Old Dirty Feta and the MS500i--the Hi-Tech Wood Lobotomizer

[AlfA01]

No changes. Just some cutting. A little ham-handed and dogging it in to see if it holds RPM well.

EDIT: And, that's when I knew the little dog had to go. Lol.

 

[ABarrick]

Early port FI systems (talking multi cylinder engines) used “batch fired” injection cycles. The injectors were literally triggered in batches of 2,3,4 etc and all fired at the same time. Theory was the fuel vapor dwelled behind the intake valve til it opened. This happens in such a short window of time that it works. This would be obd-1 type systems with one injector per cylinder. They use a ckp sensor to register rpm and position of cyl#1. They can see crank speed fluctuations and detect a misfire but can not pinpoint which cylinder. The progression from batch fired port injection was Sequential port injection where the injectors are fired in sequence, individually, the same as the ignition firing order.

The point to all that was I doubt it matters much if the fuel vapor is dwelling in the boot til the port opens or if it’s timed to fire exactly when the port is open. The amount of fuel that is emitted would be more important than when, especially as the RPMs increase.

 

[AlfA01]

Early port FI systems (talking multi cylinder engines) used “batch fired” injection cycles. The injectors were literally triggered in batches of 2,3,4 etc and all fired at the same time. Theory was the fuel vapor dwelled behind the intake valve til it opened. This happens in such a short window of time that it works. This would be obd-1 type systems with one injector per cylinder. They use a ckp sensor to register rpm and position of cyl#1. They can see crank speed fluctuations and detect a misfire but can not pinpoint which cylinder. The progression from batch fired port injection was Sequential port injection where the injectors are fired in sequence, individually, the same as the ignition firing order.

The point to all that was I doubt it matters much if the fuel vapor is dwelling in the boot til the port opens or if it’s timed to fire exactly when the port is open. The amount of fuel that is emitted would be more important than when, especially as the RPMs increase.

Thanks AJ. It looks like this system makes use of a spring accumulator to supply fuel on demand, whereas waiting for case vacuum to draw fuel via the diaphragm pump would likely result in lags on this saw.

 

[AlfA01]

Also, in times of too much fuel, such as rapidly returning from WOT to idle, there is a return that is used as with most FI systems.

 

[AlfA01]

Pulling and oiling the 36" bar with semi chiz. Big thanks to @Evansaw for offering to let me borrow the setup to see how the 500i would perform with it.

 

[Evansaw]

Pulling and oiling the 36" bar with semi chiz. Big thanks to @Evansaw for offering to let me borrow the setup how the 500i would perform with it.

You’re welcome

No problem to participate in anything for the good and the order! Have fun Dan

Is this my chain? I believe it had a decent sharp filling

 

[AlfA01]

You’re welcome

No problem to participate in anything for the good and the order! Have fun Dan

Is this my chain? I believe it had a decent sharp filling

It is your chain. The cutters seemed pretty sharp so I ran it.

 

[Evansaw]

It is your chain. The cutters seemed pretty sharp so I ran it.

Well lone cowboy chain.

ECO FRIENDLY and stuff... lol

 

[AlfA01]

Some more theory for discussion...The muffler design controls and limits exhaust flow in order to probably passify EPA standards and provide back pressure.

Here's a bit of a diagram on the pic to explain why I believe this thing has a strange exhaust note when stock and why the heat tends to quickly build up.

Generally, all mufflers are restricted in someway. And, they build up heat. Some worse than others. This one in particular looks open, but...

Stihl has forced gases leaving the cylinder and directed them toward the flywheel side of the exhaust can. The outlet is on the PTO side and at the far rear of the can.

The old exhaust(blue arrows) then has to build enough pressure to force it's way past the stream of incoming fresh exhaust(red arrows), which creates the strange exhaust note.

Think of driving in a car and having the window opened to just enough where you get that mind numbing percussion sound.

Too much air rushing in and filling the car, while the air inside the car is fighting to get out and normalize--ie, MS500i exhaust and the funky sound effects (buffeting).

The green indicates where I modded the flow baffle as of this point in the mods. It's not necessary/easy to take out the whole bit--a lot of spot welds going on there.

I like the reinforcement the cage adds to the back of the muffler...pretty thin metal on these new muffs.

 

[AlfA01]

Speaking of Red Arrows, the UK demo team is here for the annual airshow training before the summer season.

 

[thedude74]

That 500i is running pretty strong Dan. Is it ready to take on the 79xx again?

 

[AlfA01]

That 500i is running pretty strong Dan. Is it ready to take on the 79xx again?

I believe it is at the level of taking on the Dolmar.

 

[thedude74]

I believe it is at the level of taking on the Dolmar.

That's impressive! It would be interesting to see some timed cuts using the same bar/chain combo used on both. For scientific research of coarse.

 

[drf256]

I kinda like what they did on that muffler Dan. Not sure I’d want if short circuiting out the deflector.

The exhaust noise waves cancel each other and still maintain flow by redirecting.

I could be wrong, but that’s how I see it.

Saw looks great.

