prattvan
05-19-2016, 10:43 PM
I did a google search on modifying an exhaust system on an 4 stroke outboard. I found alot of info stating not to do it, that you would burn your pistons.
Maybe they were referring to a 2 stroke engine, controlled by a carburetor. BUT, I'm referring to a 4 stroke outboard, fuel injected engine, controlled by a ECM.
So.........I'm kind of new to outboard engines, but have worked on car/truck engines, and go-karts for about 20 years (not professionally, just as a hobby).
For as long as 100 years, people have modified combustion engines in search of more power. If you buy a new car or truck, one of the first things some people do is change the exhaust system (because most stock exhaust systems are restrictive). And also change the intake system (such as adding a K&N cold air intake). Therefore, making the engine breathe better creating more power.
So I'm kind of confused on this. If someone puts headers on a 4 cylinder or V-6 engine in a car, you get more power. But, if you open up the exhaust on a 4 stroke outboard, it will burn the pistons ?? If you were to replace the exhaust manifold on a small 4 cylinder fuel injected engine, say 1.3L, with a header and connect that header to an piece of exhaust pipe(no muffler).......you would have a open exhaust. In theory, the ECM would sense the increased airflow and increase fuel flow to the injectors. Correct ??
Take a 1998 SUZUKI DF70 for example. It's practically the same engine that was in the 1998 Suzuki SWIFT car. Engineers made a modified intake manifold, a modified oil pan, put the fly wheel on the front of the engine instead of the back, a cast aluminum modified exhaust manifold with water jackets to keep it cool and from melting the hood/engine cover, and the engine is mounted vertical instead of horizontal, like in the car.
I'm open to ALL comments.
I have gotten alot of comments when I posted this on other forums.
They posted alot of comments about 2 stroke outboards. I don't have a 2 stroke. It's a totally different engine. Most 2 strokes are carbureted, and a 4 stroke is fuel injected. If you modify a carbureted engine to breathe better by creating more intake air and/or free flowing exhaust, you have to add more fuel. You either install bigger jets or a bigger carburetor all together. When doing the same to a fuel injected engine, it's a whole different animal. The ECM senses more air coming in and/or going out and increases fuel to the injectors........to a degree. If you modify the air intake/exhaust more than just a little, you change to bigger injectors.
By reading some of the comments I received, many assumed that I would remove the water cooled exhaust manifold and replace it with open headers or something to that effect. Not the case here. Simply put, I'm thinking of modifying the stock water cooled exhaust manifold.
Please feel free to reply. I would like all comments.
Maybe they were referring to a 2 stroke engine, controlled by a carburetor. BUT, I'm referring to a 4 stroke outboard, fuel injected engine, controlled by a ECM.
So.........I'm kind of new to outboard engines, but have worked on car/truck engines, and go-karts for about 20 years (not professionally, just as a hobby).
For as long as 100 years, people have modified combustion engines in search of more power. If you buy a new car or truck, one of the first things some people do is change the exhaust system (because most stock exhaust systems are restrictive). And also change the intake system (such as adding a K&N cold air intake). Therefore, making the engine breathe better creating more power.
So I'm kind of confused on this. If someone puts headers on a 4 cylinder or V-6 engine in a car, you get more power. But, if you open up the exhaust on a 4 stroke outboard, it will burn the pistons ?? If you were to replace the exhaust manifold on a small 4 cylinder fuel injected engine, say 1.3L, with a header and connect that header to an piece of exhaust pipe(no muffler).......you would have a open exhaust. In theory, the ECM would sense the increased airflow and increase fuel flow to the injectors. Correct ??
Take a 1998 SUZUKI DF70 for example. It's practically the same engine that was in the 1998 Suzuki SWIFT car. Engineers made a modified intake manifold, a modified oil pan, put the fly wheel on the front of the engine instead of the back, a cast aluminum modified exhaust manifold with water jackets to keep it cool and from melting the hood/engine cover, and the engine is mounted vertical instead of horizontal, like in the car.
I'm open to ALL comments.
I have gotten alot of comments when I posted this on other forums.
They posted alot of comments about 2 stroke outboards. I don't have a 2 stroke. It's a totally different engine. Most 2 strokes are carbureted, and a 4 stroke is fuel injected. If you modify a carbureted engine to breathe better by creating more intake air and/or free flowing exhaust, you have to add more fuel. You either install bigger jets or a bigger carburetor all together. When doing the same to a fuel injected engine, it's a whole different animal. The ECM senses more air coming in and/or going out and increases fuel to the injectors........to a degree. If you modify the air intake/exhaust more than just a little, you change to bigger injectors.
By reading some of the comments I received, many assumed that I would remove the water cooled exhaust manifold and replace it with open headers or something to that effect. Not the case here. Simply put, I'm thinking of modifying the stock water cooled exhaust manifold.
Please feel free to reply. I would like all comments.