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'98 Impreza L 2.5swap
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Discussion Starter · #1 ·
i have a 98 impreza L with a 2.5rs swap. i rally-X'ed it for the first tiem last weekend... and i really want to get a bit more acceleration. I've been reading about high compression builds, but i dont want to sink that much money into my motor. so my question is can i just tune the ecu for 91 octane and get more pep by upping the timing? or will that kill my low end? (which is what i want)
 

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2012 Audi S4
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1,954 Posts
You can run 91 octane without a tune.
i recall a comparision that always is stuck in my mind and relates to this. When you start dating a new girl, everything is great and you find yourself trying so much harder at everything. After a while its like meh and that new feeling is just an everyday thing now. running 91 on a stock tune is the same. for a few runs your car will think oh man this is awesome, but that feeling goes away quickly and its basically back to normal.
 

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'98 Impreza L 2.5swap
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39 Posts
Discussion Starter · #6 ·
i know it can run 91 without a tune, but i want to up the timing for more power, but you cant just up the timing without at least having a faster burning fuel
 

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Green 97 OBS
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1,840 Posts
It won't be worth the extra for premium. If you want noticeable gains, throw a set of delta cams at it. The regrinds are around 100 bucks a cam, some of the best bang for your buck mods out there.
 

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'98 Impreza L 2.5swap
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39 Posts
Discussion Starter · #10 ·
im very interested in doing my cams. not so worried about class for rallyX as the modifications i have already put me into the "modified awd" and "rally prepared" classes, so im up against fully built rally sti's lol...
 

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2002 WRB WRX
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420 Posts
If you're looking for cams, the Delta 1000s cams are torque cams and should improve your low end, then throw on some headers + high flow cat + 2.25" catback + tune and it should become quite a peppy car.
 

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'98 Impreza L 2.5swap
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39 Posts
Discussion Starter · #12 ·
i guess this is a little late but i should post my performance mods:

INSTALLED
-Borla UEL headers
-stock catted midpipe
-03 WRX catback
-CAI
-kartboy trans mount
-group N pitch stopper

NOT INSTALLED YET
-ACT clutch with light weight fly wheel
-Grimmspeed phenolic spacers

i have looked at high flow cats and they seem to be too expensive lol, been thinking maybe just straight piping it.

will Delta 1000's make freeway driving be at super high rpms? this is also my DD
 

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Green 97 OBS
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Freeway driving with 1000s would probably be no different than it is now if you are going with traffic. If you are doing a 'spirited' run and going all out, I suspect that you'll run out of breath in the high RPMs.

1000s are torque grind, especially in the low end. 2000s are getting into more power on the high end with more duration and overlap, your idle will likely be rough and CELs for misfire are common. 1500s are a compromise between those two aforementioned profiles (as delta put it) which also were effective on turbo'd applications. 3000s are race only, I know that there were a couple on RS25 that went that route. Storm is the guy I would ask if you want to know about them. Delta tells me they aren't street friendly at all.

I'd say the first 3 profiles are bolt on cams, they would be fine without a tune. 3000s I have no idea. But if you want the best out of your setup, a tune would be necessary.
 

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99 2.5RS
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86 Posts
what about a pulley set? I just picked one up for my car 40$ shipped with belts. should help the motor rev alittle easier. I run 91 in my RS just for piece of mind, considering we have some shitty ass gas here in AZ to begin with.
 

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'98 Impreza L 2.5swap
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Discussion Starter · #18 ·
Freeway driving with 1000s would probably be no different than it is now if you are going with traffic. If you are doing a 'spirited' run and going all out, I suspect that you'll run out of breath in the high RPMs.

1000s are torque grind, especially in the low end. 2000s are getting into more power on the high end with more duration and overlap, your idle will likely be rough and CELs for misfire are common. 1500s are a compromise between those two aforementioned profiles (as delta put it) which also were effective on turbo'd applications. 3000s are race only, I know that there were a couple on RS25 that went that route. Storm is the guy I would ask if you want to know about them. Delta tells me they aren't street friendly at all.

I'd say the first 3 profiles are bolt on cams, they would be fine without a tune. 3000s I have no idea. But if you want the best out of your setup, a tune would be necessary.
thanks for the info, i cant throw CEL'd cuz this needs to pass emissions every so often... im gonna contact delta and see what kind of numbers im looking at
 

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2002 WRB WRX
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420 Posts
In that case, you might wanna look into the 1500 grind. I had a set of Delta 1500s on my 05 RS and the car pulled noticeably harder from about 2500 RPM to 5000 RPM. I didn't get a CEL either and idle was pretty normal.

I had Delta 1500s + WRX catback + WRX intake funnel on my car before I sold it to a member here 7 months ago and since then, he's done UEL + HFC + Tune after which the car made 167 AWHP on a road dyno. (Delta 1500s + Catback + UEL + HFC + Intake + Tune =:hydrogen:)
 

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09 Forester
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656 Posts
In that case, you might wanna look into the 1500 grind. I had a set of Delta 1500s on my 05 RS and the car pulled noticeably harder from about 2500 RPM to 5000 RPM. I didn't get a CEL either and idle was pretty normal.

I had Delta 1500s + WRX catback + WRX intake funnel on my car before I sold it to a member here 7 months ago and since then, he's done UEL + HFC + Tune after which the car made 167 AWHP on a road dyno. (Delta 1500s + Catback + UEL + HFC + Intake + Tune =:hydrogen:)
thats impressive numbers.

on the octane note, i read somewhere that using a higher octane than the car is tuned for (so stock 87, but running 91/3) is actually worse for it due to the timing retardation of the stock map, causing burnt valves..if he is tuning it, then no big deal. but just to throw in higher octane without doing anything else is actually bad, correct me if im wrong. (excluding newer cars with stuff like flexfuel)
 
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