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Old 04-02-2002, 10:15 PM   #1
poowrx
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Default sorry, intake questions...

so my friend bought the aem cold-air in blue. it looks awesome, sounds beautiful, and his car seems much more responsive than before.
it looked so cool, that now i kinda want one. im not a racer, but i just want one for fun. the sound was sweet and it looks sooo good. the extra pick-up aint bad either.

however i did a search and it seems that the lines are split 50/50 with the intakes. i tried to make sense of it, but i guess its too complicated for me.
now i know that with just his intake, his car feels noticeably better than mine.
i can totally tell that the turbo spools up much faster than normal, and the hum of the engine is more muscular.
but people have been suggesting that intakes dont do anything, and in-fact they could be bad for the engine.

with just an intake alone would i run the risk of hurting my engine? people say that it makes the engine run a little leaner, how bad is "a little leaner"?
is there a way to counter that? where and how much?

do some people here have the aem? what do you guys think? have you had any problems?

ty
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Old 04-02-2002, 10:52 PM   #2
WRX n Efct
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I have a silver AEM cold air intake on mine and I too feel an improvement on the performance. 9500 miles and still no CEL. I like it and the way it sounds. I have no down sides to report.
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Old 04-02-2002, 11:20 PM   #3
local420
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Intakes will make a big difference...

Here is the formula for speed and horsepower

You are limited by how much air you can breathe, how much you can exhaust and gas you can burn...

Any improvements you make along the way will help your overall power and speed/performance.

This is why an intake will help. I wouldn't go out and buy one based on a hp gain... but it will be a side effect.

Will it harm your car? Not sure who told you that... but it is false unless you over do it and try to make Too much air available. Typically this occures on Carborated cars when people go from a small 2 barrel carb to a mammoth Holly double pumper with out making any other improvements.
In our cars the ECU handles the gas air fuel mixture to keep an excess amount of air from causing an overly lean mixture...

Josh
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Old 04-02-2002, 11:22 PM   #4
Concillian
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It will make your engine run leaner.

The fact is this is exactly how it gets most of its power.

The way to counter this is to make your car more able to handle leaner conditions (higher Exhaust Gas Temperatures...EGTs)

The single best way to lower EGTs is to replace the up-pipe with one that has no cat in it. This will reduce the localized backpressure that causes more exhaust to remain in the cylinder as well as keeping gas velocity up to help turbo spool and help your ability to hold boost better towards redline.

An inexpensive purchase that is a total pain to install.

Probably the leaner condition in open loop mode is tolerable for the car, as long as you're not open tracking it. The danger arises when you combine it with other mods, especially with things like Unichips that have maps based on the air sensor and the stock airbox. Since the intake essentially mis-calibrates the air sensor, you can end up in a more dangerously lean condition (since the program would be leaning it as much as it considers safe, yet the inake leans it further)

I think the consensus in the FFI forum is that if you're doing OTHER forms of fuel tuning, then the intake is near the bottom of the list of things to get you power. IF you're not and just doing MINOR bolt ons then the intake can give you a nice pop in performance. Most people choose to skip the intake to start with, and get some form of fuel tuning, with 90% of the benefit as otherwise stock, and with more peace of mind when adding more mods.
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Old 04-02-2002, 11:29 PM   #5
Concillian
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Quote:
Originally posted by local420

Will it harm your car? Not sure who told you that... but it is false unless you over do it and try to make Too much air available.
It's an issue with the design of the air sensor. Apparently it's placed in a location where the air is densest to get the most accurate reading. Aftermarket intakes will change the fluid dynamics such that the engine thinks less air is entering the engine than there really is. The result? More air for the same amount of fuel...or leaner running condition.

Since the WRX design already pulls in ambient air, the only additional gain over the leaner condition is the lesser pressure drop. While a good thing, the unknown fueling issue is somewhat sketchy, especially when adding other mods.

Note that shiv has made public that he highly recommends using the stock airbox design on the WRX. Silencer removal and K&N panel filter were said to dyno at LESS HP than stock, though he never posted the plots to my knowledge. This after he DID use the silencer removal and panel filter design on the turbo RS, so if he thought it would be better, I'm sure he would ahve done it.
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Old 04-03-2002, 11:11 AM   #6
BlueWRXWagon
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I have heard that running a intake will create a leaner condition but that a BOV will create a running rich condition. So if you run both would the engine then be running normally? This is just what I heard in the FFI forum.
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Old 04-03-2002, 11:41 AM   #7
Concillian
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BOV won't do anythign to the way your engine runs EXCEPT when you shift.

