So my rings are pretty much toast, so I'm planning a bottom end build. When I do this, I want to replace my SR20 turbo with either a 2560 or a 2860, but which one? What is the maximun amount of boost these 2 turbos can run before exceding their efficiency levels? How much different is the spooling? At what psi will these turbo's excede the amount of fuel allowed with 460cc injectors?

 

no experience with either one, but judging by how much everyone absolutely loves the 2560 you cant go wrong

(though I'd go with the 2871 to be honest)

 

If you dont already have a better fuel pump that will need to be changed as well. @ 11 psi on a built 1.9L my 2560 had maxed out the injectors at 11psi (460s) Now i have a walbro 190 and am @ 15 psi around the 78% duty cycle. Im currently sending off a set of 550s and plan to jump the boost up to 17 psi or so.

I wouldn't want ANY more lag than the 2560 has, which isnt to much. To put it in perspective i had that same turbo you have on my 1.6l and it almost felt a bit faster because of the "no lag"

 

I'm swapping to a 2871 from the 2560, although everything is still being assembled, so can't give you any numbers. I will say that in the top of 5th gear at 15psi the 2560 started to lose it's breathe, but had good low end power. The 2860 and the 2871 share the same outer housings and compressor wheels, but the turbine wheel on the 71 allows for more flow which is more power, albeit a little bit later, so I'd second 18psi's comment on the 2871. I'm willing to sacrifice a little down low for more up top since I'm also adding 3.636 gears, but didn't want to go overkill on the turbo since it's a daily driver and I don't want to wait all day to build boost.

 

I really like the 2560, and I bet it would spool even faster witht he 1.8L. But I'm sure the 2860 rocks as well.

Corkey will point you in the right direction. I was going to get a 2871, and he told me that the 2560 was better for my goals. And I am happy. Give begi a call, they will make the descision easy. According to your personal expectations and goals, they will hit the nail on the head. They will even throw some factors in the equation that you didn't think about, or extra better options.

Good Luck!

 

Corky pushed me toward the 2860rs as he likes the better thermal efficiency. The 2560 spools a touch faster. Some guys here, Johndoe for one, have had more overboost problems with the 2860 (even with porting) and dropped back to the 2560 which fit the mid 200hp power goals just fine.

Take a look at the spool up thread. The 2860 spools maybe 1-300 rpms later than the 2560 depending on the system. I'm seeing full boost around 3200rpms with my 2860rs with the BEGI S4 system and 2 1/2" exhaust.

Here's the spool up thread - https://www.miataturbo.net/forum/t26641/

 

BEGi should have my 8.8:1, 1.9l, 99, slight headwork, s3 with the "tater" dyno up this week.

I had a solid road tune on it with 400 miles on the clock and it made 10psi at 3600rpm. the minute I told Corky it was a track toy, he pointed me to the tater.

 

I'm thinkin GT2860 with 550's. If I have a built bottom end, I'll want to run somewhere around 18 psi. What I basically want is an engine that I can drive dependably everyday, but when I take it to the track I run low to mid 12's. Daily driven I try to stay out of boost unless a respectable opponent wants to play. I'm just gettin ideas now...I'm still in the tuning stage with my SR20 and 460's. I just figure that after the summer beat session that my car is going to receive, and since it burns oil now; it's going to need rings before I know it. I just want to spend money on the right ****.

 

If you haven't read that entire spool up thread yet here's what I'm doing with BEGI's S4 and the 2860rs. Again, 550's, 2 1/2" exhaust with race cat, MSpnp using EBC.
1psi = 1863
2psi = 2060
3psi = 2225
4psi = 2456
5psi = 2549
6psi = 2733
7psi = 2880
8psi = 2990
9psi = 3090
10psi = 3190
11psi = 3250

The 2560 in a similar system would spool maybe 200rpms quicker. I really like mine though. Feels more like a big motor. The power comes up incredibly smoothly. Far better than the O2 Saab Viggen I had. That thing was turbo lag city. Nothing, nothing, nothing then BANG.

The 2860 should be good for low to mid 300hp range engines. Some guys around here are talking a lot about the 2871 though. Haven't seen much spool data with that one though.

 

I have driven Cueball's car - the power comes on very smooth and very nice. The motor just keeps pulling harder. Looking at compressor maps and flow numbers etc, the 2560 on paper seems to be the better turbo for my power goals, but after having driven Cueball's car I see no reason not to do the same thing.

