FM2 2.5 vs 3.0 exhaust - Miata Turbo Forum - Boost cars, acquire cats.

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Old 03-11-2012, 02:00 PM   #1
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Default FM2 2.5 vs 3.0 exhaust

Last December I upgraded my ~ 10 year old FM 2.5" exhaust to one of their new 3.0" ones. Finally got around to dynoing it yesterday, and both spools up faster and picked up 10 hp on the top end despite running slightly less boost (unfortunately, the setting on the boost controller wasn't identical between the two runs, it's down about 10 kpa which explains the lower torque in the midrange).

The car is a 99, has Carrillos & 9:1 Supertechs, headwork, FM2 hardware, Hydra, and a 2560. Stock 99 intake manifold. The first dyno was a couple years ago with about 200 miles on the motor, the second with about 5000. Both are DynaPacks, although different physical units.



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Old 03-11-2012, 02:51 PM   #2
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I wonder how much of that gain is from the exhaust and how much is from the motor "wearing" in. Is there much difference in sound or butt dyno?
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Old 03-12-2012, 12:19 AM   #3
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The butt dyno change was significant and I needed to retune the boost controller settings after installing the exhaust, so I think most of the effect is from the exhaust change.

The 3.0" exhaust is, as you would expect, quite a bit louder than the 2.5" as well.

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Old 03-12-2012, 01:22 AM   #4
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Lol @ having to google instructions on how to capture a screenshot. Also, props for googling.

How much difference did you find there to be in the noise level? Especially things like droning.
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Old 03-12-2012, 01:37 AM   #5
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Quote:
Originally Posted by Bryce View Post
Lol @ having to google instructions on how to capture a screenshot. Also, props for googling.
I only use Windows for Hydra tuning, and that only because they somehow managed to write the software such that it doesn't work under VMware.

Quote:

How much difference did you find there to be in the noise level? Especially things like droning.
The noise level is noticably louder at idle. There's a minor drone on the freeway which I'm only noticing now that I've taken the hardtop off the car. It doesn't bother me, but then again it's not my daily driver (as was probably obvious since it took 2 years to put 5000 miles on the new motor).

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Old 03-12-2012, 04:48 PM   #6
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You can always add a spring loaded flapper to the FM 3" exhaust.
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Old 04-10-2012, 04:35 PM   #7
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What downpipe are you using?
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Old 04-10-2012, 04:36 PM   #8
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wish i could see the pic.
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Old 04-19-2012, 04:29 PM   #9
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Quote:
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What downpipe are you using?
It's all current FM hardware -- manifold, GT2560, downpipe outlet casting, 3" DP, 3" exhaust.

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Old 04-19-2012, 04:34 PM   #10
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I don't find mine (same hardware) to be annoyingly loud or to really drone badly. I quite like the sound of it, very deep compared to my friend's 2.5" FM.

my .02
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