Noob quesiton: Greddy vs GT25 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 06-21-2006, 01:54 PM   #1
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Default Noob quesiton: Greddy vs GT25

More turbo newbie-ness for you all

Assuming you had two cars both pushing out a solid 180rwhp; one is running a Greddy setup, the other a GT2554.

I'm guessing the GT25 would spool sooner, but what would the difference in driveability be between the two cars?

Thanks
John
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Old 06-21-2006, 02:07 PM   #2
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Garrett turbo would be ball bearing and water cooled, so it should last much longer than the GReddy/Mitsu turbo.
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Old 06-21-2006, 03:07 PM   #3
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Because the T25 would spool sooner, you'd likely have quite a bit more torque in the 2000-3500 RPM range, making around-the-town driving more pleasant.

I don't think the turbo cartridge would "last much longer" than the Mitsubishi's, though. If taken care of properly, the difference should be near negligible.
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Old 06-21-2006, 03:39 PM   #4
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I have driven both. The GT2554r in almost instant boost were as the Greddy kicks in around 3000rpm which isn't bad. Both feel comparable in the upper rpm range. You probably have to run a higher boost level with the Greddy to achieve 180 compared to the gt25r depending on your setup. I give the edge to the gt25r, but I own one
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Old 06-21-2006, 03:44 PM   #5
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Quote:
Originally Posted by Stripes
I give the edge to the gt25r.
While I agree with you....we'll see soon enough....
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Old 06-21-2006, 03:55 PM   #6
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To actually add something useful here is a merged dyno graph of a GT25R vs. a Greddy both at 8 psi. Both on dynojets. Both relatively not well tuned. Both with 2.5" exhausts. GReddy with stock 1.75" DP and GT25R with 2.5" DP. (Yes, I am making excuses) Not done on the same dyno, nor the same day, but good for a general comparison.

Look at that early spool! So jealous....

Almost forgot two more excuses...below dynos GT25R was on a 1.8L and GReddy on a 1.6 and who drives under 3K rpm in a miata anyway? :gay:
Attached Images
File Type: jpg dyno.jpg (94.9 KB, 77 views)

Last edited by brgracer; 06-21-2006 at 04:24 PM.
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Old 06-21-2006, 04:03 PM   #7
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i'll know in a little while.
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Old 06-21-2006, 04:25 PM   #8
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We'll to make Greddy owners feel a bit better....the sleeve bearing turbo's are rebuildable (rebuild kits available), where as ball bearing are cheaper to replace than repair (alot more $). Also since your not in boost in the lower rpms, your saving some gas. I kind of like the dual personality of my Miata with the Greddy.
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Old 06-21-2006, 04:33 PM   #9
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Is that my dyno chart?
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Old 06-21-2006, 04:39 PM   #10
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Wow, great info, thanks!

That Dyno chart was interesting, a 2.5" DP on the greddy would help narrow the spoolup gap wouldn't it?

I see this isn't going to be an easy decision. Once I've decided on the GT25 the Greddy's low price tempts me...and when I've decided on the Greddy someone says they wished they had thrown a GT25 in to start with.

Hopefully getting a ride in a Greddy next week so I'm hoping that will help me decide.

Thanks!
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Old 06-21-2006, 04:39 PM   #11
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Stay tuned...Brgracer is installing a 2.5 inch downpipe and new intercooler system. I just installed a link so we will both have similar setups and will be pushing 12+psi. I'm look forward to seeing what these cars will do side by side.
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Old 06-21-2006, 04:50 PM   #12
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I realise the dyno graph isn't a super-accurate comparison, but it's surprising how similar the two turbos are once they're up and running.

I can't wait to hear about the 12psi battle
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Old 06-21-2006, 05:31 PM   #13
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An extra 200cc and a 2.5" downpipe went a long way toward decreasing spool-up on that setup. Add that to the fact the Mitsu. is a slightly bigger turbo...
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Old 06-21-2006, 06:17 PM   #14
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Quote:
Originally Posted by Stripes
Is that my dyno chart?
Yes it is. I hope you don't mine. The other graph was when I was running 8psi awhile back.
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Old 06-21-2006, 07:31 PM   #15
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Quote:
Originally Posted by brgracer
Yes it is. I hope you don't mine. The other graph was when I was running 8psi awhile back.
No, not at all. It just looked familiar.
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Old 06-21-2006, 08:31 PM   #16
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Quote:
Originally Posted by Stripes
No, not at all. It just looked familiar.
Well if you keep changing your screen name we will think you're in the witness protection program
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Old 06-21-2006, 09:01 PM   #17
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i had a highly customized greddy. for a little more, i'll have the equivalent to an fm2. i also have the flexibility of moving to a full fm3 with the manifold i have. the installion will be a helluva lot more clean, too.
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Old 06-23-2006, 10:00 AM   #18
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Quote:
Originally Posted by olderguy
Well if you keep changing your screen name we will think you're in the witness protection program
:gay: You noticed. I never liked my screen name. I still don't like this one, but it's the best I can come up with until I have to relocate
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