1989 Blaster Engine Rebuild - Part 9, Two-Stroke Software Review

1989 Blaster Engine Rebuild - 9

Part 1 - Part 2 - Part 3 - Part 4 - Part 5 - Part 6 - Part 7 - Part 8 - Part 9 - Part 10 - Part 11 - Part 12 - Part 13 - Part 14

Evaluation Of Changes

Two-Stroke Software Review

Part 1

Evaluation Of Changes
Here's where I'm at with this project - after almost a month delay due to my summer vacation schedule, I'm back on task. I have a couple of things I don't want to forget, so I put them in here.

The degree wheel is still bolted to the engine as I'm checking the port timing and head volume. Here it's easy to see the base plate spacer and additional base gasket needed to seal it up.

Inside the cylinder I noticed a much better port match as well as improved time area numbers. This area increase is necessary for improved output at higher rev levels.

The intake port on the right has had its area increased. I'll match the left port to it.

This is the setup I use for applying torque to the flywheel nut. It's tough with such a short flywheel holder, but it works.

By The Numbers
Using two-stroke design software to guide me through this I have decided on porting numbers which will give me the power characteristics I want. The increase in transfer port timing created well over 130 mm^2 of additional port area. The exhaust port received no area change other than the little bit it gained from raising the barrel - a total of about 24 mm^2. The mean port area has been increased on both the exhaust and transfer ports - a result of raising the whole barrel, this may be the most important change I've made to this engines ports. The intake ports received some attention after I noticed the total area indicated by the tuning software. The fact that its port timing was mellowed out by the raising of the barrel contributed to the decision to increase its size. The port roof was raised 1 mm and the floor was lowered an additional 3.5 mm - its width remained the same. The port area was increased by 175^2 after doing this to both of them. This put the intake numbers right in place.

I could have easily narrowed the port bridge, widened the outer port walls or drilled holes in the bridge to increase the intake area, but I decided not to. In an effort to keep as much thrust surface as possible I decided to treat the port this way. By making vertical changes I gain back some timing I lost (and a bit more), keep a lot of area for the piston to thrust against and weaken the cylinder very little. The top of this port could have been raised quite a bit more as well as widened and lowered too - I'll keep that in mind for the next phase of this engine project.

Notice the light scribe marks on the piston. Though the port roof was only raised 1 mm the port corner radius was made tighter yielding increases as well.

I like the way the piston aligns with the port floor at BDC after the changes. The bumpy area on the crown is actually grease left over after I sealed and CCed the head.

1989 Blaster Engine Rebuild - Part 9

Part 1 - Part 2 - Part 3 - Part 4 - Part 5 - Part 6 - Part 7 - Part 8 - Part 9 - Part 10 - Part 11 - Part 12 - Part 13 - Part 14

Evaluation Of Changes

Two-Stroke Software Review

Part 1

Evaluation Of Changes Here's where I'm at with this project - after almost a month delay due to my summer vacation schedule, I'm back on task. I have a couple of things I don't want to forget, so I put them in here.
The degree wheel is still bolted to the engine as I'm checking the port timing and head volume. Here it's easy to see the base plate spacer and additional base gasket needed to seal it up.	Inside the cylinder I noticed a much better port match as well as improved time area numbers. This area increase is necessary for improved output at higher rev levels.
The intake port on the right has had its area increased. I'll match the left port to it.	This is the setup I use for applying torque to the flywheel nut. It's tough with such a short flywheel holder, but it works.
By The Numbers Using two-stroke design software to guide me through this I have decided on porting numbers which will give me the power characteristics I want. The increase in transfer port timing created well over 130 mm^2 of additional port area. The exhaust port received no area change other than the little bit it gained from raising the barrel - a total of about 24 mm^2. The mean port area has been increased on both the exhaust and transfer ports - a result of raising the whole barrel, this may be the most important change I've made to this engines ports. The intake ports received some attention after I noticed the total area indicated by the tuning software. The fact that its port timing was mellowed out by the raising of the barrel contributed to the decision to increase its size. The port roof was raised 1 mm and the floor was lowered an additional 3.5 mm - its width remained the same. The port area was increased by 175^2 after doing this to both of them. This put the intake numbers right in place. I could have easily narrowed the port bridge, widened the outer port walls or drilled holes in the bridge to increase the intake area, but I decided not to. In an effort to keep as much thrust surface as possible I decided to treat the port this way. By making vertical changes I gain back some timing I lost (and a bit more), keep a lot of area for the piston to thrust against and weaken the cylinder very little. The top of this port could have been raised quite a bit more as well as widened and lowered too - I'll keep that in mind for the next phase of this engine project.
Notice the light scribe marks on the piston. Though the port roof was only raised 1 mm the port corner radius was made tighter yielding increases as well.	I like the way the piston aligns with the port floor at BDC after the changes. The bumpy area on the crown is actually grease left over after I sealed and CCed the head.