Upgrading to 1800- Same or bigger Turbo?
 

Looking for some experienced answers.

and not sure if this should be in the race section or here..?

But as stated, we are upgrading the race car to 1800cc built, flowed etc. motor this season.

Coming from a built 1600 with T2871rs making 260 whp.

It looks like the Turbo will need some attention soon ish (maybe another season) so wondering if we don't put that aside as a backup and buy a new one.

Goals are to be around the 6 speed threshold of 340 WHP and associated torque.

That also leaves me wondering, do we stay the same and hopefully see some really early boost (and hopefully big time gains out of corners) or go bigger and chase HP.

Also for 340 WHP what sort of boost numbers on an 1800 is that around for t28 and whatever other options become apparent..?

The 2871 should get you close to that power when running between 15-20psi. On my absurdflow setup with a 2871 I was right around 300whp at 15psi.

If youre not already.... running a .86 hotside will make your goals much more obtainable. The 71mm compressor is capable of 400whp the hotside will be your limiting factor here. Youll need over 20psi to get to 340whp most likely.

just run it as is, and see.

I wouldn't swap turbos or housings until I actually tested it out in the real world. For your goals, I see no reason you need to.

a .86 will only make the spool back to 1.6L joke levels. and it's simply not required. Pump the boost to 20psi, and you hit your goal: https://www.miataturbo.net/dynos-tim...55/#post821027

I think I would get away from a 2871R no matter what motor it were attached to (1.6 vs 1.8). A GTX2867 is going to make the same power and spool/respond better. A GTX2863 would probably hit your power goals and spool/respond substantially better.

An EFR6758 will also make your power goals and spool/respond way better than any of the above turbos. :party:

I completely agree that an EFR is the correct route to go if OP is going to buy a new turbo. I wouldn't shell out for one until I have at least tried to max out the 2871 on the new motor. At worst you have when going from the 2871 to an EFR you would have to change the down pipe.

this would be ideal for sure, if OP was going to modify the turbo configuration, replacing the coldside with a better compressor (that wasn't designed in 1980) would be the way to go.

The GT2871 was a great turbo when I graduated high school. For some reason, they retain their value due to the nissan/sr20 fanboiz. That was THE turbo to have if you did a SR20 swap. But, I am going to upgrade to a ball bearing turbo from a churbo finally, and with the cost of new garrett turbos, you would be silly if buying new not to buy an EFR. It isn't like it is $1000 dollars difference. Like $100 difference. If you're getting a smokin deal on a garrett that is one thing, but if we are talking turbo upgrade here, I would go EFR all day every day.

That being said, I would keep the turbo on the car as it is, I'm on board with everyone else. Get some VVT and e85 to help with that bottom end a little more.

You might lose what...200rpm at most of spoolup with a bigger hotside and itll be FAR better on EGT's and backpressure since it looks like he tracks his car.

Also that dyno link you sent is nice, looks like full boost around 3900-4000rpm which is really good for a gt2871. I know people love the EFR turbos but the 6758 seems to spool in that same range even though people say " OMG ITS SO MUCH BETTER". So I dont drink the EFR koolade.

Have you used an EFR before? It's not coolaid. It is a lot better.

But like Lars is saying, OP doesn't need to shell out for all that. I'd also just run the current config and not waste money...yet

I have not used an EFR, so no I have personal experience with them. The biggest improvement with the EFR seems to revolve around spoolup time being shorter but from the dyno charts Ive seen Im not sold on it honestly. They seem to hit full boost around 4000rpm still....

Not saying the EFR sucks Im just not wowed by it either. Sorry for getting OT for the OP. Good luck with your build OP.

Drive one, you'll be wowed. The improvement is not in spool, but in response. My 6758 repsonds like a 2560R on the road but has enough compressor to make 150whp more power than a 2560R can. My 6258 in the race car is virtually instant, better than my old 2554R in the real world. It is freaky.

Isn't spool a way to measure response?

Isn't your point essentially that it spools like a smaller turbo?

I'm just a bit confused about how you're differentiating spool and response here.

No it's not. Boost threshold =/= transient response.
Poast less, read moar, nub

Off topic is still on topic for me so go for it. I have little knowledge of turbos, so it's all very interesting from this seat :)

For my own future reference, what flange do EFR's use, T2 style?

Also down here Holsets seem to be gaining market share and have good support. Only references I have noticed here haven't been particularly good....is that right?

I ask because I suspect we'll only get 1 more season out of this turbo....hopefully.

edit: also for reference it is mostly race car so quite rare to be under 4k revs but when it is (slow corner, odd gearing) there is time to be gained by having good spool.

Calling it transient response makes more sense to me.

Ie on/off throttle while driving vs one long pull. But it's physically still measuring spool... Albeit in different conditions.

holsets are great, but many (most?) of them were made for diesels, have odd configurations, and most (all?) are oversized for a Miata, unless you like street racing freeway pulls lol

If the EFR has transient response on par with the GT25 and GT28 that youve mentioned then that is simply amazing. I need to experience this magical unicorn turbo soon I think. Anyone in the louisville ky area running EFR? LOL. You make the EFR sound cooler than the other side of the pillow. I want to ride in one for sure.

There's 20 years worth of technology and engineering separating the efr from the old garrets. Of course the differences are significant

Right, but you're still dealing with a larger compressor wheel and larger turbine wheel configuration on the efr when compared to a gt2554r. So it almost defies logic that it'll respond faster knowing how small a 2554r is. On the dyno charts I've seen the efr isn't spooling faster by much if at all than similar sized Garrett turbos. But real world driving on the road is something a dyno can't simulate. I really need to ride in one to truly be sold on it. Sorry I guess I'm kinda skeptical, and kinda love Garrett since I've always had such great luck with them.

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.