boost level?
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This is a discussion on boost level? within the Comparison: WRX vs World forums, part of the Community - Meet other Enthusiasts category; hey, im gonna be getting an 02 wrx pretty soon here (couple months) and was wondering about a few things. ...

  1. #1
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    Question boost level?

    hey, im gonna be getting an 02 wrx pretty soon here (couple months) and was wondering about a few things. first of all the rex runs what 13.5psi stock? what does the stock turbo max out at? 18? the main thing i was wondering is if you'll have air/fuel ratio problems running 17/18psi on the stock fuel system. like when its cold would it tend to lean out w/ that much boost...especially if youre running it over 100? im just wondering b/c ive seen quite a few problems as far as high boost levels go and didnt want to run into w/ the subie. my brother used to have an 01' lightning and was running 17psi (maxed on the eaton blower) and blew one of his heads due to a lean ratio. granted he was going about 115 or so and was in the cold. i was just curious to see how the wrx holds up w/ stock parts. thanx.

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    Registered User soon2BWRXd's Avatar
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    my brother used to have an 01' lightning and was running 17psi (maxed on the eaton blower) and blew one of his heads due to a lean ratio. granted he was going about 115 or so and was in the cold.
    HOLY $hit!!!!!!! Your brother didn't blow the head cause he leaned it out, he blew the head cause he was over boosting!!! A SC is unlike a turbo you don't want to throw as much boost as possible at it, and SC works best with other supoorting mods, because if an SC produces 17 PSI of boost at 6K rpm it will change less than 1PSI from 2000K rpms upward. My freinds GTP makes 11 PSI at 5800 rpm, but at 2000RPM he has 10PSI, a SC has NO spool up time, so you don't build boost, you have boost on demand!

    The WRX, IIRC comes with 12 or 12.5 PSI, and is safe up to 16 PSI most people here have MBCs set at 15.5 PSI. If you are worried about running more boost, the best bet would be to get a new Turbo that can handle higher boost amount....however who knows if the trans or the engine will be able to handle increased boost amounts?

    OH BTW NICE KILL!!!!!

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    yeah, his cylinder head did lean out from high boost b/c it wasnt getting enough fuel for all the air that was coming in. it may not have been 17psi now that i think about it but it was up there. he had a 3 lb upper pulley and a lower pulley too. so maybe it was around 14/15...who knows. plus those stock eatons arent very efficient pumping out that much boost supposedly the truck was only meant for bursts of accerlation up to 100, like 1/4 miles sprints...past that who knows what could happen. at least thats what the lightning board said. back to the rex.... i know that getting a bigger turbo would make a lot more power and be more efficient w/ lower boost levels but the same question comes up. what about engine knocking, lean ratio etc.? from what ive read on this board the past few months it appears that the stock trannie isnt very stout (mainly the clutch) and that the Sti is more well suited for big hp. plus i dont know how well the rods and pistons could handle 300+hp on a daily basis, especially on a 2.0l 4 banger oh and btw it was a double kill for my bro...he was racing an 01' cobra (which he totally obliterated by several cars) but in the end he got killed too unfortunately

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    Re: boost level?

    Originally posted by torqueterror
    my brother used to have an 01' lightning and was running 17psi (maxed on the eaton blower) and blew one of his heads due to a lean ratio.
    its not cuz of the cold or going lean. its a ford. the 5.4sc and 4.6 sc are having problems with the heads. they either blow the heads off or blow the spark plugs out of the motor.

    woohoo!! blue oval engineering
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    Registered User soon2BWRXd's Avatar
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    its not cuz of the cold or going lean. its a ford. the 5.4sc and 4.6 sc are having problems with the heads. they either blow the heads off or blow the spark plugs out of the motor.
    Actually it isn't a poor design, it's owners who don't realize what happens when you add a smaller SC pulley without doing a full exhaust...including headers, and a full exhaust of larger diameter....put it this way, it would be like someone taking a WRX and turning the boost up to 22PSI and wondering why they destroyed something.
    Stock or something close to it.....

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    its a ford. the 5.4sc and 4.6 sc are having problems with the heads. they either blow the heads off or blow the spark plugs out of the motor.
    yeah, ok...that wasnt at all ignorant . yes, the OLD 5.4 sc motor wasnt bulletproof...but this problem could have been easily solved if it had iridium spark plugs in it and/or a programmable chip. you dont hardly see any problems w/ the new 03' cobras motor...forged pistons, iron block, eagle rods. thats right, BLUE OVAL ENGINEERING!

    it's owners who don't realize what happens when you add a smaller SC pulley without doing a full exhaust...including headers, and a full exhaust of larger diameter
    i see where yer coming from w/ the wrx scenario but w/ sc's its not AS crucial. they dont run off the exhaust fumes like the turbo cars do and anyways, my bro's lightning had a full bassani exhaust

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    Originally posted by torqueterror
    i see where yer coming from w/ the wrx scenario but w/ sc's its not AS crucial. they dont run off the exhaust fumes like the turbo cars do and anyways, my bro's lightning had a full bassani exhaust
    i think its just as crucial. if you're not getting the exhaust out of there the efficiency of your blower decreases and then since we got a supercharger instead of a turbo, myself included ( gtp ), we have to take even more hp to make our overall hp.

    i dont think my comment was ignorant, lol. just poking fun. without a doubt i'd buy a lightning or cobra if i had the money. i think a few more things could have been done to them that would have taken care of a few problems. as far as i know the cobra's do not have a knock sensor, just a mildly tuned computer to keep it from detonating when somebody decides to floor it in 5th uphill. apparently this hasn't proved to be a problem like i thought it would yet. we shall see...
    1998 Grand Prix GTP
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    Well, the only and closest experience I have is through a friend who had a SC on his late 90's Cobra. Blew the engine somewhere around 30K, and I assure you that he ran that car conservatively.

