Echo 330/360t improving air intake, time cuts comparison

[heyduke]

That's not how a carb works. An accurate carb would hold a constant fuel/air mixture as the air velocity changed - more air would pick up proportionately more fuel.

These are not accurate carbs, as they eliminated the air corrector jet system when making them all-position. So with an uncorrected fixed jet fuel volume approaches the square of air velocity, and even a small increase in air velocity will make it very rich - this is why saws "4-stroke".

The fact that you had to lean the mixture tells me that it wasn't really acting as a choke, but that you successfully increased the air velocity through the carb.

chris-pa-

i don't know much about how a 2stroke carb works but understand venturis. we're pretty much in agreement, though i didn't know the correct exponent. i also suspect it is 2 because that's so common in nature.

negative pressure [at the high and low speed jets] would likely increase exponentially with volume and/or speed, like when you open the throttle. to correct that one would need to close the metering needles.

i still haven't done the math on the percentage of restriction going from 19mm to 14mm, 'cuz i'm lazy and besides don't know fluid dynamics or calculus well enuff to put that value to use.

one thing is certain though, the saw runs a lot better now. i finally decided that the reason the bore was designed at 14mm was to increase the strength of the bracket and prevent it from failing due to prolonged and repeated vibrations. now i just gotta figure the angle of the dangle...

 

[cedarshark]

chris-pa-

i don't know much about how a 2stroke carb works but understand venturis. we're pretty much in agreement, though i didn't know the correct exponent. i also suspect it is 2 because that's so common in nature.



i still haven't done the math on the percentage of restriction going from 19mm to 14mm, 'cuz i'm lazy and besides don't know fluid dynamics or calculus well enuff to put that value to use.

one thing is certain though, the saw runs a lot better now. i finally decided that the reason the bore was designed at 14mm was to increase the strength of the bracket and prevent it from failing due to prolonged and repeated vibrations. now i just gotta figure the angle of the dangle...

Chris, Thanks for the clarification on the increase in air velocity.

HeyDuke, are you suggesting that even though the saw runs better, that the mod may have substantially weakened the bracket ?

 

[heyduke]

Chris, Thanks for the clarification on the increase in air velocity.

HeyDuke, are you suggesting that even though the saw runs better, that the mod may have substantially weakened the bracket ?

cedarshark-

i'm saying it is a possibility and that material strength may have contributed to the engineer's decisions. i'll do my best to perform destructive testing in the months to come. i don't feel like it will break and i think "substantially" is probably inaccurate. i'm not having any misgivings about what i did. the performance improvements are substantial. fuel consumption has improved too. i think long and hard before performing field mods and have little desire to hack at saws that come across my bench. i value reliability and repeatability. i think i've done one porting job in the almost twenty years i've been wrenching on saws. in this case fifteen minutes work on a $3.50 part did more than most porting jobs.

 

[bikemike]

cedarshark-

i'm saying it is a possibility and that material strength may have contributed to the engineer's decisions. i'll do my best to perform destructive testing in the months to come. i don't feel like it will break and i think "substantially" is probably inaccurate. i'm not having any misgivings about what i did. the performance improvements are substantial. fuel consumption has improved too. i think long and hard before performing field mods and have little desire to hack at saws that come across my bench. i value reliability and repeatability. i think i've done one porting job in the almost twenty years i've been wrenching on saws. in this case fifteen minutes work on a $3.50 part did more than most porting jobs.

My saw filter adapter has been honed out since the first week I owned my saw and that part has not broke with the saw banging around hanging from a 4 foot lanyard or when clipped on my saddle. My guess is fuel consumption. To help vaporize the fuel so it burns more efficient. fuels burn better with less waist byproduct then a liquid drops that take longer to burn. And my saw also does run great in all throttle positions. Yeahya

 

[bikemike]

Sorry guys I don't have detailed pics for you. I'm using my wife phone to reply to these. My phone is broke and duct tape won't fix it.

