The virtually equal length runner, four into one A/O manifold also provides for a remote wastegate. A remote gate is only a distinctly better boost control if positioned properly.
The A/O manifold creates equal exhaust gas access to the turbo and the wastegate, whereas all other Miata turbo manifolds that feature a remote gate, position the gate in a manner the same as the standard integral gates, requiring the exhaust gas to make a sudden right angle turn to just get to the gate.
This is not the path to power, but the accountant loves it. Please note, a large turbo fit to our A/O manifold does not intersect the framework of the car.
While getting through the turbo and the wastegate, the smooth, least restrictive flow path for the exhaust gas remains just the first half of the equation.
Do not under estimate the performance advantages of getting the exhaust gas out of the turbo and gate in the least restrictive manner, and this is where the A/O turbine outlet pipe does a better job than any other TO pipe available today.
There are several reasons why we believe our TO pipe design is superior:
- The intersection of the turbine exit port and the entry into the tubing must be of the same inside diameter. We have done that.
- The shape of the pipe should be slightly conical, and of course, larger as the pipe proceeds rearward. We have closely approximated this by starting with the port exit diameter and stepping up the pipe size in increments of ¼ inch.
Thus, a pipe starting at 2.25 inch diameter will grow in steps eventually reaching either 2.75 or 3.0 inch diameter as it arrives at the rear tailpipe flange. We have also done that.
- Integrating the remote wastegate’s vent tube back into the exhaust system has two rather serious configuration requirements:
- First, the vent tube needs to be in excess of 18 inches long before joining up with the TO pipe. The purpose is to avoid messing up the smooth flow exiting the turbine.
- Second, and substantially more complicated, is the need to NOT disrupt the increasing flow path created by the conical shaped TO pipe. An example of this can be illustrated by the intersection of two tubes.
Suppose the TO basic pipe is 2.5 inches in diameter and the gate’s vent tube is 1.5 inches. Intersecting these two tubes, as all other manufacturers will do, creates a reverse cone restriction. Compare the flow areas into the intersection (internal area of 1.5 and 2.5 is 1.86 + 5.36 = 7.22) and it’s easy to see the intersection entry is a total of 7.22 square inches and the exit area is only 5.3 square inches. This is akin to pumping into the wrong end of a cone. The solution is easy. Simultaneous with the intersection of the main pipe and the gate’s vent tube, expand the pipe size by a slightly greater increment.
Example: Swage the 2.5 diameter to 2.75 at the intersection and the total internal flow area will change from an entry of 7.22 to an exit area of 7.10 square inches, or virtually the same. Thus, no restriction is created.