Efco 8200 transfer ports

[parrishturf]

Here is what I found while porting an Efco 8200.

The transfer ports are a split pair. I knife edged the inflow tract, blended the walls, and decided to do more than just pointowardds the intake. Surprise!!! The exhaust side port was cast over by about 1/3 the size of the tunnel. I opened up all four ports. Raised .020" and lowered .040" but the width is now hugcompareded to stock. Squish without base gasket was .018

After some readon lineline I think the 2010 8200 got a cheap retool for emissions standards and they simply cast over the existing tunnel forms in the sand casting.

Any way this saw came alive and required about 1 turn of h/l screws out to tune.

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[Soilarch]

Am I reading this correctly? Are you thinking efco may have intentionally "cast over" some of the transfers in the newer saws in order to pass emissions? Or this one was just a fluke?

 

[wigglesworth]

If your refering to the upper transfer tword the exhaust, it is cast over for a reason. It helps directs the air/fuel mix twords the rear of the cylinder, to help keep the fresh air/fuel mix from blowing out the exhaust.

 

[parrishturf]

Yes!

Am I reading this correctly? Are you thinking efco may have intentionally "cast over" some of the transfers in the newer saws in order to pass emissions? Or this one was just a fluke?

The metal of this jug is high quality. The plating is excellent. I could not believe how thin thmetalal was covering the exhaust side transfer port. Yes-I am saying the transfer tunnel is cast wider than the port opening, intentionally.

The 8200 is a big saw with tiny ports. Open'em up...

Also: Blsnelling, Thank you for the Like, I respect your opinion...

 

[wigglesworth]

The metal of this jug is high quality. The plating is excellent. I could not believe how thin thmetalal was covering the exhaust side transfer port. Yes-I am saying the transfer tunnel is cast wider than the port opening, intentionally.

The 8200 is a big saw with tiny ports. Open'em up...

Also: Blsnelling, Thank you for the Like, I respect your opinion...

How did u come up with they cast over transfer ports to pass EPA? Most all transfers I've seen have a significant ridge on the front tword the exhaust to help aim the charge back.

Also, did u take into account the velocity u lost by "hogging" out the transfers?

I'm not saying it doesn't run better now, but I am saying there is a lot more to porting a cylinder than made up hypothesis and a dremel tool.

What were ur timing numbers?

 

[Stihl Crazy]

The 8200 cyl is different than the older 980 cyl for sure. My 980 port layout is like a 181 Husky. Old style 2 port.

 

[Terry Syd]

"What were ur timing numbers?" - Since the OP appears to have made the port openings wider, I think the real question to ask is what was the time/area before the mod and what was it after the mod?

 

[parrishturf]

OK here we go...

Gentlemen:


Please do not take my response critical.

Yes timing changed.

Yes the port area changed.

And yes its a hypothesis that the ports are smaller due to emissions. What one change would you make if you were one of the oldest engineers of sand castings.

I have no clue how much wider the ports are now than stock, so for the data folks I did not help you. As I stated I went up .020" and down .040 I think the squish was .020 with no gasket.

As always I pointed transfers toward intake. When I found the hollow space it was not a ridge, it was a cover over about 1/3 of the port tunnel. When I got to the tunel I make a little j that also reflects back away from exhaust.

If you fail to see any value in that piece of information then just do not respond.

But do not acuse me of using a dremmel, I will have you know my grinding tools are the finest Harbor Freight has to offer and two flute end mills work great for porting! (That is a joke...see.):msp_scared:

IMHO The 8200 is a saw that was stretched lean, every thing about the saw says quality and it is a viable candidate for tuning. Get you one!

 

[wigglesworth]

If I came off harsh, my apologizes.

I've been where u are. I've ground on stuff without taking any numbers, shooting the moon so to speak. I made some really good running saws that way, and I also made some real turds.

