please post your turbo model, comp ratio, exhuast size, and how much boost at 4000rpm
 

oh, and maybe at what rpm you make...lets say 8psi.

I know you all hate me, but I have to pick between the gt2560 and gt28rs by tomorrow if I'm going to exchange this turbo. Thanks for the help.

GO BIGGER
GT2871 or GT3071

I would go with the GT3071, but I think you'd like the 2871...

:vash:

Dude, 250whp is enough. I'm a pussy and scared of that much power when I suck as it is on the 4 tracks I've driven. Seriously, I have a tiny penis.

It's called roll around at WG until you are comfortable. Your confidence will grow very quickly, and hunger for more power will come with it. 250 will feel slow after a month.

If you need to, convince yourself that the bigger turbo will be safer for you because it won't need to heat up the charge as much.

I'm worried it won't spool with the low compression. I'd like to be able to get the car moving at 2800 (without putting the pedal on the floor) and like to have 8psi by 4k rpm.

Hawk blues are $100 per set...250whp will be just fine. I'm still toying with the idea of wilwoods.

250rwhp??? get the 2554. or I gues sthe 2560 if you think that's too small. you dont need big anything.

matt
GT2876R
10:1
3"
7 psi @ 4000
ummm with my boost set at 7psi.
but it basically goes like this:
http://y8spec.com/dyno/turbospool.gif

t3 S60 .48 A/R (in between the 2560 and 28RS)
9,5:1
2.25"
8psi @ 3500RPM
15psi @ 4000RPM


I'd get the 2871.


This assumes 300BHP at 2.2PR (17.5psi)

https://www.miataturbo.net/braineack/random/gt2560.jpg
https://www.miataturbo.net/braineack/random/gt2871.jpg
https://www.miataturbo.net/braineack/random/t3.jpg

+1 on getting a bigger turbo. Turbo lag is not an issue at the track as you should be in the higher rpm range on the track 99.9% of the time. As already mentioned, you have the benefits of upping the boost later for even more power as well as creating less heat (compared to a smaller turbo at higher boost) which is definitely a plus for the track.

this was me slowly shifting into 5th from 4th gear....300RPM and fully spooled agian...that's about .8sec (no joke)

https://www.miataturbo.net/braineack/logs/5th_boost.jpg

I'm torn between this:
and this:
:dancegay:

the reality is on a road course you can only use so much power accelerating out of the turns anyway. So whether you're accelerating with the small or big turbo, you're still using XXX ftlbs to get moving. Your suspension and tires (and balls) are the real power limiter in the turns. It's the point at which your lateral gs have leveled out that you'll take advantage of the bigger turbo. And at that point, if you only want 250hp/ftlbs - just don't press the pedal to the floor. :D I don't think there's any "con" to either turbo that you can't drive around without thinking about it. It really comes down to how fast do you want to be going at the end of the straight?

I'd personally go with the bigger turbo (and more power) because most of my hours on track have been driving NA Miatas with no power, getting romped on the straights by cars that have LOTS of it. Power can compensate for a mistakes, bad driving and make you look like the "bigger dick" to the uneducated observer - especially big power in a Miata. That said, learning how to drive road courses in a high power car is more difficult than learning in a powerless car. When you make a mistake in the powerless car the result is absolutely painful - yet in the big power car you just mash on the go pedal. :bigtu:

In the end, I don't think the track is the governing criteria here. I think the street driving is- since that'll will more clearly show the differences between the two turbos.

You're exactly right. Hopefully a year of monthly track days at 96whp has taught me something. I'm not going out to kill everything on the track, just don't want to be so bored on the straights, and have some fun around town. As long as I can make 8psi by 4k rpm, I think I'll be happy. If I could make 12 psi at 4k rpm in the gt28rs, there is no absolutely no question that I'll be happy...and won't be so worried about egt's.

