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Old 10-07-2010, 10:51 PM   #1
JJ21
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Question Getting the most out of an N/A engine?

Alright, so i'm just looking at options on increasing the performance/power output of my '07 impreza. I'm relatively new to this, so any help would be appreciated. Also, I'm sorry if there are already stickies on this topic.


I'm trying to stick more with add ons/swap outs instead of replacing/modifying parts of the engine like the piston heads etc.


Obvious things that come to my mind...

Tune

CAI/SRI(although there have been reported problems with them messing up the fuel/air mixture. Not sure how though. Might just leave it out.)

Exhaust(but what? Again, I'm pretty new to this.)

Suspension(not engine related, but help improve handling. But again, what exactly?)



Anything I am missing? Just thought I'd get some of your opinions/recommendations! You are all such a big help!
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Old 10-07-2010, 11:13 PM   #2
nairbmik
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Honestly, search. There have been tons of threads that ask this same thing, and they all have great information in them.
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Old 10-07-2010, 11:26 PM   #3
PhatBotti Tuning TKR
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JJ21,

You heard right about the CAI, however..

I drove from CT to FL to tune some cars and I did quite a few N/A's. Down in FL, I tune a kid who happened to put a 3" maf diameter'ed intake on his car. The air/fuels were in the 17's for most of the pulls until they dipped 15.0 at redline. Now, if you know anything about N/A tuning, that is absolutely horrible for a car.

Tuning solves this, as the maf scaling can be moddified as well as target fueling with a larger intake. A few ponies can definitely be had here.

From what I have seen tuning in the N/A world:

-headers (no cat)
-CAI
-cat deletes
-tune

All should be done together for the biggest difference in feeling and performance.

If you willing to get into the motor, delta cams make these cars shine. I had an 08 N/A with cams that It tuned that would run neck and neck with stock 2.5l wrx's.

If E85 is available, high compression pistons, delta cams, and the mods above will give you a REALLY peppy car.

-Mikey
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Old 10-07-2010, 11:40 PM   #4
JJ21
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Quote:
Originally Posted by PhatBotti Tuning TKR View Post
JJ21,

You heard right about the CAI, however..

I drove from CT to FL to tune some cars and I did quite a few N/A's. Down in FL, I tune a kid who happened to put a 3" maf diameter'ed intake on his car. The air/fuels were in the 17's for most of the pulls until they dipped 15.0 at redline. Now, if you know anything about N/A tuning, that is absolutely horrible for a car.

Tuning solves this, as the maf scaling can be moddified as well as target fueling with a larger intake. A few ponies can definitely be had here.

From what I have seen tuning in the N/A world:

-headers (no cat)
-CAI
-cat deletes
-tune

All should be done together for the biggest difference in feeling and performance.

If you willing to get into the motor, delta cams make these cars shine. I had an 08 N/A with cams that It tuned that would run neck and neck with stock 2.5l wrx's.

If E85 is available, high compression pistons, delta cams, and the mods above will give you a REALLY peppy car.

-Mikey
Cool stuff.

Any recommendations in the way of
-headers (no cat)(what are these)
-cat deletes(what are these/this)


Also, what is involved with switching the cams?


Not sure how I feel about switching the pistons. I guess that might be a future project. There's a family friend that has a car garage with the means to lift the engine(if that is needed).
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Old 10-10-2010, 12:56 AM   #5
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Quote:
Originally Posted by PhatBotti Tuning TKR View Post
JJ21,

You heard right about the CAI, however..

I drove from CT to FL to tune some cars and I did quite a few N/A's. Down in FL, I tune a kid who happened to put a 3" maf diameter'ed intake on his car. The air/fuels were in the 17's for most of the pulls until they dipped 15.0 at redline. Now, if you know anything about N/A tuning, that is absolutely horrible for a car.

Tuning solves this, as the maf scaling can be moddified as well as target fueling with a larger intake. A few ponies can definitely be had here.
Keep in mind that MAF Scaling does NOT fix the resonance that causes the extreme rich condition on the low end when you use a CAI/SRI with a MAF-based car. So it's not like MAF scaling suddenly makes the intake perfect.
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Old 10-10-2010, 01:10 AM   #6
PhatBotti Tuning TKR
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Quote:
Originally Posted by williaty View Post
Keep in mind that MAF Scaling does NOT fix the resonance that causes the extreme rich condition on the low end when you use a CAI/SRI with a MAF-based car. So it's not like MAF scaling suddenly makes the intake perfect.

uhhh, what? I never see any rich conditions with the 3" intakes. All I see is cars so lean they want to turn off
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Old 10-10-2010, 01:11 AM   #7
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Quote:
Originally Posted by PhatBotti Tuning TKR View Post
uhhh, what? I never see any rich conditions with the 3" intakes. All I see is cars so lean they want to turn off
Read the stickied thread on the major problem with CAI/SRIs and the MAF-based Subarus. If you're not aware of that problem already, it's kinda scary that you've been tuning cars for money.
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Old 10-10-2010, 01:25 AM   #8
PhatBotti Tuning TKR
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Quote:
Originally Posted by williaty View Post
Read the stickied thread on the major problem with CAI/SRIs and the MAF-based Subarus. If you're not aware of that problem already, it's kinda scary that you've been tuning cars for money.

With all due respect, I've read your sticky.

I commented on a 3" maf housing. While you speak of a rich condition down low, I was pertaining to when the car owner does a pull on the stock map and hits high 14's low 15afr at redline pulling 5 degrees of timing with the IAM already knocked down.

Isnt that a bit concerning as well?

