Thucydides

So I'm trying to make a final decision about either the BEGi S2 or S3 systems; the only difference being the S2 has the GT2554 and the S3 has the GT2560 turbo. The system I end up with will be used on the wife's '95 M/T daily commuter and my weekend scratcher. We're in California so that means 91 Octane and no funny business under the hood. 185 brake hp is the initial goal, then perhaps a bit more after navigating it's first smog test.

Anyway, I printed out both turbo efficiency curves and at 8psi boost = 1.8 pressure ratio, and 20.4 lbs/minute flow rate both the 54 and 60 turbos look great; likewise up to about 225 hp, after which the larger 60 looks like it begins to become the better choice.

But, I've yet to find anyone who really thinks the 54 is a good choice, even considering my modest objectives. It's like the Rodney Dangerfield of turbos. Mostly it's damning by faint praise, like, "it's a sweet little turbo but really you want the bigger one", but sometimes it's more like, "don't bother, you'll want the larger turbo real soon anyways." Sometimes I'm left wondering why they even sell them; the cost difference is $69. Hell, that hardly fills the tank any more, but yet for some strange reason I'm still curious about them and how they'll run.

I know some of you are running 54's, and some of them are making way more power than I'm looking for right now. Maybe some of you have even run both, and can fill me in on their differences. How do you you folks like them and would you do it again, or is once enough?

Oh, yeah. I asked this question in the Noob section, and some of you have already given me your feedback. I really appreciate your advice, Samnavy, Rafa, and Braineack! But understandably there's not much traffic there so I'm casting with a larger net this time cause this question is still bugging the hell out of me.

jayc72

iTrader: (14)

I love my 2554R. Spool is retarded and it makes good power on my 1.6. Having said that, I've never experienced the spool of a 2560 either.

I like it, fits my goals just fine.

Rafa

iTrader: (22)

Jay, have you ever had your car dynoed? Do you have any idea what whp you're making?

Zabac

iTrader: (39)

Wow, a noob with a brain, welcome aboard good sir!


Simply put,
The 2554 is to the 1.6L what the 2560 is to the 1.8L!
I hope this helps you make your decision, which either way you go, you will not regret it, both are fantastic from what I hear.

kotomile

iTrader: (24)

Seems the only people springing for 2554s are autoxers and generally those who want their turbo to mimic a supercharger's power delivery. If <225 is ok with you and the wife, might as well get the 2554 and enjoy the extra spool.

jayc72

iTrader: (14)

Haven't had it on the dyno yet, but I would think I'm in the 200whp range. I've got a shitty tune on the car right now, and a pretty restrictive exhaust. I have traction issues in 1st and 2nd running 215/50/13 v710. It doesn't have that kick in the *** my TD04H-15G did, but I know that the car is faster now. The power delivery is so different it really doesn't feel like the same car as it did with the Greddy kit. Yes I know comparing the Greddy to a 2560 is not even remotely a good comparison.

The GT2554R is the **** in my book!

jayc72

iTrader: (14)

IF you go with a GT2554R and plan on running lotsa boost, I'd spring for the largest IC you can.

J.T.

Idk what the lb/min flow rate of the 1.8L is at 250hp but the GT2560R looks like its effiecient in a much broader range of pressure ratios and flow rates. The GT2554R looks like its a bit smaller of an area to work with. But for a street car if you want that instant power and drivability I would say the GT2554 would work well because the boost would come on quicker, but I've heard the spool difference between the two is barely noticable. But IDK from experience, someone whose driven both would have to comment.

blkmx-5

i have a 2554R on my 1.8L and im very happy with spool time and HP numbers. i dyno'd 180 whp and 175 wtq @ 7psi w/ walbro 190 fuel pump, 2.5 inch exhaust (with cat) and stock injectors. i have since put bigger injectors, turned the boost up to 10 psi and took out my cat converter. if i had to guess my power now id guess around 195ish/200whp? oh and this was on a dynojet and running off the rising rate fuel pressure regulator.

