triple88a

iTrader: (2)

I'm curious why isnt the flange cut between the runners? (Flange that goes to the head)

As far as the other one looking at the split turbo seems like it will need to be braced after all.

nitrodann

Well there's your problem...

Anyways, having not read the entire thread, is this why you didnt make 500+?

Dann

18psi

iTrader: (76)

Tims mani's aren't relief-cut either, nor are the ETD longtubes, as well as many of the other top shelf mani's, and none of those have issues.

Given his setup and how its run though, I'd definitely consider a brace or crane. Way too much weight and way too much post-chamber combustion going on for that poor mani to handle.

Pen2_the_penguin

iTrader: (4)

wait, **** just got real.

300+ hp with a cracked mani?
gawd dam




pen2 fail:
Miata is at 11psi (partial band-aid) with a rich 11.7ish idle (lolz) and a 10.6 WOT.




I reset my wideband

DeerHunter

Fae, do you have an exhaust brace? It seems this would help support the whole contraption.

18psi

iTrader: (76)

Also now the super slow spool makes a WHOLE lot more sense.

y8s

iTrader: (8)

going lean at a zillion psi must have raised your EGT to something up around "crack that ****"

18psi

iTrader: (76)

doing it 10 times in a row didn't help either

Ryan_G

iTrader: (8)

He would have to fab his own brace though since his exhaust is 4" IIRC.

vehicular

iTrader: (3)

It appears that unless the brace is fabbed from donuts, this is out of the question.

Ryan_G

iTrader: (8)

I am sure he can figure something out with the sawzall. I mean it can't be THAT hard, right?

shuiend

iTrader: (24)

He did say he wanted to buy a welder. Things could start getting very good.

kaboshe

iTrader: (15)

i did have most exactly the same problem with my artech manifold.
i bought an ram/short runner side-mount manifold for a gt25, with artech downpipe/whole exaust setup.

cracked a 3 places within the first 2 months, and my turbokit/downpipe is about half the weight of yours(fae)

got i welded back , and cracked AGAIN at different places within 2-3 month
i'm still around 15psi on resoneable street tune.
as boost got slower and slower to spool, and my afr going leaner and leaner(air going through the crackS) i got it re-welded a second dime, while been positive that i was the only one on the planet having trouble with artech exaust parts

(i mean, i never tracked the car, and if i would have , my turbo would propably had fell off the car by now, if street/daily driving is destroying the welds that quick, i'm in for a manifold change..)

i even emailed abe@artech, and told me that the flanges must have been badly decked and that made my runner cracks while getting heated.

that was all in 2011.this summer i had a great time with the car.noticed yesterday that i had an exaust leak(again!)
mine cracked now exactly where yours cracked, about 3/4 all around the the turbo flange , both side of runner 1 and 4, AND the downpipe started to crack too , directly on the v-band welds.
quick pic, that was the first time it cracked.




i'm getting that stuff off my car asap, and i'll make one myself using my buddy's tig.

Leafy

iTrader: (1)

The FM bracket is literally and exhaust U clamp and a bent piece of sheet metal with some holes in it. You should be able to make one with hand tools.

bcrx7

iTrader: (5)

Wow that's a big crack. That must've been loud.

Faeflora

iTrader: (2)

I don't know how a pre-turbo exhaust leak affects ultimate power. It definitely slows down spool.



Lean out your fuel by 5%. Ideally 8%.



Again, it wasn't spooling that slowly on the street. It has however, been spooling more slowly since I installed it. I thought that was largely due to the fact that I first ran this setup in cold weather. On my old GT30, the difference between a 60* and 100* day was about 500RPM before full boost.



I think I am going to have to re-support the whole exhaust and downpipe. Probably not enough exhaust braces or hangers. Yay yet another high stakes engineering project.




