Thanks for the research link, Def, it was a good read. And sorry for all the 3076 comparisons. It just seems like I keep finding comparisons done against that; I'd love to see a 7163 against a GTX3071.
I'm getting a vibe that you're thinking mostly of the first gen EFRs though. I realize that the first gen models weren't all they were hyped up to be; the title of the thread even implies they were a letdown. The first gens delivered in terms of transient response but weren't anything spectacular in terms of power, flow or efficiency for the reasons you just stated. But I think the 7163 is going a long way to fix that and the link you posted seems to support that.
The negative you pointed out about the TiAl wheels needing more backplate material is one thing countered by a mixed flow design. To quote the paper: "In addition to this, mixed flow turbine wheels offer the chance to design turbine wheels with reduced inertia. One key benefit is that the back disk is clearly reduced in diameter." So there's some mass at a large radius removed but even before that mass was removed on an MFT, the paper still claims a 46% improvement in inertia for the turbine alone and 30% improvement for the entire rotor assembly with the regular radial turbine.
Another disadvantage is countered by mixed flow: "To achieve the same flow capacity, the blade angle distribution needs to be modified for readjustment of the throat area of the wheel ... because of the aforementioned γ-TiAl design constraints a turbine efficiency penalty of 5% is assumed." With a mixed flow design and it's greater swallowing capabilities, this compromise doesn't have to be made and the efficiency penalty that you mentioned is present on the first gen EFRs isn't incurred with the mixed flow design of the 7163.
Seems like TiAl and MFT tech goes hand in hand. The combination of the two technologies enables what seems like a no compromise turbo. Lower inertia, greater efficiency especially at lower velocity ratio and greater flow. The inertial savings also gives BW a lot of room to play with sizing and the greater air scavenging ability of the MFT means greater torque production which lets them go with a more aggressive compressor design too.
Just look at the 7163 vs the 7064. Nearly identical sizes but the 7163 flows 4lbs/min more. The MFT clearly improved things on the overall flow/power front and data would suggest transients will be improved too from the further reduction in inertia along with low down power from the increase in efficiency at low velocity ratios.
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Originally Posted by McRussellPants
There is no magic.
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You're right, it's not magic, it's technological advancements. Just in the same way carbon fiber enables better parts, TiAl and MFT enables a better turbine. It's about time we stop using a turbine design from the 70's don't you think? Also, you're still comparing to the first gens which were admittedly underwhelming. Yes, they sized up the turbines slightly but that's because they could with the weight savings from TiAl. Have you ever been in a car with an EFR? In overall power it's going to be similar as you said but the transients of the EFR are unmatched. BW made a design compromise on the first gen turbos. Depending on their wheel sizing, they could have made either a quicker or more powerful turbo but went for balance while improving on transient response instead. They didn't have to make that compromise with the 7163 though thanks to the MFT. It responds like a 6758 but yet it flows more than a 7064. I find that to be a great improvement and am surprised to find little agreement with that in this thread.
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Originally Posted by PoorMans180SX
Almost everyone that runs one, regardless of what turbo they switched from, raves about the transient response though.
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Check this link out:
http://blog.perrinperformance.com/bo...-tuned-part-2/
The 7670 isn't one of BW's best EFRs but I think it still showcases your point nicely. On the dyno it's looking like the 7670 is trading blows with the 3076 and spooling slower but when he logged it by time instead of rpm, the 7670 hit full boost a whole half second faster than the 3076. Add up those half seconds coming out of every turn on your favorite race track and you have a significant lap time improvement. Also, even though the Garrett arguably dynoed better, he still preferred the BW for the "feel". Driving just felt snappier and I think that's the whole point of the BW's that people missed on the first gen. To quote a friend who drove a 1.8 vvt Miata with a 6758, "I can't imagine a turbo spooling faster, it was already transparent. It felt pretty much like a v8." He owns an LS1 swapped FC RX-7, I imagine that's what he was drawing a comparison to.