DaWaN

I expect the EFR to have better transient response due to the material of the turbine.
On the flipside: the G25-550 is physically smaller in every dimension: compressor wheel, turbine wheel, turbine A/R (0.49 on the T25 housing).
So I am curious to know how spool-up/boost threshold compares to the EFR6258.

k24madness

iTrader: (6)

I think it's great Garrett is trying to step up to their game but they got a looong way to go. The GTX Gen 1's looked pretty good but struggled in some applications. The Gen 2's got better flow but lost a ton of efficiency. The G25 looks promising to replace my twin GT2860RS (in 911 twin) but alas they don't offer a legacy t25 housing. If I am going through the effort to re-fab things for v-bands it's getting EFR's.

18psi

iTrader: (76)

Oh yeah competition is always great. Once they finally catch up hopefully borg responds with the next hotness

Pintobeantoes

So has anybody else been watching for updates on these? ATP only has them in reverse orientation currently.

Curious to see how they put up compared to the EFR series. Which turbine/compressor config would be the best for our application? On other car boards, there seems to be some real interest in these.

Savington

iTrader: (31)

They will respond worse.

Michael Chandler

der_vierte

+1.

everyone wants "real data" and driving experience before talking ****, but in this case...

now hate me!

18psi

iTrader: (76)

in this case no one still has any, so it's speculation until there is some posted.

so which one of you has one on order?

RalliartRsX

I'll just lift and shift from my post on another forum November of last years (since opinions are indeed facts.........#amirite??)

In opinion, Garrett turbine wheels were 30 years outdated across the line. The NS111 wheel was great.......20 years ago. Not so much now. An updated compressor wheel can only net you so much gain

Savington

iTrader: (31)

If we both have a ball of similar size, but my ball is aluminum and yours is lead, the answer of "which one will hurt more if I drop it on my foot" probably doesn't need an awful lot of data to be answered

18psi

iTrader: (76)

HATER!!

RalliartRsX

Edited my post

Meant to say the engine blew. The turbo remained in tact.

Serious bizzznaaazzz!

Ted75zcar

iTrader: (2)

no intent to start **** here, but the EFR CHRA (using a ruler on a CPU screen) appears to be ~2x longer than the Garrett. Steel is ~2.5x - 3x heavier, but requires a smaller wall thickness... just sayin

Savington

iTrader: (31)

I was referring to the turbine wheel. The EFR's wheel is half the density and thus roughly half the weight.

The parallel is to wide, heavy wheels. They are always faster than light, narrow wheels. I don't really care about the weight of the turbo (within reason), but I very much care about the weight of the spinny bits inside.

Ted75zcar

iTrader: (2)

gotcha, totally agree. Rotating assembly mass is of critical importance.

JKav

iTrader: (1)

When it comes to transient response, inertia and efficiency both play a role. A bit more of one can offset the other. The G Series turbine wheels look to be of substantially higher efficiency than the ones they replace. Plus they're higher specific flow -- a given diameter wheel flows like larger one.

Of course, the compressor wheel you pair with it has to be of similarly high specific flow, else turbine-compressor speed mismatch starts kicking your ***. Fortunately it looks as though the G Series compressors are indeed higher specific flow than the ones they replace, with no compromise on surge margin, plus deliver higher efficiency. For a given power target, it is possible you could run a G Series that's one frame size smaller, with the associated reduction in inertia that that entails.

Will a G Series turbine wheel have lower inertia than a similarly flowing EFR wheel? Likely not. But the delta isn't as large as the material density difference suggests since EFR is full backdisk wheel while the G Series is heavily scalloped (full backdisks impart more structure, inertia to the wheel but can raise efficiency a touch). Also an intermetallic wheel (like titanium aluminide) will typically also require thicker blades than a nickel based one (Inconel, Mar M) provided they are to achieve similar resistance to foreign object damage. All else equal, thicker blades reduce flow and increase inertia.

The unanswered question is how does overall turbo efficiency (turbine & mechanical efficiency times compressor efficiency) of G Series compare to EFR for a given application? It is the key flip side of the response coin to inertia.

