Justifying a 2860RS in my build
 

Can the Mt.net wizards help me out? I've opened this thread on m.net (T2560 vs. T2860RS flow @ 8/10psi - MX-5 Miata Forum).

I have not dyno'ed the car yet, I'm basically tuning off street pulls and being ---- with my collection of gauges...

I should be near my turbo's limits by now at 10psi correct?

Where would I need to be with 2860RS?

I thought I had reached a conclusion to the mess until the last guy posted what he did...

Just a quick reply should set me straight...

2560? 14.5psi = sweetspot

I'm going to stop using the internet and sleep in a corner if thats true...

2560s love the 12-14psi range. I stand by what I said there - for a stock motor, anything larger than a 2560 is wasted.

I agree, you can see just by reading the charts that shooting for maximum efficiency the 2560 is still within the island at 15psi shooting for approximately 250hp

http://img.photobucket.com/albums/v3...gton/2560R.jpg

The 2560R is a really bitchin' little turbo.

Cool beans, S4 manifold and 3" exhaust is go for shopping list! Thanks guys

/thread

but if you ever plan to build it, suffer with too much turbo now rather than buying two turbos over the long run?

Let's be honest, though: most people who "plan to build it" aren't planning to build it 6 months after going turbo. Look at how long it's taken you, and you've got like eighteen motors worth of forged parts sitting in the shed behind your house. :fawk: If you plan to build it later on, you can either suffer with a big turbo (all the lag and none of the power, like VTEC) or you can get a cheap T25 and run that for a year, have great spool, perfect power for stock internals, and lose virtually no money when you offload it in a year.

Or run a 2560 on a built motor at 15psi and love that it spools at 3100rpm like none of the larger thrboz.

I absolutely love my 2860. I was running 18psi and it was a monster.

I'm betting a 2860 with a .64 a/r housing would be comparable with just a touch more top-end. It's the same turbo with a slightly larger turbine, hell my turbine is bigger and I'm on a 1.6L. But everything I've seen suggests a well built 300rwhp miata should use a 2560.

i need to get me a 2860rs for my build ><

Oh, damn. I actually forgot I'm running a disgustingly high CR from the factory. No more boost for me without some new slugs and looser bottlecaps...

If I ever make the leap, which will be almost never now with these added costs, should I punch out the stroke or stick with the stock bore/stroke ratio for bigger boost?

Read my post over there, I still stand behind it. The "sweet spot" on the tater has a really small window, but when you're in it, its great. I like the big housing only if you have low static compression and can use the extra spark angle, if not then stick with the little housing.

However, after 250whp you're going to run into internal wastegate problems especially with the smaller housing. This forum has learned quickly that IWG and cast manifolds are a general failure. Its going to be even worse with a turbular manifold.

How come nobody told me about the 2854r? Anyways, all this is irrelevant considering I'm running 11.5:1 CR with stock rods. I'm almost certain at 220hp, the motor is starting to frown.

You know, I had always assumed that everyone thinks the T2860RS, 2871, and 3071 were a lot bigger than they really are. But I guess coming from you, they really are. I just wanted more power for cheap and to break free from the M.net snails.

Your sig says sr20 t2560....is that correct? sr20 T25s are very very small and not in the same league as even the 2560.

http://www.boostedmiata.com/random/t3_vs_t25_wheel.jpg

the sr20 wheel is tiny compared to a 50 trim t3 wheel (which is the same exducer size as the 2560 and 2860). a sr20 t25 :ne: a non-BB GT2560. It's more closely comparable to a gt2554.

This is a sr20 t25 compressor map:


http://www.boostedmiata.com/technica...60trim_map.jpg

you're best bet is to run the biggest turbine you can find with a tiny compressor. That's the only way to win with high compression.

FFFFUUUCCCCKKKK. Must be a busy little hairdryer then. So I basically need a turbo with a more linear onset of boost to keep my internals from getting free right? The 2860RS seems like a violent little shit compared to my current turbo.

not to sound like a dick or anything, but it sounds like you don't really know what's going on. WTF is "linear onset"? What does that have to do with anything?

