Garrett G Series

[r32-25t]

Damn they’re so bad they are maccas nuggets lol

[BK]

On 07/09/2021 at 5:16 PM, Piggaz said:

 

i'm pretty sure you were referring to a different type a of nugget 💩

[Super Drager]

On 04/09/2021 at 12:16 AM, Full-Race Geoff said:

Lith... basing anything on a counterfeit amazon knockoff seems disingenuous

Pulsar turbos make power and spool exactly the same as their garrett counterparts. 

[joshuaho96]

On 9/6/2021 at 10:22 PM, BK said:

Yep, with the Mitsubishi cores. They were the GTIII-SS, RS, 2530, 4R and 5R turbos.

Almost went a 5R myself as the T51R replacement, until the SAU faithful shot me down in flames and slapped some sense into me 🤣

Be interesting to see how the HKS G series turbos compare, as they obviously realised they made a mistake and mustn't have sold well.

The RS/2530/4R/5R all looked pretty mediocre IMO, looks like they recently announced something that is no longer based on the MHI cores as well: https://www.hks-power.co.jp/product_db/turbo/db/29690

I've yet to figure out what could possibly replace the GTIII-SS for the weird corner of "basically stock but not ceramic turbine". Basically the same "design concept" as what HKS says for the GT4135 in that link. Nismo is busy rehashing R34 N1 turbos and calling it a new turbo, only Garrett makes bolt-on turbos and the designs are decades old at this point. Tomei has the T550B but nobody has tested them and talked about it on the internet and their old ARMS M7655 was just garbage. 

[gik0geck0]

Hi all, been a long time lurker of this thread, ultimately leading me to a G30-770 w/ 0.83 T4 flange. Just wanted to share the results I've gotten so far; though compared to the last dyno chart shared by Lithium, I feel like there's something off or inefficient about my setup. Now that ATP has a T4 twin-scroll housing available, that might be my next move to try to fix the laze (not soon) and reduce the number of cheap parts on my build. Also, sorry about the low-res image.

Important parts:

Altitude! 1519m/4984ft

RB25 neo (stock longblock & cams)

G30-770 0.83 single-scroll T4, normally at 20psi (the run at 22 was a quick one to verify there's still headroom)

Haltech Platinum Pro

E70 ish ethanol

CXRacing exhaust manifold (unsure whether an inefficient manifold would cause this much laziness)

OtakuGarage intake manifold

3" exhaust with cat

[Dose Pipe Sutututu]

Your manifold and an open housing turbing housing would be the culprit here, also is your VCT runing still?

[gik0geck0]

Yeah, I did a basic test of VCT at idle, and have it configured to be ON from 2000 - 5500, though I forgot to do an ON/OFF comparison on the dyno, so it's possible that's still a factor.
 

I'll also share how this looks in Autocross, where the lag is far exacerbated -- in my data-log, I was only seeing ~14psi peak and 5900 RPM in 2nd (barely into the meaty part; also possible I should just run a smaller turbo for this application; looking at you G25-660). Gear ratios are pretty close to stock R34 GTT 5speed, which is fairly long for autox as well -- lots of factors that are not ideal, ever a work in progress.

[Lithium]

On 19/09/2021 at 2:55 PM, gik0geck0 said:

Altitude! 1519m/4984ft

G30-770 0.83 single-scroll T4, normally at 20psi (the run at 22 was a quick one to verify there's still headroom)

Haltech Platinum Pro

E70 ish ethanol

CXRacing exhaust manifold (unsure whether an inefficient manifold would cause this much laziness)

OtakuGarage intake manifold

Wow, that's lazy - definitely not right for that kind of setup. 

I personally am not a fan of the ATP T4 housing and actually have no idea how you have a T4 open housing G30 - Garrett don't have a native T4 open housing so I'd wonder what that housing spec and quality is and how much it could be contributing to that result.   Otaku intake manifolds seem to have a pretty dodgy reputation at least from what I've heard, I'd make sure there has been no sneaky cracks for boost to leak out of.   I know nothing of the CXRacing manifold either, but the smorgasbord of cost cut spec parts and a sub-par result definitely make it feel like this could turn into a "the poor man pays twice" kind of story.

I would at least be going through a diagnostic process to rule out the typical "something ain't working right" process.   A genuine Garrett G30 with a .83a/r exhaust housing on a stock cam RB25 with VVT working, and quality intake and exhaust manifolds with no leaks should NOT be that lazy.   G30s are a little later in boost threshold than other turbos with the same wheel sizes, but no way near that later - twin scroll or otherwise.   I know of an G35 1050 running an open housing on an RB25 and it's significantly less lazy than this.   

