Ok. Hi Everyone. As you are all aware, the Garrett GT30r is a great upgrade for the RB25 for any user looking between 240rwkw and aboout 300rwkw.

Before I continue - here's a few things about my car. Its a Standard motor, 3% leakdown. Water meth injection, powerfc, 555cc Nismos, Full exhaust, FMIC, etc. 18psi of boost.

As a few may know, I managed to get myself a poor GT30r, one with a badly setup Compressor wheel and a Turbine wheel that I've been told is letting it down also. My Setup has a .7a/r compressor cover, and a ground out RB25 Stock turbo Exhaust housing. It apparently has a T04S wheel in it. 700177 is the first half of the part number on the plate.

Mine is not too bad though - Managing over 240rwkw with heaps of torque, (haven't got dyno figures because I haven't dyno'd the car) but I'm running 12's with 112mph.

Anyway....

Full boost on my Turbo is at about 4000rpm in second, and thats at 18psi. There is no evident surging issues, or boost creep. I'm using the $22 boost controller.

I've spoken to the turbo guy in mackay here and he's offered to help me out by taking my turbo and sending it to garrett and getting the comp and turbine wheels changed to my choice, and this for less than $500 which i think is better than spending $2000 for a new one.

I've been speaking to Disopotato03 and he's suggesting the GT3071 (.63 ex internal gate) or the GT3076 (.86 internal gate). (and thanks for putting up with my extreme lack of knowledge Disco, you're a real champ)

I've managed to get some Compressor maps, and I'm looking at the difference between these two turbos and I'm not really sure what it is. I only have a few small questions and are after a little bit of feedback from anyone that is using one of these turbos.

1. What sort of lag are you looking at with the two combos mentioned above? (the GT3071 (.63 ex internal gate) or the GT3076 (.86 internal gate).
2. What size compressor cover should I be going for? Is .7 too big?
3. General opinions on anything at all?
4. What is the difference between the 3071 nad the 3076 other than the wheel sizes? One has more top end maybe?


If anyone has any opinions or ideas - share them here. I'm more than willing to post up befor and after Dyno results, and changes etc.

Here are some compressor maps of the two turbos - does anyone know how to read them properly? Feel free to m paint them explaining lol. I'd love to know this!

Also, Just adding that I've now decided that I'm only chasing anything less than 300rwkw. 280rwkw would be so nice.

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I went with the GT3071R on my RB20 which i think was a perfect match for it.
I have now put a Rb25DE+GT3071R into the car that is getting tuned on 1 bar tomorrow morning so i will post up dyno charts tomorrow night if all goes well



http://www.skylinesaustralia.com/forums/in...=107517&hl=

Thats the link to my thread when it was on the 20.

less is always better if you want more response and less lag
i would go for the .64 housing

the .63 can be a little choking for higher power levels though. It affects the turbo characteristics quite a bit.

Holy crap you're hitting 18psi by 3400rpm? I should look into getting one of these! Are these GT30 series turbo's straight bolt onto the stock manifold?

yeah, problem is - in 5th, you can hit full boost much earlier - but with only needing 1\4 of the throttle. The exhaust housing is a chokey little bastard me thinks.

That depends if you want to upgrade.

In regards to a power upgrade, the GT3071r won't be. The slightly larger and laggier GT3076r will be.

But saying that the GT3076r .63 will still be an upgrade over what you have now. There's no reason it shouldn't crack 280rwkw with your alchy/water setup. Its not optimal on paper but it works.

Hi all , Mafia two of those turbine maps you have there are not from what I call the REAL GT3071R turbocharger . You will note that those maps show turbine housing AR or area to radius ratio as .64 and .86 , those are the bored out or re profiled T28 flanged GT28 turbine housings not the propper GT30 turbine housings . Just on this compare the maximum efficiency of those two compared to the one on the second row which is the GT3076R turbine map - huge difference real world . So basically these (pic 1 and 3) are the dreaded GT3071R - "WG" turbos that I try to steer people away from . These have the same cropped or ground down turbine as you have in your turbo .

Where there seems to be some confusion going on is comparing similar turbine housing AR ratios but with different families of turbine housings .

1) GT28 Turbine housings - designed for approx 54mm major diametre turbines .
2) GT30 Turbine housings - designed for approx 60mm major diametre turbines .

I you held a GT28 and a GT30 turbine housing of the same AR ratio the GT30 would be larger and bulkier because the area and radius are larger/greater even though the ratio is similar/same . As a rule of thumb housings with .64 or .86 on them won't be GT30 housings , Garrett got away with calling the GT3071R - "WG" a GT30 based turbo because the turbine (although modified) started out as the normal GT30 turbine . Its name has nothing to do with the butchered GT28 turbine housing they come fitted with .

