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.