???'s Regarding crank stuffing, Primary Compression, scaveng
Dec 14, 2015 21:06:44 GMT -5
90GTVert likes this
Post by niz76 on Dec 14, 2015 21:06:44 GMT -5
Ok, so this seems to be a somewhat controversial topic in the 2t internet world, and one of those where there seems to be varying opinions and no real concrete answers...
I've been doing some research on Primary Compression/Case Volume/Stuffing and now seem to actually have even more questions than answers...
Regarding case volume and "stuffing" with either JB weld or stuffer cranks or both, I've read that stuffing on modern 2t cranks/cylinders isn't necessary because the designs are good and the new "modern" expansion pipes do a great job of scavenging...
On the other hand, I've also read that in the case of "old technology" and small transfer area cylinders- I'm assuming this is where our 90cc+ Minarellis fall, correct?- that it's beneficial to have a high case compression (low volume) to "squirt" the charge through the transfers... Where "modern" cylinders with nice big transfer areas the expansion pipes do a good enough job of scavenging to where stuffing the crank case and using a stuffer crank isn't really necessary.
Sooooo, in my case in particular- I have trenched the cases HEAVILY with HUGE trenches and I'm also running a non-stuffer crank- stock 90cc Eton. Like this:
For the benefit if the up-and-coming 2t tuners, here's what a "stuffer crank" looks like:
See how it's "stuffed" with plastic?
So, with my (our) huge trenches and small transfer areas, it seems that my (our) primary compression is probably too low? I should probably be running a stuffer crank?? I know many of you out there already are running stuffer cranks in the 90cc+ stuff...
On top of running a stuffer crank, should I consider taking it a step further and stuffing some areas of the crankcase with JBweld???
So many questions! lol.
Also, I'm not sure I could personally figure out my primary compression ratio. Do I have to glue a reedblock shut and fill my crankcase with liquid and then measure said liquid???
Interested in any knowledge on this subject!!!
I've been doing some research on Primary Compression/Case Volume/Stuffing and now seem to actually have even more questions than answers...
Regarding case volume and "stuffing" with either JB weld or stuffer cranks or both, I've read that stuffing on modern 2t cranks/cylinders isn't necessary because the designs are good and the new "modern" expansion pipes do a great job of scavenging...
On the other hand, I've also read that in the case of "old technology" and small transfer area cylinders- I'm assuming this is where our 90cc+ Minarellis fall, correct?- that it's beneficial to have a high case compression (low volume) to "squirt" the charge through the transfers... Where "modern" cylinders with nice big transfer areas the expansion pipes do a good enough job of scavenging to where stuffing the crank case and using a stuffer crank isn't really necessary.
Sooooo, in my case in particular- I have trenched the cases HEAVILY with HUGE trenches and I'm also running a non-stuffer crank- stock 90cc Eton. Like this:
For the benefit if the up-and-coming 2t tuners, here's what a "stuffer crank" looks like:
See how it's "stuffed" with plastic?
So, with my (our) huge trenches and small transfer areas, it seems that my (our) primary compression is probably too low? I should probably be running a stuffer crank?? I know many of you out there already are running stuffer cranks in the 90cc+ stuff...
On top of running a stuffer crank, should I consider taking it a step further and stuffing some areas of the crankcase with JBweld???
So many questions! lol.
Also, I'm not sure I could personally figure out my primary compression ratio. Do I have to glue a reedblock shut and fill my crankcase with liquid and then measure said liquid???
Interested in any knowledge on this subject!!!