From a technical standpoint, if u dropped the gasket, and only raised them .020, u probably didn't change the transfer timing much, but as Terry said, u did increase the time area by widening them. How much, it's anyone's guess at this point.

My only suggestion is this. Get a degree wheel, and learn to use it. And Learn to make a port map. U will thank me later.

 

[Terry Syd]

Here's a link that may assist when designing ports - Design and simulation of two-stroke engines Gordon P. Blair.pdf - 4shared.com - document sharing - download

It is an engineer's document, so it is full of math, but don't be put off by the math as there are some very large nuggets of information available. There is a very good discussion of port angles (with diagrams) and port time/areas. There's lots of information about short-circuiting, leakage, etc. in the section on port angles. Take a look at the power characteristics of the DT250 cylinders (#12 and #14). They both have the same time/area figures, but the port angles are different - and so is the power output!

In particular, the author modified a 65cc chainsaw (referred to as Loopsaw in the document). In the charts related to the Loopsaw modifications, you can see the graphs of various emissions and the trade off with power as various timing figures were tried. You will see that it is primarily the exhaust port timing that the engineers work with for emissions control.

Books like Gordon Jennings 'Two-Stroke Tuners Handbook' is a good primer for getting into two-stroke tuning and it is available on the internet. However, Blair's book takes the inquiry to a whole new level.

 

[parrishturf]

Here's a link that may assist when designing ports - Design and simulation of two-stroke engines Gordon P. Blair.pdf - 4shared.com - document sharing - download

It is an engineer's document, so it is full of math, but don't be put off by the math as there are some very large nuggets of information available. There is a very good discussion of port angles (with diagrams) and port time/areas. There's lots of information about short-circuiting, leakage, etc. in the section on port angles. Take a look at the power characteristics of the DT250 cylinders (#12 and #14). They both have the same time/area figures, but the port angles are different - and so is the power output!

In particular, the author modified a 65cc chainsaw (referred to as Loopsaw in the document). In the charts related to the Loopsaw modifications, you can see the graphs of various emissions and the trade off with power as various timing figures were tried. You will see that it is primarily the exhaust port timing that the engineers work with for emissions control.

Books like Gordon Jennings 'Two-Stroke Tuners Handbook' is a good primer for getting into two-stroke tuning and it is available on the internet. However, Blair's book takes the inquiry to a whole new level.

Thank you for the information, I have read the Jennings piece but not the Blair's book.
Ok if the exhaust port is the emissions key in his opinion then why would an 84cc saw have such huge inflow tracts and such tiny ports compared to say a 660?

 

[Terry Syd]

Bugger if I know. I've never seen the inside of either engine, nor do I know what the design parameters of either engine were.

Now that you have opened up the transfer ports next to the exhaust port, run it for a while and then check the carbon pattern on the top of the piston. If you are getting any indication of short-circuiting of the incoming charge (swirl patterns on the side next to the exhaust port), then you might go back in and put a steeper angle on the exhaust side of the transfer port to help give it a stronger bias of flowing towards the intake side.

Take a look at the port angle diagragms in Blair's book, they may be of some assistance.

 

[parrishturf]

Really?

Bugger if I know. I've never seen the inside of either engine, nor do I know what the design parameters of either engine were.

Now that you have opened up the transfer ports next to the exhaust port, run it for a while and then check the carbon pattern on the top of the piston. If you are getting any indication of short-circuiting of the incoming charge (swirl patterns on the side next to the exhaust port), then you might go back in and put a steeper angle on the exhaust side of the transfer port to help give it a stronger bias of flowing towards the intake side.

Take a look at the port angle diagragms in Blair's book, they may be of some assistance.

Are you saying you have never seen inside a 660 or any 80+cc saw?

Checking swirl patterns is exactly how I developed my "j" turn on the Ex side of the port. I do'nt get it. You have no clue of my background, you jump in post with such authority and you have never seen inside a big work saw. Sorry for the rant but, an 8200 is a neer $1000.00 dollar saw. I invested my money in order to learn how good a saw it is. And my goal in this post is to pass information on to modders who play in that league and maybe save them the cost of a jug, or create an interest.