That altitude wouldn't help, but I wouldn't expect it to hurt THAT much.   Something that is catching my eye is how linear the spool is - it doesn't seem like it's getting into a proper "ramp" like you'd normally expect.   

Just to rule out something very obvious that I've definitely seen other people miss, and end up with this kind of lag (if not actually being outright unable to build more than a few psi of boost) - did you definitely install the valve seat/fire ring/whatever you want to call it in the wastegate?  Without it you effectively end up with the effect of the wastegate being constantly slightly cracked, the exhaust will sound fairly pitchy/angry the whole time and it makes the turbo a lot laggier.

 

Edited September 20, 2021 by Lithium

[Dose Pipe Sutututu]

FWIW I have an older, albeit larger GTX3576 Gen 2 with a 1.01 divided housing and all 2bar comes in before 4500RPM on a 2.5L RB25DET NEO with 260/9.15 cams.

I believe your CX Racing manifold and turbine housing are to blame, also @Lithium's suggestion of the fire ring not installed properly OR missing altogether could be a contributing factor.

[gik0geck0]

Thanks for confirming my suspicions that something isn't right. I've pulled vaccum and pressure on the intake manifold and held it to check for leaks, so I'm confident the intake side is fine. I have verified that the WG fire ring is correctly seated and that the flange gasket appears to be holding, though I've always suspected how flat all the manifold flanges are. I stuck a smoke machine in the turbine housing, and at least at 0 pressure, it's sealed. The CXRacing flange is drilled for both T3 & T4, so that has me suspicious of that seal, but I'm not sure I'll know until I switch manifolds.

Your comments about ATP housings make me consider switching to v-band & Garrett housing, but T4 twin-scroll is still alluring; I have yet to decide on manifold choice, but I've been thinking T4 TS because it'd give me incremental confirmation of the single bad part; if it's better, then the ATP housing is fine and it was either poor manifold design or leaky flange at higher pressure.

Here's a link to ATP's listing of the T4 G30 housing: https://www.atpturbo.com/mm5/merchant.mvc?Screen=PROD&Store_Code=tp&Product_Code=GRT-TBO-M30&Category_Code=Garrett-Turbo-GSeries-G30-770

[Dose Pipe Sutututu]

This would be perfect for you, twin scroll manifold, with the scroll split to the gate seat

https://www.sincocustoms.com/shop/product/209348/rb20-or-rb25-t4-twin-scroll--turbo-manifold/

Then next logical step is to get a T4 TS turbine housing and come back to tell us it is all in by 4000RPM  

[Komdotkom]

I'd be interested to hear peoples thoughts on the merits of G30-900 vs G35-900 on a built 2.7. It appears that the compressor, CHRA and comp cover are identical, just a different turbine and housing.

I'm not looking to make 500kw and would like good response on the street, it seems to me that the G30-900 would be a good option, but I have a niggling concern that I might be trading off a reasonable amount of top end for very little transient/low rpm response. The engine is fully built but runs hydraulic lifters so max rpm is probably 7500

[Full-Race Geoff]

what manifold are you using?  If singlescroll vband, then g30-900 could be interesting.  if twinscroll t4 then g35-900 might be the preference.  these motors are sensitive to preturbine backpressure, so managing that is the key to getting this right

[Komdotkom]

Hi Geoff, the manifold would be a single scroll V-Band, I wasn't aware that there was any other option for these.

Talking to the local sales team who sell these they have recommended a G30-770 instead of a 900, they feel that in the G30 configuration they don't have enough turbine to spin the 900 compressor. I'd be interested in your thoughts on this.

[RBW49N]

On 12/12/2019 at 8:00 AM, Lithium said:

Here's a dyno overlay of a GTX3076R Gen2 with .83a/r hotside overlayed with a G30-770 with .83a/r hot side on petrol at the same boost level.  This is on a stock RB25, so more a comparison of how it goes psi for psi within the GTX3076R's limit versus outright potential - which is worth noting that the G30-770 with .83a/r hotside is on paper very similar flow wise on both hot and cold side to an EFR8374 with 1.05a/r hotside:

Any idea who’s Stagea this is and if it was RW or AW hp?

[ProjectS130]

Hey guys. New member here, but have been lurking for a while and reading (and re-reading) this thread and the other RB25-related forced induction threads.