You're all over the place. What goal are you trying to achieve by switching turbos? Less boost for the same power? More power?

Well I thought you were suggesting a turbo that didn't have a narrow efficiency range like yours for a couple seconds, and then you'd have to shift, and that I wanted a smaller turbo with linear boost all the way up to full spool? That's why supercharger boost is more friendly than turbo boost on internals? Thats what I inferred from your post when you said I'd want a larger housing with a tiny turbine wheel for my 11.5:1 CR. Please tell me I am making sense. :hustler:

Same power for less boost for now 8psi vs. my 10psi, and more power for less boost than my current turbo later 11-12psi, therefore giving me headroom for when I want to move into 250+rwhp territory. Am I being ridiculous?

the engine only knows rpm, afr, iat, and compression...it doesn't care where it gets the air or how fast it builds.

A larger turbine housing lets exhaust move through more easily, creating less pressure on the hot side, but probably spins up slower. However there's a trade off/ sweet spot between flow and turbine RPM. Since you're high-comp, you can probably benefit from the larger housing.

Yes, you're being ridiculous. I don't know anything about tuning high compression motors, but I wouldn't waste my time with that shit. I don't think we have the technology in our 30-year old motors to run high-comp with FI. You'll need to spray water to make this work.

It seems to me like money is just burning a hole in your pocket.

Not really sure what the deal is with "same power for less boost" is. You read "more efficient", I read "spools slower". Run the smallest turbo possible that will achieve your horsepower goal. I wanted 200whp, so I did a .49 A/R T25. Then I wanted 220-230, so I did a 2554R. Then I wanted 400whp, so I did a 2871R.

You don't need to change turbos RIGHT NOW, just like I didn't need to buy a 2871R when I had a stock block. Get everything else in order, get a built motor and a 6-speed into the car, and then think about turbos that will do 250+whp.

I just have like 500-600 bucks laying around, I was going to sell my turbo to some ricer fag for 350 bucks and pick up a bigger snail so I can make some more power. Guess it just doesnt make sense.

Yeah there is a handicap with the high CR 01-05 motor, VVT makes some fuelling/timing tricky, you're capped at about 250hp and I have to pull more timing than you guys.

Magna makes it sound easy in his sig, but I was looking at what's involved, and pulling my motor for the weekend sounds easier for now.

Sav, I've reached the conclusion that I'm not going to be able just swap snails and be done with it a few posts back. I'm going to order the M-Tuned rods and a torque wrench from Harbor Freight. I'm going to build a motor worthy of Mordor.

You might need a few things other than M-Tuned rods and a torque wrench... just saying

You're going to want to at least hone and re-ring, and by the time you do that pistons are only like $200 extra. You'll need bearings too, as well as a full seal kit, so don't think you can just "pop the motor open" and throw some rods in it.

Instead of wasting your time fucking up your car, why not put that energy to something useful like cleaning my apartment?

I'm gonna go read some more before I spend any money tonight. No, I didnt think it was as simple as "toss some rods in there". I was going to get the supertech pistons and rings, and belfab bearings. Like I said, I'm gonna read some more before you guys start e-thugging me.

Err.. sure Hustler, if you want a dude to come clean your apartment for you, I'll drop by if I ever visit Bell. You did help me a shit ton on m.net when I just got the car.

Your magical "500-600" dollars just turned into 2 grand for pistons, rods, oil pump gears, gasket set, bearings, as well as machining costs and labor for somone to put together a motor is well over 1000 on top of that. But if you DIY you dont need to pay for the costs. There is no real "pop it open; slap it in" cheap solution like sav said.

It's true, engine building gets expensive. It is a very slippery slope.

It gets expensive if you aren't disciplined and you don't stick to the plan. You can do a shortblock for well under $2k if you work at it, or you can just mail everything to John day in Texas and he'll do it all for $1600, including assembly.

Chris, welcome to miataturbo.net :-D haha.


I don't think they're trying to e-thug you around that bad, just trying to save yourself some time and money. Sure you could sell your t25 to some ricer fag and get a larger turbo but the cost for power benefit wouldn't be that great especially if it's not tuned right and then your stock block goes and then a small peice of a bearing shoots through the turbo and your fucked.... just saying.

