turning up the pressure
 

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.

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.

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.

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.

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.

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

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.

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.

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

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

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. :roll:

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.

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...

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.

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

Yep. STi + CAI + tuning = mo powa.

WRX + CAI + tuning = WRX + tuning.

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

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. ;)

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

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.

(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)

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.

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.

Aaaah, that makes sense.

if i just added some octane booster, that would at least cover the pre-detontation aspect, but i'de still run hotter then i'm suppost to. grrr. Car sounds soo much better with out going through the silcencer though. :( *Sniffle* now i'm going to comtemplate taking it out though ....

predontation should only be an issue at sea level right?

(So the K & N engineers ignored all that when desining an intake kit for a specific car (impreza) ? ) I rarely ever go to sea level, well i do go to sac on occasion... hmmf. would you be afriad this is going to kill the motor with in 100K miles ? or even be noticable ?

(thanks for the info again btw lot o smart guys on this forum )

This is not correct.

Fuel does provide the majority of the energy in combustion, that is why it is called fuel. Fuel is also not a catalyst as it is consumed in the reaction. Catalysts aid in a chemical reaction, but do not get changed as part of the reaction

Oxygen does not burn. If it did, lighting a match would cause the atmosphere to explode! Oxygen is an oxidizer, as is hydrogen peroxide, and most anything that ends in "ites", or "ates". Technically, oxidizers don't even have to have oxygen, just the ability to accept electrons. Halogens such as chlorine, bromine, etc are also oxidizing agents.

Combustion (the combining of fuel and oxidizer) produces energy in the form of heat, water(for oxygen based oxidizers), and byproducts (whatever is left of the fuel that did not combine with oxygen)

Under normal engine conditions, the flame initiated by the spark progresses across the chamber in a "controlled" fashion producing heat and pressure the later of which moves the piston. Detonation is "uncontrolled" combustion that is effectively multiple flame fronts crashing into each other at very high speed. That crashing is the sound you hear as a knock, or ping. The extreme heat and pressure associated with detonation can literally blow up your engine either over time, or possibly even all at once.

There is an optimal fuel/oxidizer mixture that produces the maximum energy without detonation. With modern combustion chambers and fuel, the optimal ratio is around 13:1, but most cars run around 14:1 which generates fewer emissions.

So if you add a little more air, you car may get closer to 13:1.

The problem is that if you go to far, (lean), detonation becomes more likely due to the increased heat and pressure.

There is a ton more we could talk about detonation, and A/F mixtures, but that is enough for now.

You're right Dean, fuel is not a catalyst. It is consumed. My statement is not totally accurate. Let me clarify:

On a turbo car the fuel isn't the primary power adder. The high density air mass created by by the forced induction is what allows a small displacement motor to make a lot of power, i.e. an "artificially" high compression ratio. Because of this, the ECU needs to supply an appropriate amount of fuel to match the dramatically varying amount of air that occurs at the boost level changes. In order to provide adequate cooling to combat the high temperatures of a forced induction motor, generally a rich AFR is used, as fuel is a cooling element in the cylinder. If you allow more air to enter the combustion cycle than the ECU thinks is entering (aka aftermarket intake), then you will approach a more stoich mixture and make more power at the expense of additional heat. If the heat is enough to cause knock, the ECU will have to retard the timing to prevent full-on detonation, and thus lower the actual power created by the motor.

IMO, it just a lot easier to think of the fuel as being a necessary "catalyst" for the changing amount of air entering the motor. In tuning a turbo car, you just want to cram as much air in as you can, then make sure there's enough fuel to burn it all and keep things cool to prevent detonation, all while keeping from exceeding the overall pressure that the motor can physically handle.

BTW Dean, if you think Oxygen doesn't burn, you should talk the 24 people that "pretended" to die in this fire:

http://msnbcmedia.msn.com/j/msnbc/Co...hmed_8a.h2.jpg
http://www.msnbc.msn.com/id/9449949/

Or ask Gus Grissom, Ed White, and Roger Chaffee that died on the Apollo 1 launch pad when a spark ignited their pure oxygen atmosphere.

http://history.nasa.gov/Apollo204/

thanks for the post. having the 02 burn instead of the fuel , did sound wrong to me. and it being a catalyst. too hot makes sense. and detonation (which is when the total pressure + heat is higher then Said limit of a given octane fuel) which is why we have to use 91 instead of 87 for a non turboed 8.7:1 ratio car .. ?? (think that's right but bonk me if not)

okay so by just doing a short ram air , Alone, the extra risk i have is additional heat ? how likely do you think that short ram air alone is , to kill my motor ? like would you bet me money? would you give me 100:1 odds that my motor never sees 100K miles becuase of this mod? (if so what's my bet max ? :P ) or is it just one of those things that technically is not optimal becuase of additional heat, and addtional chance for a detonation ?
like adding in 100 lbs of stereo gear is not optimal. and the 100 amp draw off your alternator, not optimal. just like my spelling :(

reading that its sub-optimal makes me want to go back. BUT the added noises literaly cuase me to smile daily, (and laugh on occasion) Plus my dad bought it for me for Xmass. (he didn't even know what he was buying me :P )

OH,
so it should then be possible to Keep the K&N and use some sort of tool to remap the ECU to use a bit More fuel then the ECU thinks it shold. (so the k & n fools the MAF sensor, but then you compensate for this by just telling the ecu to run a bit richer then the ECU 'thinks' it should) ;) then i get to hear the cool (stock ) subaru noises, but i also keep the engine cooler.
and i screw mother nature and my fuel economy goes down a bit more .
we are all happy ... except mother nature ... :P and people who hate the sounds of turbo and BOV noises.