I'm building an RB25 to drop into my 280ZX, and have nearly every bit of my build settled aside from the turbo. Goal for now is 500WHP on E85, without having to turn the boost up too high to maximize longevity/reliability (like 20-22psi), strong mid-range while pulling hard all the way to redline. It'd be a street car ~95% of the time and I'd keep the limiter 7500rpm or lower.

Doesn't seem too lofty a goal and I've had my eye mostly on the Gen2 GTX3076R and G30-770. @Lithium posted a graph in here a while back matching these two on a stock RB25 and the G-series seems a clear winner, but I've seen several posts now in different forums about G-series underperforming or failing due to overspeed, which gives me pause. It seems like maybe a bad rap brought on by early failings but....I don't know? Wondering if anyone's had any more experience with these in the recent months; I'm just not sure whether to stick with the proven Gen2 GTX or the newer tech.

The rest of my build for detail:

• Built motor (9:1 CP pistons, Manley rods, etc)
• Kelford 262/262 9.3mm lift cams & valve spring kit
• 1050cc injectors, 340lph pump, E85
• 6Boost T4 twin scroll manifold, single 50mm WG
• Plazmaman upper plenum, stock lower
• CD009 trans

🤙

[Lithium]

It depends on what you mean by underperforming?  I've seen a few unrealistic (imho) expectations being set, people seem to keep choosing similar or LARGER G-series turbos vs GTX equivalent assuming that size for size the G-series will spool better.   I know some sellers/Garrett fanbois will disagree here, but that is the opposite of what I both expected and have seen so far.  Size for size a G-series will be slightly laggier in terms of boost threshold than a GTX, but their transient response stays similar to be fair.

A lot of them are fairly ambitious in terms of turbine flow versus power they're meant to support as well, and I think Garrett haven't helped themselves with turbine offerings which aren't always that well spaced - your only options may be a turbine which gives good response but chokes the turbine, then the next size up allows the turbine to breathe easily well enough to support the power you might be looking for but it also becomes significantly lazier.... when in fact the option right in between would have been perfect, ie.  no .8x a/r turbine housing for G25s.   It's worth trying to understand and check turbine flow maps to ensure you're not going wrong here with *any* turbo you go for if you can.

The next thing is turbo failures/under performing power wise etc.   Another thing I saw coming before these were even used, they flow big numbers for their size and people automatically assume that it means they need lots of boost to do it.   They are infact NOT that suited to high boost, and at their best between 16-24psi at sea-level in most small/mid frame cases.   After that their efficiency starts dropping off hard, and to add to it Garrett gave frankly bullshit hp claims for their turbos.   

What predictably happened here is you get a bunch of turbo illiterate people going "I want 900hp from my Evo", (which needs 40psi+ to make that kind of power) so they buy a G30 or G35 900 (because it's rated to 900hp) and put it all together and give it to a tuner with instructions to push it until it makes 900hp.   If you actually read the compressor map data and make conservative assumptions that to make the power the owner would be content with requires the turbo to be able to move 90lb+/min of air at pressure ratio 3.7+.   On the compressor map for this turbo it's pretty clear the turbo can barely squeeze out over 65lb/min at PR3.7 without overspeeding, and it gets WAY worse at any more boost than that.  

What makes this worse is that the turbine is actually a pretty efficient little high-speed beast, so while exhaust back pressure will start taking off as you go off the map it will continue to push the compressor harder and harder - meaning you can SERIOUSLY overspeed these turbos pretty easily by running them on a mismatched setup.  

Soooo, yeah.   A lot of the issues IMHO so far come from poor matching.  I am not saying that these should be the greatest or anything like that - I for one still for the most part like the performance of the EFR range the most, but overall anything you can do with a GTX I suspect you can do better with a G-series *if* the option is there that appropriately matches a setup.   And this is the clincher, a good turbo match is often worth more performance wise than the extra 5-10% or whatever performance you may get from a much fancier turbo.

So, TL;DR version: There may be legit failures but I'm not aware of any beyond where people have tried pushing a setup I could have told them would cause issues before they started.  If you're going T4 twin scroll then I don't think Garrett even have a native exhaust housing option for the GTX range, and I personally wouldn't hesitate to use a G-series on an RB25 because the boost range you'd be looking at fit right in the "happy boost zone" of the G-series range.

Not sure of your power targets, but a G30-770 with a divided hotside has potential to be quite hilarious

 

 

[Full-Race Geoff]

On 3/20/2022 at 1:40 PM, Lithium said:

this is the clincher, a good turbo match is often worth more performance wise than the extra 5-10% or whatever performance you may get from a much fancier turbo.

