Your thoughts on precup's

[sctrailrider]

Hi everyone, I did a search but didn't find too much about the size of the "mouth" on precup's. I had my military square cups machined out to .850", about .100" wider than diamond cups, only the mouth was machined, nothing on the inside of the cup.

What are your thought's on this for a towing build with 18:1 compression and turbo-ed build??





I am building a new motor for towing power/tork, other pics for my build can be seen in my album " My 6.5 towing build " I will be starting a build thread soon, going to the machine shop in a few weeks.

[greatwhite]

Precombustion chambers are a "catch 22" engineering solution.

On one hand, you need the "mouth" small enough to promote good swirl in the chamber bowl to ensure proper fuel mixing. Make them too big and this suffers from a loss of velocity. But, you can gain more "power" by better propagation rates and reducing throttling losses with bigger openings.

On the other hand, make them too small and you run into problems like throttling losses and lower propagation rates. You loos power in throttling and propagation, but gain mileage performance by better mixing/swirl/velocity.

Where does the balance lie?

Dunno.....it's a balance between exposing the fuel to the most oxygen (IE: swirl) and minimizing the losses. This is done by engineers with far more knowledge of the principles than myself.

Playing around with the mouth may lead to gains in one area or losses in another. It's an expensive way to find out, but trial and error (IE: tear it down, install chambers, put it back together, see what you get, repeat as necessary) in the field does work.

My personal feeling is the diamond chambers are probably the best balance between the two requirements. But for someone looking for more of one or the other (IE: power/mpg) it's worth exploring....