Ben

iTrader: (33)

the 2560 will have lower outlet temps, thus lower intake temps, compared to the 54. I'd go for the 60 based on that and 91 octane. YMMV

Braineack

iTrader: (62)

I'd go for a 3071 turbine, with a 2860 compressor.....oh wait

left field

iTrader: (1)

i have the 2554r on a 1.8. no complaints. makes boost nearly instantly. excellent for auto-x.

emilio700

iTrader: (3)

Assuming both are set up and tuned properly:

GT2554 Lag is not part of its vocabulary, there simply is none. Better low end torque than any of the very well set up MP62 hot and coldsides I've driven. At 10-11 psi they are magic. Weak top end without an I/C past 3rd gear (heatsoaked intake tubes). With a good over the rad I/C, it's a close to a perfect powerband and response as I have ever driven in a Miata.

GT2560 Very little, but always some lag. About 60 more hp potentially. Good at 10psi, but really happiest at 12-14psi.

I have driven maybe 15 different 2560's and have yet to experience one that had zero lag. Personally, I hate even the slightest bit of lag. Faster on the track, sometimes yes. More fun, never.

Building a street car, I'd always choose the GT2554R. Building a pure track car, a GT2871 and a stroker. The GT2560 is perfect for neither IMO.

J.T.

How do you like the 'personality' of the GT2860 compared to the Gt2560?

Braineack

iTrader: (62)

I run the same compressor wheel as the 2860, with a larger turbine (journal bearing T3).

I have driven in a few miatas with small t25 and while i love the low end, i hate the top end. but emilio is right, they are a blast!

with that being said, id pick a 2860 over a 2560, since they both has the same compressor wheel and the 2860 having a larger turbine, it will make more up top. If setup correctly I don't see why it cant spool just as well, hell my t3 makes 13psi at 3800RPM. Based on my dyno plots, I have more low-end than most 94-05s with 2560s.

J.T.

Well then I'll keep that in mind when I get to that point. Right now I'm between a 2560 and a 2860. But then again I only want around 200-250whp. Any more than that will probably be more problems than its worth especially for auto-x

TonyV

iTrader: (17)

Not much to say other than I've been running the 2560 on a 1.8 @ 6psi (i know i know) and been very happy...I doubt I'm at your 185whp #, but IMO there's good power from bottom to top, and currently lag is negligible at best...

edit: this is w/ 3" exhaust

Rafa

iTrader: (22)

Yes, but in your case this is mostly due to your superb tuning skills.

For mere mortals like me, your turbo (which by the way is the one I have in my car right now) is not the best option. I see most of my car's power coming in only after the RPMs are above 4,000.

I would suggest the 2560 in the case of the OP. I think the small difference in spool is going to be negligible and he will have the chance to get more whps out of his car as he learns to tune it.

I issue I wanted to comment on for the OP to think about: one good thing that big turbos have is that they're more forgiving when anyone trying to tune the car makes a mistake. They don't stress the engine as much as the smaller ones.

Thucydides

This is great information, gentlemen, and I appreciate all of your input very much. There's no other place I could have gotten this much useful information, from so many sources, so quickly. Thanks to everyone!

Using Garrett's approach, 250 brake hp requires almost 16 lbs boost (2.38 A/F ratio) and a 27.5 lbs/minute flow rate. Plotting that on the GT2554R efficiency chart puts the point way at the upper right of the very last line, and at the 60% efficiency level. Maybe it's doable, but only barely, and a very big intercooler is probably a good idea.

On the GT2560R chart the point is also at the upper right corner, but right between the 72% and 73% efficiency lines; it's a good match for those numbers. Any more HP and you're looking at the next size up.

By the way, J.T., do you drive a white NA with blue racing stripes? Saw one yesterday going through Sacto.

J.T.

Na I don't have a car at all :( lol

I found max boost and am gonna guess that it doesn't quite take 16psi since theres people doing it lower. I would do the calculations but I'm a lil lazy.

Edit: I'll put my foot in my mouth, I threw some numbers at the equations and came up with around 15psi. So a PR of right about 2. my bad