I have a 2" crack in my GReddy exhaust manifold.

What are my options?

I have replaced everything on this piece of crap turbo kit. I am considering returning it back to stock.

 

Cracks happen. Get it welded. No biggie.

 

Yep - me too . I actually ended up getting the highest temp brazing rods I could find and useing that to weld it up . Other types of welding just proliferated the crack .
Has not melted off yet despite several dyno runs etc.
If you are going to try tig welding - you must preheat the casting .

 

From what I read on the forum it's very common to get cracks in the GReddy manifold.

I can't afford to keep tearing apart my car everytime I get a crack. Somebody needs to fabricate the exact same manifold from a better material so that we can solve the problem.

What is the manifold made from? I will need this info for the fabricator to fix it.

 

cast iron. it doesn't cost much to fix, but pulling it is a hassle.

mine cracked too.

 

here's the manifold after the repair. you can see part of the repair in the center, but it has mostly been sanded down, so not that apparent. I had it ceramic coated too.

https://www.rx8club.com/attachment.p...6&d=1216676176

 

I have not taken it off the car yet so I will know more tomorrow. It would be a great time to ceramic coat the manifold. Would that help prevent cracks in the future? What is causing these failures?

Mine is cracked right here:

 

Did you fit the brace off the transmission ?
I made up a really strong one from 6mm steel plate and have not seen the issue again .

 

mine had the brace.

 

Mine has the brace also.

It seems pretty damn heavy duty to me!

 

/\ I wonder if the stock brace is strong enough with vertical stress . Seems pretty flimsy in that plain to me .

Edit : although I must admit that I have never seen one in person as my kit did not come with one ....

 

Do you think the tranny brace is causing these cracks? If so I will get a crazy thick brace fabricated while I am getting my manifold fixed.

Would ceramic coating help prevent cracks?

 

I don't really know . I got a crack but had no brace at the time so I made a strong *** one up and have not seen the issue again - that is all I know .

As far as the coating helping - I doubt it very much . I had mine done to reduce heat in the area and think it is worthwhile for that reason alone .

 

the ceramic coating will help more of the energy go through the turbo and out the exhaust instead of escaping through the piping walls.

 

yeah - it supposedly helps with that but I can't imagine it would be very noticeable as far as available hp goes .

 

I wonder if these cracks are caused by too much heat. Our rotary engies do run hot by nature and I was thinking ceramic coating might help.

 

well the manifold does expand under the heat. maybe it is cooling too quickly or something.

 

the manifold has tiny cracks in it from manufacturing. the cyclic stresses on it cause the cracks to propagate until it fails.

 

God damn.

I wish there was a way to coat it with something to prevent more cracks in the future

 

the ceramic coating might actually help, being a thermal barrier, but the cyclic stress is gonna be there no matter what.

 

Mine had a crack as well and it was welded over.

I was actually thinking of making a stainless steel tubular v-band downpipe to connect to the midpipe and replace the heavy cast GReddy downpipe and possibly flow more. It would reduce stress on the manifold and I would put in a flex joint in the downpipe.

I think the whole exhaust system acts almost like a lever against the manifold, it moves and sways and the manifold is the one that gives (since it's usually super heated) and it cracks or fatigues and cracks later.

 

If you decide to make a replacement manifold, make two... I will buy it!

 

Mine hasn't cracked yet, but from everything I've heard from other folks who did have their's crack, it seems to be related more towards the exhaust levering on the manifold which finally wears away and cracks it. Most of the cracks seem to be in the same spot. If the manifold and exhaust pipes are properly supported to avoid strain on the cast iron it should not crack. The heat itself should not be sufficient to do it.

 

Alright so a better tranny brace should solve that issue.

Simple enough.

 

I dont have the brace, however mine is ceramic coated and heat wrapped. Been looking for a brace but never found one or had one fabricated. My manifold and back does not move at all. Maybe I should look into one again though. Anyone got any pointers on one?