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So I'm going through my "lower mileage" twins I had sitting around. I was thinking of doing a cheap rebuild. I know, I know, you all will say don't rebuild the twins go single or BNR...and I will go single eventually. I want to run the twins in stock form for a year or two first. I have already own a GT35R RX7.
Can I rebuild this housing? (A N3A1 not a N3C1 unfortunately)
Should I weld it, port the WG, and polsih it? Suggestions welcome.
Cracks look bad, but exhaust gasses don't care how it looks. Unless the cracks are so bad that it's causing an exhaust leak or causing a lot of exhaust gas to bypass the wastegate, you're fine.
N3C1 turbos are far less prone to cracking (higher nickel content in the iron).
That crack looks like it's done, it's not going farther than that. I wouldn't worry about it. People get REALLY excited about turbo cracking, but unless it's so bad that it's under a gasket surface or allowing a significant volume of exhaust to bypass the wastegate, you're OK.
Cracks look bad, but exhaust gasses don't care how it looks. Unless the cracks are so bad that it's causing an exhaust leak or causing a lot of exhaust gas to bypass the wastegate, you're fine.
N3C1 turbos are far less prone to cracking (higher nickel content in the iron).
That crack looks like it's done, it's not going farther than that. I wouldn't worry about it. People get REALLY excited about turbo cracking, but unless it's so bad that it's under a gasket surface or allowing a significant volume of exhaust to bypass the wastegate, you're OK.
Dale
Thanks Dale. I might just brazen the cracks and then do the porting and ceramic coating.
People will tell you it's generally not recommended to rebuild the turbos. I've had mixed results in my efforts and ended up putting in a lower mile set.
If they have worn to the point of leaking on the turbine seal it is possible:
1. the seal groove on the shaft is worn
2. the hot side sealing surface is distorted/damaged
3. the bearing bores in the CHRA are worn
If they aren't too bad it's worth a shot, but keep in mind you may be taking them back out.
Also, don't forget to loctite the compressor nuts. Don't ask me how I know...
from my limited experience with the stock twins, i will say that that crack should be fine, but dont be surprised if you see erratic boost levels or boost control.
ive seen cracks on stock twins (in photos, not in person) that people have gotten filled in and the pictures after the welding/brazing work has been machined... the housing looks brand new.
Does it work? Im not sure, but ive never seen or heard a complain about it.
Most people dont bother rebuilding the twins at all because for the entire cost of labor and parts to get them back to working as new, you'd have spent almost enough to either get a set of BNR twins or a good condition small single.
Me personally? If there was a way to reproduce the housing of the twins with a higher nickel content as been stated.... then I'd definitely go that route if i was sticking to a build that used the stock twins or even send it to BNR to have a higher power potential.
