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Old 07-18-2010, 05:41 PM   #1
blckout7
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Default Dyno

Has anyone dynoed a 06 2.5i stock, curious to know what the real drivetain loss is..


Thank you

Ps, I have a hybrid intake and axleback, and about to be tuned on 91 octane, what range gain am I looking at?
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Last edited by blckout7; 07-18-2010 at 05:52 PM.
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Old 07-18-2010, 06:43 PM   #2
flightwatch
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Most dyno's that I have seen have been in the 110-115whp range. The axleback isn't going to do squat except make noise. With the intake and tune, you'll be looking at around 20whp I'd guess. I'm sure that Ty or one of the other n/a gods will chime in.
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Old 07-18-2010, 06:54 PM   #3
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Thank you for the response, and hmph from what I understood from the mechanic out of the catback the midpipe = 2 hp and the axleback = 4 hp...that's what the mechanic said but you very well could be right
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Old 07-18-2010, 06:59 PM   #4
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No way...The only way to see gains from exhaust on our cars is to do a complete swap. Headers, high flow cat/ track pipe, midpipe, and axleback.
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Old 07-18-2010, 06:59 PM   #5
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Axleback = no real gain... heck, even catback = no real gain. I mean, maybe some throttle response, maybe a little gain, but nothing really. Great for sound though... defiantly a worth while mod.

Intake... eh, more gains than the exhaust. All combined together like you have and they're more useful, so there should be some measurable gains there. If you get it tuned, you will feel a noticeable difference, even from running them with the stock tune. But, that can be expensive.
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Old 07-18-2010, 07:10 PM   #6
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I know that the 2.5i is a slow car but I feel according to the numbers,

For instance with the numbers you gave at 115whp and at a 33.5% drivetain loss weighing 3067 lbs

06 2.5i = 26.6 lbs/ whp

That's basically identical to an 06 sentra 1.8s, it's possible but I feel like the impreza has to be faster then that lol
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Old 07-18-2010, 07:32 PM   #7
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When I dynoed my 02 Forester, it was around 50hp peak loss or about 29%. This was a completely stock engine with just an I-Speed reflash that adds 5-10 ft-lbs across the board. This is assuming 165hp stock is accurate and that I'm making about 5-10hp peak. If so, I'd make 170-175hp at the crank and I put down 122hp at the wheels. 48-53hp loss or 28% to 30% for me.

Note the losses are do to friction, so lighter loads = less loss. Some of the other losses are inertia based so there is more energy put in to accelerate the car and more lost when braking for the added rotating parts.
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Old 07-18-2010, 10:04 PM   #8
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Hmm interesting, you had a 28-30% loss I would assume
Being lighter that the impreza has to be slightly less of a loss right?
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Old 07-18-2010, 10:15 PM   #9
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The biggest gains you'll see out of any exhaust-related thing you can do are headers.
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Old 07-19-2010, 01:18 AM   #10
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Lol damn I would do them but it makes the car to
Loud and I've already pulled over 2 times for just an axleback lol
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Old 07-19-2010, 02:47 AM   #11
The G.O.A.T.
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so pulling 137whp @3400 ft is not bad?
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Old 07-19-2010, 03:01 AM   #12
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That's your dyno result?
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Old 07-19-2010, 04:22 AM   #13
The G.O.A.T.
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Yep but I got uel headers, hybrid intake and a "airboy " custom tune.
I wonder if ruining all synthetic helps at all.
And that was in Calgary Alberta Canada
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Old 07-19-2010, 02:36 PM   #14
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The numbers themselves on most dynos are almost completely irrelevant. What is important is less the numbers but the difference in the before and after XYZ modifications. Look around NABISCO and you will find people with similar modifications in the same models (and yrs) making substantially different numbers.
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Old 07-19-2010, 05:30 PM   #15
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hmmph will do thanks everyone for the input definately excited for my tune on wednesday...hopefully ill see some significant changes in my subie
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Old 07-19-2010, 11:39 PM   #16
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You will definitely see a significant improvement in drive-ability, but you won't gain any significant numbers. Only stickers and a body kit can give us that.
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Old 07-20-2010, 09:18 PM   #17
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Quote:
Originally Posted by flightwatch View Post
No way...The only way to see gains from exhaust on our cars is to do a complete swap. Headers, high flow cat/ track pipe, midpipe, and axleback.
Headers are where the power comes from, EL to be specific. A good EL header with the stock system (if it were possible to do) would still experience gains. the cat/catback will help maximize what the headers will allow the engine to do, though.
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Old 07-21-2010, 12:06 AM   #18
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Honestly, a tune is where you are going to see the biggest difference. It doesn't get you big gains, but the dive-ability factor will be like getting a new car.
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Old 07-21-2010, 12:20 AM   #19
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Quote:
Originally Posted by The G.O.A.T. View Post
so pulling 137whp @3400 ft is not bad?
Depends on which drivetrain loss number you want to go with. With a 30% loss, you are at 178 to the crank. With 40% loss, you're at 191. Considering that you're at 173chp stock, and taking into account the mods that you listed, I would say that you're closer to the 40% number. Now I'm also not taking into account the elevation either...
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Old 07-21-2010, 12:40 AM   #20
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Tune is tomorrow can't wait!!, then next my lightweight crank pulley will be installed! Then mods will be intake, axleback, 91 octane tune, and pulley. That must be a decent gain right?
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Old 07-21-2010, 12:48 AM   #21
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Quote:
Originally Posted by blckout7 View Post
Tune is tomorrow can't wait!!, then next my lightweight crank pulley will be installed! Then mods will be intake, axleback, 91 octane tune, and pulley. That must be a decent gain right?
Hey dude,

not sure what the shop's schedule is like tomorrow, but if they stay open past 6 we could get your car on an actual dyno for an extra $150 (for the dyno time).

I didnt know you were interested in dyno pulling, I was going to use the airboy software to see gains.
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Old 07-21-2010, 01:04 AM   #22
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Uh not sure if I'll do the dyno little short on cash but we'll see tomorrow
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Old 07-21-2010, 02:30 PM   #23
The G.O.A.T.
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Corrected sae was 213chp and keeping in mind the ruffly 3% per 1000 ft you lose( is that right???) that would put me at about 190chp in Calgary. with drive line losses of another 53 hp that puts me @ 137 to all 4 wheels. But @ only 30% loss I get -57 hp? so something does not add up. Is my switch to synthetic really making that much of a difference??? I know someone knows how this all works.
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