Custom Exhaust Manifold is cracked / has hole... what could have caused this?
 

Im trying to figure out what could have caused this and have a few ideas so far. I am yet to take the exhaust manifold off the car to see exactly what has happened. About a week ago under any throttle above 1500 rpm's theres a loud exhaust leak that ticks(usually indicates a pre turbo leak). I checked the bolts holding the manifold in place hoping a few nuts got loose and while looking around for the leak, I gave the car a little throttle and was able to see some of the heat wrap around the manifold shooting out little dust particles indicating the hole is on the front section of the exhaust manifold. The red box indicates roughly where the hole is and its on the bottom side of the manifold (the side closest to the ground). The picture of the engine is not current...and i know theres a few issues with that setup. Any suggestions are appreciated.

Possible problems
-To much weight on the manifold due to turbo set up
FIX = Build custom brackets for manifold and turbo

-Material it was crafted from is to weak
FIX = Use better material, heat coat it

-Engine shifting under load with extra weight cracked it
FIX = HD motor mounts or chains to help engine from flexing as much

Attachment 207799

What manifold is it? I'd like to see a picture of the manifold, something closer up atleast to see which one it is.
What is the manifold made of?

It's hard to recommend much without knowing which manifold it is. It might have cracked due to lack of relief cuts but that is manifold dependent.
Standard recommendation would be to fix the manifold and brace it to take the weight off the runners. Maybe brace the downpipe as well so the turbo and manifold aren't supporting the weight of the downpipe and exhaust.

I will report back with pics as soon as the manifold is off the car. It was an ebay manifold (i think made from stainless steel) that i cut the turbo flange off of and then welded on a new flange for my turbo.

That's the problem.
Read here. The ebay manifolds are built with cheap tubing, they all crack eventually, especially without bracing. Buy a real manifold.

https://www.miataturbo.net/forum/t19358/

Yeah, post up a detail pic so we can get an idea of the "weakness" that might have led to it.

Buying one is not an option as its a custom turbo setup. Other than starting with a new manifold and welding onto that one is there anything that can be done to strengthen my current POS ebay manifold?

why dont you actually get some pics so we dont have to work with only speculation.

i like your heater core outlet plumbing... and your blocked breather line.

Halp u guyz i want 2 kno y my ebay manifold broke :[

LOL @ heater routing. As far as the crank lines go, most of the big daddy turbo set ups I see have the breather end plugged with a big PCV on the other end going to a catch can and then the intake manifold. I've also seen them going to the exhaust instead of the intake manifold, supposedly if you do it correctly, the exhaust flow will suck fumes through and burn them without getting the mess into the IM.

Heater core was removed, valve cover breather has since been routed into the intake... thats why i said please excuse the outdated pics but anyways here are the pics of the crack in the manifold.
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An ebay manifold cracked. Damn, that's never happened...

was it always wrapped? it's the nature of that manifold to crack, really.

Weld it up and wait for it to crack again, brace it this time, might last an extra week.

I now realize its made of cheap metal... I am just looking for a way to use it for a bit longer until I fabricate another design. It was the first exhaust manifold ive ever made. I know that I could have bought a turbo that would have worked with begi's or another name brands manifolds but i wanted to use a wrx turbo.

To those that fabricated their exhaust manifolds, what did you use as a starting point?

Search. Search for words like "manifold" "tubular" "weld-ell" "pipe" and things like that. Schedule 10 and Schedule 40 pipe works very well to make runners for a manifold. Last forever and never cracks if you weld it up half way decent.

Turbo Header kits WARNING! FABRICATION REQUIRED!!!!!!!!!!!!!!!!!!!!!!

They sell a miata specific log manifold kit that takes all the work out of sourcing parts.

My plan for the WRX turbo:
You can take a cast mani for a T25 made by FM or Begi or HKS, etc., and buy two things from Weirtech. A T25 flange and a Subie flange. Orient them so you can get to the bolt holes on each and weld the two flanges together. Bolt the T25 part down to the mani and the Subie part to the turbo.

Or just weld the Subie part to the cast mani if you don't think you will ever go to a T25 in the future.

I'm going to try to do it the first way to preserve the integrity of the manifold.

If you are building your own mani, Weirtech has really nice flanges for the part that bolts to the head also...
weiRtech
http://weirtech.ca/images/Subaruturboflanges.jpg

or, you can bother ETD racing to make another one of this:

Attachment 10467

but seriously, you could get one of these:

eBay Motors: 89-93 MAZDA MIATA 1.6L B6 CAST T3/T4 TURBO MANIFOLD (item 250380055633 end time Mar-02-09 17:38:31 PST)

and make an adapter plate that has countersunk bolt holes for the T25 flange and through-holes for the IHI/Subaru flange.

Pipefather,
That shore is purty! I'm sure it was a few bucks more than I was willing to spend, though.

