they pull that off with just RPMs, I'd think it would at least need throttle position info.
I had even figured it to somehow use the metering diaphragm position as a crude sort of mass air flow sensor.

So it must only adjust the jet size to RPM and then of course the varying vacuum at different throttle openings/RPMs inherently pulls in x amount of fuel like any carb.

But then how does it differenentiate between increased throttle opening and an air leak if it has no idea where the throttle plate is? RPM goes up in either case...
Seems too good/simple to be true but I guess...

What took so long for them to figure this out? Coulda' pulled off that technology back in the 70's...

As far adjusting to changes, supposedly the new AT on the 572xp has a much faster response time and they sort of emphasize that as a significant feature.
So I assumed the old system had some sort of limitations in that regard.
Marketing...

The TS500i has a throttle position sensor and a cable to a butterfly just after the air filter. The intake is just air.. and dirt on a demo saw.

 

[wcorey]

It operates solely by monitoring RPMs. It monitors how small adjustments, several times per second, affects RPMs, and adjusts accordingly. It happens immediately.

Guess I was hasty in my last reply, after letting it sink in for a bit now I get it. Well more of it anyway...
Still can't reconcile the throttle position vs air leak thing, my brain needs more time for that.

I was ass backwards, stuck thinking in terms of traditional injection where the adjustments follow data collection.

This actually makes adjustments first then collects the data to see what happened.

Now I can also see where a faster data sampling rate would have an advantage wherein the adjustments are always playing catch up so to speak.

I still think a throttle position sensor would be useful, could then figure out an air leak or clogged filter and issue a warning, instead of only compensating and continuing on like everything is normal.

 

[nohoff]

The TS500i has only a throttle, Injection pump, injector and a crankcase Temp/Pressure Sensor.
It only has rpms and the case pressure to calculate the throttle position.
The Pressure is about 11 psi.

Inside of the looks like a carb without the venturi/throttle.