wigglesworth
Booned
Here is a thought. Take your numbers at say 60% of the port width on both sides I & Ex. Then you get a advertized number of the overall port timing. I'd like to see how much different they are from one builder to another. This will give a more general timing number based on the port entry and exit shaping. The port shape IMO matters much more than the final opening and closing numbers. We all know that the roof is progressive on the exhaust and the same goes for the intake. Who has one apart in stock and ported trim of the same cylinders to see where your work ends up compared to the bone stock factory numbers. Now remember, you need to use the same exact cylinder to make the check accurate. I know the port shape down the runner wall and during entry be it a bowl or a hole makes a huge difference in torque, just sayin'... Don't forget to subtract or add back in whatever you shaved off the bottom of the jug, if anything. Check your numbers both ways. You might find something very interesting there when they are all compared to one another. I'll bet the advertized numbers are real close but the saws perform much different in the cut.
What brought me to this comparison is, we I them and they have changed cam shafts of the same exact advertized numbers on a given bump stick. They were in reality totally different cam shafts based on base circles, ramp rates and valve overlap. When coupled with the same combination they performed totally different in the same motor. Now I'm not talking about going from flats to rollers, that's another story. All other factors and parts were keep exactly the same in these test comparisons. What we found even more interesting in changing a few other parameters on the same setups like ignition timing, jets, baloney tube sizes and even fuel ratings is what the final out comes were. Ever so slight changes make all that much difference when coupled with "the right combination" for that head. I'm not talking about little gains here folks. I'm taking three to four tenths and better with thirty eight hundred pound plus rides in the tens on pump gas with mild motors. This may not relate directly to a saw but the same principals apply.
I think you guys are doing the same thing in a different way with port shapes and entry exit numbers. The thing I find most interesting is most never includes their actual ignition point number for that combination. The only way to know for sure where that is is to check it with a timing light after you center point the timing mark off of TDC. Changing the plug gap also plays into that equations every single time. Hell the plug type and nose extension changes the compression to.
So tell me how do you guys ever get a base line set in stone to work from???
Ever little change can make a huge difference in every single engine combo.
Here is a few for you to think about.
Does anyone run cut-open gap or center fire plugs?
Who indexes their spark plugs that have ground straps?
This is just changeable stuff nothing like port shapes and entries.
Who knows if that given chamber and saw likes its squish shot straight across the piston top?
Does anybody factor in tumble verses fall on the incoming fuel charge?
Who's the last guy to angle mill there squish band to the chambers center point at TDC?
Who knows where 90* off of swirl is on a give combustion chamber?
I hope this all makes sense to you guys. It seems to me there are way to many variables being missed here while you guys all pissing numbers at each-other and spitting vinegar about fuel consumption. Bury the hatchet, in someones head if needed but, get past the numbers game an get a base line standard PLEASE!
Sorry JPK to jack your tread with my rant. I can move it if you like. Apologies...
And that there friends, is the single greatest post on saw porting in the history of the Internet.
Bar none, hands down, the best.
There is always more than one way to skin a cat.