Also to clue people up on the compressor housings . Virtually all GT37 76mm compressors (like in the GT3076R and all GT3037's) come from Garrett with TO4E family compressor covers and usually in .60 AR though occasionally on GT3037's in .50 AR and non port shrouded . The TO4S compressor cover is generally found on turbos with either those nasty TO4S compressor wheels or the 82mm GT40 compressors ie Mafias turbo (TO4S comp) or the GT3082R or GT3582R or HKS's GT3240R which use a variety of trims of the 82mm GT40 compressor family . I don't know if anything with a 76mm GT37 compressor uses a TO4S comp cover .

Back to the real GT3071R and GT3076R . The first one is more responsive purely because its compressor is a 71mm 56 trim vs the seconds 76mm 56 trim . It takes more turbine power to drive the 76mm wheel than the 71mm so for the same turbine power it kicks the 71mm into life sooner and accelerates it up to positive pressure type revs more easily . The maps show you that the 71mm wheel is good for around 440 Hp worth of air and the 76mm about 520 . IMO its better to have a little excess turbine flow than compressor flow because you can tune it to a degree with various AR ratio turbine housings . If the compressor is too big you lose response and generally cant use its capacity very efficiently so you lose the lower mid range for no good reason .

Now that Garrett has the new GT30 integral wastegate T3 flanged housings there is no excuse to buy the GT3071R "WG" turbos which having the T28 flange won't bolt up anyway .

Also as I mentioned to Mafia its not a very good idea to use the .63 GT30 housings on Garretts GT3076R mainly because it has the big or 56 trim compressor wheel . Its this big comp trim that makes these turbos a bit laggy (ask SK) and using small or .63 turbine housings makes for higher backpressure and increases the chance of compressor surge . Garrett did manufacture this turbo in 48 and 52 compressor trim but only High Kost Spec (HKS) market them . The 52 trim version is rated at similar power to the GT3071R , no one seems to know much about the 48 trim version . I'm making some enquiries through Jim Wolf Technology in the US who seems to discount thius kind of thing so people can get an idea what the damage is like . Last I hear a couple of yrs ago was ~ 1600 USD . The fellow in this thread could tell you what his real GT3071R cost and its probably a more reasonable figure .
For those that don't know the real GT3071R's cartridge (CHRA) number is 700177-0023 or -5023 , Garrett don't sell it as a complete turbo . You buy the cartridge and add one on the three available AR GT30 turbine housings (.63/.82/1.06) then one of the three available compressor housing kits . These are TO4E and there is one available with a port shrouded snout . Firms such as ATP Turbo in the US market them as a complete assembly with you choise of housings . So for an RB25 my guess is the .82 housing but for an RB20 the .63 . These combinations would get you similar results to HKS's GT2835 Pro S turbo but with a little more turbine and a little lower turbine housing AR ratio ie .63 and .82 vs .68 and .87 .

Fingers falling off cheers Adrian .

hmm this going ot be a intersted thread im soon going to be ordering the gt30 internal gate turbo from slide great info fellas

discopotato,

You have quoted them before, what are the CHRA numbers for the GT3076R IW, I promise to pay attention this time!

I ahve just fitted a gt3076r to my rb25 with 0.82 exhaust housing and usaly mods rebuilt motor, pfc, cams etc! I got it tuned last week but we couldnt do it cause the car is getting way too much fuel so i have to put an adjustable fpr on there then he can tune it!

But basically he just pulled out some fuel so that it can just be driven around & checked the afr. But its making 215rwkw on 8psi. But as i said it hasnt even been tuned yet but its look good to make some serious power! I am getting it tuned next week some time so i will post up the results!

Cheers

Discopotato - Have you come across anyone using the GT3076R 56T w/ .63a/r turbine housing on an RB25 and encountering surge? I've read up on people around the world using .63 to reasonable effect without any issues, they just get choked up high (ie, when trying to push well over 400whp Dynojet style).

In the RB25 Dyno upgrade thread there is a dude running a 56T GT30R who got >274wkw running the .63a/r turbine housing on a stock manifold and motor and it looked like it was all good. Mine (again .63a/r) should be running this week, so I'll be able to give driving impression this weekend - tuning is on the 30th.

I know of one that ran a GT3040 .7 comp cover VLT int. gate .63 turbine housing and didn't have issues with surge. Made a touch over 300rwkw with some healthy boost, cams and all the support mods. It apparently came on strong ~3500rpm.

It was originally machined up with the std rb25 comp cover. I remember it made 280rwkw on 17psi. Once again it did have the support mods, cams etc.

ive got my rb25 with a gt30r with .63 rear going in to be tuned this thursday. So i will post up what it gets and everything. Just rebuilt the motor, so fresh rb25 with acl forgies and thick headgasket....too thick. I farked up and im pretty sure the CR is 8:1.... Wanted 8.5:1.

So i guess lots of timing and lots of boost will fix that. Things ive noticed so far is about a 50k per tank loss, and low down response is noticeably different...in a bad way. No one said the acl pistons drop your CR to 8.5:1, of which i had already allowed the doing of this by the 1.6mm headgasket. DAMMIT!