JHctRednek
ArboristSite Operative
I am working on another MS660 and I want to build this one mainly for milling. So I am looking for a broad torque range and I am wondering how transfer timing plays into a broad torque range. I have looked at most of the porting posts and I guess I am a little confused.
The last MS660 I built was with a pre decomp cylinder and the timing was set by mildly cutting the squish band to get 99 degrees exhaust, 121 degree transfer timing and 80 degrees intake. I broke the saw down again to change the intake timing to 84 degrees. I really like how the saw runs felling and bucking rounds and it works good for milling but I would like this one to be even better for milling.
This MS660 is a STIHL decomp cylinder, I have cut the squish band to get as close to 100 degrees exhaust as I can but I can only get to 98 degrees due to plating limitations. For the intake I am planning to set around 85 degrees based on my experience with the last build but I am a little confused with AUSSIE1's post from the understanding port timing numbers thread:
Raising the transfers can bring torque down a little and flatter from a high ex duration as long as blowdown allows it.
Increasing the inlet helps balance the need of the transfers and exhaust as long as the duration doesn't exceed the crankcase.
So I was thinking of going to 120 degrees on the transfers which I think is a safe number but would 118 degrees be better? Is there something I am missing?
The last MS660 I built was with a pre decomp cylinder and the timing was set by mildly cutting the squish band to get 99 degrees exhaust, 121 degree transfer timing and 80 degrees intake. I broke the saw down again to change the intake timing to 84 degrees. I really like how the saw runs felling and bucking rounds and it works good for milling but I would like this one to be even better for milling.
This MS660 is a STIHL decomp cylinder, I have cut the squish band to get as close to 100 degrees exhaust as I can but I can only get to 98 degrees due to plating limitations. For the intake I am planning to set around 85 degrees based on my experience with the last build but I am a little confused with AUSSIE1's post from the understanding port timing numbers thread:
Raising the transfers can bring torque down a little and flatter from a high ex duration as long as blowdown allows it.
Increasing the inlet helps balance the need of the transfers and exhaust as long as the duration doesn't exceed the crankcase.
So I was thinking of going to 120 degrees on the transfers which I think is a safe number but would 118 degrees be better? Is there something I am missing?
