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Old 12-03-2012, 07:13 PM   #1
daigledangle8
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Join Date: Aug 2010
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2008 Impreza 2.5i
SSM

Default Higher Octane with Tune?

All the numbers are from a dyno at EFI
My tune was a road tune, not dyno tune
This car is my daily, I know I won't make big power/ numbers I just enjoy modding the car and doing what I can to have more fun with the car.

Stock (135 whp, 128 tq)

Current (136 whp, 130 tq)
STI Mikey Tune
Hybrid Intake (with snorkus delete)
2.5 inch cat-back

Next Setup ( ? hp, ? tq)
Retune with Mikey
Cosmo CAI
Borla Rep UEL Headers
2.5 inch header-back exhaust w/ high flow cats
Perrin Lightweight Crank Pulley
Delta Cams possibly
(any other simple suggestions?)

My question is simple..is it worth it to tune the car for 91, 93? How much of a difference would I see.
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Old 12-03-2012, 08:12 PM   #2
impreza09af
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Yes it's worth it. I have a 91 and 93 tune and I gave all those mods full exhaust rallisport Uel. It's a very noticeable difference in power.
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Old 12-03-2012, 08:33 PM   #3
Back Road Runner
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There are good gains from octane since you can run a lot more timing.

This is my 02 Forester. The Yellow line is current mods with an I-Speed SRS-10 flash (87 octane). The purple line is the torque curve with an I-Speed SRS-20 flash (91 octane). There were zero changes to the engines and the data logging was done on the same day one right after the other. The results were middle of the road results of I believe 6 pulls from 1500 to redline for each set. For reference, the original dyno was my car with a stock engine and only a SRS-10 flash, otherwise completely stock, done on a Dyno Dynamics dyno. All my data logging since has been scaled to that original real dyno pull. Results are pretty accurate up to 4500rpm, but then road logging lags behind some in results with it being low by 15hp/ft-lbs by 6500 versus a real dyno. This had been figured at a later date with another real dyno pull on a Mustang dyno and compared directly with road dyno results of the same setup.

The raw numbers are no important as they are dependent on the scaling. The differences however are pretty accurate within 1-2hp/ft-lbs and all results were done with non-favoring results (high or low) taken over at least 3 runs but more often 4 to 6 runs on a specific road each way in order to verify wind/inclination were not factors or at least could be adjusted not to matter since I have 8, 10, 12 results to work through and pick the best average representation.

http://www.rs25.com/forums/attachmen...7&d=1268966169

It might be curious to try higher octane. However, you only have so much timing to play with before it kind of gets pointless. Then, you're pretty much forced to someone generate higher dynamic compression (pistons, variable valve timing) to make actual use of the knock resistance.

For reference, timing on the SRS-10 flash (87 octane) versus the SRS-20 flash (91 octane):

http://imageshack.us/a/img257/3449/srs10srs20timing.jpg

I think both gasoline and E85 (if you so choose) can show gains upwards of around 40 degrees of advance, although don't quote me because frankly I've researched this subject matter about zero. I just know that above a certain point, you're not gaining, and that gasoline and E85 is pretty similar in this trait, at least from the brief amount I've attempted to search and read. I'm not a tuner and don't deal with this in any way, so take my comment with a pile of salt and spend time researching the matter yourself. I can only compare a 87 octane setup versus a 91 octane setup, show power gains, and you can guess and hopefully research the rest.


p.s. TWE headers are the only ones you should be looking at if you're actually serious about power gains. If not, you're only fighting your own goals.

Last edited by Back Road Runner; 12-03-2012 at 08:48 PM.
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Old 12-04-2012, 07:10 AM   #4
daigledangle8
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Thank you for the very much for the helpful information. I like seeing actual information too instead of just saying yes its faster. Did you happen to do any mpg testing? Most likely I will be going with 91. I agree with the EL headers to get the most out of the power but I like the rumble and it's a sacrifice I'm willing to make even though it's just sound vs power.
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Old 12-04-2012, 07:11 AM   #5
daigledangle8
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Quote:
Originally Posted by impreza09af View Post
Yes it's worth it. I have a 91 and 93 tune and I gave all those mods full exhaust rallisport Uel. It's a very noticeable difference in power.
Specifically what mods have you done to the car? Brands?
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Old 12-04-2012, 02:53 PM   #6
RecoveringSaabaholic
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Are you saying this because they are EL or because of the brand. There are other EL headers out there that are far cheaper than TWE. How they compare in the amount of power/torque gained, I don't have any hard numbers, but the CNT EL headers I have definitely gave me a decent bump.

