turning up the pressure

[justaddwater]

how much can i turn the boost up on a stock 04 wrx? also same question on an 06 sti? the sti has a turbo back and a cold air. the wrx is just a question of curiosity.

[Nick Koan]

depends on how you turn up the boost. Using a manual boost controller, I wouldn't do more then 1psi or 2 (actually, I wouldn't recomend an MBC at all, but thats a different story). Reflashes tend to up the boost ~4-6psi.

[sperry]

It's not really a matter of turning "up" the boost, as it's a matter of running more boost throughout the entire RPM range. At least if you're looking to make the car faster w/o blowing it up. A reflash is the ideal way to do that.

[cody]

Sounds like you're looking for cheap power. Unfortunately there's no such thing as cheap [reliable] power for either the WRX or the STI.

I always reccomend the Cobb Accessport. It's like $600 and you can just download generic maps off their website that will add power depending on your mods, but they aren't the greatest maps and you have to follow their mod path beyond stage 1 (reflash for a stock car).

However, most NorCal tuners will give you a custom tune and an Acessport for $700 ($50 more for an STI). The best bang for your buck [while not sacrificing dependability] is to install an uppipe and a turbo-back exhaust before getting tuned.

So for roughly $1,700, your pushing STI power. I have this setup on my WRX, and my boost is set at a max of 17-18 PSI.

Boost controllers are bad news for Subarus.

[justaddwater]

alright we did a cold air intake and a trubo back one the sti. much more power! this week our boost controller should be in. so we're going to allow three to six lbs of boost through gears.

[MattR]

Originally Posted by justaddwater

this week our boost controller should be in.

Enjoy ruining a great motor, you'll need this link in a few weeks...

[sperry]

Originally Posted by justaddwater

alright we did a cold air intake and a trubo back one the sti. much more power! this week our boost controller should be in. so we're going to allow three to six lbs of boost through gears.

Wow... you must not have bothered to read anything we posted.

More boost without more fuel will at the very least give you *less* power, because the car will pull timing trying to protect itself, and at the most it's just gonna blow itself up.

Get engine managment. A reflash (EcuTek or AccessPORT) is not only far cheaper than a new motor, it will also make the car far faster than it would be without it.

You're already risking the motor on that STI by running the CAI and exhaust w/o tuning... stay outta the throttle like that or you'll boost creep that thing into fuel-cut. And I wouldn't recommend taking it down to sea-level.

[cody]

Originally Posted by justaddwater

alright we did a cold air intake and a trubo back one the sti. much more power! this week our boost controller should be in. so we're going to allow three to six lbs of boost through gears.

Without tuning, any intake that gives you power does so by fooling the MAF with the impoproper diameter. If you are seeing power from an intake, it's definately at the expense of your engine. You're essentially fooling the ECU into running dangerously lean AFR's.

As I understand it, the main problem with boost controllers is that, at partial throttle, they increase boost without adding fuel...again, dangerously lean AFR's.

Some people are able to run boost controllers at the drag strip without having problems because they're only using full throttle, but it's never really safe.

[doubleurx]

Originally Posted by justaddwater

alright we did a cold air intake and a trubo back one the sti. much more power! this week our boost controller should be in. so we're going to allow three to six lbs of boost through gears.

Awesome! All you really need now is a 2.5 lb extinguisher mounted to the a-pillar. Yee Haw!

[qksubi]

Originally Posted by justaddwater

how much can i turn the boost up on a stock 04 wrx? also same question on an 06 sti? the sti has a turbo back and a cold air. the wrx is just a question of curiosity.

Just for fun and enjoyment since your not reading this anyway TURN IT UP ALL THE WAY!!! Let me know so I can watch

[justaddwater]

thanks for the smart ass comments, i'm sure they'll help. in all of the original posts no one cared to mention anything about an exhaust or intake affecting fuel ratios. so as it stands right now the sti has a cold air intake from aem and a turbo xs turbo back. when i posted more power, i did not base this on dyno numbers, just on compairing stock acceleration to current. the boost controller has not been installed, this is why i posted was to have a question about boost and engine managment answered.

so now i ask you to explain yourselves: HOW DOES AN INTAKE AND EXHAUST AFFECT ENGINE MANAGMENT TO THE POINT OF ENGINE FAILURE.

