DP Stud and fastener issues - Suggestions?
 

After 3-4 years of zero problems here, we are suddenly having issues with the down pipe studs and nuts backing off, just like the Manifold use to do before we fitted Trackspeeds inconel kit.

Anyone have any suggestions why this might suddenly be happening and / or any suggestions at a fix?

My only thought is to buy the TS kit and use it on the down pipe but it's only only four nuts and studs when we ideally would need 5.

Given that they only sell the 4 stud kit, I also wonder if we aren't having an unusual problem? Otherwise I imagine they would specifically sell 5 stud kits for this application too...


https://cimg8.ibsrv.net/gimg/www.mia...0cd2bc00bf.jpg

FM recommended oval/distorted thread lock nuts and those ridged washers... I will post what it was specifically in a few. I ordered some from McMaster Carr and I will be picking them up this afternoon.

Super clean setup!

https://www.atpturbo.com/mm5/merchan...egory_Code=FST

I ran hardware from here. Seems to be alright.

Sorry for clarity, already running the standard metal locking nuts (bronze colored) as suggested above.

Have nuts loose or gone and studs loose or gone, just suddenly. Very strange.

Stage8 locking hardware. Cured my downpipe issues. If you can use bolts instead of studs then they wont back out at all.

I had stage8 locking bolts holding my downpipe on for a few years.

Give them a call, very helpful, and can find you anything.

As for why, have you recently changed your tune? Retarded the timing, increased boost anything that would increase exhaust temps?

I retarded my timing few degrees for a track day to be safe and imediatly had stud problems.

The two-piece serrated washers are called Nord-locks. I've got those with zinc-plated stover nuts on my downpipe and it hasn't been an issue. If you're running hotter and see the same issue on the downpipe nuts as on the manifold ones, then using inconel studs there is probably a decent choice. I suspect that if you contact TSE directly they'd be happy to sell you 5 studs.

--Ian

We had a flexi joint do something weird pre xmas (photo below), was only 2-3 months old but it ended up blocked by steel strands, looking almost exactly like a cats furball stuck down it!

We now suspect it contributed to the strangely low exhaust noise the new 1800 made, the strange lack of expected power the 1800 should have had over the 1600 and the recent gearbox (4th gear circlip) failure, so to have also overheated the nuts and studs to failure isn't at all a surprise in hindsight.

We only found it because the gearbox people suggested we run a cooler to help the new modified circlip gearbox last. In relocating the exhaust to accommodate the required fittings we discovered the 90% blocked flexi.

We refitted the new gearbox, removed the flexi all in a rush pre Xmas for the dual header race meeting on the 5th Jan, Now preparing the car for the four and rotary Nationals show this weekend (its on the Superlap stand) I suddenly find all these stud problems and with your suggestions above belatedly realise its probably all associated to the Flexi issue even though we fixed that already. Dumb I guess :) .

On a side note I'm very proud and extremely greatful to Paul our race guru for all his efforts over Xmas sorting out those issues to have secured a clean sweep in the Classic Japanese races and won class in NZ Superlap.


Anyway, I think at this stage, asking Andrew about a 5 stud kit will hopefully be the best long term answer. Cheers.https://cimg3.ibsrv.net/gimg/www.mia...f4c0dd60e3.jpgBlocked 2-4 month old (3 race meetings) flexi joint.

I was having issues, went with new studs and jet lock nuts from Pegasus racing. they are single use, and must be replaced when removed but they seem to work very well, no issues during the previous 4 or so track days. for me the downpipe design is a problem. it was very nicely built but the angles and clearances are a issue so I can't easily run a longer stud to accommodate nordlock washers. really the nordlock washers just reduce the nuts ability to get get looser, once loose. if the nuts stay tight, nordlock washers seem unnecessary but I'm not a expert. I say check out jetlock nuts and new studs, but have extra on hand just in case. they are supper low profile and fit very well for me. previously I had to thread the nuts a few threads at a time and work my way around because the downpipe would get hung up when the nuts interfere with the side wall.

I was having issues, went with new studs and jet lock nuts from Pegasus racing. they are single use, and must be replaced when removed but they seem to work very well, no issues during the previous 4 or so track days. for me the downpipe design is a problem. it was very nicely built but the angles and clearances are a issue so I can't easily run a longer stud to accommodate nordlock washers. really the nordlock washers just reduce the nuts ability to get get looser, once loose. if the nuts stay tight, nordlock washers seem unnecessary but I'm not a expert. I say check out jetlock nuts and new studs, but have extra on hand just in case. they are supper low profile and fit very well for me. previously I had to thread the nuts a few threads at a time and work my way around because the downpipe would get hung up when the nuts interfere with the side wall.

https://www.pegasusautoracing.com/ke...rdStart=jetnut

Spoke to Andrew this morning and have ordered the inconel kit + 1 stud and spare lock hardware.

