Rebuilding a T25 Write-up
10-16-2006, 11:46 PM
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Rebuilding a T25 Write-up
I used this writeup as an example, but noticed slight differences which I'll point out: http://photo.platonoff.com/Auto/2005...Turbo_Rebuild/ First, this wasn't hard. The hardest part was one small retainer I spent 20 minutes on but have a 3second solution now that I know the trick. The rest of it was just like Lego's.
This unit is pieced together from four other turbos. It has a standard Garrett T25 turbine housing with T25 inlet flange and 5-bolt exhaust flange from an SR20det. The rest of the turbo is from 3 different 2g DSM T25's w/2" compressor ports. I'll be using the stock wastegate from the SR20 to start because it's the one that fits best. I believe they're either 7 or 10psi but the sticker has been scraped off the unit and I won't really know until I try and tune it. I'll still have to drill and tap another hole in the compressor housing to mount the wastegate.
Anyways, here we go.
First things involve disassembly. It's not to hard providing things aren't welded together... Remove the compressor housing with c-clip pliers and remove the turbine housing's 4bolts and brackets.
Then unscrew the compressor blade nut (the thread pattern is backwards from normal). I used a (I think) 8mm 12pt socket on the compressor and a 13mm 6pt socket on the turbine... just be gentle. Once the nut is off, hold the blade sections in your hands and twist... the compressor wheel will loosen and pull it off. Then I clamped the CHRA in a vice and gently tapped on the shaft while jiggling the turbine wheel until it popped out. It might be a little tough, BUT THERE"S NOTHING AT THIS POINT TO PREVENT THE SHAFT FROM COMING OUT. The reason it's a little tough is because of a small clip on the shaft that just needs a little assistance in fitting through is hole.
Once the shaft is out, start taking things out of the inside... the rings, bearings, c-clips, etc...
When it's gutted...
USING A DREMEL WIRE WHELL ATTACHMENT, CLEAN THE ---- OUT OF EVERYTHING!!! I soaked the CHRA in engine degreaser and Simple Green for four hours before I started in with the Dremel. It looked really clean.
Here's a pic of the cleaning process and all the turbo parts laid out in order. At the top of the pic are a couple parts not used but included in the rebuild. (one seal, 2 bearings, one funky c-clip). Also a pic showing the old bearings and the two different sets included in the kit depending on your particular T25. Also a pic of that extra seal that goes on the compressor side to seal the compressor housing to the CHRA.
NOTE: In the second picture, the larger left-most C-clip inlcuded in the kit that holds the compressor housing on is to small. I had to re-use an original one.
This unit is pieced together from four other turbos. It has a standard Garrett T25 turbine housing with T25 inlet flange and 5-bolt exhaust flange from an SR20det. The rest of the turbo is from 3 different 2g DSM T25's w/2" compressor ports. I'll be using the stock wastegate from the SR20 to start because it's the one that fits best. I believe they're either 7 or 10psi but the sticker has been scraped off the unit and I won't really know until I try and tune it. I'll still have to drill and tap another hole in the compressor housing to mount the wastegate.
Anyways, here we go.
First things involve disassembly. It's not to hard providing things aren't welded together... Remove the compressor housing with c-clip pliers and remove the turbine housing's 4bolts and brackets.
Then unscrew the compressor blade nut (the thread pattern is backwards from normal). I used a (I think) 8mm 12pt socket on the compressor and a 13mm 6pt socket on the turbine... just be gentle. Once the nut is off, hold the blade sections in your hands and twist... the compressor wheel will loosen and pull it off. Then I clamped the CHRA in a vice and gently tapped on the shaft while jiggling the turbine wheel until it popped out. It might be a little tough, BUT THERE"S NOTHING AT THIS POINT TO PREVENT THE SHAFT FROM COMING OUT. The reason it's a little tough is because of a small clip on the shaft that just needs a little assistance in fitting through is hole.
Once the shaft is out, start taking things out of the inside... the rings, bearings, c-clips, etc...
When it's gutted...
USING A DREMEL WIRE WHELL ATTACHMENT, CLEAN THE ---- OUT OF EVERYTHING!!! I soaked the CHRA in engine degreaser and Simple Green for four hours before I started in with the Dremel. It looked really clean.
Here's a pic of the cleaning process and all the turbo parts laid out in order. At the top of the pic are a couple parts not used but included in the rebuild. (one seal, 2 bearings, one funky c-clip). Also a pic showing the old bearings and the two different sets included in the kit depending on your particular T25. Also a pic of that extra seal that goes on the compressor side to seal the compressor housing to the CHRA.
NOTE: In the second picture, the larger left-most C-clip inlcuded in the kit that holds the compressor housing on is to small. I had to re-use an original one.