[sperry]

Originally Posted by justaddwater

thanks for the smart ass comments, i'm sure they'll help. in all of the original posts no one cared to mention anything about an exhaust or intake affecting fuel ratios. so as it stands right now the sti has a cold air intake from aem and a turbo xs turbo back. when i posted more power, i did not base this on dyno numbers, just on compairing stock acceleration to current. the boost controller has not been installed, this is why i posted was to have a question about boost and engine managment answered.

so now i ask you to explain yourselves: HOW DOES AN INTAKE AND EXHAUST AFFECT ENGINE MANAGMENT TO THE POINT OF ENGINE FAILURE.

You got smart ass comments because 3 people told you turning up the boost is a bad idea w/o going to full engine management, and in your next post you tell us the MBC is on the way.

And, you're clearly still not reading (or not understanding) the posted suggestions. Cody pretty clearly explained why a CAI will hurt the car. If you cram more air into the motor without the propper amount of fuel, you blow it up. At altitude you can fudge it a bit, since there's less air to begin with, but and CAI that "adds power" on a turbo Subaru is doing it by leaning out the mixture.

And on an STI, high flow exhausts cause boost creep because most STIs don't flow enough through the wastegate, which leads to overboosting and fuel-cut... which are again bad for the motor. Boost creep can be controlled to a point with tuning, but the real solution is a ported wastegate.

These are all topics that have been covered on this board, and on the larger boards (NASIOC and I-Club) ad nauseum.

And from experience (I ran a MBC in conjunction w/ a UniChip back in the day) manual boost controllers kinda suck. The stock boost solenoid does a great job smoothing out the power delivery... a MBC makes the car lurch all over the place, as the boost is not applied smoothly. Plus, MBC's drift their target boost with weather changes. In the winter, I had mine cranked all the way down, and would still overboost.

I get the impression you haven't done much research about available tuning options. Do you have a boost gauge and EGT sensor coming w/ that MBC? How are you going to know what the controller is set to? How are you going to know when the car is dangerously lean from a full-boost partial-throttle condition... do you even know what the FBPT problem is?

My advice is to un-bunch your panties and do some research. There's a buttload of info here and on the rest of the 'net regarding what works and what doesn't on Subaru motors. These things *are not* DSMs. What works on an Eclipse breaks a Subaru. Do some background research, then pick our brains with some pointed questions, we'll be happy to help, and we'll leave the smart-ass comments at home.

Otherwise, I've got a busted EJ20 short block I'll sell you... maybe between my broken motor and your broken motor, you can cobble a working engine together.

[Dean]

Short answer: I'll let others go into details if so inclined.

No intake on the market perfectly matches the flow characteristics of the stock pipe, so MAF readings can be significantly wrong, and cause the mixture to lean out and possibly destroy the engine.

On an STI especially, some exhaust changes can allow boost creep to occur causing excessive boost leading to engine failure.

Edit: Damn, Scott beat me to it...

[cody]

The most important thing is that you take the AEM intake off immediately. That intake is the devil.

[MattR]

Originally Posted by cody

The most important thing is that you take the AEM intake off immediately. That intake is the devil.

It's fine on the STi, just lame on a WRX.

[sperry]

Originally Posted by MattR

It's fine on the STi, just lame on a WRX.

No, with tuning a CAI will make power on an STI, but not on a WRX. Without tuning it's bad for both cars.

[Kevin M]

Yep. STi + CAI + tuning = mo powa.

WRX + CAI + tuning = WRX + tuning.

[doubleurx]

Originally Posted by BAN SUVS

Yep. STi + CAI + tuning = mo powa.

WRX + CAI + tuning = WRX + tuning.

and.........STI+CAI+MBC-TUNING = BOOM

[dknv]

Sometimes the smartass comments are a quick way to get someone's attention.

Part of the reason why they were posted that way too, is because no one here who's done power mods wants to see a fellow enthusiast blow up his motor. We are trying to keep you from hurting yourself, tough love.

[MikeK]

A thread from nasioc saying basically the same thing about intakes and mbcs. This is on a WRX:

http://forums.nasioc.com/forums/showthread.php?t=884119

[justaddwater]

thank you. thats what i wanted. this is the first time i've had real experience with a computer controlled engine, before this i have only dealt with carbed big blocks, so excuse my inabilaty to always catch the point.
the sti belongs to my boss, so when i ask about an sti i'm just trying to get some info to relay. i don't like spending lots of time in front of a computer, i'd rather be working.
thanks again, and how much do you want for the EJ20 and how busted is it?