Hopefully this is a long term solution. I don't like these niggly, race or performance costing issues.

It's also possible the nuts were over-torqued at some point, causing the studs to yield and reducing pre-load. I'm not sure that the blocked flexi completely explains repeated loss of pre-load after the flexi had been fixed. Increased temperatures cause bolt load loss through dissimilar thermal expansion; but unless it got so hot that the metallurgical properties of of the bolts were permanently altered, they shouldn't loose pre-load again once the blockage was removed and temps brought down. At least, that's how I understand it. Anyway, just something to keep in mind; watch the torque.

You hit the nail on the head, studs got hot enough to yield, that's how you loose pre-load. So by definition once that's happened the stud is compromised and will continue to stretch since it's yielded. They ded......

I've just had a trackday at Silverstone GP last weekend and had a few turbo hotside fastener issues. It was my first dry trackday in this car, at a track with a very high percentage time WOT..... To make matters more complicated, I've got another trackday booked for next weeked so don't have long to solve these issues.

Spec as run at Silverstone
Garrett GTX2860, FM2 hotside parts. 2.5" exhaust. 10-16psi (16psi to overtake non-compliant traffic) EGT 900C (1650F) max on 99 RON pump fuel. Revving to 7500rpm (ST heavy doubles)

The issues (in the order which I noticed them)

1. Turbine housing to DP locknuts with nordlock washers came undone
2. FM2 lower DP half to midpipe flange bent! (bolts took a fair bit of torque when I went to tighten them, fastener stretch?)
3. 2 of 6 turbine housing bolts fell out (perhaps one use? I had removed turbine housing and reused bolts)
4. One of the FM stage 8 nuts (on inconel studs) came loose (one of the ones I can't get a torque wrench on, too loose?)

After noticing the first fastener issue and spanner checking everything else, I limited myself to 10psi and 7000rpm but issue 1 would re-occur.

I'm guessing inconel studs are the answer to 1, though getting some in time for next week will likely be an issue.
I was going to machine the flange flat and perhaps add a gusset for 2, and replace the normal nut and bolt with some form of high temperature locking fastener. Interestingly, it was the thicker FM flange (8mm) that was most warped, rather than the 6mm flange of the midpipe.
3 may be installer error (me). I couldn't get a torque wrench on them. I've bought new Garrett bolts.
Though for 4, I don't know what to do. Have others seen this? Or is it user error and I need a better calibrated arm (or some crows foot spanners...)

Or perhaps, am I just wasting my own time and money trying to get the FM2 kit to work at 300hp on track and I really ought to bite the bullet with a TSE kit? On the plus side, when the car was working, it was absolutely brilliant. First dry day with 9J 6ULs, 225s and Supermiata big grip kit.

https://cimg4.ibsrv.net/gimg/www.mia...0986bbbc52.png

Many before you have tried and failed. FM kits are simply not designed for your usage. TSE kits are.

Piss your gaskets off and use inconel and stage8 on everything.

Solved.

Dann

That's the conclusion I'm coming to. If the turbo kit works as well as your brake kit.... Despite 132mph on the Hangar straight and just 2.5" ducting, I could only turn the lowest temperature strip of my brake disc thermal paint.

I did 4.5hrs in my turbo car last weekend and lifted the hood once, on Sunday morning, to check the oil.

(It hadn't used any.)

Gaskets gone already except in midpipe. Will give that a try.

That is the stuff of dreams. Rather than me making it 3 laps before hearing a new exhaust blow that wasn't there the session before....

FWIW, while I've had many, many issues with my turbo track Miata, the FM hotside hardware hasn't really been among them.

Andrew's stuff is really nice though.

--Ian

Update - I couldn't get stage 8 fasteners in time, but inconel studs on the turbine to DP flange with Nordlocks and Philidas lock nuts (the best recommendation from Owen Developments, the local Garrett distributor) seems to have resolved the issue. Though this is with a couple of caveats.

1. I wasn't looking for the issue before, so maybe took more than a day to develop
2. I never tried more than low boost (~250whp) since I was going to wait to the afternoon for high boost in case of running into issues (that way I'd only lose a few hours of track time, not half the day!) but a rain shower just after lunch removed all grip for the rest of the day so I didn't try more boost.