 

[bikemike]

Ok i can confirm that drilling the holes in the filter box cover really helps this saw breath better and the biggest bounus is that my filter box isn't being filled up with the big wood chip. i went 3 days without cleaning my filter and it wasn't bad at all

 

[cedarshark]

Ok i can confirm that drilling the holes in the filter box cover really helps this saw breath better and the biggest bounus is that my filter box isn't being filled up with the big wood chip. i went 3 days without cleaning my filter and it wasn't bad at all

Thanks for the update...we appreciate the work you put in this.

 

[stubnail67]

Ok i can confirm that drilling the holes in the filter box cover really helps this saw breath better and the biggest bounus is that my filter box isn't being filled up with the big wood chip. i went 3 days without cleaning my filter and it wasn't bad at all

got a pic? when i dis it on that blower i used a 3/16ths drill bit....

 

[bikemike]

Yeah these holes placed abovethe spark plug cap make a huge difference in the debris build up in the air box went 3 days with lots of use and filter was mildly dusted and not caked up like it always has im the past

 

[bikemike]

4.5 tanks of fuel today this is my saw and filter filter use to look like the saw not anymore

 

[stubnail67]

took me a few trys to like it..... the site is having some issues....

 

[stubnail67]

took me a few trys to like it..... the site is having some issues....and a few trys to post this reply......wont even discuss the search engine LOL....

 

[bikemike]

To add to this echo 360t thread. Carb venturi. I ended up punching out My carb venturi by removing the choke plate e ring and shaft. So here are a few pics and I think it made a bit of a difference but it's hard to compare with it being so cold and frozen logs.
Before
After it's not a lot that I took off but it has worked wonders on weed whips in the past

 

[drf255]

Highly cool

 

[Chris-PA]

28/64" is a pretty decently sized venturi for a 36cc already. I'll admit I have a carb that size on a 32cc Mac and it runs well, and my 40cc Husky 142 has a 34/64" WT on it stock. Still, be careful in hogging out the venturi too big on a small saw. You reduce the vacuum signal at the H jet and essentially delay the H circuit. The transfer holes are located so as to provide a smooth part throttle transition from L to H, but if the H doesn't pick up soon enough you could end up with a part throttle bog.

 

[bikemike]

28/64" is a pretty decently sized venturi for a 36cc already. I'll admit I have a carb that size on a 32cc Mac and it runs well, and my 40cc Husky 142 has a 34/64" WT on it stock. Still, be careful in hogging out the venturi too big on a small saw. You reduce the vacuum signal at the H jet and essentially delay the H circuit. The transfer holes are located so as to provide a smooth part throttle transition from L to H, but if the H doesn't pick up soon enough you could end up with a part throttle bog.

I know what ur saying there. If I had to do it all over I'd use the Poulan pp4620avx carb and change fuel inlet tube and throttle choke shafts. But the echo seems to like it so far. It definitely has a bit more in cut rpm with a stihl full chiz low pro in fresh frozen pine almost 14". For the use it has on it she runs great. Wish eCho had a carb heat option.and a second piston ring

 

[pro94lt]

What's wrong with that 020t? 100psi?

 

[bikemike]

What's wrong with that 020t? 100psi?

Hard to find and expensive. Best saws out there tho

 

[bikemike]

To add to this echo 360t thread. Carb venturi. I ended up punching out My carb venturi by removing the choke plate e ring and shaft. So here are a few pics and I think it made a bit of a difference but it's hard to compare with it being so cold and frozen logs.
Before View attachment 477678 View attachment 477679
AfterView attachment 477680 View attachment 477681 it's not a lot that I took off but it has worked wonders on weed whips in the past

Ok echo folks. This work I did on the carb works well. Tested in 14 in fresh cut frozen pine at 5- Temps. Good idle, good midrange, snaps up wot no problem

 

[bikemike]

Anyone here with a 330 360 t want to try a bigger bore carb on there saw?I only had enough time to make 4 cuts and it didn't lag, flat spot, or act over carbureted. It was originally a husky 136 carb that has been punched out to .601" venturi. The accelerator pump has been blocked off. Choke and throttle links are made to fit echo top handle and fuel inlet is now barbed. This is a drop in and tune carb. I dont have the time to run it much so wondering who is still using there 330 360t that would like to try it for a few weeks. I'd like to get it back. Pay shipping both ways is alL I'm asking and reviews of how it's working. Original carb venturi bore below now the husky carb.