Is there any advantage using studs over the OE Bolts?

Not the studs in that picture. The ones in the pic are not a machine fit. So other than being able to add more torqe than the stock bolts, which I personally think is stupid on a RE, they do nothing.



Have a look at these, see the difference?



http://www.xtremerotaries.com/main2/engine_services.htm

http://ausrotary.dntinternet.com/forums/vi...er=asc&start=60



"As for the debate over whether dowelling is necessary. As Rohan himself told me, rotaries do not twist, they stretch. Dowelling would work if the engines twist, but they don't really do that. This the idea behind stud kits. He has measured 1mm horizontal stretch over the whole engine in a 700hp application. That's a fair bit of movement. And that's what's happening when there is no catastrophic failure. At over 350hp, there is some measureable stretching. The sump plate should go some way to inhibit stretching, but a stud kit is the best idea."

Same reason you use studs on a piston engine, especially ones with higher cylinder pressures; ie high comp/boosted applications; to keep the head from moving around. The problem with factory bolts is they yield, stretch, like bubble gum. Not to mention bolts twist and create friction at the threads, not only wearing the threads, but providing an inaccurate torque measurement. The studs pictured are the ones I sell, I had them made by the same company that ARP used to use for their" double throw down you can't get any better studs" which also cost 4x the normal price. The materials, manufactoring, and testing process used to create those studs make them about half as susceptable to stretching as the factory bolts. Not to mention vibration and breaking issues are almost eliminated.



P.S. The site is real fresh and I've got a ton of updates for it, I will have more detailed information etc for most products...

But did you ever determine what the CORRECT torque value is when the stud kit is used? And what method did you use to determine that value?

Dowelling is not meant to prevent twisting.



Its to add more support to the combustion chamber which just happens to be the rotor housing. The whole side of the housing can deflect during a bad burn. This pushes the cumbustion chamber away from the rotor. Since the tension bolts are not machine fit there is enough room for the housing to deflect about 10mm which is enough to cause serious problems. After this happens the housing is back in the shape it had and the only evidence is a crack at the stock dowels and/or some scoring on the plates and housings by the water seals.





Studs that act as dowels both add support to the combustion chamber while adding resistance to twisting.

I see no benifit in the tension bolts not streatching.

A)The engine expands when it warms up and the bolts should streatch a little.

They are designed to do this, as the engine warms up its held toguther tighter.

B)Bolts that dont streatch would not allow for this expansion and would hold the

engine toguther much tighter than stock. I am sure you can think of a few clearences

that this would be detremental to?



As for breaking. Well, we all know how much of a problem those are.

I mean damm, I can get those stupid stock bolts to stop breaking.



As for vibration, Such a major casue of rotary breakdown. Anyone that has ever played a string

istrument knows how to fix this one. Mute it with a bit of silicone. Also, when you make them a macine

fit, dowel or bolt they are not going to vibrate.

It seems that no matter how many times we ask this question we never get an answer. I am wondering if we are on the permanent ignore list. https://www.nopistons.com/forums/pub...1047683785.gif



And the saga continues.

https://www.nopistons.com/forums/index.php



Mazdatrix recommends 35lbs op to 500 hp. But thats for the studs they sell.

32 ft #s w/ a removal strength locktite

Maybe twisting isn't the best word, a more general term like "moving" should be used.

There is movement between the housings/irons no doubt, now to what extend/what exactly causes this I don't know. In agreement with what you said; you can see a "chaffing" or "etching" on the rotor housings near the water jacket areas, same thing you see on on some piston engines. Usually just seen on race engines that have been overheated, or improperly torqued; being too loose for each circumstance.

Its not a stretch or don't stretch situation, its to what extent they are allow to stretch. How much stretch is determined by how much torque is applied; with the relativly low amount of torque applied the studs are being allowed to stretch, to account for different expansion rates.

Clearances are not the issue with limiting the engines expansion, there is something else that happens first, and its only a problem once the engine cools down...



I've never personally seen a tension bolt break, but that doesn't mean it doesn't happen. I spoke with a shop owner at the PRI show who strictly builds high revving race engines, and he told me it was not uncommon to see the tension bolts break from vibration.



On a side note, don't forgot the stock bolts when torqued are twsiting. Ovetime they untwist, and inconsitent torque levels result.



Vibration and resonance still play a factor even if something is machine fit.

10...one-zero mm?

meh hrmmm

http://www.rx7club.com/showthread.php?t=559062

The studs we use are not really a "tight" fit either and they are the same exact size Guru sells. You have some play .008 oversize on the hole. We have ran them on a few motors here and I like them. I just hate the build/teardown when/if needed. I have had NO vibration issues. As for ARP some of their stuff is good for most apps. I know their stuff wasn't not sufficient for what I needed for my mains on the GTS motor.





-S-

If the Guru stud kit uses a 1/2 UNF thread then the tightening torque is exactly the same as stock. The helix angle of both threads are the same so the torque should be also.



Chris

We tighten using the factory specs correct.



-S-

https://www.nopistons.com/forums/index



Scroll down some on that page, Some info on torque specs and some other stuff.

Those are the ones my engine is getting currently..