(on my stock bov, don't see spending money just for a different sound, someone @ a car shop told me you can setup the stock bov to blow off to the atmosphere that a tangent though )

Thanks :)

don't suppose anyone rents the services of those tunner tools or do you have go and buy some fancy thing ? i won't know what to do with it , and i don't want to hurt the car. Don't suppose subaru would be happy and willing to just remap it for me ? not a chance oh , okay then ... :( lol

I don't know exactly how dangerous the K&N intake is. You could search nasioc.com and eventually get a bunch of guesses from people who consider themselves "gurus", but if I were you, I'd download Tari Datalogging Software, install it on my laptop, buy a cable if you can't borrow one from sombody who has an Accessport, and see how the car's actually doing. At least I think that's what I'd do.

Edit: Just saw the last paragraph you added. No, SOA will not tune your car for that intake. :lol:

A Protune and and AP package is like $750 for an STI I think.

Edit2: Here's a more precise link to download the software: ECU Explorer Download

Detonation isn't caused by pressure, pressure is caused by detonation. And high octane fuel is actually harder to burn than lower octane... that way you can run more advanced timing and higher boost before the fuel pre-ignites (burns out of control at it's own will rather than when the spark is fired).

At our altitude a short ram is a pretty low risk. However, I can almost guarentee you're also not making any power out of it... just noise. In fact, until you're running more mods and engine management, all an intake does is make noise, risk lean AFRs, and cause the ECU to retard the timing.

Remember this as well, at something like 6000 rpm, the knock sensors turn off since they can't hear knock over the frequency of the motor itself, so you can run lean and *not* retard the timing. Ask me how I know... :mad:

oooh oooh ooooh

how do you know ? :)

Anyone have the nice $750 acess port that may be willing to scan me ? :) lol and see how bad i'm breaking my engine ? :) alright ! lol oh i need to get gas so i don't need to fill up before going to a ski resort tomorrow. :)
ya i figured if my gas milage didn't go up very much, neither did my power. , they are not always related, but power increases from intake/ exhuast are suppost to boost gas milage also. uhm this says 12 hp and shows the hp a bit higher after 4K : http://www.kandn.com/dynocharts/69-8001.jpg honestly the only different i notice (besides the sound which i love) is that it does seem that its slightly easier to kick the back end out , on a specific spot of road , when i try it. could just be that my tires have less traction though, as that's really no guage.

I just really hate the stock subaru Silencer. i paid for a cool sounding turbo , i wanna hear it ! :D

but yeah, how the heck do you know ? :) due tell ! er do tell? gramar is not my strong suite :P

Cobb has designed the AP to "marry" to the ECU it's used on. In order for sombody to lend you an AP, they'd have to "unmarry" it from their ECU first. The problem with that is my unmarrying it, they have to reload the stock map on their ECU. Plus, you need a custom tune for that intake. Cobb's canned maps only support the stock intake.

So you have to buy your own.

The $750 package I was referring to is what I believe most NorCal tuners are charging for a couple hourse of cutom tuning and an AP as a package. Install some more mods first though. :)

Damnit, I need to start quoting you before you add to your posts. :P

You do know you can remove the intake silencer and run the stock intake right? It's night and day (sound, not performance). It won't be as loud as a short ram, but it's plenty turbo noise for me. :)

And you're nuts if you're skiing tomorrow. It's gonna storm.

Aaah. cuase other wise i'm spending 750 to tune 200 worth of mods. lmao . ;) sounds good. i really don't know what other mods i want to do . faster is better. it is my daily driver, and i do a insame amount of snow driving (in a good snow year) , mountain road blasting. lol i just don't want to end up with an esx car. lol like 40K into a car and slower then stock ....
Mods that don't kill off warentee or major parts of it, would be cool (and probably don't exist) as much as i hate to say/write this. i've only made 3 payments on my car, i should get used it a bit more and settle my butt down at times... hehehe . i think if i had 450 hp i'de be crashed by now :P lol
boot, i'm up for suggestions :) (wish i had more downfor for snow driving but that will look ugly , SPRINT CAR! LoL)

Yes, i'm nuts .

i was riding yesterday, i was riding on Olypmic char until they closed it due to wind hold. i was actually like the 3rd from the last to get off the chair when they closed it. and i wanted back on for more (I do have a beard) i should dig around i have a picture of me somewhere with ice and snow hella caked onto my beard. lol . but just learning how to go numb works better ;) snow is just awesome. driving on it, riding on it ;) it should snow every day :)

I agree man. I'm so excited about the coming storms, but I'm be happy to wait till Saturday when the weather clears up and the multiple feet of fresh powder are all mine! Haha!

ooooh science burn! That is like twice the normal burn.

