Is compression king?

[Nitehawk55]

Stupid chainsaw.

Stupid groin !!

 

[thomas1]

Seems that way, probly someone we've talked to before

I was making a general comment.

I don't get my panties in a bunch. I've read many threads that I wonder why? It wasted my time when I could be doing something.

So, you've been on the internets, then?

See?

 

[MustangMike]

.one of my 046 jugs has a real wide squish band ,it washes the edge of the piston ,but makes more power than any other 70-80cc i have so i do not think it hurts performance any .View attachment 35992

Yea, my D chamber 046s run real well also (ironically, both were formerly 460s).

 

[David Young]

No doubt they are some nice running saws. We have been building and modding to maximize compression and msv. To limit end gasses and maximize the cooling effect.

The new strato saws are looking at lowest possible emissions. Small band means less Unburned end gasses. They can cool the head by overscavenge since the first part is only air.

Maximize efficiency by fully clearing the old charge out.
Also the more surface area meeting the explosion on top of the piston the more force can be delivered to the piston/crank.

Like how a hydraulic pump/bottle jack figures the lifting capability.
Force over a specific surface area

 

[Red97]

No doubt they are some nice running saws. We have been building and modding to maximize compression and msv. To limit end gasses and maximize the cooling effect.

The new strato saws are looking at lowest possible emissions. Small band means less Unburned end gasses. They can cool the head by overscavenge since the first part is only air.

Maximize efficiency by fully clearing the old charge out.
Also the more surface area meeting the explosion on top of the piston the more force can be delivered to the piston/crank.

Like how a hydraulic pump/bottle jack figures the lifting capability.
Force over a specific surface area

I agree with everything here ^^

Just can't help but wonder about an ideal band ratio for a work saw??

As work saws don't have the same savage/pulse effect with a can muffler. Are we killing power by limiting volume in the chamber with some of these wide bands??

 

[Terry Syd]

Go back to the link I gave for Blair's document. You will notice that maximum power occurs when there is a 50% mass burn around 10 degrees ATDC. In other words, the flame front is able to get under the squish band as the piston is already moving away from TDC.

EDIT: Here is the link again - http://dragonfly75.com/motorbike/2StrokeDesign.pdf

The combustion process, compression ratios, etc, is in Chapter 4.

Don't worry about all the math, the concepts are there and you don't need to do the math. The mathematics is only to confirm the theories and to give guidance in a new design application.