ryiin2

I have had a lot of problems keeping my pfab log manifold and gtx3071r mated together, after a few days of driving not even too spiritedly the would separate and make a huge exhaust leak. i've had the sucker pulled 4 times now and it's become such a PITA to do. I have put on nord locks, stainless steel lock nuts, lock tite, I even took the sucker to a motorcyle specialist and had them safety wire the bitch together. Non of this has worked! I desperately need yall to help me out with this what can I do so this will stop. I feel like i've exhausted (lol) my options.

A few things, the system makes a lot of back pressure, I have noticed that sometimes my manifold nuts will come loose but just one of them, my EWG also has lost a few of its bolts (not sure why but probably related to this). I replaced the stainless steel turbo/manifold gasket with a graphite remflex, not sure if I should switch back to the stainless, I also have a flex pipe at the end of the downpipe.

Pics are of my last attempt of mating the two surfaces together, but even that was unsuccessful.

spdracerut

The studs in the manifold are yielding. What material are the studs and what's the turbine housing material? The coefficient of thermal expansion of the turbine housing material is probably greater than the studs, so it grows more than the studs want to during temperature increase and causing the studs to stretch/yield.

sirbikealot7

Change to inconel studs and stage 8 locking hardware, it will solve your problem. This is an extremely common problem in the turbo miata community.

sirbikealot7

You can also make sure both surfaces are machined flat and install them with grease and no gasket. It will burn off and seal up with the carbon in the grease and it helps take 1 more variable out of the equation when it comes to the different expansion rates as spdracerhut mentioned.

ryiin2

I'm not sure what material the studs are made of but the turbine housing is definitely treated for the high temps. You're likely right in that the studs are the weak link.

I took out the m8 studs on the turbo/mani once and checked them out, i didn't see any obvious deformations but they weren't any specific studs, i went to the hardware store and just got automotive m8 studs that fit between the two. So that's one part of the equation that i've definitely not put a lot of research into, i figured they would be enough but im not sure. I'll definitely look into the inconel studs that were recommended by sirbikealot, are there any other brands that are space age like inconel?

I will 100% check out the inconel studs, one thing though, I have tried stage 8 locking hardware but it physically does not fit in the application. there isn't enough space for the locks.

The turbo is a garret, i'm not sure if they come machined flat from the factory and the manifold is pfab, and i don't know about them either. If I do have to go with a gasket which do you guys recommend? the stainless gets eaten up, assuming because of the heat, however, with the thick graphite gasket i feel like some exhaust gets out even when it was initially installed with minimal escaping exhaust.

F1TwoThousand

Is the downpipe properly braced? Excessive movement/vibration of downpipe/exhaust or will rattle the turbo loose from manifold.

riceball777

ryiin2

I talked to pang @ pfab and he told me not to do this, should I disregard and do it anyways? You guys have much more experience than me.

5thgen

From the pictures it doesn't look like you use 2 sides for the nordlock washers.

You'll need a pair per bolt/stud for them to "lock" properly.

DefSport

That - you're not using the Nordlocks correctly. Your studs are also yielding like was stated.

If you're using M8 stuff like on a T25 turbine, then you are already on the backfoot, as they're *EXTREMELY* marginal on strength compared to the M10 fasteners on T3/T4 turbines. That's probably the biggest downside to T25 turbines in general.

The popular Miata aftermarket M8 Inconel studs will fix it, but they're pricey. OEM Nissan turbo studs are Inconel and go for about $7-8/ea and might fix it. You can also try stock SR20DET turbine nuts and locking plates. Those mild steel nuts won't last at all, nor will off the shelf stainless hardware.

Run no gasket as was mentioned. The tiny tiny amount of leakage is nothing to be concerned with, and it'll help keep things together and not let the gasket blow out. Also make sure you have a large flex section in your downpipe and bracing on the turbo side of the flex to the block or trans.



I ended up just welding my turbine housing to my stock SR20DET turbo manifold after pulling the thing about 5 times and losing track time after blowing it out. It never went on the street because I used pretty exotic materials (tried all sorts of A286, Inconel, Grade 19 Beta phase Titanium locknuts etc.), but at the end of the day, driving the shit out of the car on track would have things starting to fail after 1 day, then the next day on track it'd let go and nuts would start going and studs would be stretched. A few minutes with the MIG welder and it was all good to go! I couldn't TIG the two without cracking, probably due to the high carbon since it was a cast steel turbo manifold and a Ni-resist turbine housing.

Proper fastener materials will probably get you good for street usage, but M8 is really really difficult to make last on track if you push it. It's one of the main reasons I'm going T4 on the EFR I'm going to buy for my MR2 project.