Inquiry About Stock Rb25 Turbo

[gurov]

no skyline here, but a nissan none-the-less.

i guess the first question is whether an rb25det turbo is made by garrett, my whole idea depends on this.

my current setup is a qr25de-t engine with a garrett t3/t04e 57 trim .63 exh .6comp (pics available)

what i'm wondering is if I get a stock rb25det turbo, if that will fit into a t3 .63 a/r exhaust housing.

reason i'm looking to do this is because my t3/t04 setup is rather laggy, i hit about 13 psi at my altitude by like 3700 rpm (6200 redline), so i'd like to try something (cheap is the keyword here) that spools a tad quicker (ballbearings from what i understand) but i don't want to touch my exhaust setup (4bolt vs 5bolt with internal wastegate).

also, as far as compressor flow map, is there a name for this stock rb25det turbo, or a more known turbo which i could find a compressor map for mapping the flow and efficiency with my engine.

i'm looking to run the turbo at around 2.0 PR (i'm at 5000 feet elevation, so i need the 2.0 PR to make around 10 sea level psi max)

from what i hear, the rb25det stock turbo has ceramic turbine wheel, how far have people pushed this without completely destroying them ?

[R31Nismoid]

12psi is the limit if your going to give the RB25 turbo a good workout.

on the track, 10psi as the heat kills em rather fast

[Downforce]

discopotatoe3 should be able to give you the specs, he loves talking turbos

[discopotato03]

Gurov , the easiest and cheapest way to get earlier response is to use a smaller trim TO4E compressor wheel which will also need another compressor cover . TO4E's go down below 40 trim in 76mm or 3" diametre . I went to a lot of trouble some years back to get a TO4E 50 Trim from turbonetics because the map looked so good . You should be able to get some turbo shop over there to do this for you cheaply and easily . The std Hitachi's on RB25's are badly short changed in the turbine and housing dept so I would not seek one if it had something easily available . Actually I think Garrett has released some Ball Bearing T3/T4 conversion cartridges they're calling T3/T4R CHRA's .

Getting nagged by the kids again so back with more info later , cheers A .

[gurov]

i guess the question now is will a turbine wheel meant for a t3 .43 a/r fit into a t3 .63 a/r, as long as the chra is t3 ? for ex i have a t3 .63 and i buy another turbo with a .48 a/r, will that fit into my .63 a/r that's already bolted to the manifold/downpipe ?

[discopotato03]

Back again , discovered you mean QR25 not RB25 and wish to keep your turbine housing and dump pipe .

Garrett has released five new Ball Bearing cartridges designed to replace everything between the housings for some bush bearing turbos .

Over your way there has been a huge craze over TB31/TA34 + TO4E hybrids . Garrett has decided to use the 76 trim TA34 turbine (stage 3 in US speak) and match it with one of four TO4E compressors , ie 57 and 60 trim in the 75mm or 2.950 O/D . The second two are 50 and 60 trim in the 76.2mm or 3" wheel version . My lists of TO4E compressors is not complete but I would lean toward the 50 trim version because it will spool sooner for the given turbine shaft power . My list shows the 76.2mm 50 trim as 53.9mm inducer and 5.2mm exducer tip height , wheel number is 448048-0004 .

Garrett part numbers for these conversion cartridges are 757179-2/-3/-4/-5 for the respective compressor options mentioned above . The 757179-1 I left out is a TO4 PTrim combined with a TO4B 60-1 compressor .

From memory QR25's are long stroke engines so sizing the compressor to support beyond safe revs is pointless . Probably need a 3000 to 6500 rpm range which the 50 trim should handle and not overwhelm the turbine or integral wastegate .

As for boost pressure the best gauges are absolute pressure type which read zero as zero (total vacum) instead of those silly things that only read sea level pressure as zero . Sea level pressure is 1 bar absolute so at 5000 ft it will read something less . If these read 14.7 lbs of boost it will be 1 bar at sea level , 5000 ft or 20,000ft because its pressure above absolute zero . Often with aircraft turbos are there to maintain sea level manifold pressure to their desired service ceiling so that lower atmospheric pressure does not sap performance .

Cheers A .

[gurov]

Back again , discovered you mean QR25 not RB25 and wish to keep your turbine housing and dump pipe .

Garrett has released five new Ball Bearing cartridges designed to replace everything between the housings for some bush bearing turbos .

Over your way there has been a huge craze over TB31/TA34 + TO4E hybrids . Garrett has decided to use the 76 trim TA34 turbine (stage 3 in US speak) and match it with one of four TO4E compressors , ie 57 and 60 trim in the 75mm or 2.950 O/D . The second two are 50 and 60 trim in the 76.2mm or 3" wheel version . My lists of TO4E compressors is not complete but I would lean toward the 50 trim version because it will spool sooner for the given turbine shaft power . My list shows the 76.2mm 50 trim as 53.9mm inducer and 5.2mm exducer tip height , wheel number is 448048-0004 .

Garrett part numbers for these conversion cartridges are 757179-2/-3/-4/-5 for the respective compressor options mentioned above . The 757179-1 I left out is a TO4 PTrim combined with a TO4B 60-1 compressor .

From memory QR25's are long stroke engines so sizing the compressor to support beyond safe revs is pointless . Probably need a 3000 to 6500 rpm range which the 50 trim should handle and not overwhelm the turbine or integral wastegate .

As for boost pressure the best gauges are absolute pressure type which read zero as zero (total vacum) instead of those silly things that only read sea level pressure as zero . Sea level pressure is 1 bar absolute so at 5000 ft it will read something less . If these read 14.7 lbs of boost it will be 1 bar at sea level , 5000 ft or 20,000ft because its pressure above absolute zero . Often with aircraft turbos are there to maintain sea level manifold pressure to their desired service ceiling so that lower atmospheric pressure does not sap performance .

Cheers  A .

<{POST_SNAPBACK}>

eh, yeah, that's not what i really asked, heh. i know about the ballbearing garret cartidges, but it seems like shelling about $700 out for that i could find something from the stock turbos that fits, wishful thinking i guess. i'm just looking for cheap options to replace the turbo or go up/down a size of cheaply-available turbos.

yeah, it's a qr25de. the long stroke 4 cylinder, 57 works nicely, once it spools, it's fine. external wastegate here, hence the desire to keep my housing, most of smaller T3/t04 hybrids i find are in .48 with integral gate,and i don't want to redo too much of my exhaust hardware.

as far as the pressure thing goes, i say 10 psi sea level because that's what my datalogger/wbo2 displays (zt2) , it uses a uncorrected map sensor (3.5bar aem), and just gives me raw voltage to 0-350kpa in PSI my boost gauge/boost controlelr show relative pressure.

Edited January 7, 2006 by gurov

[discopotato03]

Smaller Trim TO4E compressor will bring it on earlier . You are using a 57 trim so a 54 or 50 would be the next steps down .

You could even look at usind a TO4B cover and backplate with the Buick Grand National compressor wheel which is actually a TA34 69mm 58 trim 7 blade wheel 410299-0004 that looks like 2/3 of a 60-1 map flow wise . There are 6 blade versions of the old TO4B compressors in 39/48/57/62 and 70 trims , 48 or 57 could work Ok .

Several ways to skin the cat , mainly depends on price and availability of parts .

I would NOT reduce the turbine housing a/r - anything that increases exhaust restriction is a big no no IMO .

Cheers A .