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Old 01-05-2008, 07:07 PM   #1
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Default 2.25 or 2.5 exhaust?

Hello all,

I'm planing on (assembling the parts as we speak) doing a mild turbo on my 94 with room for upgrades. To start with I'll have a GT25R using 330cc injectors, EMB, with no IC (initially) running ~6Lb boost. I want to re-do the exhaust at about the same time that I have the DP made and I'm wondering if going to a 2.25" full exhaust will be enough, or should I go straight to a 2.5". I won't be going to a 3"....that's just too much for me.

One more thing; I'm looking at the ATC group buy and I'm wondering if the HDSS would be a good choice for this setup. I don't want to increase the clutch peddle force too much as this a daily driver and not a race setup.

Thanks again.

Tony
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Old 01-05-2008, 07:32 PM   #2
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your turbo will appreciate the 2.5" Dont upset the turbo and short stick him. he won't play nice.
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Old 01-05-2008, 07:47 PM   #3
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I agree.. that .25 inches decides what genetalia you are packing.
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Old 01-05-2008, 09:08 PM   #4
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the cross directional area of 2.25" pipe is 3.98, 2.5" - 4.9. Or 23% more flow area.

turbine + breathe = power.
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Old 01-05-2008, 09:25 PM   #5
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I say go 3 inch if you can swing it the turbo will quite down the car a hell of a lot.
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Old 01-05-2008, 10:11 PM   #6
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Just out of curiosity, what is the stock diameter?

I also want to remind you that this is a daily driver and not a race setup. I'm not going to go racing....
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Old 01-05-2008, 10:14 PM   #7
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stock is like 1.8" ID
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Old 01-06-2008, 12:06 AM   #8
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go with 2.5 inch, youll appreiciate the better spool
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Old 01-06-2008, 12:32 AM   #9
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Any advise on the clutch?
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Old 01-06-2008, 12:38 AM   #10
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I have the HD 6 puck clutch from ACT and the pedal really isn't that bad. Just don't get one too weak for your torque goals. The price is right with that group buy.
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Old 01-06-2008, 01:59 AM   #11
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OK, so I know that I'm going to go with the HD plate. The question is what is the difference between the SS plate and the 6 puck G6 plate. Again, remember that this is a daily driver. Will I (and my wife) be able to live with the HDG6?

Tony
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Old 01-06-2008, 02:01 AM   #12
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Street disc has much smoother engagement. The 6 puck is like an on-off switch engagement wise. Your wife would appreciate the street disc much more. If you plan on making allot of power, the ACT XT with a street disc works well, that's what I have and there isn't much extra pedal pressure.
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Old 01-06-2008, 02:03 AM   #13
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go with as big as posible. read an article somewhere that said the only time the exhaust on a turbo car is too big, is if its scraping the ground.
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Old 01-06-2008, 02:10 AM   #14
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Not going 3" is retarded...
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Old 01-06-2008, 02:21 AM   #15
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Quote:
Originally Posted by bryantaylor View Post
go with as big as posible. read an article somewhere that said the only time the exhaust on a turbo car is too big, is if its scraping the ground.
Must have been a honda forum, 4" downipes going right under the oil pan, wtf?
I read somewhere that said a 6" cone coming off the turbo would be the most efficient exhaust possible.
I have 2.5 but i expect good gains with the 3" exhaust and larger downpipe.
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Old 01-06-2008, 02:51 AM   #16
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Quote:
Originally Posted by Efini~FC3S View Post
Not going 3" is retarded...
This is exactly what I was trying to avoid. This is not an auto-x car. This is a daily driver that my wife will occasionally drive. Moving to a 3" exhaust is not an option.....no matter how "retarded" YOU think it is.

Bryce, Thanks for the input on the clutch. HDSS it is.


Tony
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Old 01-06-2008, 02:59 AM   #17
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Quote:
Originally Posted by amagalla View Post
This is exactly what I was trying to avoid. This is not an auto-x car. This is a daily driver that my wife will occasionally drive. Moving to a 3" exhaust is not an option.....no matter how "retarded" YOU think it is.

Bryce, Thanks for the input on the clutch. HDSS it is.


Tony
well really, a 3 inch exhaust wont have any downside at all, aka it wont affect drive ability. As long as you still have a muffler it will sound similar, just with beter spool.
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Old 01-06-2008, 07:09 AM   #18
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Quote:
Originally Posted by amagalla View Post
This is exactly what I was trying to avoid. This is not an auto-x car. This is a daily driver that my wife will occasionally drive. Moving to a 3" exhaust is not an option.....no matter how "retarded" YOU think it is.

Bryce, Thanks for the input on the clutch. HDSS it is.


Tony
Dude trust us a 3 inch exhaust will be about as loud as a 2.5 inch exhaust but better flow all around. Your wife won't have anything to complain about
accept maybe the extra hp. True story my miata was quiter open DP than before the turbo, on a 2.5 inch exhaust. My 2.5 inch exhaust post turbo is so quite i can sneak up on people, almost as easily as stock. We aren't racers here persay but we are about the effeceincy and feel you would be leaving alot on the table with a just limiting yourself to an arbitrary size. Esp since a custom setup will cost the same with 3 inch as it would with 1 inch.
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Old 01-07-2008, 04:00 PM   #19
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I finished my new exhaust yesterday.
It consists on the following from Summit racing:
2.5" to 3" flowmaster venturi
4' of 3" pipe
2 3" mandrel bend U turns
3/8" stainless tubing for hangers
18" long Magnaflow muffler (straight through Center-offset) 3"
3" Magnaflow tip.

It costed $250 shipped for materials but I bought 3 U turns and 1 45 degree turn. I didnt use 1 U and the 45, so it would be $60 less ~ $200.

It looks awesome, it was tricky to fit it on the tunel without going too low and then clearing the diff but after 6 hours of work we made it look awesome. To me is perfect and the welds where made with MIG by a certified welder, (my uncle) lol.

LOUDNESS ---NOT it sounds the same as my Entuzha 2.25" with a cat resonator and muffler, why? I dont know. BUt it does sound a lot meaner, like a rally car.

I will post pictures for you guys tonight or tomorrow.
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Old 01-07-2008, 04:02 PM   #20
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I do think that 3" is kinda overkill and the next one I make will be made out of thinwall 2.5" stainless
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