I welded the crack up, despite how I kept going right through it... it really is thin metal. I ran a few thicks beads across it hoping to give it a little more structure... I only want it to last a few more thousand miles... we will see.

That is the only crack you have. LOL

Mine is about to fall apart! LOL!

Unfortunately having issues with my new exhaust manifold and looking for some advice/tips on the support braces i'm about to make. I dont want to mount to the valve cover bolts so mounting locations are limited... but welding is an option.

Attachment 200028
This is the new manifold Ive been using.

Attachment 200029

Downpipe to transmission bracket. I will defintiely use this.

Attachment 200030

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or

Attachment 200032

Other than the fact that it is a cheap POS manifold to begin with, the heat wrap was probably a contributing factor. It allows moisture to get trapped next to the manifold, which can create large temperature gradients between nearby sections of metal, which leads to stress cracking.

you cant brace it off the head, there will be dramatic differences in thermal expansion and it will cause another failure.

If that is thick material you wont need any bracing, that looks like a JGS to me, so that means its basically made of weld-els and should be plenty strong.

It is a JGS (stage 2 i believe) and is way thicker than my first. Lasted 2k street miles. If I cant brace to the head, is their anywhere safe I can brace to? The standard issue bracing from downpipe to transmission just isnt cutting it.

I don't see the new manifold being a problem...

If that's a JGS mani, you won't need to brace it. It's sched 40 pipe, plenty strong.

leave it to the brain to crack a jgs log.

http://www.boostedmiata.com/gallery2...-2/cracked.jpg

Attachment 200023

Thats what my new cracks look like.. no actual pics as its still on the car. Does the dead center location mean anything? High egt?

hey look at that, cracked in the same spot...but my turbo sat directly off #2. Mine cracked from too much exhaust bracing, I had my DP mounted firmly to the tranny.

Brace turbo mani to downpipe trans brace. Weld a tab to both the manifold and downpipe and bolt a fitted DIY steel bracket to it. I have had an ebay manifold and I was able to extend the life by doing this after it cracked a couple of times, along with an extra tab and bracket to the car's body, with swivel joints of course.

Edit: this may only work for my top mount, I forgot yours is a log... my bad. Brace downpipe to the block, where the tranny bolts to.

good idea!

http://www.boostedmiata.com/gallery2...brokeassdp.jpg

Do you have a flex joint in you downpipe?

To much bracing!?!? Didnt think that was possible. What did you do then?

Yes.

Got BEGi parts.

Read through this, Keith explains the issue pretty well: https://www.miataturbo.net/forum/t43572/
(Post #9)

Im pretty sure my downpipe is to far from the transmission to use FM's brace (already considered it) but ill check it out tonight.

A crack like that in a sched 40 pipe mani looks like the need for flange cuts. That said, the weld looks like it lacked penetration based on the rather large ridge. And I'd expect the load oriented crack to be in a weld running the opposite direction, like at the head flange or turbine flange- perpendicular to the load action.

OT but are there any reports of the ebay T3 cast manifold cracking? I haven't heard any yet.

holy roflshits!! time to grind that shit off...

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Should have made text a bit larger, sorry... but the arrows give you an idea of where the cracks are.


Its way worse than expected. On the center portion a crack runs nearly the entire way around and on the 2 outside runners cracks are developing on either side. This is a JGS stage 2 manifold (which was already welded together, which means all i had to do was weld on the turbo flange). All these cracks make me think that my bolts holding the turbo to the manifold allowed it to shift side to side thus cracking it. Im going to weld nuts to the bottom of the turbo flange to hopefully relieve me of this issue. Any advice is appreciated. This next time the manifold is being welded it will be done by a friend that welds for a living so hopefully he can do a better job.

HOLY. Buy a new manifold now.

needs more absurdness.

Fixed... I believe. Took the manifold to a friend thats been welding for 20 years and he blamed the manufacturer immediately after looking at. He claimed none of the welds by JGS (holding the elbows to the t pipe pieces) had penetrated deep enough. He drilled holes at the start and finish of each crack, then made V cuts with a dye grinder down each of the cracks (where the pieces were welded by JGS), then ran a solid bead down each of the V grooves. Its not as pretty but functional again. Pics coming soon.

now fix your gas tank too.

imo that is stress/vibration maybe throw a brace in the mix for insurance.

:Attachment 199683

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http://i127.photobuck:loser:et.com/a...n/988b587b.jpg

still needs to be cleaned up but very functional

The log gets gobs hotter than the flange, thus its gets longer by even more gobs than the flange. Cut the flange between every port, literally slice it into four pieces. Then when the log heats up, the flange will slip on the head rather than force the log to crack.
It will warp when cut, but grind it flat.


Also, tighten the manifold to head stud/nuts a bit less.

Corky