 

[drf256]

Early port FI systems (talking multi cylinder engines) used “batch fired” injection cycles. The injectors were literally triggered in batches of 2,3,4 etc and all fired at the same time. Theory was the fuel vapor dwelled behind the intake valve til it opened. This happens in such a short window of time that it works. This would be obd-1 type systems with one injector per cylinder. They use a ckp sensor to register rpm and position of cyl#1. They can see crank speed fluctuations and detect a misfire but can not pinpoint which cylinder. The progression from batch fired port injection was Sequential port injection where the injectors are fired in sequence, individually, the same as the ignition firing order.

The point to all that was I doubt it matters much if the fuel vapor is dwelling in the boot til the port opens or if it’s timed to fire exactly when the port is open. The amount of fuel that is emitted would be more important than when, especially as the RPMs increase.

Interesting stuff for sure. I recall the old Grand National going to SPFI and having a performance boost.

But even then, a 4 stroke automotive engine might need 3000 pulses a minute. And that’s with much more real estate for high pressure pumps, big injectors, etc.

This 2 stroke compact system would have to pulse fuel around 5x as fast if it were truly sequential.

I agree with you. I think it’s just atomized fuel waiting to get sucked in. I’m failing to see why the complexity of fuel injection was applied to a saw. I guess there is a coolness factor, but that’s about it.

I do wonder if a closed loop O2 sensor system is on the horizon.

It all seems self defeating at some point. I mean, I wouldn’t want to drive a 4200# 1970 Buick Riviera with points ignition and a 4 barrel to work on a daily basis. The 8 mpg might get to me a bit. But it would last me 30 years and not the 10 a new car would.

Perhaps the OEM is moving towards defined obsolescence more and more.

 

[Evansaw]

Some more theory for discussion...The muffler design controls and limits exhaust flow in order to probably passify EPA standards and provide back pressure.

Here's a bit of a diagram on the pic to explain why I believe this thing has a strange exhaust note when stock and why the heat tends to quickly build up.

Generally, all mufflers are restricted in someway. And, they build up heat. Some worse than others. This one in particular looks open, but...

Stihl has forced gases leaving the cylinder and directed them toward the flywheel side of the exhaust can. The outlet is on the PTO side and at the far rear of the can.

The old exhaust(blue arrows) then has to build enough pressure to force it's way past the stream of incoming fresh exhaust(red arrows), which creates the strange exhaust note.

Think of driving in a car and having the window opened to just enough where you get that mind numbing percussion sound.

Too much air rushing in and filling the car, while the air inside the car is fighting to get out and normalize--ie, MS500i exhaust and the funky sound effects (buffeting).

The green indicates where I modded the flow baffle as of this point in the mods. It's not necessary/easy to take out the whole bit--a lot of spot welds going on there.

I like the reinforcement the cage adds to the back of the muffler...pretty thin metal on these new muffs.



View attachment 181332

In this diagram the direction of the returning gasses of back pressure should join the calculation. If it’s added there, then it might make more sense.
Exhaust looks busy and busy means temperature building.

On a side note. To make things simpler maybe the whole baffle has to be removed likewise on 661 etc Exhaust. Then you have gasses go straight, fill the can instanlty, escaping gasses will always find their way through a better angled exit, remaining gasses maybe cool quicker.

But that’s just guessing

 

[AlfA01]

I kinda like what they did on that muffler Dan. Not sure I’d want if short circuiting out the deflector.

The exhaust noise waves cancel each other and still maintain flow by redirecting.

I could be wrong, but that’s how I see it.

Saw looks great.

I was liking it at first too, Al. It was a bit disappointing after running it in 5-10 minute intervals and have the top cover feel like it would melt.

A lot of heat retention going on there. And the saw went from sounding, and running so-so, to pretty decent at this point.

I figured most mufflers are designed with some sort of bird cage that makes use of short circuiting via holes/vents, so I went for it.

It gained at least a second in the cut from the muffler mod, so I guess the saw don't mind too much, and it's way cooler running now.

 

[RI Chevy]

Can you add another exhaust port Dan? Maybe a small one giving the exhaust gases a quicker place to exit? On the side where the exhaust was being directed by the inside flange.

 

[Evansaw]

Can you add another exhaust port Dan? Maybe a small one giving the exhaust gases a quicker place to exit? On the side where the exhaust was being directed by the inside flange.

Since most of this forums very informative tests tend to lean towards dual side ports that must be a good way.

But again as i posted before, if you wanna make it happen FIRST STEP GET RID OF A BUSY MUFFLER AND INTERNAL STUFF.

Otherwise if you look the picture Dan posted you ll see various problems with the angled baffle.
It’s heading the gasses to the weak-relieve Left side of the muffler so the gasses will exciting instantly and remaining Gas would first try to maneuver inside the can and a small amount would exit the correct Right side with returning gasses for back pressure which should enter again through the easier Left side. But as they used that returning way to the left again they gonna leak from the left port. It’s a huge mess leaving the baffle inside there if the saw doesn’t remain Stock.

My first step would be empty the can and go from there...

 

[StephK87]

Video from Wednesday or Thursday. After I had corrected the timing advance back to stock form.

got this checked again for you by fps count

stock
1. cut MS500i 8,56 sec

with muffler mod
1. cut MS500i 6,86 sec
2. cut MS500i 6,63 sec

after the mods
1. cut Ms500i 6,53 sec
2. cut MS500i 6,56 sec

after mods phase II
1. cut MS500i 7,26 sec


thanks for the content so far, i still waiting for my jug