Porting
Cylinder porting is an art, it involves very complicated science and a little black magic. I know I can never learn enough about this theory or actual process. I could go on forever about porting. We have a large pile of cylinders that did not work. If you are not exploring the boundaries it is hard to make improvements. Porting can be extremely rewarding and fun when you make gains. It also is quite painful to go backwards after a 100 hours of grinding. There is a lot of information and software in the technical links section if you take the time to read however most of this applies to real two strokes that have expansion chambers and can achieve 100% volumetric efficiency. Most two-strokes operate with a gear box or torque converter that limit the power band to maybe a 3000 rpm window. Our boats have to pull hard from idle and rev to the moon. This provides the outboard engine builder with a challenge. Hats off to Mercury for their remarkable success in this art. Most of the text book rules apply to porting an outboard, but without a pipe and gearbox we have had to trial and error to find specs we like.
OMC, Johnson/Evinrude, refrigerators, anvils….whatever you want to call them, their porting is embarrassing. We have seen better cylinders out of the 70’s. However in their defense, OMC only had a target of around 225 hp and they accomplished just that. Their F-1 V-8 engines were strong back in the day. Enough bad mouthing as this downfall is our opportunity to make these engines haul ass. Porting is the key. This porting thing can make or break your build. You can have the best parts bolted onto your engine, but pair that with a bad port job and you have one expensive slow ride. I have been there before and I imagine some of you have as well. The great thing about these engines is that they are horrible stock and we all seem to be able to make some gains. If Yamaha Racing came up with a 3.3 liter engine design, I would be all over it. Huge numbers would be possible. Yamaha would probably have trouble building a gearbox that could handle the power.
At DBR we have taken 30 years of two stroke porting experience with all types of engines and have tried to build the fastest possible outboards in the world. We haven’t tried it all but I estimate we are well over 5,000 dyno pulls developing what we race today. To properly port engines you can acquire thousands of dollars in tools and tool bits.
Back To Technical 101
OMC, Johnson/Evinrude, refrigerators, anvils….whatever you want to call them, their porting is embarrassing. We have seen better cylinders out of the 70’s. However in their defense, OMC only had a target of around 225 hp and they accomplished just that. Their F-1 V-8 engines were strong back in the day. Enough bad mouthing as this downfall is our opportunity to make these engines haul ass. Porting is the key. This porting thing can make or break your build. You can have the best parts bolted onto your engine, but pair that with a bad port job and you have one expensive slow ride. I have been there before and I imagine some of you have as well. The great thing about these engines is that they are horrible stock and we all seem to be able to make some gains. If Yamaha Racing came up with a 3.3 liter engine design, I would be all over it. Huge numbers would be possible. Yamaha would probably have trouble building a gearbox that could handle the power.
At DBR we have taken 30 years of two stroke porting experience with all types of engines and have tried to build the fastest possible outboards in the world. We haven’t tried it all but I estimate we are well over 5,000 dyno pulls developing what we race today. To properly port engines you can acquire thousands of dollars in tools and tool bits.
Back To Technical 101
