Turbine outlet studs + Downpipe Q's
 

OK, did a search, and there is alot of talk about manifold studs. I couldn't find anyone talking about turbine outlet studs.

I just bought a used GT2560R from an S14 240SX SR20. There are a few turbine outlet studs missing.

I also just bought a used BEGI 1.8L log manifold, and an older BEGI downpipe. Based on how the BEGI downpipe bolts up to the turbine housing the few remaining studs in the housing could be another 5mm longer for better nut engagement.

Luckily, it appears that the BEGI manifold I bought came with the TSE Inconel stud kit already installed. Although one of the studs has some of it's threads worn off (vibration??).

So, what is the hot ticket for turbine outlet studs?
-Standard black oxide coated steel studs and nuts?
-CAD coated steel studs?
-Stainless studs and nuts??


Another question about the downpipe- it looks like this:

https://www.miataturbo.net/attachmen...ine=1347510221

So, it doesn't have a divorced wastegate feed. Or really any sort of special provision for the wastegate.

I could:
-Add a divorced wastegate tube (say 1.5"), but that is alot of cutting and welding, and may cause me boost creep issues.

OR

-Add a kickout piece of tubing for better wastegate flow. A little easier to do, and won't require me to mockup in the car. Kinda like this:

http://www.tuningdepot.com/ebay/images/dp11501b.jpg

OR

-Say Fook it and slap it on as-is?

Second part first, fook it.

Now for the first part. It would be best to get inconel studs and resbond for the turbine outlet to downpipe connection because they will also stretch, crack, loosen, etc over time. If Trackspeed doesn't have them in the smaller size (m8x1.5) you can get them from Full Race. Resbond is available pretty cheap from McMaster Carr.

The cad coated hardware will just flake the cad coating off from the heat.

I search for Resbond on Mcmaster site and come up with nothing. I see they have something called high temperature pipe sealants and threadlocker.

Part number 7604A56 @ $31.18 per 4 Oz. bottle.

"Make strong, secure bonds even in extreme temperatures. These no-drip liquid adhesives withstand temperatures from -300° to +2100°F and resist oil, fuel, acids, and alkalies. They form an electrically resistant bond on metal and ceramic threads. Seals can be broken using hand tools. Begin to harden in 24 hours; reach full strength in 2-3 days. Come in 4-oz. bottles. These products are compliant under all state VOC rules in effect on October 1, 2008.

Green penetrates fine openings, such as for set, adjustment, and instrumentation screws. Fills spaces up to 0.003".

Blue prevents loosening from vibration for medium-sized fasteners, pipe threads, and bearings. Fills spaces up to 0.005".

Red provides high-strength bonds for studs and large fasteners, bolts, and pipe threads. Fills spaces up to 0.01".

Is this the stuff?

Also, the Full Race Inconel studs come in a pack of 4, and I would need 5 for the turbine outlet. They also don't mention a stud length, so not sure if they would fit the downpipe or not.

Pack of 4 for $50. Would need 2.

Full-Race T25 Turbo M8 Stud Hardware Kit - Full-Race.com

That is the Resbond, you want the red.

Get the four studs, and use whatever other one you find for the fifth and you should be good enough.


Shake the Resbond well before each application.

The turbo to downpipe area sees MUCH less heat than the manifold to turbo area. That's the point of a turbine after all. Convert heat and pressure to mechanical work.

I recently did a teardown after 1.5 years and 15,000 miles of aggressive, windy-road daily driving (cherry-red turbo every night). On my initial build, I cheaped out and put in mild-steel bolts safetied with Inconel wire. Here's the ugliness in the manifold to turbo area on my teardown:
https://www.miataturbo.net/attachmen...ine=1357947490
TSE's studs are in there now.

What was interesting is that the same bolts used in the turbo to downpipe area were fine. They were still tight and came out without drama. The only issue there was that the zinc coating had burned off.

In the interest of belt and suspenders, I've upgraded these to Inconel as well. I was able to find some Nissan OEM Inconel bolts in M8x1.25. At $3.50 per bolt, they were pretty darn cheap for black-oxide Inconel. Wrote about them here:
https://www.miataturbo.net/engine-pe...e-bolts-68918/

A word about bolt material. We use Inconel for two reasons. The first (obviously) is that Inconel retains its strength at high temperatures. The second (less obvious) is that Inconel's thermal expansion coefficient is a near perfect match for mild steel and iron. There are some SS alloys that have excellent strength at high temperatures. However, the thermal expansion coefficient for typical SS is quite a bit higher than mild steel or iron. Keep that in mind if you are considering SS.

Good find on the cheap inconel bolts. Unfortunately, it looks like they won't work for my application. The downpipe flange is 22mm, leaving only 5mm of thread engagement. Looks like the general rule of thumb is 1.5 x D for thread engagement in cast iron, so 12mm in this case. Bummer.

I'm still not sure how long the Full-Race stuff is. Anyone know?