Please consider the point of my post. It does no one reading this any good to have to wade through our chatter.

 

[wigglesworth]

Are you saying you have never seen inside a 660 or any 80+cc saw?

Checking swirl patterns is exactly how I developed my "j" turn on the Ex side of the port. I do'nt get it. You have no clue of my background, you jump in post with such authority and you have never seen inside a big work saw. Sorry for the rant but, an 8200 is a neer $1000.00 dollar saw. I invested my money in order to learn how good a saw it is. And my goal in this post is to pass information on to modders who play in that league and maybe save them the cost of a jug, or create an interest.

Please consider the point of my post. It does no one reading this any good to have to wade through our chatter.

What's an Efco? Don't they make drink mixers and vending machines?



Dude, seriously....

All myself and him have been doing is try to help. You "Big Leage" Efco folks are some thin skinned critters.

 

[Mastermind]

Timing numbers? I'm just curious if these engines have as tall of an exhaust port as the ms660. It seems that a lot of newer saws have tiny exhaust ports and crazy timing numbers (from a tuners point of view).

 

[parrishturf]

Timing numbers? I'm just curious if these engines have as tall of an exhaust port as the ms660. It seems that a lot of newer saws have tiny exhaust ports and crazy timing numbers (from a tuners point of view).

I will get a rubbing of the ports and post later.

 

[Mastermind]

I will get a rubbing of the ports and post later.

It's much simpler to mount a wheel and check total duration. With those numbers you can figure opening points, etc.

We've been mapping and documenting all the different jugs for the 046 and 066, seeing the progression into epa ruled saws. As the smog laws changed the timing numbers changed as well. It seems that the exhaust and transfer timing increased to make up for a choked muffler. I feel that the engineers were shooting for a hotter exhaust temperature to burn off more hydrocarbons.

Modding these newer saws with any success means knowing where you're at and where you want to go. I'm not saying you can't build a stout running saw without studying the effects of alterations in port timing, but doing it consistently would be a miracle.

 

[parrishturf]

It's much simpler to mount a wheel and check total duration. With those numbers you can figure opening points, etc.

We've been mapping and documenting all the different jugs for the 046 and 066, seeing the progression into epa ruled saws. As the smog laws changed the timing numbers changed as well. It seems that the exhaust and transfer timing increased to make up for a choked muffler. I feel that the engineers were shooting for a hotter exhaust temperature to burn off more hydrocarbons.

Modding these newer saws with any success means knowing where you're at and where you want to go. I'm not saying you can't build a stout running saw without studying the effects of alterations in port timing, but doing it consistently would be a miracle.

Excellent point!

 

[mtngun]

Ok if the exhaust port is the emissions key in his opinion then why would an 84cc saw have such huge inflow tracts and such tiny ports compared to say a 660?

When porting transfers, consider that transfer flow is pumped into the cylinder, not sucked into the cylinder. Because it is pumped, the friction losses in the transfer port are not important. What is important is length and velocity and direction. Length and velocity give the charge momentum that keeps charge moving into the cylinder even after the pumping action has shut off.

When Joe Porter makes the transfers wider and shorter, he loses velocity and length and momentum. Bigger is not necessarily better. Shorter is not necessarily better.

 

[parrishturf]

When porting transfers, consider that transfer flow is pumped into the cylinder, not sucked into the cylinder. Because it is pumped, the friction losses in the transfer port are not important. What is important is length and velocity and direction. Length and velocity give the charge momentum that keeps charge moving into the cylinder even after the pumping action has shut off.

When Joe Porter makes the transfers wider and shorter, he loses velocity and length and momentum. Bigger is not necessarily better. Shorter is not necessarily better.

Good input.

Are you sugesting for any given timing that working the transfer tunnel yields limited results?