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Old 10-24-2016, 10:57 PM   #1
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Default Water/Meth injection and small turbo

Hello hello,

I'm about to turbo my NA and I'm hesitation between a GT2554R and a GT2560R. I really want quick spool as the car is my daily but I would also like to hit 250WHP (which I think is a reasonable limit to keep a reliable car,no?). So my plan was to us the smaller T25 GT2554R up to 10 psi and add the water meth injection above that boost in order to cool the very hot compressed air of the turbo running at low efficiency.
Has anyone done that? What do you think?
I know that injection adds failure point but I think its kind of cool to be able to have a big red switch for high power
Cheers
Seb
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Old 10-24-2016, 11:25 PM   #2
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caveat: non-miata experience.

I've only ever run water/meth on my subie. When you compare the meth dyno curve to the non-meth dyno curve, the whole curve is moved up about 15whp/wtq. Like you propose, I did this pushing the limit on the stock relatively small turbo. I gained a bunch of area under the curve, but the high end still feels breathless. While it's punchy down low, it tends to encourage me to shift before redline and makes the power band feel narrow. If I could do it again, I'd go bigger turbo.
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Old 10-24-2016, 11:55 PM   #3
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Quote:
Originally Posted by wackbards View Post
caveat: non-miata experience.

I've only ever run water/meth on my subie. When you compare the meth dyno curve to the non-meth dyno curve, the whole curve is moved up about 15whp/wtq. Like you propose, I did this pushing the limit on the stock relatively small turbo. I gained a bunch of area under the curve, but the high end still feels breathless. While it's punchy down low, it tends to encourage me to shift before redline and makes the power band feel narrow. If I could do it again, I'd go bigger turbo.
Basically this. I have a bunch of experience with the GT2554R (DD'd one for ~30k miles). It's got plenty of midrange and would benefit from more octane up to ~5500rpm or so, but on top it's going to fall off no matter what.
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Old 10-24-2016, 11:57 PM   #4
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So basically there's no point?
I don't understand I thought the whole point of water and meth was to drop intake temp, wouldn't that offset the low efficiency at high flow?
Btw thanks for the great answers
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Old 10-25-2016, 10:59 AM   #5
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Water injection stops knock. It doesn't do this by lowering intake temps, it does it by changing phase in the cylinders and other demonic magic.
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Old 10-25-2016, 11:08 AM   #6
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Water yes, but meth drops then temp by changing phase no? I thought that by mixing both you would get best of both world, less knock with H2O, and less temp with Methanol.
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Old 10-25-2016, 01:10 PM   #7
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I don't think a 2554 will spool one iota faster than a 2560R. the 2560r will stay on top a little longer too.
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Old 10-25-2016, 02:17 PM   #8
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Quote:
Originally Posted by SuperSeb View Post
Water yes, but meth drops then temp by changing phase no? I thought that by mixing both you would get best of both world, less knock with H2O, and less temp with Methanol.
Other way around. Water is for intake temps, methanol is for octane. You would ideally want to run more than 50% meth in the system, but at that point it has to be plumbed like a fuel system with an eye towards safety.

Water isn't going to magically produce more air. If you aren't making the most of the air you can move (detonation limited), then water/meth will help, but if your compressor can't move more air, lower intake temps won't help make more power.
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Old 10-25-2016, 02:26 PM   #9
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Well technically the 2554 can produce more air at high boost, just with a crappy 50ish% efficiency. From what I understand everyone runs the GT2554R at 10-12psi. I would like to push it to 16-18psi.

I shouldn't be detonation limited because I'm still at power level below what the car can do with bigger turbos. Assuming the IAT stays low thanks to injection+intercooler.

I'm not sure I get the point of water/meth for anything that isn't det limited.

I will get a 3" exhaust, Ryan you think both turbos will spool the same way?
Sav, you would rather pick the 2560 if you had to do it again?
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Old 10-25-2016, 07:30 PM   #10
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I mean, I'd rather have an EFR6258
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Old 10-25-2016, 09:12 PM   #11
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Agreed, if I had to do it all over again I'd use an EFR
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Old 10-27-2016, 05:16 PM   #12
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It's my first turbo build, I'm gonna start with a cheap used Garret. When I build the engine then I'll put an EFR, baby steps...
Anyone has a dyno plot?
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Old 10-27-2016, 05:26 PM   #13
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No, shittard. Nobody has ever posted a dyno plot of the most common turbo on this forum. If they had they definitely wouldn't have posted it in the "dynos and timesheets" thread.

Geez. Am I the only one?
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Old 10-27-2016, 05:41 PM   #14
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From Florida, I see, that's all I needed to know, "shittard ". I obviously am talking about a methanol injection dyno plot for a 2554 or 2560, because guess what section of the forum we are in...
I did google it but there's not much. Wackbards and Sav do you have some of your old plot?
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Old 10-27-2016, 05:51 PM   #15
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Sure, call and pay my hourly labor rate and I'll dig it up for you.

Alternatively, type "site:miataturbo.net savington 2554R dyno" into Google and see what turns up.
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Old 10-27-2016, 06:03 PM   #16
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Here's a freebie. This community has a ton of amazing info, and super low tolerance for spoon feeding. Asking for spoon feeding and insulting mods will not help you acquire said amazing info.

This is a '04 STI on stock turbo, bolt ons, & '91 oct.
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Old 10-27-2016, 08:12 PM   #17
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Well there was no way for me to see your plot wackbards without asking. And Sixshooter misunderstood my question and insulted me, admin or Jesus himself that's no excuse. I get it, we're on the internet and all, still doesn't hurt to be polite. Admin should show the standard, not lower it.

Anyways from what I see it seems like injection isn't the right idea for a small turbo.
FYI for future reference Sav plot is post #37 here:
https://www.miataturbo.net/dynos-tim...i-49948/page2/

Sav, correct me if I'm wrong but that is not water injected,is it?
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Old 10-27-2016, 08:24 PM   #18
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Quote:
Originally Posted by SuperSeb View Post
And Sixshooter misunderstood my question and insulted me, admin or Jesus himself that's no excuse. I get it, we're
You have been a member for a year and you don't know yet that us mods are ********?
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Old 10-27-2016, 08:29 PM   #19
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Haha good point, I'll aspire to be like you then
Nice turbo kit btw, I almost bought it!
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Old 10-28-2016, 06:02 PM   #20
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Yep, started drinking early yesterday because the surgical pain was making me testy. Welcome to the forum.
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