Out of 15 pulls or something, only three were lean. And the manifold was leaking from the moment I pulled it into the shop. There may be "issues" with York's dyno, but they are very good mechanics. Ted there noticed it ASAP. Again, Ed did a great job building my motor. I want to be the first to put 40psi through a BP. I want to be the first to put 40psi through a BP and dyno it. I have already actually run 40psi. May have already been done by some escort tho...





yum



Very interesting. I pinged Abe about this post- I am curious what his thoughts are. I thought that his welds were perfect, and another local custom fabricator thought the same. That said, they did break. I hope this is not a wonderful miata-specific problem like turbo studs barf.

Also, a preturbo exhaust leak like this shouldn't be causing the car to go lean above 20psi. Should it? There's 20psi in the manifold, air is getting forced out not in, right?

concealer404

iTrader: (3)

I think this one had 40psi through it at one point. The Familias are the ones more likely to have seen that kind of boost on a BG barring a Miata.

(Though didn't that one white drag miata see that kind of boost?)

STPmotorsports 545rwhp+ Escort GT - YouTube

Leafy

iTrader: (1)

Doesnt matter how pretty the welds are, they are weaker in fatigue than the metal around them. Because they will always be more porous. But your manifold seems to be to the point where it would have been worth it to use a stronger welding rod and have the manifold stress relieved before decking the flanges.

kaboshe

iTrader: (15)

i tried em all, rewelding em with more material, did releif cut, and even test it with a leak detection stuff to find cracks.

on the second time i filled it completely to be sure that there was no other cracks, and there was none.that's about 3-4 weeks ago.i never tracked the car, and use it only for dealy beating/street driving/daily driver.

now it had cracked a third time, on 3 different spots that i havent re-welded yet,one bein the manifold to turbo flange, wich had cracked about 3/4 all around, i mean i don't even want to drive it by fear of my turbo decide to fall off burning the car down on the highway side.

my downpipe,testpipe,catback were flawless since 2010, but as i was working on the car yesterday,i spotted a crack on the downpipe and on the weld between the downpipe/testpipe vband.

having a sidemount with a small turbo as a gt25,and by only daily driving it , i cant even thing about the ''too much weight on it''

why is it so specific to the miata, i mean the whole heat warp/crack/studs backing etc etc etc.
i had a built boosted BP in a mx-3, with a much heavier 60-1 ona huge ramhorn wich was heatwrapped,and a much, much bigger/heavier downpipe that goes all around/underneath the engine wich wasen't braced anywhere.

i live next to a drag strip and i was there like 3-4 time a week, made at least 100 run a season,(making my point on heat cycle) and i never experienced anything like the troubles i'm having with a much smaller setup on a miata.


Fae, a pre turbo leak kills everything, as the explosion/pulsation are going to the turbo ,air can goes in the mixture(not can, but is) take it as if each of your runner shot a fireball and that air can be sucked in by the draft of each fireball going through your exaust system.

i had a wonderfull tune, super-steady 11.5-11.7 underboost@18 psi, steady as a rock, now i'm seeing 12.5-12.6 underboost and i havent changed a thing.
didin't took any chance, and got my map richer and richer every week or so.
once i founded those cracks, i rewelded and reinstalled it, my afre were around 10-10.2 underboost since i was allways getting it richer and richer.

as i re-welded my manifold, i re-loaded my old maps(pre crack)and my afr were back on track,spot on.

stefanst

iTrader: (1)

My opinion FWIW: This crack is not caused by weight, it's caused by internal stresses due to thermal expansion/contraction. You have a rather extreme heat-gradient in your manifold. The tubes are kept nice and cozy by the blankets and are probably glowing a nice orange under sustained boost.
The flange is thick and takes a while to heat up and it's better cooled than the rest (assuming it's not blanketed).

Then, when cooling down, the tubes are relatively thin (in comparison to the flange) and cool down quickly. The flange stays nice and warm for a little longer, exacerbating your problem.

Whenever you have extreme heat-cycling and extreme changes in material thickness, you can expect heat-stress induced cracks.

But a lot of more experienced member say it's weight. And a brace sure can't hurt (other than power/weight ration of course!)