So, if you think you can make 200 crank hp, the formula works out like this:
Which is great, except for the fact that Nissan injectors are all rated in cc/min. You now need to plug 31.25 into another formula to convert to metric units:
Which would give you 328 cc/min. Time to shop for something at least that big.
Don't forget, of course, to use flywheel horsepower in that formula. If you use wheel horsepower, the result will be too small an injector.
The Stupidity of SpiralingAt work I was loading some bus exhausts onto a trailer and was surprised to see that they were mandrel bent. That got me to thinking about the flow of different size exhausts with different bending methods and out of the blue I think about water being emptied from a bottle-everyone knows the quickest way to get water out of a bottle is to spin the contents so it creates a vortex.
Then I thought about how a bullet travels down a gun barrel that is rifled, which causes it to spin and stay more true to its intended path.
Now my question is this: would rifling an exhaust system yield any performance gains or would it cause more restriction?Eric RudenosOxford, Pa
The empty-the-bottle trick has nothing at all to do with how air gets into or out of your engine. When you pour water out of a bottle, you don't empty the bottle, you just replace the water with air. Getting water out and air in through the same hole is notoriously difficult, but spinning the water forces the water to go down the sides of the bottleneck, allowing air to come up through the middle.
Your exhaust has no such problem, of course, as everything is flowing the same direction. The fastest, way, in fact, to get water out of a bottle is to make everything go the same direction like it does in your exhaust. Just drill a big hole in top of the bottle as you pour the water out the bottom. No spiraling necessary.
The gun example also has nothing to do with your exhaust. The goal of a gun is to make the bullet hit the intended target. Doing this is much easier if the bullet travels through the air pointy-end first. If it starts tumbling through the air, it will both slow down and wander off target. The spiral grooves cut into the gun barrel in the rifling process make the bullet spin, and the resulting gyroscopic effect encourages the bullet to stay on the straight and narrow.
Any time you make your exhaust change directions-and spiraling is just the contstant chaniging of direction-it takes some sort of force to make all that gas alter course. The only source of energy to steer that exhaust is the pressure up at the exhaust port that's shoving all that exhaust down the pipe. The more energy you ask for, the more backpressure will result.
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