Last edited by curly; 02-24-2012 at 08:36 AM. Reason: Add bolded content
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10-16-2006, 11:53 PM
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The first things that go in are the funky shaped wavy c-clips. There are two of them that sit in very skinny(obviously) races towards the center of the housing. IF YOU DO NOT OWN A SET OF DENTAL PICS, GO TO HARBOR FREIGHT OR SEARS RIGHT NOW! I put them in as shown in the first pic and then rotated them with the Dental Pics until they slipped in. One goes in each end of the CHRA. This is real easy, just a little patience with my big hands and the instruments in a small space.
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10-16-2006, 11:58 PM
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Next the turbine side.
I used q-tips dipped in oil to lube everything.
Lube up one of the appropriate-sized gold bearings and slide it in.
Next up is the aforementioned only REAL PAIN about the whole thing. I could not get this damn silver retaining ring in the first pic to click into position. It was to stiff to bend which you need it to for it to go in. So, I pried it apart a little and kind of "threaded" it down into place. Once it's in, it's compressed by it's track and the fact that it's bent a little is negated. Guess what, the turbine side is done now.
1. Funky wavy clip
2. Gold bearing
3. Funky retaining clip
I used q-tips dipped in oil to lube everything.
Lube up one of the appropriate-sized gold bearings and slide it in.
Next up is the aforementioned only REAL PAIN about the whole thing. I could not get this damn silver retaining ring in the first pic to click into position. It was to stiff to bend which you need it to for it to go in. So, I pried it apart a little and kind of "threaded" it down into place. Once it's in, it's compressed by it's track and the fact that it's bent a little is negated. Guess what, the turbine side is done now.
1. Funky wavy clip
2. Gold bearing
3. Funky retaining clip
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10-17-2006, 12:06 AM
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Now onto the compressor side.
There are four pieces in the first pic and they go in next.
The fourth piece you may not see right away is the small clip on the spaceship looking thingy. Also, the smoother side (not the side with all the channels in it) of the C-shaped plate with the three holes in it goes to the outside. The channels are underneath for oil to flow through.
Once the small clip is on the spaceship, slide it over the C-shaped piece and ratched down with an appropriate sized Torx bit. (I bought a bitchin' security bit set at HF the other day, see pic). I used a good deal of force on those bits.
Once those pieces are in place and tightened, then it's just the Seal, Backing plate, and C-clip. You can see in the last pic the seal is already seated. It takes some light tapping and jiggling to get the backing plate to seat properly. DON'T FORCE IT... just keep jiggling and it'll go all the way down.
There are four pieces in the first pic and they go in next.
The fourth piece you may not see right away is the small clip on the spaceship looking thingy. Also, the smoother side (not the side with all the channels in it) of the C-shaped plate with the three holes in it goes to the outside. The channels are underneath for oil to flow through.
Once the small clip is on the spaceship, slide it over the C-shaped piece and ratched down with an appropriate sized Torx bit. (I bought a bitchin' security bit set at HF the other day, see pic). I used a good deal of force on those bits.
Once those pieces are in place and tightened, then it's just the Seal, Backing plate, and C-clip. You can see in the last pic the seal is already seated. It takes some light tapping and jiggling to get the backing plate to seat properly. DON'T FORCE IT... just keep jiggling and it'll go all the way down.
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10-17-2006, 12:15 AM
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Now it's time to actually put the shaft through:gay:
There are two races on the shaft next to the turbine blades. The writeup linked above complained that his turbo when taken apart didn't have anything in the second race except baked oil. None of the 4 turbos I took apart had anything in that second race. In the first pic, you can see I've already inserted the retaining clip in the race closest to the blades. There's also a washer on there. Don't forget the turbine backing plate.
Lube the shaft up with some oil so it goes in easier, and then just put it through... maybe a little jiggleing and wiggling, but it will go. Once through, slide on the compressor wheel. Then tighten down the nut. I used as much force as I could with a 1/4" drive socket... I'm sure there's a torque setting, but I'm sure it's not going anywhere.
There are two races on the shaft next to the turbine blades. The writeup linked above complained that his turbo when taken apart didn't have anything in the second race except baked oil. None of the 4 turbos I took apart had anything in that second race. In the first pic, you can see I've already inserted the retaining clip in the race closest to the blades. There's also a washer on there. Don't forget the turbine backing plate.
Lube the shaft up with some oil so it goes in easier, and then just put it through... maybe a little jiggleing and wiggling, but it will go. Once through, slide on the compressor wheel. Then tighten down the nut. I used as much force as I could with a 1/4" drive socket... I'm sure there's a torque setting, but I'm sure it's not going anywhere.
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10-17-2006, 12:20 AM
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Attach the Turbine and Compressor housings (clocked to your application).
NOTE: The included larger C-clip in the rebuild kit is supposed to hold the compressor housing on was too small and I had to reuse the original.
I also had the stock water feed lines that came with one of my turbos that I will definitely be using. I've still got to bend them a little more to get them pointed the direction I want... but all looks good.
Tips:
Spend some quality time Dremeling.
Blow off everything with compressed air.
