Thanks!
As for torque values with studs: I built my most recent engine with standard size studs around ~45 ft-lb as I didn't want to pull any threads or crack the front iron. I couldn't imagine going much past that, yet have also seen suggestions much higher. What's the happy medium for you guys?

 

I torque to 28, same as factory.

 

I wasnt thinking of the light load of static compression caused by the cold clamping load from the fastener torque spec.

I meant the much greater compression force caused by aluminum rotor housing thermal expansion versus the higher tensile yield force of the aftermarket stud versus the stock easy to stretch tension bolts.

That will compact the rotor housing aluminum much more quickly leading to shrinkage.

 

That's fair. I've yet to see an issue on any of the stock torque aftermarket studded engines I've assembled. I HAVE torn down a block with some of those CX racing studs that were probably torqued to 45ish causing significant crush - not really apples to apples due to the titanium's presumed lower coefficient of expansion (I say presumed because who knows if they're real titanium).

 

An elegant solution would be to make hardened steel sleeves and eurathane bond them over the stock tension bolts. Ream housings to tolerance.

This would combine the torsional reinforcement of oversized studs and the old MFR trick of skim coating the tension bolts with RTV to damp harmonics.

While keeping the Mazda engineered clamping load of tension bolts versus thermal expansion.

 

Very interesting - and definitely not something I had in mind when I studded my engine. Thanks for the enlightenment.
Sounds like I should sort out my water injection sooner than later, haha.
Hopefully my engine doesn't have to come apart any time soon but I’m interested to see how it ages.

Is it possible that this active thermal expansion of the housing is exacerbating the banana seal issues seen recently?

 

i don't think so, i didn't look for studs when i looked into it. a couple years ago, i looked at every engine "warped seal" thread i could find, and then eventually looked at more
the common thread was that the majority of the "warped seal" cars were big builds, IE it was a new engine, turbo, ecu, fuel system etc. most of them were in the end tuning/setup problems

i should have just collected the links, instead of taking my word for it, i could have just posted the links and you could make up your own mind or minds, lol

 

or you could run an overly thick oil pan spacer, and maybe a brace on top of the engine, which is what Mazda did on the 787's
which used the engine as a stressed member in the chassis

 

The stud kits, solid 1 piece dowels and extra dowel pins of previous years werent so much to prevent stack twisting as far as I can tell.

They were ways to limit the bowing out of the unsupported rotor housings between compression and combustion zones when the air fuel mix detonates. This puts forces into the upper dowel pins which crack the less robust at dowel area rear and front housings.

 

That could be interesting, though I think you may run into mis-matched bores requiring machine work - at that point tried and true extra dowelling as you've mentioned is really the way to go - and what I tend to suggest, though again I've used aftermarket studs at stock torque levels.

No, I don't think so. I'm pretty much of the opinion that people are using extremely retarded timing numbers/over rich mixtures/crazy EGTs and reaping the rewards. I don't believe for a second that the fix for Ianetti's steel seal bowing as quickly as claimed (a single dyno session/pull) is the crazy high premix numbers I see thrown around, or that the smoking gun is fuel cut on decel - don't get me wrong I don't think you should turn on fuel cut and I do think it can cause premature wear but I think that's a separate problem to solve.