Hi guys, I just bought a pair of second hand T25 turbos to rebuild for my car. I was wondering what it would take to rebuild them into Hi Flow units. I know the housings have to be machined but that is the easy part as I run a machine shop. Does anyone know the specs of the compressor and exhaust impellers I would have to use and where I could buy them? Turbos will be for an auto trans car if that makes any difference. Also when I dismanteled these turbos there seems to be a washer missing from the groove near the exhaust impeller as you can see in the photo, both turbos where the same. So what dose this washer do and is it necessary?
You can basically put whatever cores you want in there so long as they're not smaller than the standard one, obviously there's such a thing as too big and putting a GT35 turbine in the little housing will suck. Thirty second Garrett naming lesson: The T25 and T28 were renamed the GT2554r and GT2560r with some updates, these turbos share a turbine wheel, represented by the 25 in their name, and the 2560 has a larger 60mm compressor wheel allowing extra flow. Similarly The GT2860r uses the same compressor as the 2560 but has a larger turbine giving better efficiency and peak power. These turbos all use the same basic housing designs so swap over easily with appropriate machining. There are heaps of other wheel manufacturers out there to choose from if you want to go hunting for a better pair to suit your build. The Garret options will be available as assembled, balanced cores ready to drop in for ~$700 but if you have the balancing equipment you can assemble your own from whatever wheels. How much power are you looking for? Standard 2554r's are probably good for about 300kw at the wheels on an average build with some efficiency left. There's about 1000rpm spool difference between a GT25 and GT28 turbo.
Having another go at the photo. Thanks for the info guys, clears up a lot of things especially with the various numbers given to turbos. I might stay with standard turbos for now if they can produce 400hp (300kw) as they on a stock engine, what would the aprox boost be for that power range? Also apparentley these turbos are from a manual trans car, so what would the difference be running with my auto?
Bit more lag, but apparently negligible with a good launch. I personally noticed bugger all difference between my auto's spool up time compared to mr j zed in his manual the other week. Wouldn't stock tt injectors hit max duty cycle at that power? Probably wrong on that one, but i read somewhere the rule of thumb with injectors is the number of cc's roughly equates to the horsepower they are maxed out at. Could be mistaken tho.
Stock turbos can make 400 flywheel hp pretty easily, 400rwhp is not as easy. I'd guess my car is around the 280rwkw mark on E85 and 20PSI.
On my car I'm expecting 16psi will be right about 300kw based on my 10psi dyno run, could be from 14-20psi for others depending on supporting mods, tune and dyno (they're not very well standardised). The only difference you'll have on an auto car once you swap the turbos is the exhaust cams have a little less duration which which helps boost turbine velocity and makes the engine more tolerant of backpressure from running the turbine near it's limits. Stock Z turbos have different sized housing for the autos but T25s are all the same except for the ones they made for the RB26DETT. As slicktop suggests, bigger injectors would be a good idea with bigger turbos, my tune is super rich but already running 50% duty on 740s.
Rb26dett turbos are a T28 hot end and something different on the front. Nothing like a T25 actually. I have a pair of them at home. Your best bet for budget turbos would be T25g. These have a .64 hot end and a .80 (iirc) cold side. A good change to make to a T25g is to fit a .48 hot housing which is off the T25 and a straight changeover giving a slightly earlier and harder spool on the smaller engine than it was meant for. You cant easily swap the cold housings tho as the wheels are different. This setup will happily pump 18/20psi all day and spool up usefully around 2200/2300 rpm A pair of running T25G's off SR20's can be had for around 300 bucks and also have a bolt on snout rather than the tube type snout on the majority of T25's off CA18det's requiring a lot of buggerising around to adapt to existing inlet pipes. E
T25 and T28 have the same hot side, I could be wrong on the compressor but I thought it was 54mm major diameter so by Garrett nomenclature still a T25 wheel but with a much lower trim, maybe it's 60mm major from the T28 with low trim. Even if they aren't really T25s they're often sold as them, every couple of weeks on facebook you see people posting a pic of a GTR turbo asking if its from a silvia. You're probably right on the CA T25s, I forget they exist, generally just consider the 2554r's predecessor as the one true T25. Edit: I should probably also clarify that 'T25' is one of those names which refers to a group of thing and also to a specific member of that group, there's a wide variety of T25 family turbos out there but like most nissan driver's I refer to the silvia turbo as 'The T25'
Wow thanks for all the info guys, that gives me a lot to chew over. So from all that I have now realised that the standard 300zx turbos are not a true T25, (something I was led believe). So what is their true name? I guess fitting the T25 wheels would be the one high flow option for these? Or go for what Tassuperkart says.
They are indeed not really T25s, they're TB02 turbine wheels and TB22 compressor. The compressor is only a little smaller than the Silvia T25g and although they flow a little less they're actually more stable at high pressures so good when you don't have many other flow mods. The turbine wheel is a tiny little baby wheel and the biggest problem with the standard units. Are the turbos you have off a silvia or Z?
Ok so I think you can run all the wheels we mentioned, 2560 or even just the 53mm turbine with standard compressor would probably be reasonable. You're on your own making sure they actually fit together though, watch out for shaft sizes and stuff like that, I don't have the equipment to do much of the rebuilding/balancing myself so just buy assembled units. Similarly I'm not too sure on the seals etc that are supposed to be on the turbine shaft.
Would this be a suitable compressor wheel? http://www.ebay.com.au/itm/Garrett-...essor-Wheel-/151847225242?hash=item235accc79a Garrett TB28 TD25 Turbo Comp. Wheel Turbo Compressor Wheel for Garrett TB28 / TD25 APPLICATION P/N 707747-0005 SPEC. Diameter: 39.6 mm / 56 mm (Inducer / Exducer) Shaft Size: 6 mm 6+6 Blades, Superback Brand New; Balanced already!!! Or am I better of going with a 60mm? I did hear that putting a 60mm wheel in those standard ZX housings can cause excessive heat, true or false?
"Your best bet for budget turbos would be T25g. These have a .64 hot end and a .80 (iirc) cold side" +1 Keeping it simple is a good thing...............
Should be ok, has a very low trim (area ratio of the wheel's minor and major diameters) though so possibly more of a diesel wheel for high pressure rather than the high flow you want for a sports car, something with a larger inducer might be a better choice. Something like 42mm/56mm (if it exists) would give you a map similar to standard but shifted maybe 5lbs/min higher The heat issue is better to test than calculate so I'd be looking for people that have used those high-flows, pretty sure people have done T28 internals for stock turbos a few times over the years.The problem with bigger wheels is that the standard housing becomes a serious restriction due to its small A/R.
Found this very useful chart, great for comparing compressor wheels. http://www.turbomaster.info/eng/applications/compressor.php
The plot thickens !! So after poking around under the car I'm thinking "bloody hell those turbos look a bit big bro" Looks like what I've got is a pair of JM-25's from JM Technology, USA. Copy of a T25 I would think. Even though I have never driven or worked on another 300ZX I thought the thing was a bit bloody quick, now I know why. Must remember I bought it as a wreck off a lady that knew very little about it. Got to have some luck sometimes aye, on the downside they still need rebuilding. P.S. Anyone need a set of rebuilt standard ZX turbos?
Well that's a score! Don't go putting those stockers on. I wonder if it's got a tune and injectors done already too? A quick google showed their only turbo currently listed for a Nissan is a T28 (GT2560) equivalent, wonder if yours are the same or a discontinued T25 version. Hard to tell from this angle but looks like the inlet pipe may have had it's flange cut and rotated to suit that housing, just in case you go to fit something that's designed for the Z and wonder why they don't line up.
