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Garrett G Series

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  • 1 month later...

Here's a thing I discovered in my travels which may be of interest in here, this is the kind of comparison I've been hoping to see but not expecting to, finally... 

This is a dyno plot of a 1.05a/r divided EFR8474 (dotted line) and a 1.05a/r divided G35-1050 (solid line) with otherwise identical specs, including boost curve on an Evo X.

Both hit target 2.15bar at 4500rpm and creep out to 2.35 at peak, which is as far as they were willing to push the engine at this point. Apparently the EFR8474 had stopped giving gains at this point however the G35 still seemed to have more to give, which they said they may try sometime if they get brave.

So yeah, seems like the G-series range get a bit more interesting now that the divided housings are starting to seep into circulation!

No photo description available.

Worth noting that "km" stands for koń mechaniczny, or "horse power" in Polish

Edited by Lithium
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On 24/08/2021 at 6:08 AM, Lithium said:

So yeah, seems like the G-series range get a bit more interesting now that the divided housings are starting to seep into circulation!

Firm beliver of them delivering the goods but unfortunately the majority of the internet has experienced something else and now they have a bad name.

They should have gotten the divided housing sorted out on launch day.

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On 02/09/2021 at 5:33 PM, burn4005 said:

would love to see a datalog of transient boost at 5500rpm from off throttle to WOT between those two.

Me, too.  It would be pretty fascinating stuff - I don't know what we should expect, I can say "for the supported power" the G-series seem really good transient response.   

The only first hand experience I've had is with a Mitsi Evo which I tune which previously had a TD05-20G-esque thing, kinda really almost the equivalent of the original FP Green but using a 7cm TD05 hotside instead of the 8cm TD06 that FP used to use, and a non-Mitsi 50lb/min compressor wheel.   It had a fairly decent boost threshold, we were seeing 20psi by around 3700rpm in a 3rd gear pull but it was ultra surgey mid throttle load, and its boost response was atrocious.  You could literally feel it having to re-spool in gear shifts... a very strong case for the whole "dyno plots don't tell the story" thing, as you could expect it to be a response monster from how it looked on the dyno.

Another thing about on the dyno is it was HEAVILY knock limited by 17psi/18psi, enough that I was not happy to continue.  The owner swapped to ethanol to try and get around that and we were able to get a bit more boost into it, but when we got past 20psi I (not exactly surprisingly) noticed that VE was plummeting at higher MAP levels.   EMAP was clearly getting up there, quickly.

In this case the owned decided to give a Pulsar (Garrett copy) G25-660 with a .72 hotside a crack, basically with the hope of trying to sort the choking issues with minimal sacrifice to response while also having headroom for more power when he got a built bottom end.   Also went back to pump gas as ethanol is shockingly expensive and hard to get in NZ again now, so man cams/big turbos and pump gas tunes are back in season in here.   So far have only road tuned it, but the fuel map needed massive changes from 17psi and up and the old timing map which was still knock limited - not a peep so far, have gone past 20psi and called it there for until we get to the dyno.  Unfortunately we're in lockdown atm so the dyno booking we had for tomorrow has gone up in smoke, no idea when it will happen now.

What I can say is that, as expected - the turbo feels a lot lazier than you'd expect if you were comparing the wheel sizes with the likes of a GTX series Garrett turbo.  In GT series nomenclature it would be a "G2567" which paints the picture of something that would be in much earlier than a "20G" type sized turbo, but it was the opposite by a bit.  Noticeably doughier up until around 3500-4000rpm, but from there it's ramping up quick - probably seeing 20psi marginally after 4000rpm in 3rd gear.    What is different however, is that it "feels" much snappier anywhere but the basement... basically once over 3500rpm it takes less provocation than the old turbo to start "winding up", just that it can't wind up to quite the same boost level the old one could until up to around 4000rpm.     Once over those rpm it is almost NA-like, WAY more snappy than the old turbo.   Like the car feels much more alive pound for pound, and "back into throttle".   

This is kinda what I predicted before they were used, but it was nice to experience it - basically, the boost threshold of something half way between what you'd expect from a GTX2867R and a GTX3071R, while providing the flow of something halfway between a GTX3071R and a GTX3076R, but the transient response of a GTX2867R... or even slightly better than that, which I guess makes sense given its a lower blade count and similar dimensions (so less inertia) than the old turbine.  Something I feel compelled to add here, I've experienced a twin scroll EFR7163 on a 2litre Toyota engine and it makes both other turbos on this particular engine feel lazy <4000rpm BUT I doubt I'd be able to tell the difference between the G25-660 and the EFR7163 once above 4500rpm.   The G25 660 in this comparison is open housing.

I would guess that this kind of behaviour would translate through the rest of the range to a degree, both the EFR8474 and the G35 1050 are likely to have way better transient response than the boost threshold shows when keeping in mind the best of the "2000s" ball bearing turbos.   

It's quite interesting to see how they've both done it, both turbos have exactly the same compressor wheel measurements but the EFR has the 74/68mm 11-blade TiAL turbine wheel versus the 68/62mm 9-blade Mar-M turbine wheel to result in different ways of reducing inertia while allowing enough turbine efficiency to give a reasonable performance level.  They both will have very low inertia for things making the kind of power they're making, and will probably be significantly snappier under foot than pretty much anything else capable of 750+whp - other than perhaps the Xona Rotor UHF range, but that's a whole other kettle of fish.   Beyond those, if I were a betting man I think from this result if anyone tried EITHER of these two turbo specs on an RB they would probably smash the transient response over any of the other typical Garrett/Precision/whatever combos you normally see for this power level on RBs.


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On 9/2/2021 at 3:18 AM, Lithium said:
On 9/2/2021 at 3:18 AM, Lithium said:

the owned decided to give a Pulsar (Garrett copy) G25-660 with a .72 hotside a crack,


What I can say is that, as expected - the turbo feels a lot lazier than you'd expect

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

Edited by Full-Race Geoff
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On 04/09/2021 at 2:16 AM, Full-Race Geoff said:

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

That's fair, though I did make it clear it was a copy and not the real thing - a lot of people consider the Pulsar turbos in this part of the world so in the interest of general data sharing I thought I'd pass it on and let people make of it or disregard it as they will.  Probably should have added that to the Pulsar thread.

On 04/09/2021 at 2:32 AM, Full-Race Geoff said:

 HKS new line of turbos  based on G series chra:


GT_4950BB = G25 (49mm exducer turbine wheel)
GT_6290BB = G35 (62mm exducer turbine wheel)
GT_7595BB = G42 (75mm exducer turbine wheel)

Interesting that HKS are more or less sticking to their "old" airflow to PS estimation method, instead of using Garrett's ultra generous power claims that they moved to from the release of the Gen2 GTX.  Either way, nice modern Garrett turbos feels way more "HKS" to me than the strange Mitsi JB period they went through recentl

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On 06/09/2021 at 6:15 AM, Lithium said:

Either way, nice modern Garrett turbos feels way more "HKS" to me than the strange Mitsi JB period they went through

Yeah, they seemed to have canned the MHI GTIII turbos pretty quickly

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On 07/09/2021 at 10:56 AM, burn4005 said:

the GTIII was a journal bearing wasn't it?

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.

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