Good luck with your build :)

I built my "wonder-motor" for $2k. I don't think that's remotely expensive for what you get.

Sorry for the minor threadjack, but do you have any of John Day's contact information? Thanks

972.235.7405
Trey Rozelle sent you.

Thank you very much

This thread is a good illustration of the boost obsession. You guys are never satisfied. I understand the love for a specific vehicle ie. the Miata but thousands of dollars for built motors, going through 2 even 3 turbos on the same car. A car worth less than the turbo setup. This is madness! Do what I did and buy an Evo - 19.5psi factory.

Then again, I have yet to pilot a turbo Miata so what do I know?

Being a former 2560 owner, it is all you need for a stock motor, and it is a great turbo. It is fully capable of blowing up your shit. Ask me how I know. And the sweet spot is indeed 15 psi. It really came alive raising it from 12 to 15; it even sounds better.

I just want to reiterate:

Attachment 204395

:ne:

http://www.boostedmiata.com/technica...60trim_map.jpg

My experience with turbo choice is to choose a turbo that can achieve your hp/torque objectives with about 30hp headroom.

On my 1.6L (with headwork) the 2560 had a 'snappy' response and happily made 260bhp at 16psi. A nice turbo. I moved to a 2860rs (0.86A/R turbine) and it felt sluggish when getting on it, but made 280bhp+ at the same boost level.

Later, the same GT2860rs felt great on my 2L build, 'snappy' again and capable of 320 to 340bhp. Near perfect. For some reason I fancied more power and opted for a custom GT3076r (a blend of the 71 and 76 with a larger ported wastegate) so that I could push for 450bhp, it feels like the 2860RS on the 1.6L, a little sluggish, but makes plenty of power. I'm going to dump it soon and spring for something a little smaller, maybe even go back to the 2860rs. On my daily driver 300 to 350bhp is plenty.

BTW on all these turbos spool was only 200rpm slower (boost vs rpm) on the larger units (at most), so they actually made near the same torque at a given rpm, the larger turbos just didn't feel as snappy when getting on it.

Edit: FWIW the GT3076r spools in 5th gear as follows:
120kPa by 2150rpm
140kPa by 2600rpm
160kPa by 3050rpm
180kPa by 3350rpm

After 180kPa boost rises more quickly.

no, actually I know exactly what I want and I almost got there but had to rethink a couple parts. I went in circles on my turbo vw, but on this car I knew exactly what I wanted from the start and didn't buy too much stuff twice.

Heavy, slow, etc

And the base cost is a shitload more then our build and the car. The Miata's handling is superior to most sedans. Then you want to get new parts for your evo and that shit isn't cheap either.

Miata parts aren't as cheap as they should be.

Lightly used Evo parts (stock and aftermarket) are abundant and as a result quite cheap.

You guys are still crazy and I'll keep saying that to keep myself from spending thousands to modify my ugly $3,000 Miata.

^ so WTF are you doing in this forum?

What is the fun in buying a car that is already fast.. Half the fun is installing the parts, feeling the change. I can buy a good condition Miata for cheap, which gives me extra funds for mods.

Thanks, I will spend money on what i want because,
"i wanna go fast" - Ricky Bobby (Talladega Nights)

Change his name to TROLLican.

Good deal on a GT2560 in the for sale section.

trust me, I saw it

for the price you spend on track rubber and brakes, I can get the same for my car, a hooker, and a party ball.

Now that's little a more valid lol.

But...I don't need to invest in a rollbar just to be allowed on the track AND I dont have to try and shoehorn a proper seat in the car since it comes with a PAIR of Recaros...

But evos also weigh 2800-3000+ lbs. Little more weight that a little Miata, let alone a race prepped one

Edit*** This has nothing to do with the thread, sorry for the thread jack

that's fine, you'll still get skull-fucked by the Cali Miata crew.

People like you are a lot of fun to pass on-track. :loser:

I'm thinking of running a sr20 gt28 since they are so cheap here in japan($50-150). I was wondering what you guys think of this turbo.

i think you should mail me a few. seriously

170rwhp, piss poorly tuned and I still win.