~60cc shootout 962 Efco vs 361 Stihl vs 036 Stihl

[timberwolf]

Johnsred 625 Piston on the right. Nice piston, but not enough room in the lower transfers to make it work.

 

[weimedog]

Have question on the intakes with rubber boots. Assume you can open both the boot and the carb some percentage additional x-sectional area from stock. How much do you really gain by widening an intake port past the percentage x-sectional area gained by opening the boot and carb? Is the theoretical gain based on the x-sectional area change as it approaches the crank case? If you can't really change the carb or boot x-sectional area much, does it make sense to widen the intake much vs. add some intake duration?

 

[mtngun]

Have question on the intakes with rubber boots. Assume you can open both the boot and the carb some percentage additional x-sectional area from stock.

Sometimes you can install a bigger boot from another model, but otherwise, there is not much you can do to mod rubber boots.

How much do you really gain by widening an intake port past the percentage x-sectional area gained by opening the boot and carb? Is the theoretical gain based on the x-sectional area change as it approaches the crank case? If you can't really change the carb or boot x-sectional area much, does it make sense to widen the intake much vs. add some intake duration?

You need MOTA to answer those questions. :msp_w00t:

In general, yes it does help to enlarge the carb venturi and the intake port, even if the rest of the intake tract does not change.

 

[timberwolf]

361 came out about 0.1 slower than the 036, but there were a couple knots in the wood. Could go either way but the 036 does have more torque no question.

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[mtngun]

And the 962 ?

 

[timberwolf]

Soon as I get a new piston.

 

[madhatte]

Oh, this is good stuff. I am pleased and not at all surprised to see the 036 performing so well. Very curious about the Efco.

 

[Anthony_Va.]

Oh, this is good stuff. I am pleased and not at all surprised to see the 036 performing so well. Very curious about the Efco.

I figured they would come out about the same. What is the difference in the engine between the two? I've wondered that for awhile.

 

[timberwolf]

Likely the biggest difference is the transfers, 036 is 2 port running higher velocity, 361 is 4 port and a little lower velocity. The 361 has more work done on it though to get to roughly the same performance. 361 is a bit more limited on exhaust port width with the location of the ring end pin.

I am going to run a tank of fuel through the 361 and see where the compression ends up, I may go for a little more compression on it yet.

I have a feeling the 962 is going to end up the fastest of the 3 saws.

 

[Stihl Crazy]

TW, any thoughts on the 165 cyl that I sent up as compared to the 962 cyl?

 

[timberwolf]

Ports all look good and lots of potential there. But the combustion chamber offset to the exhaust side would worry me on detonation if pushing the compression up.

I really am at a loss as to why they would have done that?

Correction 165
View attachment 178407

 

[husq2100]

nice work as usual Brian, great to see more from you again. Say hi to Frank.

 

[Stihl Crazy]

The 156 cyl is better. Has port layout similar to the 165 but centered com chamber like the 962. Stock with 16" bar the 156 will run with the 962 in small wood.

 

[tdi-rick]

Ports all look good and lots of potential there. But the combustion chamber offset to the exhaust side would worry me on detonation if pushing the compression up.

I really am at a loss as to why they would have done that?

That goes against all the theory I've read ?

The engineers must have had something in mind, but what ?

 

[J.W Younger]

That goes against all the theory I've read ?

The engineers must have had something in mind, but what ?

Emmissions?

 

[weimedog]

But the combustion chamber offset to the exhaust side would worry me on detonation if pushing the compression up.

I really am at a loss as to why they would have done that?

Wonder if dropping the pressure on the exhaust side helps flush the combustion chamber..or wonder if it was about spark plug location driven by the external packaging (covers & other stuff)

 

[8433jeff]

The plug is in just about the same spot on a lot of saws, and at about the same angle. I think emissions played a part in it, but we may never know for sure.
The 165 cylinder will not bolt on the 156-962 chassis, is that correct?

 

[timberwolf]

if it was about spark plug location driven by the external packaging covers & other stuff

That would be about my best guess.

In theory this chamber forward design would not be good for scavenging, would put more thrust on the intake skirt, and would be prone to detonating near the exhaust port.

By the looks of it the 165 should go on the 962 but did not try.

 

[mtngun]

That is one weird chamber layout. :msp_confused:

Did you bother to CC the 165's chamber ? It looks kinda big.

[/QUOTE]

 

[Stihl Crazy]

The 165 cylinder will not bolt on the 156-962 chassis, is that correct?

The 165 is a direct bolt on to a 156 case. The difference is a 1 mm longer stroke on the 165.