Porting Echo 265L

[Nutball]

I'm going to leaf port? lawn port? yard port? this 265L because nobody should wear a backpack blower that is outperformed by a bottom of the line hand held.



The way I figure it, to modify a blower it is best to start with a model that has a narrowing nozzle tip, because that will be the first part to go. Once that is gone, the tube diameter becomes larger allowing more volume to flow. This reduced restriction that increases volume decreases fan speed by putting more of a load on the engine. Then you increase engine power to make up for the lost rpm and add a little more.

First I got some reference numbers:
10,920rpm stock
10,450rpm with the small end tube removed.

11,400rpm without air filter

Around 13,560rpm max with the tube blocked, so I don't want to exceed that rpm with a blocked tube by much after the mods, so the fan doesn't break.

I will assume, but could be wrong, that reducing the ignition timing will be an effective way of reducing the max rpm without affecting the normal running rpm anywhere near as much if I needed to dial it back some.

Next I will open the muffler and check both the loaded rpm and rev limited rpm to see how sensitive the max rpm is to change.

 

[Egg Shooter]

There is only so much air the fan and housing can move. Above a certain point, wherever that is, you are just making more noise.

 

[Nutball]

A muffler mod brought the rpm back up to 10,980rpm, but I wonder if there is even a rev limiter because the max rpm seemed capable of increasing by the same amount as the loaded rpm, well on its way over 14k I stopped it at 13,900rpm. What I need now is a rev limiter or this may be a short thread.

 

[Nutball]

There is only so much air the fan and housing can move. Above a certain point, wherever that is, you are just making more noise.

That may be, but I think in most cases a lot more air can be moved before that limit is reached.

 

[Nutball]

I wonder if I could put a low pass filter on the spark wire to get the desired rev limiting result?

 

[Egg Shooter]

I wonder if I could put a low pass filter on the spark wire to get the desired rev limiting result?

You need to build this.

 

[Egg Shooter]

I wonder if I could put a low pass filter on the spark wire to get the desired rev limiting result?

You could sneak up on raising the exhaust so as not to over rev vs trying to limit spark some how.

 

[Egg Shooter]

A muffler mod brought the rpm back up to 10,980rpm, but I wonder if there is even a rev limiter because the max rpm seemed capable of increasing by the same amount as the loaded rpm, well on its way over 14k I stopped it at 13,900rpm. What I need now is a rev limiter or this may be a short thread.

It your tach correct? My echo blower, muff modded and tuned sharp turns 7800-7900 wot with tube in place. Its 25cc.

 

[ayoungtexan]

Looking at the manual for your blower, it should turn just a hair under 7k stock at WOT. My Stihl 450 runs at about 7750 and my 9010 at about 7950 WOT. Your tach is definitely off

 

[legdelimber]

I have a pb-500 Echo with side throttle.
I've noticed that at around 3/4 or so of max throttle provides the smoothest air flow from the tubes.
There is a slight notched feeling to the throttle lever at about that same rev point.
I've dabbled in the ports and deleted the base gasket, so the matching of the throttle notch to air flow is probably a bit out of (factory) sync as a result.
Revving it further will push the air a bit harder for scouring willow oak leaves and kicking Gumballs out of the grass a bit better, but you can tell that the air stream is noticeably more turbulent or erratic, and thus harder to steer leaves with it.
Pipes being tapered or strait seems to have only moderate affect on the rev point and onset of the turbulence.

Echo also made two (slightly ) different impellers that will fit the pb-500 and the pb-620.
I'll try to get photos of both of them after while.

 

[Nutball]

I can check the rpm again, I was surprised to find it spinning over 8000rpm, but it is only 25cc. My 25cc poulan only goes up to about 8000. I'm checking the rpm by ear, so I could have picked up on the wrong harmonic, but I doubt it. I've read chainsaws correctly. It should have been easier to tell with the muffler mod.

I have no doubt I can dial in the rpm to whatever I want, but I don't want it to explode if someone sticks the tube in the ground or against something.

 

[Nutball]

I have a pb-500 Echo with side throttle.
I've noticed that at around 3/4 or so of max throttle provides the smoothest air flow from the tubes.
There is a slight notched feeling to the throttle lever at about that same rev point.
I've dabbled in the ports and deleted the base gasket, so the matching of the throttle notch to air flow is probably a bit out of (factory) sync as a result.
Revving it further will push the air a bit harder for scouring willow oak leaves and kicking Gumballs out of the grass a bit better, but you can tell that the air stream is noticeably more turbulent or erratic, and thus harder to steer leaves with it.
Pipes being tapered or strait seems to have only moderate affect on the rev point and onset of the turbulence.

Echo also made two (slightly ) different impellers that will fit the pb-500 and the pb-620.
I'll try to get photos of both of them after while.

I hadn't thought about turbulence, I'll have to experiment with my muffler modded poulan to see if I notice a difference. I could always try vortex generators too.

The manual says 6950rpm

 

[Egg Shooter]

I can check the rpm again, I was surprised to find it spinning over 8000rpm, but it is only 25cc. My 25cc poulan only goes up to about 8000. I'm checking the rpm by ear, so I could have picked up on the wrong harmonic, but I doubt it. I've read chainsaws correctly. It should have been easier to tell with the muffler mod.

I have no doubt I can dial in the rpm to whatever I want, but I don't want it to explode if someone sticks the tube in the ground or against something.

By ear? As in you think you know the rpm by listening? Interesting.

 

[Nutball]

I'm not quite that good. I match the engine's speed to a sound generator on my phone. Like tuning an instrument but sort of in reverse.

 

[legdelimber]

I finally got a chance to get photos of those Echo impellers.

Notice how the vanes have a bit more lead in on the pb-620 unit (unit on the right, with red arrow).
Notice how the one that's supposed to be stock on the pb-500 doesn't have those small crescents at the beginning of the vanes (unit on the left).

The one the left is what's supposed to be inside the pb-500
(I've not dismantled my pb-500 yet, this one is an extra from an order mix up).
The one with the red arrow on it, is one that I removed from my pb-620.
The red arrow is just a reference mark for reinstalling it later on.

I'll have to hunt for the rest of the pics I snapped while I had the pb-500 apart after I first got it (used, from a garage sale).
Some port stuff and that "interesting" reed system.
Allergies are just making it a B#### to try looking through all the images right now.

My original intent was to try the pb-620 type impeller on the pb-500 after getting the carburetor sorted a bit better than the lean mess that the factory set it up as.
Just seems to be a few other family things keeping me distracted though.