Savington

iTrader: (31)

Not for me, but for another guy in the area who is getting ready to order a BEGI S2. The 2560 has a larger turbine, which means less bottom end and more top-end, but what does that mean in the real world? Why would you go with a 2560 over a 2554?

neogenesis2004

iTrader: (12)

They are practically the same turbo, just one has a LITTLE bit more room up top. You have a gt25r so you know first hand the the thing can get full boost faster than you can look at the boost guage. The gt2560r is gonna be the same.

Al Hounos

which engine? if it's a 1.8, 2560 no doubt. I like my little 1.6 with a 2560, a 1.8 is an easy choice.

Savington

iTrader: (31)

Al, why bigger? What's that smidge of top-end cost in spool?

neogenesis2004

iTrader: (12)

nothing you will ever notice.

neogenesis2004

iTrader: (12)

I used to run a gt25r before my motor blew. I'm running a holset he351cw this time around, MUAHAHAHAHA

Al Hounos

I'm pretty sure you'd notice.... the compressor side is quite a bit bigger.
http://www.turbobygarrett.com/turbob...R_471171_3.htm
http://www.turbobygarrett.com/turbob...R_466541_1.htm

As for why, just a personal preference. The 2554 is a good turbo, but I wouldn't want any smaller than my current 2560 on my 1.6, and there's no way I would step down to a smaller turbo if I had an extra 250cc. The 1.6 doesnt really make any power, turbo or not, below 4000rpm, and my 2560 hits full boost around 3900, if I remember correctly.

If he's an autocrosser, go for the 2554.

If he wants 250whp, get the 2560.

neogenesis2004

iTrader: (12)

I would bet there wouldn't be more than 300rpm difference. With the miata's gearing 300 rpm is nothing.

y8s

iTrader: (8)

breaking the *** loose every time you need a little acceleration gets old fast?

JasonC SBB

There's a big difference in feel between the 2 turbos.

Stitches

This is my first post and first turbo envelop comparison I have ever done. If I've made a mistake anywhere, I'm sure you'll let me know, just be nice:

So I've gotten about 50 pages into Maximum Boost (Croky Bell's book), past the section about how to read turbo envelope maps and calculate what CFM your car needs at boost. I went though those two maps for the turbos from Garrett. Here is what I found:

This is all while at full throttle by the way. The turbo spools as exhaust gas leaves the motor to push it along. If you are at 1/2 throttle, then only 1/2 the total potential gas is hitting the blades. At lest that's what I understood I read.

This is all based on Boosted Air Flow (lb/min) = ((displacement x.5x.85) / 1728 ) x (1 lb/14.7cf) x (boost in bar)
Efficiencies are guesstimates based on the efficiency envelopes inside the map.

T2554:

8psi - Fully spooled at 2550 RPM.
- Boost drops off at 7900 RPM
Efficiency: ~69%

12psi - Fully spooled at 2550 RPM
- Boost drops off at 7800 RPM
Efficiency: ~69%

15psi - Fully spooled at 2500 RPM
- Boost drops off at 7380 RPM
Efficiency: ~67%

Boost Potential:
Can boost the 1.8 miata motor ~16psi at 7000 RPM. The max output though is almost 25psi between 3500 and 5500 (kinda useless). You can boost up to about 17.5 psi and get a full spool at 3000 RPM and then the boost will drop off at 6700 rpm. That's about as high as you can go unless you don't care how late your turbo spools or how far before the redline the boost drops off. You might change your redline to 6700 rpm and crank your boost to 17.5psi. You'll do fine.

T2560:

8psi - Fully Spooled at 2600 RPM
- Boost drops off at 8600 RPM
Efficiency: ~70.5%

12psi - Fully Spooled at 2700 RPM
- Boost drops off at 8400 RPM
Efficiency: ~71.5%

15psi - Fully Spooled at 3000 RPM
- Boost drops off at 8200 RPM
Efficiency: ~ 68%

Can boost the 1.8 miata motor ~21 psi at 7000 RPM. This turbo though isn't capable of much more than 21 psi, but you can get a full spool at ~3500 rpm @ 21psi and it won't run out of boost until 6995 RPM.

