ZX-Tex

iTrader: (15)

^ Keith Verges? Ahh ok guys he knows a thing or two about racing Miatas. If A286 hardware works for him, it will probably work for you too. Keith where do you get your A286 fasteners from?

kverges

It is pretty hard to come by. I happened to find some from an aircraft mechanic on eBay.

I stocked up on 3/8-24 bolts and 5/16-24 bolts; I could not find metric. I use 3/8-24 bolts to hold the turbo to the manifold (and I safety wire the bolts and modify the turbo to accept bolts rather than studs), and I heli-coil the downpipe to accept 5/16-24 bolts, which I also safety wire. These fasteners hold as permanently as I can tell.

Someday I want to see how a Porsche 962 is held together. Anything that won 24 Hours at LeMans is good enough for me.

ZX-Tex

iTrader: (15)

Yeah I am having trouble finding metric as well. I suppose I could drill out and tap the turbine flange on the exhaust manifold (stainless steel flange, tubular header). But since it is already an M10x1.5 it would end up being a big bolt, like a 7/16" or larger. A helicoil could work too I suppose, since it would close the hole back down again. I would rather just try to get metric hardware though.

You know, it may not be an 'A286' spec bolt, but the Europeans have to have a spec bolt of equivalent strength made from a similar alloy, in metric. Searching for metric A286 fasteners may be the problem since they will all be standard threads by default. American standard, American threads. I'll check around here at work and see what I can find out.

Interesting that you are using bolts. I suggested this earlier in the thread, and am still considering it, good to hear that it works for you. Sounds like you are using hex-head bolts? Did they come drilled for safety wire, or did you drill them? I need to check the Rockwell C on A286 but if it has been through hardened to 160 ksi it is probably going to be difficult to drill. EDIT: A quick search shows it is about HRC 35, which is still machinable IIRC.

Once you install and torque them, do you have to retorque them later on? Seems like that would be a PIA to cut the safety wire, tighten the bolts, and rewire them with the manifold in the car. That is the only thing I do not like about the safety wire approach.

kverges

no re-torqueing required. I use 12-point head bolts, actually, and have to grind some of the head off and modify a box end wrench to tighten them but I promise you they do not come loose. In fact, you have to pull the manifold to R&R the turbine. Had to drill them with a special carbide bit.

JasonC SBB

So how does this A286 stuff help i.e. not loosen with heat cycling? Is it that it stretches more than regular studs thus maintaining its clamping load? (i.e. it's got a higher modulus of elasticity)? M@? Bueller?

ZX-Tex

iTrader: (15)

The Young's Modulus (elasticity) for A286 and 316SS is about the same. But A286 has a much higher yield strength than say 316ss, about twice as high depending on the treatments. So yeah that is the idea, it will not yield (stretch) as much as a lower strength bolt.

While we are discussing exotic materials for bolts, titanium like 6Al4V (something I use a lot) is also very strong, with about the same yield/ultimate as A286, again depending on the treatment, and is in the same price range. And metric titanium fasteners are common. But, and this is a big BUT, its coeff of thermal expansion (CTE) is about 1/2 that of A286. That means, as it heats up, it does not elongate as much at the A286. This is bad since it means it would be loaded more by the expanding cast flange, more than the A286, all else being equal. For a metal, titanium is also a crappy thermal conductor, so it would tend to heat up/cool down slower than the parts around it, exasterbating the problem.

Keith thanks for chiming in, very helpful real-world experience on your part. Now I am thinking A286 (or equivalent) bolts, safety wired. Are you using regular stainless safety wire? Do you know the gauge?

y8s

iTrader: (8)

so you want a material that's expanding at the same rate as the flanges but has a very high elastic limit so it doesn't stretch permanently and leave your nuts loose...

I still wonder if a nickel-titanium super-stretchy alloy is the way to go. you get 6-8% stretch WITHIN the elastic limit.

ZX-Tex

iTrader: (15)

Exactly. One thing about A286 (and 316ss) is it matches pretty well with cast iron on CTE, at least a cast iron alloy I found that is used to cast exhaust manifolds. That is why 6Al4V titanium would suck IMO. Even if it did maintain the same temperature as the flange, titanium would only elongate about 1/2 as much at a given temperature as the flange, and thus load the bolt more.

I do not know what casting alloy Garrett actually uses for their turbine housings but I have put in an inquiry. The alloy they use could have a different CTE.

JasonC SBB

Finally I think we may be getting somewhere.
Spooky's (?) Resbond experiment is encouraging too.

May work even for he-men second-coming-of Ayrton-*******-Senna himself drivers like Sav and Crashncar.

Savington

iTrader: (31)

I hope so. I don't have the patience, but there are local guys who might. Once Nick (snowboarder) gets his car together and he can no longer break it, I'll see if I can.

Laur3ns

I'm getting the turbo and manifold off this morning if time permits and take it to OTS for mating surfaces and some bling bling studs. Hopefully back together before the end of the week.

Meanwhile Savington, entertain us with some v-band galore.

BenR

iTrader: (2)

Go ahead and swallow his ****.

Savington

iTrader: (31)

Not until someone buys my 2554R setup.

thesnowboarder

iTrader: (15)

ZX-Tex

iTrader: (15)

I'd rather take your word for it that **** swallowing is not a pleasant experience.

BTW I am still looking for A-286 (or equivalent) bolts in metric, no luck so far. I did find sources for grade 12.9 metric bolts that have the same tensile strength as A-286, about 150 ksi. But they are not corrosion resistant, just black oxide coated. That might be OK, though I would prefer the A-286.

I have ordered these, and will use them if I cannot find any A-286 equivalent metric bolts. These have a minimum tensile strength of 174 ksi. I'll either drill them for safety wire or use resbond.
http://www.mcmaster.com/#catalog/115/3085/=2jjwpq

hustler

iTrader: (6)

today its v-bands...but I'd like to see what turbo cars from 20-years ago did since we're in the same technological group.

wayne_curr

iTrader: (8)

So my studs are backing out just at autox now :( Does anyone think one of the methods mentioned here would atleast hold my **** together for DD and Autox? All i'm using now is what I found at the autoparts store so it may be total junk...

thesnowboarder

iTrader: (15)

I bet stage 8s would be fine for you. They lasted 3 sessions on track for me. Try it with that high temp locktite and you will be set.

wayne_curr

iTrader: (8)

Such as the FM ones? The BEGI mani is 8mm, right?

ZX-Tex

iTrader: (15)

The new BEGI manifolds are 10mm x 1.5, on the inlet side that is. The DP flange is 8mm, but that is determined by the threads on the turbine housing.

I am still going to use Stage-8 fasteners on the DP side, though I am using bolts, not studs/nuts. It should make it a lot easier to install. One of the reasons installation is such a PIA is having to separate the assembly past the end of the stud.