port timmings

[23champ]

I've recently had the chance to compare multiple cylinders from different builders, one of which seems to pull taller gears easier than the rest. The hardest pulling motor seemed to have less agressive durrations than the rest. While most of the cylinders seem to be around 187*-188* of exhaust, and 127*-128* on transfers, the hardest running motor degreed out at 121* transfers (which is close to stock), and 187* exhaust.
I degreed a stock cylinder out at 177.5* on exhaust, and 120.5* on transfers

I was always under the impression that the transfers needed to be raised approximatley the same number of degree (maybe a little less)as the exhaust to make the most amount of power? The longer the transferes are open, the longer the cylinder will fill right (or atleast as long as possible without not having the proper amount of blowdown)?

The cylinders with the taller transfers seem to make a little milder hit than the other.

[AlisoBob]

The jug with the most transfer timing isnt the one filling the cylinder the most.... its the one sending the most fuel out the pipe.

Too much fuel out the pipe cools it down..... and cold pipes dont make power.

[100hp honda]

if you want no bullshit cold hard facts about 2stroke engines then check out gp blairs 2t simulation book. 600 pages will fry your brain . probly could be another 600 pages and still not discuss eveything.

[gammabusa]

I am out..........

[blownbillybob]

Kinda like if a young kid goes to the hot rod shop and buys a huge cam for his stock SBC and it doesn't make as much power as a smaller cam would make!

Bigger isn't always better!!!!

[100hp honda]

high transfers have their place, just as low ones have theirs also. any legitimate literature will explain the how and why and show proof in theory and practice. high ones can let excess charge into the pipe and also have reverse blow back into the tunnels. key word is CAN. depends what the rest of the cylinder is doing.

[100hp honda]

I've recently had the chance to compare multiple cylinders from different builders, one of which seems to pull taller gears easier than the rest. The hardest pulling motor seemed to have less agressive durrations than the rest. While most of the cylinders seem to be around 187*-188* of exhaust, and 127*-128* on transfers, the hardest running motor degreed out at 121* transfers (which is close to stock), and 187* exhaust.
I degreed a stock cylinder out at 177.5* on exhaust, and 120.5* on transfers

I was always under the impression that the transfers needed to be raised approximatley the same number of degree (maybe a little less)as the exhaust to make the most amount of power? The longer the transferes are open, the longer the cylinder will fill right (or atleast as long as possible without not having the proper amount of blowdown)?

The cylinders with the taller transfers seem to make a little milder hit than the other.

have you done a map on all the cylinders ? that could give you some insight why one works better than the others. it goes well beyond just a degree wheel. takes a fair amount of time and requires good math skills.

[bigred1977]

if you map all the cylinders with 1-2mm grid paper and send them to me i will give you all the answers to each one blow down comparison time area calculation sec/sq,mm this will give your perfromance differnce on paper.