+++
So as you can see, the smaller turbo can spool up slightly faster, probibly not noticibly faster between 8-12 psi, but about 500 rpm faster at 15. It can't boost higher than 17.5 psi and be fully spooled for any length of time.

The bigger turbo does have more boost potential if you think your motor can take 21psi from it.

There is one slight thing that is noteworthy, though. The T2560 is a little more efficient. I know that the more efficient the turbo is, the cooler the charge is, but I haven't gotten far enough to be able to put numbers to it yet.

Savington

iTrader: (31)

Do tell. You run a GT2554R, right? Would you ever switch?

Markp

There is a big difference between these two turbos. The spool is remarkably different because the turbines and compressors are different.

He needs to be honest with himself. What is the purpose of the turbo.... On the street with a 2554R you have a car that makes boost everywhere. If you are not worried about exceeding 220-230 RWHP, then this is the turbo for you.

Nice thing that even if the boost bug bites is that he can upgrade to a nicer turbo... I don't like the 2560 for one reason. It does everything well but nothing great, it's a good turbo... Like I said it does everything well... The 2871R or 3071R make big power (for a T2 cartridge.) The 2554 does a great job down low.

I guess the only reason I would consider the 2560R is if I could not make up my mind on a HP goal between 200-300 RWHP. While the 2560 is theoretically capable of 300 RWHP it is really pushing it beyond reason and making 200 RWHP on this turbo is overkill. This turbo is happy between 230-250 RWHP, and many people love it. It certainly is a good turbo... (and while I feel it's not a great turbo, good may be good enough.)

Mark

Savington

iTrader: (31)

Mark, Garrett's site says the turbines are the same. Only difference is a 54.3mm exducer on the compressor of the 2554, vs a 60mm exducer on the compresor of the 2560.

I like the "does everything well but nothing great" bit. It seems like if you want spool, go with the GT2554R; if you want big power, go to a GT2860R or a GT2871R. No reason to mess with anything in between.

Al Hounos

And that's why I like it, I can autocross it and then take it to the strip and beat up on STis and Mustangs.

I wouldn't want anything more 'focused'.

Stripes

iTrader: (8)

You want a gt2560 if your goal is above 230hp. Go with the gt25r if you can look yourself in the mirror and say you are completely happy with 200-230 hp. I had a gt25 on my car for two years and it was a blast. This turbo spooled instantly and the car was very very fast. I could drive circles around local Greddy setups. I would not have swapped this turbo out for my potato if I did not get the horsepower bug.

If you decide to go with a gt25, you'll wish you went with a bigger turbo the first time a mustang or camaro pulls you from 60-90 mph.

Markp

GT2560R - 707160 - 9 actually has a larger turbine. You are right about the other two GT2560R's having the same size turbine... My bad.

Mark

Markp

And that is a perfectly valid reason to pick it. After all it's about picking the right tool for the job.

Mark

paul

iTrader: (21)

just the thread i was looking for. decided on the 2560 today since i run an absurdflow 3" turboback exhaust. now do i wanna go with the more expensive exhaust housing material and exhaust impeller

TurboTim

iTrader: (9)

I just love Garrett.




I have what is supposedly the most recent Garrett catalog open in front of me.

GT2554R has the same turbine as the GT2560R, except the 2560 can come in an inconel turbine wheel and Ni-Resist turbine housing.

The compressors are:
2554: 42.0 inducer dia, 54.3 exducer dia, 60 trim, 0.80 A/R
2560: 46.5 inducer dia, 60.0 exducer dia, 60 trim, 0.60 A/R

After eyeballing the compressor maps, they do look decently different.


There is no "707160 - 9" part number; however the 707160 - 5 and 707160 - 7 are the two GT2860R, the oddball "R34 Skyline GT-R replacement" turbos with the matches-nothing "compact" 5-bolt turbine outlet flange. The 707160 - 5 turbine has the same specs as the GT2860RS turbine (0.64 A/R), the 707160 - 7 turbine has the same specs as the GT2854R turbine.

I don't know which is best for a street 1.8.