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Old 08-01-2009, 03:51 AM   #1
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Default 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...
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Old 08-01-2009, 04:30 AM   #2
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2560? 14.5psi = sweetspot
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Old 08-01-2009, 04:35 AM   #3
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Quote:
Originally Posted by Spookyfish View Post
2560? 14.5psi = sweetspot
I'm going to stop using the internet and sleep in a corner if thats true...
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Old 08-01-2009, 05:10 AM   #4
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2560s love the 12-14psi range. I stand by what I said there - for a stock motor, anything larger than a 2560 is wasted.
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Old 08-01-2009, 05:19 AM   #5
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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
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Old 08-01-2009, 05:37 AM   #6
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The 2560R is a really bitchin' little turbo.
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Old 08-01-2009, 07:41 AM   #7
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Cool beans, S4 manifold and 3" exhaust is go for shopping list! Thanks guys

/thread
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Old 08-01-2009, 11:31 AM   #8
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Quote:
Originally Posted by Savington View Post
2560s love the 12-14psi range. I stand by what I said there - for a stock motor, anything larger than a 2560 is wasted.
but if you ever plan to build it, suffer with too much turbo now rather than buying two turbos over the long run?
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Old 08-01-2009, 07:09 PM   #9
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Quote:
Originally Posted by y8s View Post
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. 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.
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Old 08-01-2009, 07:12 PM   #10
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Or run a 2560 on a built motor at 15psi and love that it spools at 3100rpm like none of the larger thrboz.
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Old 08-01-2009, 07:23 PM   #11
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I absolutely love my 2860. I was running 18psi and it was a monster.
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Old 08-01-2009, 07:36 PM   #12
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Quote:
Originally Posted by wes65 View Post
I absolutely love my 2860. I was running 18psi and it was a monster.
stock motor, chief
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Old 08-01-2009, 08:36 PM   #13
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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.
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Old 08-01-2009, 08:39 PM   #14
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i need to get me a 2860rs for my build ><
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Old 08-01-2009, 09:55 PM   #15
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stock motor, chief
I was running it on the stock motor, chief. The only reason it blew up is because it got revved to 10 grand.
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Old 08-01-2009, 10:09 PM   #16
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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?
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Old 08-01-2009, 10:21 PM   #17
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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.
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Old 08-01-2009, 10:31 PM   #18
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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.
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Old 08-01-2009, 10:49 PM   #19
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Your sig says sr20 t2560....is that correct? sr20 T25s are very very small and not in the same league as even the 2560.



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 a non-BB GT2560. It's more closely comparable to a gt2554.

This is a sr20 t25 compressor map:


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Old 08-01-2009, 10:50 PM   #20
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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.
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