Though despite this, the seeds of doubt have been planted so maybe I should be planning for a TSE kit in my future....

Does anyone know which MX5 series in the UK is closest in pace to spec miata? I'm trying to work out how hard many people have pushed this kit and comparing back to spec miata lap records seems to be the benchmark. (For reference, the track was Rockingham International Super Sports Car and I was lapping just under 1:35s on 205 Federal RS-R on 8s (and 225 Federal RS-RR on 9s -oddly no faster), ~250whp and ~#2750 weight since I was taking (heavy!) passengers all day)

Are you asking how hard people have pushed TSE kits, or how hard people have pushed FM kits?

I can answer the former pretty definitively - an off-the-shelf TSE kit is the basis for the fastest Time Attack Miata in the world (949Racing's car). Roughly 20 seconds faster than a Spec Miata on a 2-minute course

I've been having these same issues on my FM2 kit at 220hp. Also have lost center section bolts before. 1 weekend at NCM and every bolt was loose down to the down pipe. Including my FM inconels.

Have a TSE inconel set and going to try resbond on everything down to the down pipe this year. Also planning on adding another exhaust hanger. Right now its unsupported to the rear subframe. If I can't get more than 1 weekend still, it's time for the EFR.

No qualm's against FM but if their kit worked really well on track; Andrew from Trackspeed engineering wouldn't have a business model.

Again, the studs & other fasteners on my (resbonded) FM hardware have not been an issue. No loosening despite 300+ rwhp and Laguna Seca lap times a second or more below the Spec Miata record. No, I'm not as fast as Andrew around that track, but that's got more to do with my driving and the suspension that was on the car than anything related to the motor.

AutoFreak57: did you resbond the FM studs?

--Ian

FM doesn't include resbond AFAIK.

I believe that's correct, so it would only be resbonded if AutoFreak57 did it himself.

--Ian

I'm sure the Trackspeed kit is bulletproof, however, my FM manifold/downpipe has been bulletproof for the past 3 years. And yeah, it's been Resbonded.

Mine was no resbond. Main turbo studs won't last a weekend. The downpipe bolts make it 2 with cheap studs.

I'm hoping resbond is the magic glue everyone says it is. Efr is better, but I need good enough for st4 power.

Do you monitor EGTs?

--Ian

No. 14psi, 220whp on a dyno dynamics. Never had issues until I tracked the car (imagine that).

14 psi is plenty of boost to get 1800F+ EGTs if you don't have enough timing. Might be worth adding a sender to monitor it.

--Ian

TSE Inconel has worked well on the manifold for me. Nord-Locks on the downpipe and a good transmission attachment has been critical.

What octane do you run?

--Ian

That's good to hear. Gives me hope in my setup. Can you share a picture of your trans attachment?

Don't have a picture of it handy. It attaches to a factory trans side bracket with a custom made clamp around the pipe about 1.5" wide strip. A U-bolt clamp wont work it will just crush into the pipe. Too high of contact stress when tightened and it will never stay tight. welding a bracket directly to the pipe also won't work it will just rip out the welds. long bolts are your friend factory uses a bolt that's about 4" long connecting the clamp to the transmission bracket try to use something similar.

Side note I use a long runner mild steel schedule 40 weld ell manifold. It's is not near as robust as a cast Iron short manifold like TSE's It needs even more protection from the weight of the exhaust system. It is not without troubles. after some design refinement and reinforcement to the collector portion of it and a good design for a support bracket for the turbine housing It will generally last about a season of track use at best. The mild steel does allot better with thermal expansion than stainless but eventually enough heat cycles will crack it.

Usually 93, if I screw up logistics, 91. Canadian, don't know if that's the same as the states. This is a stock B6 btw.

Not my Miata but the Turbo FE3 B2200 I'm currently building. Very similar clamp.
https://cimg0.ibsrv.net/gimg/www.mia...5ed3a5a775.jpg
https://cimg1.ibsrv.net/gimg/www.mia...f1d9d51344.jpg
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2 further days on this and the DP studs still haven't come undone. Did 2:31 round Silverstone GP which is 9 secs quicker than the BRSCC Supercup record (with a light passenger, call it ~250whp and ~#2650). A brace like Bob's is on the list of things to do though.

I don't like being a high percentile user of anything since then you can run into the limits of the equipment, I'm guessing I'm 50th percentile with my TSE 11.75 kit and Xidas, but perhaps I'm getting on for 90th percentile for the FM kit so I'm mindful I may need a TSE kit in the future, especially as I plan to up the boost at the next trackday, but my time spent wrenching to time spent driving ratio is awful over the last 24 months so I'll see how I get on before doing anything major.

