GreyGT-C

so... if you have to install them after you build half the engine, and remove them to tear the engine down.... they are really just bolts without heads on them. Other than them being oversized,,, what is the benefit here?

1Revvin7

Yes, but having a harder and denser fastener works just like the ribbed section.

heretic

There are two ways to look at it.



Primarily in this instance, the studs are also acting as locating dowels. (Machining is required) Instead of two dowels, there would be 19-20 dowels. The benefit for the effort is somewhat debatable, but let it be known that Mazda determined that part of the reason for chattermarks in the chrome is partly because the rotor housing itself would oscillate.



Ordinarily, studs are used because they are more predictable than bolts. The torque stretches the bolt or stud, but the act of torquing a bolt also twists the bolt since the area you're torquing is so far away from where that torque is acting, the threads. Additionally, the bolt is threading into what can we can consider to be a old cast iron nut. The threads can gall or pull out on occasion. (I have never experienced it on a rotary, yet, but it gets depressingly common on certain popular engine blocks from the 1980s after a few head torquings) Using a stud helps this, since it is threaded in under no load, and the nut that applies the load is nice and hardened just like the stud.



I would worry about how well the studs can stretch to accomodate the aluminum housings, or if they will get crushed the first time the engine gets a little too hot. Probably not a problem for drag use.

RONIN FC

You make a good point here, and its something to consider. But to me the benefits seem to be greater than the downfalls at this point.

Kim

Im pretty sure that Gurumotorsports has put some research into this mod.

The bolts is a pretty tight fit and will follow the engines heatrange, using the proper steel and it will not cause a problem with engine expansion.

rotarygod

One of the key benefits to s stud system is where the tension of the bolts is located. When you have a simple bolt system like stock, all of the stress of tightening them is located only at the threaded end with relatively lieelt stress throughout the bolts. With a stud system, you are splitting this stress in half between both sides, even if you torqued everything down the same. Instead of all of the rotational forces of tightening them down being all located at the front iron, half of the force is now also on the nut end. The bolts are stressed far less than they were before and more evenly over a larger area. It is even between the front and rear housings. This means you can apply more torque to tightening them down without worrying about stripping out a housing or breaking a bolt at the far end.

RONIN FC

This is an e-mail I recieved from mazdatrix So, it seems machiening is a little more extensive than I thought for the oversized studs... But there must be an easier way to line up the holes.

Speedworks

And what flywheel should be used with it? (FD engine)?



Both standard and oversized kit require a non- OEM flywheel

RONIN FC

Im assuming any one using an auto counterweight.

1Revvin7

Well if you don't want to go that route; I sell a stock diameter stud kit for $325 shipped...