What is the best engine?

[7sleeper]

You obviously have little experience with strato saws, the amount of work done per tank is greatly increased. I have a stock ms261 & a strato gutted ms261.....the stock saw will do double the work per tank. People gutt strattos to get more air/fuel in to obtain more power. It comes at a cost though.

To be honest I do have experience with strato saws. But I have no experience with gutted strato's.

I presume that the gutted strato's are also more powerful because the fuel has more air volume to mix evenly in the same time frame compared to the strato intact saws.

7

 

[Chris-PA]

I presume that the gutted strato's are also more powerful because the fuel has more air volume to mix evenly in the same time frame compared to the strato intact saws.

The only volume of air that matters is what is trapped in the cylinder after the exhaust port closes. Whatever that volume is, there is a certain amount of fuel that is required, and you (or the feedback system) will adjust the H screw to make it so. If you must put more fuel in to account for what gets blown out the exhaust, then so be it but that fuel makes no power - it is lost to the air or turned into heat in the cat.

In the end it is all about the air, and the fuel is the dependent variable - you cannot get more power by forcing more fuel in, that just makes it rich. So anything that increases the amount of air trapped in the cylinder after the exhaust port closes will make more power (i.e. a pump with better volumetric efficiency). On some designs no doubt you can improve the power by removing the divider and mixing the two flows, but this is only because improving the intake flow helps these engines, NOT because putting fuel in the strato path is helpful. If you can improve the flow while keeping the separation it will work too.

I think it is an important distinction, because I see that people are beginning to think introducing fuel into the strato path is a goal, and a way to make more power. It is always about the air, as long as you can get enough fuel (which you can).

 

[7sleeper]

The only volume of air that matters is what is trapped in the cylinder after the exhaust port closes. Whatever that volume is, there is a certain amount of fuel that is required, and you (or the feedback system) will adjust the H screw to make it so. If you must put more fuel in to account for what gets blown out the exhaust, then so be it but that fuel makes no power - it is lost to the air or turned into heat in the cat.

In the end it is all about the air, and the fuel is the dependent variable - you cannot get more power by forcing more fuel in, that just makes it rich. So anything that increases the amount of air trapped in the cylinder after the exhaust port closes will make more power (i.e. a pump with better volumetric efficiency). On some designs no doubt you can improve the power by removing the divider and mixing the two flows, but this is only because improving the intake flow helps these engines, NOT because putting fuel in the strato path is helpful. If you can improve the flow while keeping the separation it will work too.

I think it is an important distinction, because I see that people are beginning to think introducing fuel into the strato path is a goal, and a way to make more power. It is always about the air, as long as you can get enough fuel (which you can).

I believe you misunderstood me, my comment was meant that not introducing the fuel through the strato port, but that the fuel mixes earlier and more even in the common port compared to the strato technology. This is what I presume makes a difference, although this is only an assumption.

7

 

[Chris-PA]

I believe you misunderstood me, my comment was meant that not introducing the fuel through the strato port, but that the fuel mixes earlier and more even in the common port compared to the strato technology. This is what I presume makes a difference, although this is only an assumption.

7

OK, I see what you were getting at now. The strato engines are not like the "stratified charge" engines of the 70's, in that the mixture is not supposed to stratified or separated at the time of ignition. The fuel is intended to arrive in time to mix thoroughly before ignition. Whether it does that well is another question.

 

[Oleo-Mac 999]

Thank you all for your knowledge sharing