T25g, should I go for it?

[mdb4879]

sorry for the lack of searching and my own prep work for this post, but this opportunity kinda just popped up. I just found what i think is a t25g (craiglist post that said sr20det t25, so i'm assuming its a t25g. i'm going to call him in the morning to ask some questions about it, though) with minimal shaft play for $120, and idk if I should go for it or not. also it says for this weekend only cuz he's moving (i'll be sure to make sure it's not a scam), so i didn't really have a lot of time to search and making this thread is kinda a long shot anyways because of the time restraint

here's my situation:

I got my CA in my pulsar about 3 weeks ago and have been tinkering with it here and there. the turbo was, to the best of my knowledge, professionally rebuilt less than 5000 miles ago, but when first got the car driving and was troubleshooting boost leaks and stuff one of the intake pipes became disconnected about a mile from my house. by the time i got back to check it out there was oil all over the pipe where it disconnected. so my thinking is that the compressor side is leaking oil (although i had thought it was a lot more common for the exhaust side to leak). the car doesn't smoke unless i wind it up a bit for a little while (floor it for maybe 10 or 15 seconds, shifting at 6k-6500rpm). but when it does smoke it will only smoke when i let off the gas and will clear up if i rev it freely a few times (possibly valve guide seals, not the turbo?)

i haven't checked the intake plumbing recently to see if and how much oil is in there. also, when i had the motor out the turbo seemed to have quite a bit of shaft play. i know journal bearing turbos are suppose to have some, but to me it seemed like too much. i was thinking of having the turbo rebuilt, but if i can upgrade for only around $120 instead then that would be great. so i guess what i need to know is if my turbo is crapping out or not?

also, i would like to know specifically when the t25g would start to spool and when it hits full boost. for instance, my stock CA T25 will start to build boost at 2300 or 2400 rpm and have full boost by 2800 or 2900. it has the turbo elbow and about a 3 inch long pipe after that and that's my whole exhaust for now.

another thing i've been wondering about, when it hits boost it will go to 10ish psi then drop to around 7. well i looked up explanations of what boost creeping and spiking are and i don't think its either. spiking would be going past the set point (7 psi in this case, right. it's the stock actuator with no boost controller, although i guess 10psi should be normal with a free flowing exhaust, right?) then going back down. well my car will hold 10psi until around 5k-5500rpm. i can brake boost and it won't drop back down, just a steady 10psi then it'll settle around 7 once it's past around 5k. and boost creep would be rising boost as i stay in the throttle, which it's not doing that either. so what exactly is going on? is it something to do with the wastegate or do these turbos really start choking out after 5k because they're so small?

and does the CA turbo elbow fit this turbo? i think i read one of the holes on the elbow has to be slotted, but I would just like some confirmation

it will also miss a little bit once i get past 6k, so i was wondering if that could be the oil or if its an air/fuel mixture or timing problem? and there is a line that is split that goes to the intake boot, and because its split the motor will suck in unmetered air and run lean at idle and cruising and cause it to try to die at idle and miss at cruising. i was messing with it the other day and i think i got it to seal better because the idle smoothed out a lot, but not totally, and it stopped missing when i'm cruising (it always ran fine when i was in boost). i clamped off the line and the motor died, so i'm guessing it has something to do with crankcase ventilation, but i haven't tried taking off the line and not clamping it, but plugging the hole on the intake boot. so even though i haven't tried it myself yet, could someone tell me if it will run fine if i had a hard pipe made for it and just let that line vent to the atmosphere? i would like to figure out why this car does some of the things it does before i go to upgrading it (like spending money on the t25g i am talking about). and it didn't have the high rpm miss before i fiddled with that line (at least i don't think it did. i don't drive the car every day because i'm still working out problems and don't want to get stranded somewhere and my gas gauge doesn't work and i'm trying to only put 93 octane no-ethanol gas in it, but the nearest station with no-ethanol is 10 miles away so i fill up very regularly)

sorry for my total noobness. i do all the searching i can. this is my first turbo'd car, and i'm a workaholic so i don't have too much time to mess with it (i guess i shouldn't have a toy like this if i don't have time for it, huh?)

and once again, sorry for bugging you guys about all this stuff that probably could've been searched. i do my best to search what i can (not using that as an excuse cuz i'm sure i could do better)

[float_6969]

Too many questions, but I'll deal with the turbo stuff. Oil bypassing on the compressor side with the outlet pipe off isn't unreasonable. The main thing that keeps the oil bypassing the seals is the pressure in the housings (both compressor and turbine), so if there is little to no boost pressure in the housing and the crankcase pressure starts to build up, it's possible it just bypassed the seal. Not a big deal.

As for the stock turbo going to 10 psi and then falling off to 7 psi, that's normal. The stock turbo is small, and that old actuator is probably weak, causing it to drop boost in the high RPMS. I know for a fact that the stock CA turbo won't make more than 17psi at redline. It just can't breath up there and chokes out.

If the T25G is in good shape, I say go for it. It's a nice upgrade, especially for the money you're looking at, and it really wakes up the top end, with negligible impact on the bottom end.

[boost_boy]

To add to what my boy said, your current turbo was rebuilt by Poppa Smurf turbo which means someone probably rebuilt it themselves which also means it's a dud. When those T25s start doing that, the thrust washers are worn and seal failure is eminent. As for the T25G, it is not that much better than the turbo you got. The SR20 is a tad bigger in displacement than the CA, so to make it put a bit more power, nissan gave it a slightly bigger (not that much bigger) turbo, but with a bigger back housing .64 as opposed to the CA18s .48 which will give you a bit less back pressure and help accomodate the extra CFM from the SR20. You can get the T25G and put your .48 housing on it and you got a quick spooling turbo, but it will be out of gas at or around 10psi whereas the T25G will be out of gas at or around 13psi and that's with the .64 back housing. So if you're thinking of upgrading, stay away from the stockers on the CA18DET and the red top and early black top SR20s. Don't cheap-out in the area of turbocharging or you'll find out how much time you'll lose in labor and headaches.

[mdb4879]

yeah, sorry for all the questions. it was late and my eyes were getting tired and sore from searching for about two hours (not just this stuff, just searching in general plus this stuff). i got to typing and started on about the other non-related questions i have. for future reference should i make a bunch of threads for each topic or just consolidate them?

the t25g is gone now so i guess the topic has changed now. and believe me, i'm not wanting to cheap out on anything. it was just that if my turbo was crapping out and i could find a good replacement then i would want to go with that instead of rebuilding mine or something. my ultimate power goal is like 250hp at the crank, so i would want to find the fastest spooling turbo suited to that (i know the t25g definitely will not get me there). at first i was thinking the s15 bb would be too big, but it looks as though that's about my best option.

but that's down the road a ways. right now i'm mostly concerned with it running correctly