Last edited by PhatBotti Tuning TKR; 10-10-2010 at 02:23 AM.
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Old 10-10-2010, 09:12 AM   #9
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To the op, your best bet for now is to carry speed through corners. Tires and suspension is where you will get bang for your buck. Engine mods on our cars really won't give you much in terms of power. Cost benefit just doesn't make sense.


What exactly do you plan to do with the car?
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Old 10-10-2010, 12:10 PM   #10
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Quote:
Originally Posted by PhatBotti Tuning TKR View Post
With all due respect, I've read your sticky.

I commented on a 3" maf housing. While you speak of a rich condition down low, I was pertaining to when the car owner does a pull on the stock map and hits high 14's low 15afr at redline pulling 5 degrees of timing with the IAM already knocked down.

Isnt that a bit concerning as well?
Oh, definitely, but you made it seem as though running lean on top were the only thing going wrong.
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Old 10-10-2010, 01:49 PM   #11
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Quote:
Originally Posted by PhatBotti Tuning TKR View Post
JJ21,

You heard right about the CAI, however..

-Mikey
this subject has been beat to death and had cinder blocks strapped to it and thrown into the hudeon river. Why would you want to run a SRI or non OEM CAI....? Why? A hybrid intake with WRX trumpet is far superior. Flows just as good. IAT are excellent, and its very cop friendly....in other words you don't sound like a honda stop praising the CAI. You should know better!
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Old 10-10-2010, 02:00 PM   #12
PhatBotti Tuning TKR
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Quote:
Originally Posted by Subyroo2.5 View Post
this subject has been beat to death and had cinder blocks strapped to it and thrown into the hudeon river. Why would you want to run a SRI or non OEM CAI....? Why? A hybrid intake with WRX trumpet is far superior. Flows just as good. IAT are excellent, and its very cop friendly....in other words you don't sound like a honda stop praising the CAI. You should know better!

Suby,

No praise here, if it was up to me I would simply do a drop in filter. I believe in the stock airbox.

I tuned a car last sunday that that made 356whp with the stock box, maf was just shy of being maxed.

-Mikey
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Old 10-10-2010, 03:33 PM   #13
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Quote:
Originally Posted by PhatBotti Tuning TKR View Post
JJ21,


From what I have seen tuning in the N/A world:

-headers (no cat)
-CAI
-cat deletes
-tune

All should be done together for the biggest difference in feeling and performance.

If you willing to get into the motor, delta cams make these cars shine. I had an 08 N/A with cams that It tuned that would run neck and neck with stock 2.5l wrx's.

If E85 is available, high compression pistons, delta cams, and the mods above will give you a REALLY peppy car.

-Mikey
Quote:
Originally Posted by PhatBotti Tuning TKR View Post
Suby,

No praise here, if it was up to me I would simply do a drop in filter. I believe in the stock airbox.

I tuned a car last sunday that that made 356whp with the stock box, maf was just shy of being maxed.

-Mikey
Recommending is the same as praise.
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Old 10-10-2010, 05:44 PM   #14
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^^^ to be fair... he merely commented on the fact that headers, CAI, cat deletes, and a tune should all be done at the same time.

He never said that he recommends doing any / all of them.
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Old 10-10-2010, 05:57 PM   #15
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Quote:
Originally Posted by royalnewjersey View Post
^^^ to be fair... he merely commented on the fact that headers, CAI, cat deletes, and a tune should all be done at the same time.

He never said that he recommends doing any / all of them.

If that is the case why did he reply at all?
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Old 10-10-2010, 06:17 PM   #16
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Originally Posted by Subyroo2.5 View Post
If that is the case why did he reply at all?
Agreed.


I wouldn't run CAI with a 2.5i. Headerback, Air filter, Stock air Box, Tune, Done.

Then put your money into suspension.
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Old 10-10-2010, 06:47 PM   #17
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Trade for wrx...... lol
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Old 10-10-2010, 09:31 PM   #18
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Honestly, the equal length stock exhaust manifolds on the 07 2.5i are pretty efficient. Many people go to unequal length headers to get more boxer rumble, but you don't really gain any performance with that selection.

If you want some gains without a lot of trouble, start with a hybrid intake and a 2.25" cat-back with a high flow muffler like Magnaflow or something similar. You can get a tune later for more gain.
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Old 10-10-2010, 10:07 PM   #19
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you really shouldn't do any intake mods, even a hybrid, without at least rescaling the MAFv table. a muffler will do zero for performance... its a sound only mod. the factory headers are not actually EL on any n/a impreza, although the 06+ headers are pretty good.
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Old 10-10-2010, 10:07 PM   #20
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Quote:
Originally Posted by RaineMan View Post
Honestly, the equal length stock exhaust
Have you measured the pipe lengths? There's something like 1.5" difference between the runs. That's not EL in anything other than a marketing brochure.
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Old 10-10-2010, 10:13 PM   #21
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Trade for wrx...... lol
Typical response.
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Old 10-11-2010, 06:09 AM   #22
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Old 10-11-2010, 10:40 AM   #23
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stromung catback exhaust.

suspension- strut bar(s), swaybar(s), end links, anti-lift kit, lateral links and steering rack bushings if u really want, and coilovers. i would look at cusco, whiteline, tein, ksport, kartboy. if u have any questions on specific parts, just post.
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Old 10-11-2010, 11:11 AM   #24
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Quote:
Originally Posted by williaty View Post
Have you measured the pipe lengths? There's something like 1.5" difference between the runs. That's not EL in anything other than a marketing brochure.
They are more "equal" than the UEL headers that people buy. It's a relative term.
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Old 10-11-2010, 12:37 PM   #25
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Quote:
Originally Posted by RaineMan View Post
They are more "equal" than the UEL headers that people buy. It's a relative term.
Your engine doesn't think so. The phasing either is right or wrong.
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