2871 vs 3071
 

All else equal, what would you expect the spool difference to be between a setup with a 2871 with an A/R of .58 vs a 3071 with an A/R of .50.

I realize that this is a pretty basic question, but I've searched through a ton of build threads and looked at a bunch of dynos and the most info I've seen is that most folks consider the 3071 a bit too big, but that was with a higher A/R. I've seen a lot of folks have good luck with the 2871 and I'm not trying to reinvent the wheel. Miataman has a 3076 and is pretty happy with it, though that spools way slower than both the 2871 and 3071 from what I've seen.

That is all. Thanks in advance.

(In b4 dumb question :party: )

Buy an EFR.

+1

You should twin scroll 7163 and report back

I wish I had built my own manifold and went twin scroll EFR. That's probably going to be my next power upgrade.

You keep asking for validation and everyone is tired

A few hundred RPMs, probably 500-700 is my guess. I assume you are talking garrett turbos.

Yup. That I am. Thanks. That just about made my decision for me. I didn't realize it would be that drastic given the lower A/R. I figured it'd spool a bit faster.

Thanks Pat!

+2

Seriously OP if you're gonna go with an EFR sized turbo, why don't you get an EFR? They are nearly the same price as the garretts for a vastly superior product

The hell are you finding dumbass a/r housings like that for those turbos? The smallest generally accepted housings for those is .64. Source: I own(ed) both.

Cheap

eBay? Neither of those turbos will get anywhere near their power potential with those A/Rs, so it doesn't really matter. They will both spool like ass and make crappy power to boot.

If you really don't want an EFR then buy a 2863 or a 2867 with a proper T25 housing, or buy an EFR and enjoy the same power with much better spool.

We're all apparently wondering how he's coming up with oddball ideas and wondering why he's going through the mental gymnastics to try to justify taking an alternative path.

It's totally possible that the number for the 3071 is wrong or that it's just the compressor housing A/R, but that's what I was told. Because I am finding some with that when I search.

For the 2871, I was going off the part number and A/R that the seller was reporting.
QIM77319 446179-50329 is the part number.
It led to this CHRA
https://www.atpturbo.com/mm5/merchan...e=CHRA-GT2871R

I'm guessing he might have reported that wrong as well haha. No matter...

why are you asking about the compressor A/R on two vastly different turbos and the effects of spool that might have between the two?!?!?!


go back to school and stop playing with turbos.

Wasn't asking about the compressor A/R per se.... I asked for the A/R, but looking at specs online... it looks like that was what was reported to me. /shrug.

But turbo's are fun Scott!

Is pawning off all responsibility for lack of knowledge and general silliness onto misinformation and other people a millennial thing? kekeke

eleventy billion times +1

(is there such a number? no worries, I'll just say it was reported to me wrong)

Just do everything Pat did. Start at the beginning of his build thread and work your way forward.

:bowrofl:

turbos. possessive? come on.


https://cimg2.ibsrv.net/gimg/www.mia...163f9a705d.png

Thanks for that. Like I said, I asked and was apparently given the compressor A/R instead of the turbine. I couldn't make out info from the pictures but that's what I was told.
Re: possessive. Thank you swype!

On it!
:party:

just fwiw: compressor a/r has little to no affect on spool.

Here's an easy one: don't buy a turbo from a vendor stupid enough to give you compressor a/r instead of turbine a/r

lol vendor

he's trying to swoop it up on CL or some jank forum member who doesn't even know what a/r means.

my only question is: you were saying you wanted to do things right. why are you looking at jank setups again just to save a few bucks? isn't the definition of insanity doing the same thing over and over and expecting different outcomes? or something to that effect

OP...before you go buying stuff with specs that you don't understand, figure this out.
What is "A/R" and what does it mean?
Let's say you have a 2560 turbo with a .64 housing, then you have the exact same turbo with a .86 housing.
Which one will spool faster? Why? How does this number impact these effects?
Seriously, figure the answer to those questions out, and you will feel much better about what you're looking to purchase.

Is there anyone that has a twin scroll 6758/7163 on this forum.

Give me 6 months, I'll probably have a twin scroll 7670 by then.

I like dis.:likecat:

You are Pat, by default you cannot run anything smaller than 9180

do it

DO EEEEEEEEET

I give it 4.

:idea:

For the OP, The 2871 and 3071 are almost identical turbos. The "28" is referring to the T2 exhaust flange, and the "30" is for a T3 flange style. I believe the 2871 uses the same exact compressor wheel but the turbine is cut down a little smaller to fit into the T2 exhaust housing. The difference in spool between the turbos assuming .64 a/r for the 2871R and .63a/r for the 3071R will be within 300-400rpm...the 2871 will outspool the 3071. The 3071 can make more power once you hit the 350whp threshold.

i.e., not the same turbo.

you also forgot the compressor IS actually different...

Which of the three available 2871R compressor wheels are we referring to?

(Buy an EFR)

i may have been looking at the wrong turbo, rofl. (for some reason I thought the 2871 had a different trim size wheel) still differences in turbines make a big difference -- not even the difference in overall size/trim, the 2871 has 9 blades where the 2071 wheel has 10 blades.

there are plently of turbines that share the same compress wheels, but i wouldn't call the "almost identical"

like a 2860 and 2650.


(buy an EFR)

Are you referring to the 56.5mm T25 3071R turbine, or the 60mm T3 3071R turbine?

(please buy an EFR so someday I can forget all I know about Garretts)

So see how it can be a little confuzzling for someone that's been doing this for a year and change when you've been at it for over a decade and still get bamboozled!

Someday!!!
:party:

But for now...
:eggplant:

Lol @ 2071 and 2650.

But I walk to school...

Safest possible answer for all of us.

Cheaper too

:drama:

turbobygarret.com only lists a 60mm turbine for the 3071.
the 2871 turbine is 54mm.

and they only list a t3 housing for the 3071 or a v-band.

what am I missing here?

Dig deeper, padawan

https://www.atpturbo.com/mm5/merchant.mvc?Screen=PROD&Product_Code=GRT-TBO-025

https://www.turbobygarrett.com/turbo...00382-3_20.pdf

The 56.5mm wheel is why FM always made decent numbers from their 3071R 0.64a/r setups, but everyone with a 2860RS or 2871R (54mm turbine) needed the 0.86a/r housing.

The EFR's 58mm turbine is one of the secrets behind the huge power numbers it can produce. It makes up for the loss in spool that normally accompanies that extra size by using trick materials to keep the weight and response time down.

you gotta go "off the menu"

still a different turbine wheel than a 2871... 56.5mm =/= 53.85mm

and I wonder if it's a 10 vs 9 blade design. anyway, a standard 3071 and a standard 2871 are not "almost identical"

When I went from ebay 3076 to EFR 7670 (same size compressor, but vastly larger turbine on EFR) the spool stayed the same, but power went up about 20%. Flows wayyy more than the smaller turbine.

also probably has something to do with going from an ebay turbo to an authentic turbo. was the ebay 3076 ball bearing? I haven't looked at ebay turbos in so long I wouldn't be surprised if they have the ability to offer BB now....

your engine is probably happier with a larger turbine too... less backpressure in the turbo manifold.

They do in fact offer BB turbos now, but mine was a regular journal bearing one.

The engine does like the larger turbine. Interestingly I tried .63 and .82 A/R turbine housings on the ebay 3076, the .82 was a touch faster up top, but spooled a lot worse and overall the car felt slower. Car went faster at the drag strip with the smaller A/R turbine housing.