[sperry]

Originally Posted by justaddwater

thank you. thats what i wanted. this is the first time i've had real experience with a computer controlled engine, before this i have only dealt with carbed big blocks, so excuse my inabilaty to always catch the point.
the sti belongs to my boss, so when i ask about an sti i'm just trying to get some info to relay. i don't like spending lots of time in front of a computer, i'd rather be working.
thanks again, and how much do you want for the EJ20 and how busted is it?

The EJ20 has rod knock caused by detonation in cylinder #3 (according to the shop that pulled it out of the car).

I'll have to try to figure out what it's worth, I've got no clue what it'll take to repair... probably just a new set of bearings, plus all the labor to do the swap, and of course whatever 1 time use parts need to be replaced when fixing a crank bearing... I've kept my hands out of motor internals, so I don't know the details.

[A1337STI]

(again an old thread but it raised a question for me)

i have an air intake kit. (K&N short ram air like on my sig) . and yes the MAF sensor is now on a K&N tube which is slightly larger then then the stock tubing. (i also reset the cpu of the car by disconnecting the battery during the install) .
Now if the air intake kit allows more air , but it 'tricks' the MAF sensor into thikning that slightly less air is going by, then ecu then uses slightly less fuel then it really should,
now i'm no rocket scientists but i took some chem and physics. if you fool the ecu into using less fuel then it should, (known as running lean) all the fuel burns, and there is left over O2 . If this is the same amount of fuel that is burned before, and 1 piston firing should produce (picking a number for examples) 100 nuetons of force.
the new configuration should also produce 100 nuetons of force, IF the same amount of fuel gets burned.
If less fuel gets burned , it should produce < 100 nuetons of force. OKay it clear to see why that would produce LESS power. how on earth is producing LESS power going to cuase harm, (or addtional wear and tear ) on the engine?

i could see an increased risk of engine knock if the pressure in the cylinder was increased from the previous pressure (more air molecures, under the same compression ratio = more pressure, once compressed) and if that pressure exceded the limit for your air Temp + octane combo, you get engine knock. is it really let THAT much more air in? (and its na until you are in the turbo) once i'm into the turbo boost i'm limited in how much air it can Stuff into the engine by the max air flow rate of that turbo, minus air resitance of the entire air-intake flow.

did subaru dial that exact post turbo air flow rate in so closely that any increase (cuased by reducing resitance) will cuase it to over boost and destroy?

i've actually increased my gas milage since i put the kit on. which tells me the car is producing more power, per gallon of gas, then before. (as the resistance for distance traveled hasn't changed any)

??? either i'm missing something, or an air intake kit really won't cuase damage to your motor. if the air intake kit fools your MAF sensor too much, it should decrease your gas milage. ?? no ?
something must be wrong with my logic here, or i'm ignorant to some Key fact that ties it all together.
please help me out thanks

on my WRX changing from the paper filter to a K&N replacement filter raise me 3.5 mpg (no ski rack) (i record all milage and all Fuel ups changes to tires, ski rack on / off, etc) my STI has the short ram air, and i only am doing 1 mpg better. (ski rack on) the % changes are a lil closer. the wrx went from 20 to 23.5 my STI went from 17.8 to 18.8 . the wrx paper filter was dirty at the time of upgrade (that's sure to skew results)

[Nick Koan]

Your main assumption is that it is fuel that burns, but in reality it is the air and fuel mixture that burns. Fuel helps ignite and regulate the burn, and more air actually makes more power but its also more uncontrollable and can cause detonation of the mixture too early in the cycle.

[sperry]

Fuel does not provide the power in a combustion engine, oxygen does. The fuel is just a catalyst to make the oxygen burn more easily. Fuel also has a cooling effect. A car that runs rich, runs cooler, at the expense of mileage of course.

That's why if you up the air into the car while leaving the fuel the same, you are actually making more power, but it's at a higher temperature making the car suseptable to pre-ignition (aka knocking/pinging/detonation/bad things).

Most turbo cars are tuned to run a little rich simply to combat detonation... by changing the intake w/o tuning for it, you get closer to stoich (when all the fuel and all the air are burned in the combustion reaction) which is "ideal" for mileage purposes, but is actually a little too hot. If the car starts knocking, then the ECU retards the timing to prevent detonation, which is why you ultimately make less power than you would with the stock intake.