    As far as the WRX. Stock boost is always the "safest." I run the TXS Stage 4+ 18-19 psi. Car runs like a charm. Though I only have 23k on the car, many people have been running the same set up for 50K, perhaps even longer? I think that much of it has to do with how you drive and maintain the car. But do not be fooled, no way is it going to last as long as if it was stock.

    BTW, this might be the wrong forum for you question.
    Last edited by MrSwede; 12-16-2003 at 06:53 AM.

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    Registered User soon2BWRXd's Avatar
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    i see where yer coming from w/ the wrx scenario but w/ sc's its not AS crucial. they dont run off the exhaust fumes like the turbo cars do and anyways, my bro's lightning had a full bassani exhaust
    Actually it is MORE important, because if you don't have ALOT of exhaust mods, then you run the risk of boost stacking...that is where the SC continues to produce boost, but the engine is unable to releave all the pressure from the previous compression stroke. so you continue to add compressed air to previously compressed air. And by full exhaust I mean headers with larger than stock primary tubes, to effectivley move the exhaust gases out the rest of the exhaust. Also unlike a Turbo car, SC cars don't have BOVS so there is no way to releave the pressure if you over boost.

    My freind with a GTP was having a problem with his cat, and was having SERIOUS boost stacking, he was seeing 20+ PSI of boost, turns out that the screens from the cat had clogged the cat outlet, and was blocking exhaust flow. It ended up cracking his rear head gasket due to the pressure.

    And yeah this is the wrong forum....oh well
    Stock or something close to it.....

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    i dont think my comment was ignorant, lol. just poking fun.
    i'll admit it that im a paranoid blue oval enthusiast, i guess it probly came from posting on ls1.com all the time. all those ford haters

    I run the TXS Stage 4+ 18-19 psi. Car runs like a charm.
    thats pretty cool that your rex is running good w/ that much boost, but i would like to see how it is 30k miles down the road. what kind of turbo does the TXS stage 4 run? from what ive collected it seems like the internals run pretty good w/ 16psi or so but the clutch is the main problem w/ wear and tear. thats a lot more easily replaceable then a blown head

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    Registered User MrSwede's Avatar
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    Originally posted by torqueterror



    thats pretty cool that your rex is running good w/ that much boost, but i would like to see how it is 30k miles down the road. what kind of turbo does the TXS stage 4 run? from what ive collected it seems like the internals run pretty good w/ 16psi or so but the clutch is the main problem w/ wear and tear. thats a lot more easily replaceable then a blown head
    Like I said, many people have running the stage IV for 50K without problems. The stage IV comes with a VF30 and is mapped for 18psi. My clutch is still working fine after many hard launches.

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    The stage IV comes with a VF30 and is mapped for 18psi.
    well, thats good to know then. i know that the vf30 turbo is quite a bit more efficient than the stocker and everything but why are most people hesitant to run more than 16psi on the stocker? doesnt it max out at 18 or 19psi? b/c going from 13.5-16psi isnt going to be too much of a gain is it?

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    Originally posted by soon2BWRXd


    The WRX, IIRC comes with 12 or 12.5 PSI, and is safe up to 16 PSI most people here have MBCs set at 15.5 PSI. If you are worried about running more boost, the best bet would be to get a new Turbo that can handle higher boost amount....however who knows if the trans or the engine will be able to handle increased boost amounts?

    OH BTW NICE KILL!!!!!

    Stock boost is anywhere from 13.5-14.5psi depending on weather and elevation........
    2003 WRX 5spd Sedan
    ~Stage 4+ 20g~

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    Registered User Master Of Pain's Avatar
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    Guys,

    Concerning the Lightning motors blowing sparkplugs - I can tell you from experience this is true, and higher-than-stock boost can be a mitigating factor but it isn't the root cause. The heads only have 4 to 4-1/2 threads, the tolerences aren't all that great, and it's cut straight into the aluminum of the head. I lost my first motor due to ejecting 2 plugs + instant lean condition (cyl 3 and 4), NO MODS. The reconditioned motors (motor, 5.4L, complete) have heli-coils inserts in the sparkplug threads. The factory screwed up and that's the fix, pathetic as it sounds.

    Besides, the stock Eaton's peak efficiency (heat and drag) has been determined to be around 14PSI. Anything past that starts to increase tuning difficulties and diminishes returns on HP and Torque.
    Last edited by Master Of Pain; 12-19-2003 at 08:42 AM.

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    Registered User Shawn's Avatar
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    Originally posted by torqueterror
    well, thats good to know then. i know that the vf30 turbo is quite a bit more efficient than the stocker and everything but why are most people hesitant to run more than 16psi on the stocker? doesnt it max out at 18 or 19psi? b/c going from 13.5-16psi isnt going to be too much of a gain is it?
    I have never read that the stock TD04-13G maxes out at 18-19 psi. As I remember, that little snail dies out right around 16-16.5.
    '02 Silver WRX
    - PDX Tuned Stage 2.5 w/ APS FMIC, ACT Street clutch & flywheel

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