Maybe, there is more then 1 way to skin a cat.
The OP is just trying to understand the basic's, you guys throwing out fancy forumla's is just going to confuse him. He needs to just learn some basics first, then progress futher once he gets that.
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Maybe, there is more then 1 way to skin a cat.
The OP is just trying to understand the basic's, you guys throwing out fancy forumla's is just going to confuse him. He needs to just learn some basics first, then progress futher once he gets that.
[snip]
I've found stroke, but I've never been able to find rod length.
It would appear I've opened Pandora's Box![]()
Parrisw has it, They are the same thing. if you know when the exhaust opens after TDC, then you know duration. If you know duration, you know when the port opened.
say the exhaust opens at 90*. There is 180* from TDC to BDC, so if it opens at 90*, then it's open for the 90* on the way down and another 90* on the way back up...duration is 180*
if you know duration is 160*, then it's open for 80* on the way down and 80* on the way back up. It must have opened at 100* after TDC.
if you know one, you can figure the other. Saying the exhaust opens at 105* after TDC is the same as saying there is 150* of exhaust duration.
you need to know, and understand, mean time area of each port and how they relate to each other befor you can determen port timing.
scott
Ok, back to the original question... how do these numbers look. I checked the wheel with a piston stop in both directions and split the difference to zero the wheel. Here are my new numbers:
Intake 69* BTDC
Exhaust 105* ATDC
Transfer 121* ATDC
This is a 346xp OE
I’m listening if you care to elaborate a little more.opcorn:
Do those look right for a bone stock 346xp?
Here's a good explanation of time/area. It's a follow on from Jennings forty years ago and yeah, more equations![]()
http://www.macdizzy.com/cylinder_map5.htm
and this is the original chapter from Jennings http://microcarproject.tripod.com/html/port_timing_alteration.htm
I’d say they look pretty darn close. Below are the timing #s from Brads thread on porting an NE346 and what I found when I checked my 2150. Measurements on both saws were taken without base gaskets.
Stock NE 346XP
Squish: .013"
Intake: 76°
Exhaust: 108°
Transfers: 123°
2150
Squish: .018"
Intake: 71°
Exhaust: 101°
Transfers: 126°
Sorry about hijacking your thread but it has been a good one.
Yeh I have two versions of Gordon Jennings’ book on my computer, talk about exhaustive and more scary formulas.
Guess I’m looking for a condensed version.
I’ve been to macdizzy.com before searching for info on a couple 2-stroke four wheelers we have… tons of great info there. I don’t remember stumbling across the webpage you linked to though. The one at tripod is all new to me. I’ll check them out for sure, thanks.
Yeh I have two versions of Gordon Jennings’ book on my computer, talk about exhaustive and more scary formulas.
Guess I’m looking for a condensed version.
I’ve been to macdizzy.com before searching for info on a couple 2-stroke four wheelers we have… tons of great info there. I don’t remember stumbling across the webpage you linked to though. The one at tripod is all new to me. I’ll check them out for sure, thanks.
Maybe, there is more then 1 way to skin a cat.
The OP is just trying to understand the basic's, you guys throwing out fancy forumla's is just going to confuse him. He needs to just learn some basics first, then progress futher once he gets that.
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