I'll make sure to pack down all the powder for you torrmow Cody. you know so it doesn't blow away er something ;) or if all the chairs are on wind hold i'll just drive around :P its win win :D lol

Detonation is caused by the air fuel mixture spontaneously combusting due to temperature, pressure, and possible one or more ignition sources such as hot valve or other metal edge, hot exhaust particles still in the chamber, etc. But the ignition source is not required. That is how a diesel works without spark plugs. Continuious detonation.

And you can post all the pictures of burned buses you want, Oxygen is not combustable. Put a spark plug in a container of pure oxygen, and generate a spark, and nothing will happen. No explosion, no flame other than the spark itself. Same thing happens with a fuel. a container of pure hydrogen will not burn either.

Fuels combust in the presence of an oxidizer, and will not do so without them with very few exceptions. The only one I can think of off the top of my head is hydrazine which is really nasty stuff and is basically an extrmely unstable compound that is more or less self oxidizing. But from a chemical perspective, the majority of the energy comes from the breaking of the chemical bonds in the fuel, not the oxidizer.

So back to the original question. If your K&N filter has magically moved you from about 14:1 air fuel ratio to closer to 13:1 by causing the MAS to send an inacurate reading, then yes, you are making more power as long as you are not detonating, and the ECU is pulling timing to compensate.

Are you in jeopardy of hurting your car? Yes. To what degree, I don't know.

hmmf .. the tube the MAF sensor is in, is barely any bigger then the stock one. like i think its about 1/8 of an inch bigger diameter. but it makes sense, bigger diameter tube means that you have more air coming by at the same air speed . compared to stock. the MAF doesn't know. hmmf. what i need is a restrictor plate :P or i could glue / epoxy something into the tube. hell i could just cover the inside with a layer of epoxy / glue , let it dry. and then the inner diameter will be reduced . ;) (that will be a weird project)

Seriously, log your car. It's free. You can borrow my AP cable.

really Sweeet? awesome ;)
and oh duh. lol way better just to log it , then go guess if its running that lean. ;)
so i Just need the AP cable and that software to Read what my ecu has been up to?
and i need that $750 kit if i want to remap it ... ? :)

think i got it ! (maybe) :) thankx

Add a laptop, and yep, that's all you need to data log, which will tell you how everything is running.

Then you can decide what to do based on that. The $750 is for an AP and a couple hours of tuning by a professional. This custom ECU tuning is called a Protune by Cobb and is a fairly new addition to the AP's list of features.

I have a CrapTop ... but it sucks . guess i need to take a better one from work . hehehe ;) i'm on a P2 laptop (horrible) i should be able to borrow one with a P3 (cracked case but it works)
:) i have that software downloaded but figured it won't do a lot of good on my desktop. thanks for the help :)

That's right. But the *dangerous* pressures... i.e. the engine breaking pressures... come from the improperly timed combustion pressure. Basically, the piston's in the compression stroke, and the cylinder is too hot, allowing the compressed gasses to start to burn w/o spark. The combustion then occurs well before the piston reaches TDC, which means you've got a piston going up and an explosion going down... welcome to broken motor land. :(

Let me get this straight. You're saying oxygen "isn't combustable"? And you say you can't have combustion w/o an oxidizer? So which is it? Does the word "combust" only apply to the fuel in the reaction? The oxidizer is just along for the ride? 'Course, if I combust hyrogen and oxygen, I get water. If I then use electrolisis to split that water back up, hey look there's my hydrogen and oxygen... I guess I never really "burned" anything, did I? I better not apply the word "combustion" to anything!

And if you don't think hydrogen can burn by itself...

http://library.thinkquest.org/17940/...ages/hbomb.jpg

http://antwrp.gsfc.nasa.gov/apod/image/sun_skylab.gif

They call it fission and fusion... it's not "combustion", but it's certainly burning.

(Three things: Never get involved in a land war in Asia. Never go in against a Sicilian, when death is on the line. And don't waste your time trying to out symanticize sperry. :P)

Ew, pretty solar flare.

I apologize for attempting to use actual science in a discussion. Maybe it has to be in the Tech forum for it to have actual factual science in a post... Oh, wait, it is...

Heat <> combustion. Fusion <> combustion, Fission <> combustion...

When you bring your Mr. Fusion stale beer and banana peal powered Delorean to a meet, then we can talk about non combustion powered vehicles.

http://www.davetheguitarplayer.com/delorean.jpg

This thread has been very informative.