As an aside to the response discussion, the move to Mar-M 247 is pretty significant. This is the stuff that's used in the highest-temperature applications out there, whether production or motorsport,

RalliartRsX

@JKay

Agreed on most points. However, you missed one aspect; the mixed flow wheel of the 7163. That is somewhat of a game changer and what accounts for a majority of the 550 WHP capability (yeah, I use that lightly. I have personaly seen more) and efficiency with the response time of a 6758-6258.

Gollum

I quite seriously had to register just to show people how retarded it is to base inertia performance on density.

And before I get too deep into this, I don't care about brand adherence or what turbo you enjoy sleeping with at night. I don't even care if the new G series ends up being better than the EFR turbos.

Now, the contention here is that "light wheel is always better" and I tend to agree to a point. You also want the wheel to be durable, and blindly copying physical designs without regard to material design has lead to many Chinese products being branded as crap. Engineers spend no small amount of time discussing material design and how it affects their work. OEMs have engineers that inspect materials deep into the microscopic level to measure grain pattern uniformity and abnormality commonality. In fact, these measurements are one of the leading causes of the "wear bell curve" that causes some parts to fail before others which in turn causes the OEMs to push really hard to ensure material consistency because it'll better help them predict failure rates.

Now, regarding the age-old "what material is better" debate. The V8 crowd flocked to aluminum rockers in the late 80's and 90's. Then about twenty years, later everyone switched back... why? Because to get the strength required for a rocker in the right areas, it required significantly more mass further from the pivot points. So the solution was: better designs out of steel. The steel designs had a lot of meat in areas it wasn't needed. Once designs were more optimized, rocker performance of good steel rockers far surpassed the aluminum rockers (of the time). Aluminum rockers are starting to make a comeback, but they're far more advanced and require more tool changes in the machining process, and thus are even more expensive than ever.

But lets analogy for a moment.
Take a string, and tie it to a basketball. Hold the string at 2' from the ball and now try to swing the ball over your head.
Now tie a string to a baseball and hold the string at 12' from the ball and try to swing it over your head.
Which will be harder to swing? The baseball. Why? Because the weight is further from the center. This is inertia 101.

This is exactly why steel generally ends up being better for rockers. The other factor is that steel takes repeated bending more favorably than aluminum, which also further reduces thickness requirements. This is also why we use steel for connecting rods, and why aluminum is only used for con rods in drag racing. The rod absolutely hates changing direction at TDC and it causes massive stress that requires the rods to be insanely fat (so big that an h-beam design is often too big for long stroke engines), just to deal with its short life expectancy. Here again, we see a scenario that the lighter material isn't generally better.

So, all that to say you can never assume that material density will lead to a better design. And I think we see this in the below comparison.


EFR7163 wheel left, G25 wheel right.



Notice that the EFR wheel has heavy thickness tapering as it meets the middle of the turbine? Likely because otherwise, the fins wouldn't stay rigid in transient moments under load. Also, I know I don't have both in my hands with a micrometer handy, but the overall fin thickness of the EFR looks thicker too. Both of these facts already put the aero in the G25's favor because all things equal thinner fan blades always work more efficiently as they're less "in the way" of the air they're pushing. Obviously, other factors come into play, and "all things equal" never is.

The next point is to look at the massive scalloping on the back of the wheel the G25 has. This is a giant amount of mass AT THE OUTSIDE OF THE CIRCUMFERENCE of the circle which will have huge benefits on inertia.

Seeing them side by side you can tell that the G25 wheel is far more "petite" than the EFR, but anyone looking at material densities should already know that because less dense materials are generally always designed thicker when comparing similar materials in similar use cases. The same is true when comparing variants of plastics, Chromoly versus DOM for cages, or bread for a sandwich (trust me, chefs think about these things because nobody wants a sandwich to fall apart nor have the bread interfere with other flavors).

So no, we won't know "which spools faster" until someone A/B's them. Which is why I've been scouring the internet. Which is how I found this thread...

