I'm on my first rebuild, and learning one system at a time. The engine is all together except the turbo and accessory parts. Now I'm trying to learn all about turbochargers. I read a basic 20 year old textbook and some good internet columns, but I'm a bit overwhelmed by the terminology, and could use some practical advice.
The problem:
I've got cracks on two different ct-26 exhaust housings, both are cracked just around the flapper. One just has a slight crack, the other has three, the longest extending 5-8 mm from the wastegate hole. These were both working turbos. I heard this is a typical place for cracks to start due to hot gases funneling through a small hole at pressure. I'm sure somewhere there is a great discussion of it, and I would be grateful for a link.
If not, then I could use help. Is this just normal wear, a minor problem, or a prelude to catastrophic failure? On one of these I milled (ground with precision steel wheel on machine shop drill press, charged with 180 grit) the seat for the flapper just enough to be flat, and it looks like it would seal okay. Both also have a little play in the shaft, about 1/2 mm at the end of the intake side of the shaft, I guess, I don't have a dial guage to measure properly in the coolant opening like the manual says to do, so I can't tell if it is out of spec.
As I see it, I have three choices:
1) Is it worth buying the tools to measure if the housing has those cracks,
2) Am I fussing too much and making a problem where there isn't one
3) or are both turbos toast so I have to blow the cash on a new one anyway.
If I keep the turbo, should I avoid boosting it altogether to avoid further damage? I just need a turbo to last a year or two and not damage anything else, but it would be fun to learn to experiment with tuning with boost if it isn't going to be dangerous.
For reference: My goals are just to set up the engine for upgrades later and perhaps a modest performance increase now, so I certainly will plan to buy a new turbo and exhaust in the next year or two. Current mods are head port and polish - it was supervised by an experienced NASCAR engine builder, so it's probably ok, street performance cam regrind (Colt Cams), Titan 1.3mm MHG, exhaust manifold reshaping (an experiment what the hey), MSD wires, and and racing muffler that is probably useless until I get the rest of the exhaust system upgraded.
Thanks.
The problem:
I've got cracks on two different ct-26 exhaust housings, both are cracked just around the flapper. One just has a slight crack, the other has three, the longest extending 5-8 mm from the wastegate hole. These were both working turbos. I heard this is a typical place for cracks to start due to hot gases funneling through a small hole at pressure. I'm sure somewhere there is a great discussion of it, and I would be grateful for a link.
If not, then I could use help. Is this just normal wear, a minor problem, or a prelude to catastrophic failure? On one of these I milled (ground with precision steel wheel on machine shop drill press, charged with 180 grit) the seat for the flapper just enough to be flat, and it looks like it would seal okay. Both also have a little play in the shaft, about 1/2 mm at the end of the intake side of the shaft, I guess, I don't have a dial guage to measure properly in the coolant opening like the manual says to do, so I can't tell if it is out of spec.
As I see it, I have three choices:
1) Is it worth buying the tools to measure if the housing has those cracks,
2) Am I fussing too much and making a problem where there isn't one
3) or are both turbos toast so I have to blow the cash on a new one anyway.
If I keep the turbo, should I avoid boosting it altogether to avoid further damage? I just need a turbo to last a year or two and not damage anything else, but it would be fun to learn to experiment with tuning with boost if it isn't going to be dangerous.
For reference: My goals are just to set up the engine for upgrades later and perhaps a modest performance increase now, so I certainly will plan to buy a new turbo and exhaust in the next year or two. Current mods are head port and polish - it was supervised by an experienced NASCAR engine builder, so it's probably ok, street performance cam regrind (Colt Cams), Titan 1.3mm MHG, exhaust manifold reshaping (an experiment what the hey), MSD wires, and and racing muffler that is probably useless until I get the rest of the exhaust system upgraded.
Thanks.