I still want to enjoy driving the car on the street when the weather is nice. People seem to think the gt2560 is perfect for the NA 1.8 motor...so I thought the 99 motor with the better head would move more air, and I wouldn't notice the larger turbine too much, and yeild lower egt's.

i run a larger turbo on my 1.6 and it spools plenty good 12psi by 4300 rpm very linear. to spin my 225's i only need to downshift or goose the throttle when i am past 5K rpm. as far as driving around town the feeling is very satisfiying + the larger turbo doesn't have me constantly in boost and this helps with my gas mileage as when i press down abit more the usage of fuel goes up by a whole lot :D

If your hp goal is 250, get the gt2560, gt28rs or bigger. Having owned both the gt25r and the gt28rs, I'm much happier with a bigger turbo at 12psi. The gt25r is a great turbo for the 200-220 range but still runs out of steam in the upper rpms. Instant spool is overrated IMO. When I first set out to build my kit, this was the most important thing to me. Now, I can live with a tad of lag(200-300rpms with the gt28rs). I would much rather have a turbo pull hard all the way to the redline. Now I'm thinking GT3071:)

I've got to finish my post review of the gt25r and gt28rs this weekend....

thanks.

28rs and 2560 are similar turbos.
http://www.flyinmiata.com/tech/dyno_...emy_potato.pdf
honestly I don't think that makes the 28rs look very good.

I think you'd be exstatic with a GT2871r, but I've said that already. It's going to spool a little slower than the 28rs, but the tradeoff is minimal considering it will make a lot more power per psi.

You've also got more RPM to work with with your fancy rods and solid lifters.

If it were my motor, and I were playing with your budget, I'd go 3071r. My motor (which will be similar to yours) is probably getting an ebay T3 or T3/T4.

My budget is spent...I just bought another car, lol.

There is no sense in running something bigger than the gt28rs though, because the car will not put down more than 250whp. I don't want to break the thing. There is no sense in pushing the limits of the drive train...considering that I'll make 150% more power than I have currently. The rev limit is going in at 7500rpm. I know you guys hate me...but if I learned anything with the turbo vw's, it was to tune it conservatively, then enjoy it.

gt28rs... but we think it might actually be a gt2871rs....

Spool.. no clue... not running yet :p

just get the large of the two...do it, do it now. You'll be happier.

if you dont like the spool charaterics, which i doubt, you can always find a fmII guy or BEGi guy that will swap.

I like the 2871 though, same turbine, large wheel, better efficiency.

Incidentally, with regard to the track use of a turbo car.... you wont notice spool with any of these turbos.

https://www.miataturbo.net/forums/at...3&d=1183134698

Basically when you shift at 7500 and the RPMs drop back down to 5000 something.... you'll have boost. no problem.

A faster spooling turbo will be more fun on the street. I say go with the smallest turbo that will support your ultimate power goal. The problem is that your ultimate power goal will likely change once you get used to the power ... if you aren't too much of a pussy to got WOT every now and then.

Hopefully staying at 250whp means I can keep the 1.8 brakes with hawk blues...rather than pay $1600 for a bbk, then $160 for a set of front rotors, and $100 for pads. I'd rather swap pads and spend half as much on brake maintenance. I also don't want to deal with breaking transmissions and rear ends constantly.

I litterally went to fucking hell and back with the vw, and even though its a toy...I don't want to constantly search for transmissions and rear ends. The whole idea is to build a car which is cheap to take to the track.

I understand this...but at 8.6:1 will the car move at all when the turbo isn't making boost? I have too many variable, and too much time to think about it.

Gary at TDR thinks the lower compression is a bad move, and this scared me.

Coincidentially my new GT2871R will be here Monday. I got a pretty good deal on it and could probably get more at the same price, PM me for more info.

ALSO, there are more than one GT2871R (three in my catalog):
Compressors:
Inducer dia/exducer dia/trim/AR:
49.2/71.0/48/0.60
51.2/71.0/52/0.60 (plotted above)
53.1/71.0/56/0.60 (mine)

That last choice has the same specs as the GT3071R except for a "larger" 0.60A/R compared to the GT30's 0.50A/R. The GT3071's compressors can be used too, to make things even more complicated.

For turbines, all GT2871's use the same two exhaust housing options (either .64 A/R or .86 A/R). Y8S went with the .64 A/R on his larger GT2876R and is getting pretty decent spool.

I'm starting to think I seriously fucked up with the 8.6:1 pistons. $400 down the shitter.

Dude, 4/10s of a point in static compression is not the end of the world. You'd probably be hard-pressed to tell the difference between 8.6:1 and the usual 9:1.

You'll be able to run a little more timing advance to help out.