So, here's a pic of my BEGI manifold with the TSE studs in it. I just bought this used, so have no history on it. But, two of the studs have the threads worn away. Also, most of the studs can be turned by hand like about 10-20 degrees, so will probably need some new resbond.

https://www.miataturbo.net/attachmen...ine=1357952376

A286 is a well-known heat resistant stainless alloy (often used to join jet engine sections together). It has a high thermal expansion coefficient vis-a-vis your nearly 1" thick downpipe flange. You want to make sure you use a metal gasket to handle the mismatch. You'll also want a nut that offers a positive locking feature (like Stage-8 or a metal locknut).

Another option in A286 . . . you can find A286 bolts of various lengths pretty reasonably from industrial suppliers (search on A286 and they'll pop up). These usually have allen heads and can be drilled for safety wire. Obviously, you have to have enough clearance to tighten the allen head. It looks like that might be a challenge on one of your downpipe bolts.

Are the studs only worn in the turbo flange area or does the thread damage extend into the nut area?

I can't seem to find anyone that sells metric A286 bolts. Looks like there is a MIL-SPEC for close tolerance Metric, pre-drilled for safety wire (NA0045), but I can't seem to find a website selling them. MIL-SPEC = hard to find and really expensive.

The threads that are worn away on my TSE studs all should be below the nut engagement portion. Makes me wonder how they got worn away though - I assume the studs came loose on the car, and vibration wore away the stud. Not a good sign for a good sealing robust setup.

My turbine outlet studs were constantly cracking or becoming loose until the Resbond was added. Regular cheapo studs did not last there for me.

In my case, the turbine outlet bolts were cheap, but they were safety wired with Inconel. I'm sure that's what kept it together. Heck, that even kept the manifold to turbo joint together, even though the mild steel bolts had a severe case of thermal creep and the turbo was loose.

Things get very hot around the exhaust system.

https://www.miataturbo.net/attachmen...ine=1327330030

Well, I just heard back from Full-Race about their 8mm turbo studs. Apparently they are only 40mm in length, and are also out of stock. Bummer.

22mm flange thickness + 1mm gasket + 7mm M8 nut height = 30mm stackup. So, only 10mm of thread engagement into the turbine housing, which wouldn't bottom out the stud on the shoulder. Maybe this is OK with Resbond, but seems pretty marginal. Also less than the 1.5 x D thread engagement rule of thumb for cast iron.

Anyone know where to buy some longer inconel or A286 studs?

You could try these guys. They claim to have A286 in stock in M8 socket head bolts. Haven't tried them myself.

Sockethead Cap Screws | Ocean State Stainless, Inc.

BEGI has black oxide in something thats a lttle over 35mm, I just got these for my turbo/downpipe setup,(circa 2007) called Stephanie, got them in less than a week. They also have inconel in catalogue, 44mm for 175.85. black oxide 8.50

Hey hornet, for the turbo to DP nissan inco bolts, how necessary do you find the safety wiring? Did you run it on the previous mild steel bolts? I didn't think this location was in need of it.

Also thank you for the post of your unfortunate street driven manifold stud situation. I've been trying to cost-benefit balance my street/some autox car for the regular steel studs (already have them) vs TSE inco studs on a begi mani and your post has helped make it a little clearer.

How much did it run you to remove the broken studs?

Anyone tried something like this?
ARP 400-8012 Stainless Steel Exhaust Manifold Kit 8x Studs/Yokes/ Nuts

Curious if they would be any good for the turbine to downpipe connection.

I had safety-wired all of the previous bolts. Exhaust systems see enough vibration that I always ensure the connectors use self-locking features of some sort. I also enjoy safety wiring -- personal thing.

Removing the studs wasn't a big deal because the manifold was being drilled and tapped to go from M8 to M10. So, essentially "free."

There are numerous stainless steel alloys (alloy = mixture of base metals) available. Not all of them offer heat resistant properties. Would be nice if you could find out which particular alloy this is (available on ARP's website perhaps?).

Don't forget that exhaust manifold studs in the head can get away with less heat protection because they are water cooled. The studs in the manifold to turbo and turbo to downpipe connections only get air cooling, with the manifold to turbo being, by far, the highest heat connection in the car.

Well, I still need to call that fastener place listed earlier, but so far, it looks like the BEGI 8mm inconel downpipe studs are the only "good" option.

Miata Downpipe Mounting Hardware - Inconel studs /8mm BEGi

$175.85 + $18.64 Shipping. Fuck that.

Also - I have been fighting removal of my turbine housing from the CHRA for days. I finally got it off, but some of the turbine housing to CHRA bolts are a bit rounded.

Are these special material too?

I think Hustler wrote about his CHRA bolts over in the EPIC thread. Thankfully, my Mitsu turbo uses a V-band for that.

It looks like Ford uses M8 studs for 4.6 and 5.4 V8 exhaust manifolds. At some point furing production they switched from standard steel to some sort of stainless alloy to try and cure stud breakage.

Ford 9K494SUB Exhaust Manifold Install Kit 8 Studs Washers Nuts | eBay

Looks like you can get a full set of 8 studs, nuts and washers for pretty cheap. Not sure why the studs have a copper color though.