Alright I'll bite I've got some analysis to procrastinate. Obligatory not-exactly-my-wheelhouse and Andrew's stuff has a huge following and great reputation with the fastest hombres for a good reason aside.....

I don't believe this is a particularly useful way of approaching the issue given the huge diversity of operating conditions and mechanical design of parts in the FM (or any turbo kit). What makes me a 90th percentile user? How do I know what the tolerances and safety factors on the design are to begin with? If I idle my FMII with AC on in traffic for 3 hours and charge temperature spikes should I throw out my intercooler? From a strictly reliability point of view (e.g. manifold flow efficiency, easy of installation, cost, etc. set aside), I haven't heard/seen any FM cast manifolds, elbows, or downpipes suffer huge cracking or warping issues -- just the DP fastener issue you described. Of course the TSE cast stainless is much more corrosion resistant (and sexy) but you're talking an order of 10s of years before that's an issue with the FM manifold (but for real the TSE kit is perdy friggin swell). So what's the problem? Simply put, creep and vibration.

The reason gas turbines are so dang expensive, and why almost every Jet engine produced outside of US/UK/RUS pales in performance and lifetime in comparison comes down to metallurgy -- which in a lot of ways is only a step or two further towards science than black voodoo magic. When you axially load any metal part under very high temperatures the part will begin to elongate over time. If that part is providing a critical function and/or is built to a tight tolerance then you've got a serious problem on your hands. Think turbine blades spinning at 30 kRPM with a .001 mm tolerance between tip and turbine wall. How do I make sure they don't elongate enough to contact the housing and blow my engine to shreds?

This is why you see so much money going into development of things like single-crystal, gooseneck grown turbine blades made of wild 30+ component superalloys which cost an EFR6258 weight's worth of gold to produce. (This creep behavior is generally thought to occur along the grain boundaries in a metal hence the monocrystalline blades I mention). Loosely, how much it effects your application is a function of loading on the part, operational temperature, and material composition. This is where Inconel comes in and trounces more traditional fasteners, as a Ni-Superalloy it exhibits vastly superior creep performance compared to standard 304 stainless or alloy steel.

Why do I care? Well it turns out jet turbine blades aren't the only problem, albeit they're one of the hardest to solve. Exhaust gases into a turbo can top out in the 800-1000 C range, and operating that close to the melting temperature of the material makes creep a real problem. Moreover, with a big heavy downpipe hanging off the end the problem compounds as creep rate scales with part stress (e.g. DP tugging force divided by stud area).

Some example creep rates at varying loading and temperatures for a couple superalloys can been seen here but the gist is that at these high temperatures it's pretty significant, and is very sensitive to overall loading as well.
(and more fun reading is attached -- seriously check out the old Argonne National Lab paper, its a hand typed study about inconel as a Nuclear Fuel Rod liner)

https://cimg9.ibsrv.net/gimg/www.mia...bc454cc336.png

OK OK, but how does this make my turbo no longer trubo? That's where the vibration aspect, and high cycle times seen with track use, come into play. The function of the studs and nuts on the DP flange is to provide a high clamping force to keep the flanges mated, gas flowing where it should, and to make sure your competitors aren't running over steel exhaust parts. This is achieved by torquing the nuts such that a preload is applied by slightly stretching the stud without yielding it, essentially making it act as a super duper duper stiff spring. That's all fine and dandy, but the issue remains, all those vibrations the engine experiences hour after hour on a track really really really want to loosen that nut. This generally isn't a huge issue if the preload force provides enough friction on the face of the nut to prevent the vibrations from rotating it, or if some sort of anti-vibration device is employed (safety wire, nordlok, etc. -- I actually stumbled upon a nordlok product that incorporates a belleville washer to maintain nut preload, might be useful https://www.nord-lock.com/en-us/nord...eries-washers/).

BUT, throw creep fatigue into the mix and suddenly those studs are elongating over time, and faster at the higher heats one might experience on track. Now that preload force is shrinking and shrinking until all of the sudden there isn't enough friction to keep the nut tight, or the stud has grown enough that the distance between nut and turbo flange is actually greater than the thickness of the downpipe flange it's supposed to be holding -- all of the sudden your DP is hanging by a thread stud and your precisious nordloks are flapping in the wind.

My (extraordinarily wordy) point here is there's no reason to throw out a rather expensive bit of kit to solve an issue that Andrew and many others on this forum (in terms of our application at least) have already been so kind to solve for you.