The trickery is in the materials used. The fancy Garretts use an Inconel turbine wheel, the EFR uses a Titanium Aluminide turbine wheel. The two materials have similar high-temp properties WRT strength, but the TiAl wheel in the EFR has half the density. Same size + half the density = half the weight.

This weight difference doesn't make much of a difference when you are spooling the car from its boost threshold at ~1700rpm, since you introduce airflow slowly (as RPMs rise) and the turbo comes up to speed slowly (this is what is coloquially known as "spool"). When you stomp the pedal from 3500 or 4500rpm, though, you introduce a huge amount of airflow very quickly. In the latter case, the rotational inertia of the turbo makes a huge difference. This is what I call transitional response, and because the EFR rotating assembly weighs so much less, it is able to change speed more quickly, and this manifests as substantially improved response.

Or, in fewer words, the EFR spinny bits are lighter despite being larger.

"Any sufficiently advanced technology is indistinguishable from magic." - Arthur C. Clarke

Right you are talking transient response vs spool. I did not know that the efr turbine was this advanced that's actually some pretty trick engineering on bw's part right there. Did they do anything fancy with the compressor side? I know the turbine plays the biggest role in response of a turbo, but it looks like they use billet for the comp wheels which everyone seems to be doing at the moment. So just looking at it the turbine side is where the real magic is being employed. How's the internal bov working for people? I'm total rice I want my vta bov lol. Thanks for clarifying things a bit on the efr it does sound like a bunch of VTEC unicorns are living inside it.

Modern tech on the compressor side, Garrett is probably on par. As you said, the magic is on the turbine side.

IIRC billet wheels don't actually perform any better, it's mostly a cost savings for low-volume runs which is why they were originally limited to the biggest (i.e. lowest volume) turbos for each manufacturer.

The internal BPV is extremely good and very easy to hook up, they do make different springs if you feel the need to tune the cracking pressure for your application. The internal wastegate is also substantially better than the design Garrett and most others use.

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Well thanks a lot bc now I want one LMAO. Damn you, damn you good sir. I will get by with my gt2560 for a while once I build a motor next year I think I'm gonna go efr, no reason not to really. I saw where bw designed the iwg correctly to actually flow well, I only ever used ewg because the internal wg sucked so bad on mitsu and Garrett turbos.

this says enough to me:

https://www.miataturbo.net/attachmen...vs-efr6258.jpg


or listen to wisdom:

http://www.flyinmiata.com/uploaded/i...vs2560_155.jpg

what that says to me is why even get a 6258, the 6758 rolls into boost just a TAD later but look at the glorious torque plateau......wow. FM being FM they know everything and since they still plug garrett....well....i would have to say they somehow doctor the results to always be in their favor. Their dyno is notoriously bad, and they have dogs and no cats around their shop so SHAME ON THEM.

On the compressor side, billet wheels are thinner in the center where they mount on the shaft, have thinner material at the back, and sometimes have thinner blade bases and therefore have much less mass. At least that's what I think I read.

6258 vs 6758: The dyno performance is very similar, the 6758 is just that little bit less peppy. I can feel the 6758 hit, sort of like you would feel a 2560R or 2860RS hit. The 6258 is smoother and more linear. I typically say that the jump point is 325whp - if you want 325whp or more, get the 6758. If you're OK with 325whp, get the 6258.

You can also upgrade very easily - the turbine wheels and housings are the same, so you just buy a supercore (CHRA + compressor housing) and swap it in. Same IC pipes, same intake, same BOV, same oil/water lines. Our turbo bits (manifold, downpipe, oil/water lines, upcoming IC/intake/heat shield bits) will fit all the B1 frame turbos which covers everything from 160whp to 500+whp with just a turbo change.

And....... An efr 6758 costs the like exact same as a gtx2867.

Exactly. Not fair to compare to a turbo that is half the price of an efr.

Huh? No I was saying second gen garrett ball bearing turbos cost the exact same as a EFR. Maybe you were thinking of a GT2876, which is a 2871 with a larger compressor.

I meant that there were comparisons to the 2554/60.

What he was comparing was spool/response of the small garrets, power of the big garrets, and price of the new garrets.
the EFR matches or beats all 3. at the same time.. check mate

What about the new GTX GEN II Garretts?

A gen2 GTX sounds nice, but EFR :drool:

IMO, Depends if someone wants to swap their hotside parts or not, and just throw in a slightly better trubo if they already have a garrett setup.

I can attest to a totally untuned, not a good example, 6258, instant, like 95% N/A response over 3000rpm. it doesn't so much as hit as it does, go. It feels like my Focus ST which has an acorn sized turbo on a 2,0L, but it has 100whp more capable turbo. I honestly wouldn't have it any other way. The response is greatly improved from even a GT3071r on a 3.2L that I drove.

+1 6758 if you need the dyno numbers up a few notches, 6258 if you want crazy, "don't even think about spool time" response.

So since we are doing all of this comparison, and we have all of the EFR guys here touching nuts....

How does the TD04-13t compare to the 2554 and the 6258 in regards to transient response? I know it has nowhere near the HP capability, but if one is only looking to make 200-220 with the quickest transient response possible, how would it compare?

Confession, I will eventually be dropping in a 1.8 and likely ditching the supercharger at that time, but I am really liking the instant boost of the super....

I think dnmakinson has that turbo. He has a VD in the last couple of pages of his thread. It's pretty fantastic.

Edit: link
https://www.miataturbo.net/build-threads-57/moderate-power-1999-a-76499/page6/#post1398266

Stock piston/stock head BP05 with EFR6258 at 10psi is essentially instant. Give it a 1 second roll from 0-100%TPS at 4500rpm and it's at full boost (10psi) before your foot hits the ground. That is 90% of TPS applications on a race track with 200+whp.

I did a session or two in a customer's fully built BP6D (CNC head) making similar power (~205whp) at 6.5psi and it just doesn't feel turbocharged at all. That's not a euphemism, it's just reality - the car responds and reacts like a big V6 would.