best fix for broken exhaust downpipe bolts?
 

Running qualifying in about 30 mins. After looking into an exhaust rattle I found that my downpipe had come loose (again). This time breaking off 2of the top flange studs. Since the big separated gas pipe flange won't allow for one of the lower nuts... It leaves me with only 2 of the 5. Bailing wire for now. Suggestions for a more permanent fix?

Use all the bolts next time? You just have to ground down a nut to get it to fit under the DP.

Yes. I was able to do that with the original install, but you had to first bolt the downpipe to the turbo and then install the turbo/downpipe as a unit. On this attempt, I've already got the turbo installed with respond, inconel and locks.... Just couldn't get the turbo off. So 4/5 bolts. I did try aviation nuts... still couldn't get a wrench on it. At this point I'm going to have to pull the manifold and turbo.
I guess my question is: Is the Garrett stud/nut combo as supplied in the kit adequate, or is there a better way? Also, I do not have a downpipe hanger (to the bell housing). Are these a necessity?

Which manifold/downpipe set is it?

My advice is not to attempt to remove the broken-off stud using an EZ out or screw extractor. I've never actually seen one of those work on a fastener like that, they just wind up breaking off inside the broken stud and making it even harder to get out. Personally, I would remove the turbo, remove the turbine housing, and take it to a machine shop for extraction. They'll charge you a lot less than they will when you bring it to them with a broken off EZ out in it. :)

As for the bottom nut, if it's an FM setup (with the cast elbow), you always assemble/disassemble that out of the car and install it as a unit. If it's a more traditional downpipe, then the best way I've found is to put the DP over the stud and start the nut before you seat it all the way. Move the DP flange towards the housing as you tighten the nut to keep maximum clearance around the nut.

--Ian

The baling wire held and I finished the race...6th/12 in SPM. Not great... Not bad. Fun times!!

Question: Has anyone been able to disassemble a turbo-manifold (with resbond/inconel) once it's been put in service? I tried to disassemble mine at last engine refresh and I felt that I was going to break the studs if I put anymore pressure on it? Maybe just order a new manifold/turbo diffuser housing?

Also, my set-up (Garrett 2860) showed boost creep after 16#. Is there a better (Garrett) turbo choice for a track-only miata?1https://cimg9.ibsrv.net/gimg/www.mia...820dbb84dd.jpg
While I couldn't find actual "baling wire", I was able to daisy chain a couple of hose clamps together for an awesomely ghetto fix!

Heat resbond to release it.

I've had my resbonded turbo off once, didn't do anything special just put a wrench on it. I guess running it hard at the track took care of the necessary heating. :)

There are lots of better choices than a tater, but it really depends on your budget. The GT series is old, the somewhat newer GTX series are a nice step up -- I'm quite happy with my GTX2863R. The new G series look interesting, but I don't know anyone who's actually used one yet.

--Ian

I just noticed that Garrett offers a V-band design for their down pipe outlet. This, in conjunction with an external wastegate might be a good fix. I'm still on the fence about the turbo. I love the quick spool up, but I'm open to a better match for the car (track-day only).

FM recommended a 3071 turbo kit. I noted that their kit has a 2-peice downpipe...(I'm thinking " more bolts to rattle loose"). They don't incorporate a bellhousing to downpipe mount either; so likely not needed. They did say that they've never had issues with the downpipe bolts loosening under severe use and never felt that it was necessary to offer inconel, stage 8 locking hardware or safety wired fasteners. They also say that they don't have issues with boost creep on their turbo systems. ...So, it's got me feeling a bit like an odd case.

I'd recommend buying a turbo kit that was actually designed to do what you are doing, from a company whose cars do what you are doing with pants-on-head levels of reliability, vs. one that was designed for street use, from a company which has never done what you are doing.

what one do you suggest?
lol

A bit of misinformation here -- FM's inconel hardware will fit the turbo-to-elbow and elbow-to-downpipe bolts, and they'll happily sell you extra studs, but they're not cheap. If they're not necessary on those joints, then why spend the money?

I have ~30 track days on my FM2R hardware, driven pretty hard, with stage 8/inconel on the manifold-to-turbo fasteners only and have had no issues with it. Lots of things have broken on my car in that time, but not the turbo-related hardware bits.

--Ian

I'd save yourself a lot of headache and get TSE's setup now, preferably with an EFR.

I love your budget tenadicy, but remember that ANYTHING you do to this setup, drilling the holes out, re tapping the studs, planning the surfaces, or relief cutting the runner, it's going to warp, crack, strip, and in general be a PITA until it's replaced. You also have massive interference between your down pipe and subframe/chassis due to a poor DP design, so this would be a great opportunity to spend money once for a reliable system that solves multiple issues at once.