When you shift, it vents out air.
That air has been metered/counted by the air sensor, so if it vents it to atmosphere, the car will think there's air in the system that isn't there (you vented it just to get your ricey sound).

Now the engine is going to try to put in enough fuel for the air that's there, so it dumps in a bunch of fuel, but, hey, there's no air, because you PHHHst-ed it out.

Now the engine will stumble, perhaps backfire, and generally have worse performance when you shift.

The result? A recirculating blow off valve (like the stock one) will provide better performance unless you have an aftermarket ECU that can handle the conditions you're creating with a BOV that will vent to atmosphere.

Anyway people in the FFI forum have reported that when they removed their noisemakers (Vent to atmosphere BOVs) and replaced them with the stock BOV, they had better 1/4 times because of the increased boost response after a shift.
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Old 04-03-2002, 11:47 AM   #8
local420
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Quote:
Originally posted by Concillian

Now the engine will stumble, perhaps backfire, and generally have worse performance when you shift.

Never had any of this happen! At maximum... I get a funky bounce in my idle and thats it...

Josh
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Old 04-03-2002, 02:25 PM   #9
KAuss
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A lot of people say the same thing about the CAI...

But what I wanna know is, how bad/good is it if you just put an intake in your car and no other mods?

And I heard that if you mess with fuel tunning, there is a given that you'll shorten the life of the car. Obviously if done right, the results vary and might be arguable depending on the dirving habits of some.

But which mod makes your car's life shorting per say, without adding anything else on there??

actually make this a 3 part question.

Intake only

Fuel controller only

both....

Would a cat back system have anything to do with this issue also?

I'm such a newibe..

Ka Man
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Old 04-03-2002, 02:54 PM   #10
Concillian
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Quote:
Originally posted by local420


Never had any of this happen! At maximum... I get a funky bounce in my idle and thats it...

Josh
Sorry, I was feeling overdramatic this morning. Most won't feel the issues as severe as that. You'll run rich, which can manifest itself in many ways. Generally a loss in performance over the stock BOV if these 1/4 mile guys are posting correct times.


As far as the CAI by itself goes, it should be cool, obviously you'll run leaner, which could cause EGT and/or CEL issues, but in all likelihood wont.

And if you don't get other fuel tuning, there is margin to lean out the mixture, and this is a way to do it.

As far as where the benefit of the CAI would be felt, I'd guess all the way across the powerband. Leaner = more power...as long as you don't end up running TOO lean, because running TOO lean = no power. There's a long way to go on the WRX before you run too lean, but replacing the up-pipe is good insurance if you don't get an EGT gauge.

Last edited by Concillian; 04-03-2002 at 02:59 PM.
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Old 04-03-2002, 03:16 PM   #11
Concillian
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Quote:
Originally posted by KAuss
Would a cat back system have anything to do with this issue also?
Frankly, I don't know enough to properly answer that question, but I think exhaust components shouldn't cause a significant issue. I know that shiv doesn't change the Unichip map for Stage 0 + catback.

I do know about how power curves change with mods like this though

Catback tends to affect a relatively narow region of the powerband, more specifically up top. Even more specifically full boost at the top end. Note that this probably doesn't include redline, as the boost will taper as the turbo runs out of breath, and/or the ECU drops boost (which it's programmed to do at about 5000-5500 RPM to redline)

Again referring to shivs work, he showed dyno plots of Stage 0 and Stage 0 + catback. The + catback gave in the neighborhood of +7 HP or so. As mentioned, this was in a relatively narrow range, somewhere around 4500-6000 RPM or so, elsewhere there wasn't a ton of difference.

You can find the chart I'm talking about, just search for 'brospeed' with 'shiv' as a user name. The plots will be in the thread that comes up.

Anyway, for turbo cars, exhaust mods far from the turbo are much less gain than nearer the turbo, this is because the turbo is where most of the power is coming from, and things are generally quite restrictive in factory exhausts.

For the same price as most catbacks, you can get an up-pipe + installation, and see gains throughout the power band. Similar in peak HP, around 7-10 HP or so, but you'll have added benefit of power in the midrange, throttle response for daily driving, faster spool, lower EGTs (better for engine longevity/reliability), and getting rid of that cat that can crumble into the turbo.

The downpipe also poses a significant restriction, and can give gains equal to or greater than an up-pipe (though it costs more, but is much easier to install)

Anyway, that's my take, and preferred path, mostly because I don't WANT a loud exhaust...most of the time anyway...after hearing the BPM TT at WOT screaming away from me, I can think of time that would be a good sound But usually I prefer not to attract attention.
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