As a side note, $2k for a turbo isn't insane in my book. That's what it cost me to get an OEM Subaru snail for my Outback (because some people actually prefer to leave things stock when they're not a project). If saving $500 on one turbo matters that much to you, then I don't think gaining or losing 100-400rpm of spool in 3rd gear should change your decision. BW makes great turbos. And it looks like Garrett is trying to claw some market back in this segment. We all benefit from this.

Savington

iTrader: (31)

The theory is nice, sure. Scallops good, thin blades good, all good. The reality, however, is that T25 turbine wheels has had very similar scalloping for decades. Perhaps not identical from an airflow standpoint, but certainly close enough from a rotational inertia standpoint to call them identical.

Here's a GT2560R wheel for reference. Very similar scalloping. I did my best here to find what I believe is an OEM wheel, vs. a stock photo of a Chinese copy. I believe this is either an OEM Garrett Aftermarket or OEM Nissan GT2560R wheel.



And yet, empirically, the EFR responds substantially better to throttle inputs, despite being ~4mm larger in diameter. So I'll go out on a limb (pretty stout limb IMO) and call bullshit on scalloping making a substantial enough difference to overcome the difference in material weight.

As far as blade thickness, they sure look similar enough to me, perhaps the EFR is a skosh thicker, but certainly not 2x except maybe at the leading edge, where it would have almost no impact on rotational inertia. It's also impossible to see the profile of the blade as it hits the shaft.

It's also misleading at best to state in this context that "less dense materials are generally always designed thicker". We are not comparing steel and aluminum here, so your rocker example is completely out of place. A more apropos comparison would be Titanium. Titanium has roughly 60% the density of steel, but a piece of titanium with the exact same dimensions as a piece of steel will have 95% of the strength of that piece of steel. Add a few thou to make up the gap, and you have a part which has exactly the same strength at perhaps 2/3rds the weight, conservatively. I don't know if titanium rockers exist, but if they did, I'd bet they'd weigh a lot less than steel and cost an eye-watering amount of money as well.

Titanium Aluminide is in the same ballpark as Inconel when it comes to strength at temperature, so unless Mar-M is significantly better than either one (doubtful, and no info on Matweb yet), it's perfectly reasonable to infer weight from density, given that the two parts are designed to function in the same environment. The Mar-M part would have to be substantially smaller to achieve the same inertial performance as the EFR. Not "feathery", but like 2/3rds the overall size.

One last tidbit on turbine blade thickness as it relates to flow. Yes, thick blades are in the way of the air. To combat that, all EFR turbines are larger in size than their Garrett counterparts. Like, a lot larger. A GTX2863R has a 53.9mm turbine and a 63mm compressor, an ER6258 has a 58mm turbine and a 62mm compressor. If you're well-versed in turbo sizing, and you seem like you might be, you'll know that 4mm on the turbine wheel is huge. The EFR can get away with that because of that low weight. Empirically, they seem to have absolutely no problem moving nigh-unbelievable amounts of air. I've lost count of how many B1-frame EFR Miatas have cracked the 400whp mark, and I know of at least 3 that have cracked the 450whp mark, all on that 58mm turbine wheel through a 0.64a/r housing. That does not indicate a restrictive turbine side in the slightest.

Empirically, the EFRs outperform a similarly-sized Garrett GTX. They do so substantially when it comes to throttle lag and torque linearity. The T25-550 gives me absolutely no reason to believe they are substantially better than the outgoing GTX units in this respect. I might be proven wrong, but I don't think I will be.

oreo

Come on. This Garrett marketing line says it all.
G Series models offer previously unimagineable power levels by frame size and improvements in spool!
nuff said -they're not saying the G Series is offering previously unimaginable improvements in spool!

Also, the selling features of this turbo seem to be small size, and high temperature. Sounds like a good OEM solution, where you want to run 14.7:1 under boost under a tightly packed hood.
This turbo needs to spin quite a bit faster to flow the same as the EFR, which also makes it hard to compare.

I guess we will eventually find out how this turbo performs, but I would not want to be an early adopter on this.

PS. I am currently sleeping with a Garrett turbo. :(