So do I run with the gt28r to spool the thing faster and deal with high egt's, or swap it out for the gt28rs (that I ordered) and deal with the sluggish spool and run happy egt's?

I'm leaning toward the gt28r.

slugish spool.....you're talking like 300rpm difference at most.

if you got the .64 A/R 28RS it'll spool pretty well. that's the same hotside I have but it uses the T3-60 compressor which is a little smaller than mine.

Ask Jason Cuadra what he found by going from a 9.4:1 motor to an 8.2:1 motor and headwork. more low end that's what.

I was just going to reccommend searching Jason's name. I knew he went with some low compresion pistons for his rebuild. Hustler, you remind me of myself in that we both seem to over think things and second guess decisions. the 8.6 pistons were a good choice, period. the car will be making boost all the time. it will be so much better than what you're used to. I'm no expert on these turbos but I have had mine for 5 years and tracked it for the last 3 and I would reccomend going with the larger turbo. because it will make more power per lb. of boost. if you want 250 (which is a number I like) then you may be able to reach it at 10 or 11 psi instead of 12 or 13 psi. less heat and backpressure is a good thing. on the track with sustained boost.

+1 on everything... that dyno graph made me completely disinterested in the potato and I posted it before for hustler i think... go big (3071) or get a 2560, don't get something that does neither very well.

I'm a government planning analyst...over thinking is what I do.

he got more low end torque and/or power by lowering compression?

I like the gt2560 better in that dyno, but what are egt's doing at that boost level? I don't need melt-down from running the car for roughly 30 minutes at its maximum levels. I don't want this motor or turbo to come apart because of some stupid decision which I could avoid with a little more research. Also, if I stick with the 8.6:1 pistons I'll have to run more boost to compensate for the lower static compression...and is that outside the flow parameters for the turbo on the compressor side...because that's borderline on the turbine. That's why I am leaning toward the gt28rs...it has the larger turbine.

well we are turbo planning analysts overmaking hp and getting shit done is what we do try to fit in :gay: If my 16g spools on a 1.6 very nicely then the 3071, or 2860 will be a wonderfull turbo on a worked over 1.8. Trust me a little lag at less than 1800 rpm is good for wet weather driveability and general fuel economy that being said it isn't hard to stay above 3K rpm in my setup where i was initialy making more torque than you did at redline with your setup now. So imagine if your motor skipped from 2K-6.5K instantaniusly and that is how the turbo feels from there on you have the G's telling you damn this torque isn't half bad, and the speedo telling you if cops could see this they would call ahead to get you picked up trust me man. The driving experiance excentuates stock and adds to it 1 million fold.

QUICK SPOOL IS OVERRATED. As long as you make full boost by 4000-4500RPM you'll be plenty happy. When's the last time you shifted at WOT and you were below that mark?

OK I did leave out that he uses the GT2554.

He also was running about 240 rwhp at 10 psi. on that turbo.


I *think* the GTX motor died though (the 8.2 one) and I think now he's running an old 94 short block that I sold him. for cheap :(

I still want to get the car to move in traffic. My 8.5:1 turbo vw was a fucking turd off boost. It was really bad.

that car also wieghed about 1000Lbs more didn't it?

I'm a big fan of driveability myself. My T25 never surprises me. I don't ever have to worry about stomping it in a corner and gaining 80whp in 100rpm like you get on a big laggy bitch when it comes on boost.

The .80/.64 pulls steady and smooth and makes great torque down low. I love having 12psi and 160ftlbs on tap @3500rpm... too bad I'm down to 7psi on my craptastic Spec clutch.

You should be fine with 8.5:1. My awd talon was a 8.5:1 comp from the factory and never had a issues with driving out of boost. Yes I know it was a 2L but it also had hella more weight to deal with. Also the stock 1gen DSM run a 7.8:1 ratio

You should be fine with you 8.5:1. Now you spot a small difference if you jump from your car into a 9:1 ratio car but not by much.

If you really worried about it, just run shit ton more timing out boost in the lower RPM, like what us still NA people have to run.

The gt2560 sounds more appealing every step of the way...especially with the 40lb/ft gain at 3500rpm according to the FM dyno.

whens the last time you shifted and the tach was at 3500RPM while running thoughout the gears?

by all means I like a little quick turbo, however, the torque drop after it's spooled is a BIG compromise....