So, TL;DR version: There may be legit failures but I'm not aware of any beyond where people have tried pushing a setup I could have told them would cause issues before they started.  If you're going T4 twin scroll then I don't think Garrett even have a native exhaust housing option for the GTX range, and I personally wouldn't hesitate to use a G-series on an RB25 because the boost range you'd be looking at fit right in the "happy boost zone" of the G-series range.

a G30-770 with a divided hotside has potential to be quite hilarious

 

 

Hi Lith

-100% agree that a good turbo match is mission critical for any of these modern turbos.  the old mindset of "go big or go home" just isnt the right way to go about selecting a turbo anymore

-for G25 and the entire G series lineup, I prefer the smaller A/R housing.  agree that 0.9 is too big, but i also think 0.8 is still oversized.  the 0.7 is my preference in almost all instances.  I did like the 0.49 for some applications too but thats no longer available.  Overall GTX/GT used larger A/R and G series likes the smaller A/R with its "little beast" of a turbine wheel

-i dont fully agree about the "bullshit claims for numbers".  I also was dubious originally, but ive seen many cases where the turbo is pushed to the limit (or beyond the limit) and the crank HP claims rang true.  BUT larger A/R does not mean more power.  as you said its all about getting the turbo match right

-I fully agree that the turbines are very impressive and will overspeed if you let them!  As you know the turbine wheels are Mar-M which isnt quite as forgiving to abuse as inconel.  In the case of g series failures, all that we've seen here were consistent with overspeed.  I have a Civic Type R customer who broke (2) G25-660s, both 0.72 a/r and IWG, at 650-660whp both were overspeed failures.  I was kinda mindblown that its even possible to reach that power level on the G25

 

[discopotato03]

Just thought I'd check in with something that you may not have seen .

GCG Turbos is advertising a G25-550 with a T3 flanged integral waste gate turbine housing in 0.73 AR for Nissan Patrol diesels - I think the TD42 engine . I think there is also a 0.64 AR turbine housing version .

https://gcg.com.au/turbo-charger-garrett-g25-550-0.73a%2Fr-iwg-std-t3-nissan-patrol-td42-outlet-g871389-td42-73.html?ref_cat_id=Performance-Turbochargers-Garrett-G-Series

With what Geoff just mentioned the 0.73 AR could be ok with that turbine if you wanted the typical 300ish Kw at the wheels in an R33/34 GTST/GTt .

The G25-660 may be more suitable depending on power goals .

 

Edited March 26, 2022 by discopotato03

[Lithium]

On 23/03/2022 at 3:15 AM, Full-Race Geoff said:

Hi Lith

-for G25 and the entire G series lineup, I prefer the smaller A/R housing.  agree that 0.9 is too big, but i also think 0.8 is still oversized.  the 0.7 is my preference in almost all instances.  I did like the 0.49 for some applications too but thats no longer available.  Overall GTX/GT used larger A/R and G series likes the smaller A/R with its "little beast" of a turbine wheel

-i dont fully agree about the "bullshit claims for numbers".  I also was dubious originally, but ive seen many cases where the turbo is pushed to the limit (or beyond the limit) and the crank HP claims rang true.  BUT larger A/R does not mean more power.  as you said its all about getting the turbo match right

Sounds like we're mostly on the same page.  "Bullshit" may be a slightly strong word, but historically Garrett (and other) manufacturers tended to set the hp claims as something that were pretty achieveable without relying on ethanol or pushing the turbo to the max.   Garrett's rule of thumb was basically hp = massflow @ PR2 x 10, so a semi-conservative estimate of what power it was capable of at ~1bar of boost on premium gasoline.

Now it appears to be if you run it potentially off the map on E85.

Back in the day Garrett used to claim the GT3582R as a 600hp turbo, they've now refactored their claim for the same turbo to 675hp (which is still pretty realistic, the old claim was probably overly conservative for a guideline) but then you have the G25-660 which is advertising it as being suited for 15hp less than a GT3582R.

I would *love* to see someone make an honest 660hp @ crank on an RB26 on pump gas with a single .72 G25-660.  In fact I'd like to see one get anywhere near what a GT3582R is capable of.   If it could be done it would be a very rewarding street setup, but.

On 26/03/2022 at 11:59 PM, discopotato03 said:

With what Geoff just mentioned the 0.73 AR could be ok with that turbine if you wanted the typical 300ish Kw at the wheels in an R33/34 GTST/GTt .

The G25-660 may be more suitable depending on power goals .

The native .72a/r G25 hotside flows less than a .63a/r GT30.  I'd not feel super confident running that to 300ishrwkw on pump gas on an RB25.