Also not sure what type of stainless they are made from. But, I might try these instead. The local parts store (O'Reilly) had a set of these studs in the "HELP" section. Of course the HELP ones are shitty chinese brand, so I didn't buy them. Length is 56mm.

Well, after removing the TSE inconel studs that came with my manifold - it looks like one of the threaded holes in the manifold is boogered up. It has only about 20% thread height on one side.

I'm not sure if this happened before the previous owner installed the TSE studs or after. No way to know. In any case, it looks like I will have to fix this somehow.

So - on to the question. Should I use a Time-sert (unknown material), or an Inconel 725 Helicoil?


Versus:

Helical Thread Inserts: M10 x 1.5, 15.0mm (1.5xD) Length, Free Running, Inconel X750 (Package of 1)

I'm kinda leaning towards the Inconel helicoil. It is cheaper as I already have a helicoil installation tool, and I only have to buy one (probably 2 to be safe) inserts. It is Inconel, so should be plenty strong at high temps versus the unknown quality of the TimeSert at high temps.

Any thoughts on this?

I agree with you. I would go with the known material that is suitable for the temperature requirement.

Time-serts- I've never seen many good things come from heli-coils. Never known of inconel ones, but never liked heli-coils for anything important. Brackets-maybe. Sparkplugs and such-no.

I did a little more research, and it looks like a standard Time-sert insert is just carbon steel.

http://www.timesert.com/html/12L14CarbonSteel.pdf

You can special order them in 303 stainless as well.

That being said, it looks like neither 303 or carbon steel would be recommended for high temp applications. It's looking like Inconel is the better solution.

For what it's worth - I have never had an issue with Helicoils in the past. I've used them for motor mount holes into an aluminum block - which should have some pretty high load and vibration. Seems like Helicoils don't work very well for headbolt/stud applications though.

One of my cast manifold stud holes is helicoiled.

I know this thread is a month old, but I'm going to resurrect it with what I'm sure will turn out to be a stupid question...

I'm seeing turbine housings with studs and bolts in various locations. Is there a reason to use studs over bolts in specific holes, or is this an OEM packaging thing? Why not run all studs? Or all bolts? :confused:

Actually, a pretty good question.

Speaking from personal experience:

Bolt:
1. Cheaper (1 part vs. at least 2 parts)
2. Easily drilled for safety wire
3. More prone to getting frozen due to corrosion -- a definite consideration in a high heat environment
4. Requires enough clearance around hole to insert the bolt

Stud and Nut:
1. More parts
2. Both stud and nut need to be secured -- you'll end up using things like high-heat thread lockers and stage-8 fasteners
3. So long as you never want the remove the stud, the only corrosion/freezing you care about is between the stud and nut -- usually easier to control
4. Handles situations where clearance to insert a bolt may not be present

In my case, Inconel studs on manifold to turbo and Inconel bolts on the downpipe seem to be working just fine. Of course, I had to learn the hard way.

Nissan also used M8 Inconel downpipe studs on their turbos (e.g. 300ZX). Part No. 14414-17F00.

http://ep.yimg.com/ca/I/yhst-1534229...2252_459260986

I count 8 threads on the turbine side. 8 x 1.25mm = 10mm engagement. 16 or so threads on the other end plus about 10mm without threads? 40mm overall length? Not quite as long as BEGi's 44mm long Inconel studs but definitely longer than their 37mm long grade 8 studs.

$7.00 each here, but shipping is $14:

1990-1996 Nissan 300zx OEM Turbo to Downpipe Stud

$7.75 each here with $3 shipping:

Nissan OEM 300ZX Turbo to Downpipe Stud Z32 - Nissan performance parts

Awesome explanation, thanks Hornet!

I went out of my way to remove the 2 studs from my exhaust housing before sending my turbo in for the Garrett CHRA exchange, and the guys replaced them (for free, along with all the other hardware) with 2 new studs in the same location. I figured "well, they must know something I don't" so I didn't question it until now.

skou: FM also has a kit of 8mm Inconel manifold-to-turbo studs along with Stage 8 fasteners for $99.95. No length listed though.

Flyin' Miata : Turbochargers : Parts and upgrades : Stage 8 hardware with Inconel studs
https://www.miataturbo.net/attachmen...ine=1362208144

Humm... "10mm master race" is obviously the solution, but I'm not convinced I could drill out my turbine housing or drill/tap my manifold accurately enough. I should go find pricing on those Stage 8 nuts.

Edit: FM sells the Stage 8 8mm nuts for $28.95. Summit is only slightly less at $27.95

$20.04 direct from Stage 8 on Amazon.

Kit 3950 for (4) 8mm-1.25 Nuts.

Stage 8 3950 Turbo Locking Nut Kit with 8mm-1.25 Nuts : Amazon.com : Automotive

Kit 3952 for (4) 10mm-1.50 Nuts.

Stage 8 3952 Turbo Locking Nut Kit with 10mm-1.50 Nuts : Amazon.com : Automotive

Neat! It'd be nice to know the actual lengths on these studs, maybe I'll order a few more for the downpipe and see how they measure up.