Also, I do not believe that TWE makes any products for the '08. At least not that they list on their website.
Quote:
Originally Posted by Back Road Runner View Post


p.s. TWE headers are the only ones you should be looking at if you're actually serious about power gains. If not, you're only fighting your own goals.

Last edited by RecoveringSaabaholic; 12-04-2012 at 03:06 PM.
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Old 12-04-2012, 06:22 PM   #7
impreza09af
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newport pearl blue

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Quote:
Originally Posted by daigledangle8 View Post

Specifically what mods have you done to the car? Brands?
I have the Perrin LCP, rallisport racing Uel, custom magnaflow catback, rallitek plug wires, Cosmo CAI, N/A accessport with several maps (currently 93 tune). That's just the power mods I have.
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Old 12-04-2012, 07:01 PM   #8
Steve2.5i
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Quote:
Originally Posted by RecoveringSaabaholic
Are you saying this because they are EL or because of the brand. There are other EL headers out there that are far cheaper than TWE. How they compare in the amount of power/torque gained, I don't have any hard numbers, but the CNT EL headers I have definitely gave me a decent bump.

Also, I do not believe that TWE makes any products for the '08. At least not that they list on their website.
They do produce EL headers for 08-11. I spoke with Tom at TWE just a few minutes ago. They start at 920+, they also have it so the cat can be relocated.
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Old 12-04-2012, 08:16 PM   #9
klaus_b2
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ive got your whole set up you want. headers, hfc, catback, cai, perrin lw pulley, and im tuned on the 93 map i have on my accessport and i notice a difference but not enough for me to pay more money for the gas :/
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Old 12-04-2012, 10:44 PM   #10
DrInline6
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Default

Quote:
Originally Posted by daigledangle8
All the numbers are from a dyno at EFI
My tune was a road tune, not dyno tune
This car is my daily, I know I won't make big power/ numbers I just enjoy modding the car and doing what I can to have more fun with the car.

Stock (135 whp, 128 tq)

Current (136 whp, 130 tq)
STI Mikey Tune
Hybrid Intake (with snorkus delete)
2.5 inch cat-back

Next Setup ( ? hp, ? tq)
Retune with Mikey
Cosmo CAI
Borla Rep UEL Headers
2.5 inch header-back exhaust w/ high flow cats
Perrin Lightweight Crank Pulley
Delta Cams possibly
(any other simple suggestions?)

My question is simple..is it worth it to tune the car for 91, 93? How much of a difference would I see.
go with
el headers to 2.25 pipe 2.5 is to big!
high flow cats or no cats would be better
intake
91 oct tune
that should give u 15-20 hp
Lt pully waset of money
cams cost to much better off doing a swap
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Old 12-05-2012, 07:39 AM   #11
NH8991
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Location: Montreal, QC
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Sport, DGM

Default

Quote:
Originally Posted by daigledangle8 View Post
Thank you for the very much for the helpful information. I like seeing actual information too instead of just saying yes its faster. Did you happen to do any mpg testing? Most likely I will be going with 91. I agree with the EL headers to get the most out of the power but I like the rumble and it's a sacrifice I'm willing to make even though it's just sound vs power.
BRR is right, if you go the UEL header route, all your other mods will be fairly pointless from an overall improvement point-of-view, the stock EL header is not bad to start with.
I would (and did) go with a 91 octane tune also, with all the mods I have I would say the mpg is at least as good as the stock car, maybe better.

Quote:
Originally Posted by DrInline6 View Post
go with
el headers to 2.25 pipe 2.5 is to big!
high flow cats or no cats would be better
intake
91 oct tune
that should give u 15-20 hp
Lt pully waset of money
cams cost to much better off doing a swap
- Yes to EL headers, HFC, 2.25" piping, 91 octane tune.
- The jury is still out on intakes for the 08+ cars, a lot of people have reverted back to stock, myself included. Driveability suffers for the few HP you gain at redline. (Note that I haven't yet tried a tune to account specifically for the intake yet).
- A LW pulley is one of the easiest, cheapest and (probably) safest engine mods you can do. Yes, HP gains are probably unmeasurable but the engine revs a little easier, and (for those with a 4EAT) engine breaking is greatly improved.
- Cams are dirt cheap, a set of Delta 1000s cost around $250, it only gets expensive if you have to pay for the install labour.
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