Everything that goes inside the turbo and all the inside surfaces get Q-tipped with oil... especially the seals.
Have a WELL LIT work area.
DON'T FORCE ANYTHING... IT WILL ALL FIT!
NOTE: The included larger C-clip in the rebuild kit is supposed to hold the compressor housing on was too small and I had to reuse the original.
I also had the stock water feed lines that came with one of my turbos that I will definitely be using. I've still got to bend them a little more to get them pointed the direction I want... but all looks good.
Tips:
Spend some quality time Dremeling.
Blow off everything with compressed air.
Everything that goes inside the turbo and all the inside surfaces get Q-tipped with oil... especially the seals.
Have a WELL LIT work area.
DON'T FORCE ANYTHING... IT WILL ALL FIT!
Last edited by samnavy; 10-19-2006 at 10:38 PM. Reason: Add bolded content
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10-17-2006, 03:52 PM
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I've heard both 7psi and 10psi for stock wastegate settings. I think the difference is between whether you have a red-top or black-top SR20det. I don't know how the two motors are different, but I think there are actually two "stock" wastegates with different settings. I COULD BE WRONG!
Either way, I'll know when I start tuning. I've got three wasegates and I'm almost 100% positive that the 2g DSM wastegates are 9psi. I like the bracket on the SR20 better though.
I went with the DSM compressor housing because it's a completely different design. It's got the 90* bend in the outlet. The stock SR20's are all flanged, so I'd have to buy a flange for the end, and it would take more engineering for the IC piping. The thread here explains how easy it's going to be to route IC piping... just one pipe: https://www.miataturbo.net/forums/showthread.php?t=5120
The compressor inlet on the Nissan housing is a 2 3/8 vice just a 2" on the DSM. The compressor outlets are both 2". Either way, I'm only looking for maybe 10psi max after full tuning...more like 8or9. It's the best compromise.
Either way, I'll know when I start tuning. I've got three wasegates and I'm almost 100% positive that the 2g DSM wastegates are 9psi. I like the bracket on the SR20 better though.
I went with the DSM compressor housing because it's a completely different design. It's got the 90* bend in the outlet. The stock SR20's are all flanged, so I'd have to buy a flange for the end, and it would take more engineering for the IC piping. The thread here explains how easy it's going to be to route IC piping... just one pipe: https://www.miataturbo.net/forums/showthread.php?t=5120
The compressor inlet on the Nissan housing is a 2 3/8 vice just a 2" on the DSM. The compressor outlets are both 2". Either way, I'm only looking for maybe 10psi max after full tuning...more like 8or9. It's the best compromise.
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10-17-2006, 05:06 PM
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Posts 15/18. With pressure drop, I guess 7 lbs. Course I'm only right every 3rd time.
You'll get to run a MBC, which is good.
Nice writeup.
Last edited by UofACATS; 10-17-2006 at 09:07 PM.
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10-17-2006, 05:15 PM
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Yup, I've got the cheapest MBC I could find off of eBay. It's this one: http://cgi.ebay.com/ebaymotors/Voodo...36603875QQrdZ1
This is the one part I totally cheaped out on. I took it apart and the design is so simple. Literally just a spring and ball. I'd love to see it work perfectly though... don't see why it won't. I've never run across anybody who says "STAY AWAY FROM CHEAP MBC's." I think the cheapo Chinese knockoff ones that imitate a more expensive design might be best to shy away from... but this thing is all about the minimum... no pretending to be anything it's not. We'll see.
This is the one part I totally cheaped out on. I took it apart and the design is so simple. Literally just a spring and ball. I'd love to see it work perfectly though... don't see why it won't. I've never run across anybody who says "STAY AWAY FROM CHEAP MBC's." I think the cheapo Chinese knockoff ones that imitate a more expensive design might be best to shy away from... but this thing is all about the minimum... no pretending to be anything it's not. We'll see.
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10-17-2006, 06:30 PM
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cause every cheap MBC is a brass unit that that built using parts from the local hardware store. Which ironically it better quality than most stuff pumped out of China.
They are easy as hell to make. I made mine. I can diassemble mine and show you guys how.
They are easy as hell to make. I made mine. I can diassemble mine and show you guys how.
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10-17-2006, 09:40 PM
#19
Somebody made a nice graph that showed why the MBC helps...but I can't remember who/where.
Basically, it doesn't start spooling any faster with a MBC, but it helps reach max boost (spool) faster, as the MBC essentially blocks the wastegate exit until a certain boost level has been reached, at which point the wastegate exit is totally opened. This differs from the wastegate opening linearly without a MBC, thereby wasting a bunch of potential as the boost rises.
Basically, it doesn't start spooling any faster with a MBC, but it helps reach max boost (spool) faster, as the MBC essentially blocks the wastegate exit until a certain boost level has been reached, at which point the wastegate exit is totally opened. This differs from the wastegate opening linearly without a MBC, thereby wasting a bunch of potential as the boost rises.
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