 

Mobius,

Good to see you pop in. I think my system spools well with the 2860 due to the S4 tubular mani. Others with cast mani's aren't spooling quite as well. If you go cast mani I'd go likely go with the 2560. For mid 200 hp goals it's a great fit. Paul, Turbo Tim, Johndoe and others really like it. Johndoe had boost creep trouble with the 2860 even though it was ported. (also involved a poorly fitting dp) . He liked the 2560 much better with his S3 system. I went 2860 due to Corky's preference and the likelyhood I'd do a built bottom end some day.

 

the '28' in 2860 and 2871 means they have the same turbine wheel. The '71' designates a larger compressor wheel. The typical 2871 likely has a larger a/r on the turbine though...

To the OP ... I suspect that at >250 hp the added efficiency of the 2860 over the 2560 will be apparent.

 

Whoops! Yes, you are correct. Don't know where my head was when I posted that. You can get the 71 with either the same size .64 or a larger .86.

Here's a quick reference chart that I made and posted when I was comparing the 3 turbos a while back:


TURBINE
GT2560R
* Wheel: 53mm w/ 62 trim
* Housing: .64 a/r

GT2860R
* Wheel: 53.85mm w/ 76 trim
* Housing: .64 or .86 a/r

GT2871R
* Wheel: 53.85mm w/ 76 trim
* Housing: .64 or .86 a/r

COMPRESSOR
GT2560R
* Wheel: 60mm w/ 60 trim
* Housing: .60 a/r
Flow : 320hp

GT2860R
* Wheel: 60mm w/ 62 trim
* Housing: .60 a/r
Flow : 350hp

GT2871R
* Wheel: 71mm w/ 56 trim
* Housing: .60 a/r
Flow : 400hp

 

so is the 2860 a T3-60 and the 2871 a T3-Super 60?

 

Compressors:

The 2871 is a lot larger than a Super 60 on the compressor side; 71mm compressor wheel over 60mm.

All T3 compressor wheels are 60mm exducer. The trim dictates the inducer size....so a 45 trim if you do the math, will have a much smaller inducer than a 60 trim.

The T3 Super 60 is still a 60mm wheel. It just has a .07" larger inducer over the standard 60trim wheel. So if you do that math, a S60 wheel is really just a 64 trim. So I could call my turbo a T3 64 trim.

The 2560 and 2860 shares the same compressor wheel as the T3 60 trim...


Turbines:

The standard Stage I T3 wheel is: 58.92mm w/ 68 trim
and can go all the way up to: 71mm w/ 76 trim
the GT2XXX Wheel: 53.85mm w/ 76 trim

The smallest T3 has a larger inlet and turbine than ANY GT2XXX


If my turbo was a brand new BB turbo...it would be labeled as GT3060, but I think the GT30 turbines are slightly larger.

 

I had the T3 from a 2.3l Tbird. I believe it had a stage 1 wheel and the turbine housing was a .48.

What is yours brain?

You have a super 60, so you have the bigger inducer correct? What Turbine housing size do you have?

 

I have a T3 Super 60. Standard turbine. .48 A/R.

 

ooops sorry I meant compressors. but was only half right.

 

Some things I've been wondering about compressor maps ...

For the following calculations I'm assuming 80%VE, 20*C Ambient, 70% IC efficiency, and a 1mm overbore.

1. Does the surge line on the compressor maps generally indicate spoolup characteristics? For instance if I map my engine on a 2560, I can't get more than about 12psi at 3000RPM without going left of the surge line. By 4000 it says I should be able to hit 18 but I'm still riding the surge line way out at the edge of the map. Is it really making that much heat over there since it looks like it would be on ~50% island? Is there any benefit of dropping the boost to 14psi@4000 to put it up to ~65%?

2. Probably the same as question #1, but whatever. I'm aiming for a minimum efficiency of 70% on the map, but my 5000RPM point can't possibly hit it. It looks like I might as well run it up to ~21psi since it'll be stuck in the 65% (maybe 68%) area on the left side of the map anyway. Is that right or do the lines on the left side of the islands matter?

3. Should I avoid exceeding the highest shaft speed listed on the map? It looks like I can achieve ~325HP at around 7000RPM@22psi with 70% efficiency if I push the shaft speed past the upper line at 143405 RPM

 

1. A steep surge limit line indicates that the turbo will produce high boost pressures at low cfm before surge is produced. A surge line that leans sharply to the right, indicates that the turbo will not work at high boost pressures at low airflow rates.

2 & 3. It doesn't sound like you are calculating and reading the map correctly. What turbo? what power goal? Try reading turbobygarrett.com "turbo tech 103"