ok this is a friend of mines turbo on his 3rd gen. wanting to know if this is normal or not and if not what kind of problems can be caused by this. and if it can be fixed.

 

wow..

no its not normal. The cast iron manny is known for cracking.. yours is excessive. Start looking...

 

Looks cracked to me!? I don't think this is a good thing. Is this a stock turbo? Probably should get replaced.

 

PS. dont reuse it. the pic looks like a chunk of that cast iron is going to eventually crack off... if that flys into your turbo..... well. you know.

 

holy ****

 

I am not sure if it is cracked. You might want to NDI/NDT that.

 

That's where the wastegate flapper is... it will break off and shoot into the DP.

 

Does your friend have little or no primary boost?

 

I've seen the same or worse work for at least another 15K miles (still going) with no problems. The WG will leak slightly but that isn't a big deal.

 

he was having problems with his secondary boost. but blew his motor. this is the front rotor/housing the turbos came off of (we are in the process of rebuilding it now)

and can that be welded back together and grinded down?

 

The housings are junk.

If the turbo(s) ate the pieces of apex seals, etc from that housing they likely got damaged.

 

actually its just the front. the rear rotor/housing is fine. and we already have a rotor and housing to replace it.

 

thats one of the worse housings ive seen
but i havent seen all that many

yes you could weld the cracks and then grind them back a little. Leave some extra on there though

 

IMO, I don't think it would be worth welding. It's pretty tight in there so getting everything cleaned out and getting good penetration would take some doing. Plus, IIRC, some people on the forum haven't had much luck in the long run with welding on the manifolds. YMMV.

My turbos currently look similar to that, ok maybe not that bad, but I noticed it about 20k miles ago and still have strong primary and secondary boost. I would be more concerned about the condition of the pre-spool area if he is still sequential.

 

dont weld it... it will just crack again and bits of the weld may come flying off. ive seen a few sets of turbos so far, and two of the ones i have seen were that bad... the exhaust tries its hardest to escape from anywhere it can... and if a little crack gets started then (my theory is) the exhaust gasses just keep eroding it... and the constant expansion/contraction doesnt help matters either.

that being said... your flapper door is still closing all the way, so youre not venting all of your exhaust pulse... just a small fraction of it. i pulled my turbos to port the WG a few months back and they had a crack the same size as yours... ported it anyway and put them back in the car. i still can make propper boost with them, so i figure why spend another $3K on turbos. just use them how they are, and if you notice that your boost pressure is dropping as a result of the crack worsening THEN get a new set. i dont know... id use it untill it fails cause it wont kill your motor if it does. now, if the fins did infact eat some apex seal thats a different story... in the case that the fins were anything but prefect i would replace them. thats my 2 cents. -heath

 

In other words, everything shown is junk. I'm sorry for your friend going through all that. My condolences.

Jeremy

 

damn that housing is a real piece of junk now

 

Wow....What did your friend do to the housings ? I have seen apex seals take a crap before but your friend's ones are the worst i have seen so far . The best bet for your friend is to get a another engine with turbos and swap it on . As for the housings, mm....there is a thread about making rotary housings into fish tanks which are kinda cool .

 

Looks like a cat got trapped in the housing and was trying to claw for dear life.

 

That sums it up....Go lookin some new ones, those are trashed!

 

holy ****.

 

Jeff is right -- I would fully expect some turbine damage from the looks of the engine internals. You usually can't see this kind of damage unless you remove the turbine housings. The damage will be little chips out of the ends of the turbine blades.

If I were you, I would pick up some new (used, maybe rebuilt) turbos that have less cracking in the wastegate area and good turbines. The cracking in the wastegate area raises the boost threshold a bit (you don't get boost until a higher RPM than you would with the wastegate in good condition), and can cause lower than expected boost elsewhere (primary, and at high RPM).

-Max

 

Would Jet-Hot or ceramic coating prevent this kind of cracking?

 

I would not expect it to work. This is often the result of prestresses and impurties in the casting, combined with stresses caused by thermal expansion. A coating might cover it, but not stop it. The thermal expansion around the cracks could cause the coating to break loose, in fact.

It would be interesting to tear down a new set of turbos and have the housings stress relieved and NDE'd to start with the best possible casting. But in the end, all that effort isn't much different than replacing them every 60-100k.

Dave

 

Ceramic coating won't help - Carlos tried all manner of coatings, they just end up flaking off.

http://www.scuderiaciriani.com/rx7/polishing.html

Scroll down to the post by Carlos Iglesias.

Dale