I'm taking my porting to the next level...STAGE II ...Oh Yeah!!!

[joeak47]

I'm going to be taking my porting to a new level to see what it can do. As you know,I've been using porting templates as a base,then have modified above and beyond that in certain areas. Mostly the exhaust port,and a little bit on the intake.
I'm going to take what I presently have,and plan on raising the roof of the intake windows about 2mm to 3mm,raising the top of the exhaust port another 1mm, widening the boost port just a little taking care not to widen it too much causing problems with sticking a ring,and I also plan on raising the tranfer ports about .5mm on the roofs and angle them up a bit to increase (advance) they're port timing.

I will be starting this on another cylinder,because I don't want to change anything on the cylinder I'm running right now,because it works incredible.

I just finished fitting the cylinder with a piston,and it is now awaiting the porting. I plan on proceeding with caution. I'll post many pictues as I go. I'm also going to try my skills at making my own porting templates. If I have the time,I'll try making video segments as I go. This should be fun. Stay tuned...

 

[slickerthanyou]

I smell full drag coming! Awesome as always popcorn and beer in hand!

 

[sicivicdude]

Stop thinking about portwork in terms of distance. Start measuring the portwork in terms of port timing and effective port area (area minus the angle, roughly).

Just like 4 stroke cams are quoted in lift and duration, 2 stroke ports don't care about 1mm or 5mm. Throw in a slightly shorter or longer rod (even by a few thousandths) and you're talking about a different port timing (even though it's the same "distance"). When you bore a cylinder, you are increasing the area of the ports just slightly. You could take a port that has the PERFECT flow volume and cause it to start to backflush (I know, I've done it) unless you consider it as a function of area relative to flow.

Also, don't touch the width of the boost port except to clean it up. All of the "slop" in the engine can allow a tiny bit of "twisting" motion of the piston. Add that to the ring gap and you could be in for a VERY bad day....

 

[joeak47]

I understand what your saying. I've degreed cams before,and understand lift and duration and centerline,over lap etc. If I could get my degree wheel back,I could get degree readings from the crank and go from there.
You can use "distance" to measure port work. For instance,... I can increase exhaust duration and open it a bit earlier (advance the timing) by raising the port roof 1mm. This also gives me more "effective port area" (larger area). This also gives increased flow through the port. Widening the port also produces more "effective port area".
A degree would make this easier to understand in numbers.

I know what your saying about the boost port too. I've measured and checked,and can see that the piston ring locating pin (1.5mm in diameter) in the piston sits a bit over 4mm to each side of the boost port,so cleaning it up a little bit,or widening it will not hurt anything. Believe me,I don't want to snag a ring. Thats also taking into consideration the ring gap. A very important tip.

 

[sicivicdude]

I understand what your saying. I've degreed cams before,and understand lift and duration and centerline,over lap etc. If I could get my degree wheel back,I could get degree readings from the crank and go from there.
You can use "distance" to measure port work. For instance,... I can increase exhaust duration and open it a bit earlier (advance the timing) by raising the port roof 1mm. This also gives me more "effective port area" (larger area). This also gives increased flow through the port. Widening the port also produces more "effective port area".
A degree would make this easier to understand in numbers.

I know what your saying about the boost port too. I've measured and checked,and can see that the piston ring locating pin (1.5mm in diameter) in the piston sits a bit over 4mm to each side of the boost port,so cleaning it up a little bit,or widening it will not hurt anything. Believe me,I don't want to snag a ring. Thats also taking into consideration the ring gap. A very important tip.

Ultimately the distance is what you are actually cutting but when you get to comparing two different engines, the distances start to lie. If you have a rod that is slightly shorter, cases that are lapped off, piston that's slightly shorter, thinner base gasket, and machined mating surface on the bottom of the cylinder (NONE of which by themself will cause any problems at all) you could change the port timing on that particular cylinder by a rather large amount by changing any of those variables. If you are shooting for a "distance" instead of a "time area" you will have less consistancy from cylinder to cylinder and setup to setup.

Considering you are using your engine as a testing platform for other modifications, you really should start thinking about your engine in time area instead of the distances. That way when you go to apply what you've learned from how your engine works to building other engines (you know, like the "best" cylinder) you will be able to apply your learnings a lot easier.

Effective port area is gained by making bigger ports but when you take a port map and lay it flat and measure the size of the ports they tell a LIE! Doesn't seem like it, but they do.

The effective port area includes the angle that the ports are aimed. The biggest liars are the transfer ports and boost port. As you increase angle (without changing the actual size of the port, if you laid the map out flat and measured) you are actually decreasing the port size and amount of fuel/air that can pass through that port.

You would actually have to increase the map size more than you think to compensate for the angle to keep the effective size the same. The boost port is the worst offender by far.