hey i just got a wrx about 3-4 months ago. the car was stock when i bought it and i have taken the lasdt few months to really get to know it. i have had two civic's before one being a DOHC with a T3/T4 set-up. i am still learning things about the boxer engine. i have just purchased a HKS 3 inch hi poower cat-back with a catless helix downpipe. i also have a hks uppipe with a RFL bov. i am looking into rasing the boost but many people seem to think it is not a good idea with the subarus to use Manual Boost controllers. i was wondering if i have a MBC with my mods what kind of boost should i run? if its a good idea at all?


Thanks Chris

 

Don't do it, stick with the up, catback and a bellmouth or divorced wastegate downpipe. If you want to increase boost shell out the 600 smackers for the cobb accessport.

 

+1 for the cobb accessport. car runs so smooth with it.. and it's so easy to use. that or get some kind of a tune/reflash. using an mbc will raise the boost, but wont get the most power possible out of it

 

i do want to go with an engine management but dont have the money right now. would it hurt to have the mbc on there? or should i really just wait. i have been lookin into the accessport but i am intrigued with the older unichips just because of the price and easy install and one of my friends has one available.

im not sure how the accesport works? do you dyno tune these or do you just upload a preprogrammed map

 

yes, it very possibly could hurt your car, I really wouldn't do it.

 

accessport is a device you just plug in and load a map that comes with it. it comes with 10 preloaded maps, and you can download more maps via the cobbtuning website. they have aps for stage1,stage2, vf34 turbo upgrades, etc. and if you ever want to dyno tune, all you need to do is find a tuner who tuns with accessport and they can give you another map that you can load up

 

Yes +1 on the Cobb AP..You will thank it later than if you were to use a MBC and have tons of posts on here as to why the engine blew or why it went into LIMP mode.. I know when it comes to mods we all want and wish we could have them yesturday but safer is always the smartest way/investment you can make

 

okay sounds like a MBC is a bad choice am i still gonna be getting alot of power gain with the downpipe and catback i aready had the uppipe on my car when purchased. i really wanted to bump the boost, but it looks like i am going to wait for the accessport. is there any point to getting a pre programmed unichip stage 2 for my set-up if i can get one at 200$ used or should i save for the cobb accessport.

 

**** the unichip, get the ap.

 

okay so i am not gonna get a boost controller. running catless without engine management will not be hurting my car at all will it? and could i install an accessport myself?

 

I had the unichip on my 2002 WRX, made decent power but threw a lot of CEL's for misfires at high RPM due to problems with the crank angle sensor and how the unichip process the signal.

I now run Vishnu's Xede with a custom tune. No CEL's good power 210hp and 225Tq on the custom tune at the wheels. Only complaint is an occasional stumble at low RPM's while cruising.

 

Save up some money for some real mods. MBC's are bad without tuning. Maybe you can do the ghetto *** 3/16th restrictor mod. It's free.

 

i ran for thousands of miles with a full decat and axleback using a mechanical boost controller and no management.

on a bugeye rex running an MBC the ONLY THINGS you must be wary of:

1) overboosting. you'll know when you overboost because the car will fuel cut and you will get a CEL. fuel cut occurs when manifold pressure hovers around 17-18psi for longer than about 1 second. it is the oem ecu's way of protecting itself, because the only time that amount of boost would occur is when there's a failure of the boost control system.

to prevent overboosting, set your mbc to run 16psi in 4th gear, and no more. you may need to adjust it as the weather gets colder but the necessity of doing this is largely overstated, in my experience.

2) part throttle full boost. unlike the factory system which limits boost to 7psi while under ~60% throttle, the MBC will only clamp the max boost. the wastegate will only open if your target manifold pressure, set by the MBC, is reached.

this will allow essentially full boost as long as there is sufficient exhaust energy to spool up the turbo. with higher load (ie, uphill, loaded car, highway, etc) on the engine, even at partial throttle angles there will be enough exhaust gas energy to do this. the result is full boost at partial throttle (aka PTFB).

the REAL issue is that the oem ecu will not necessarily be running open loop (aka enriched) fueling at this point, which is necessary for cylinder cooling and detonation prevention at higher manifold pressures.

what ends up happening (if you are not aware and do not take steps to avoid the situation) is that the oem ecu will run on closed loop fuel even at the higher boost pressure. sooner or later it will detonate, and the oem ecu will hear the det and it will pull timing. what you NOTICE is that your mid throttle powerband will be "lumpy." the car won't pull evenly as you pass through the midrange rpms (where the car is most det-prone). this is evidence of the ecu using its fine ignition adjustments to prevent additional knock. this is YOUR clue that you are not doing a very good job of avoiding PTFB.

to avoid it is simple: don't lug the engine at all. instead of cracking the throttle open in 4th, downshift, spin up the rpms, and keep the boost down. don't allow the boost gauge to sweep past 7 or 8 psi while the throttle isn't more than 2/3rds of the way down. if necessary, lift OR mash the throttle to accomplish this.

that's the technical explanation. once you learn to recognize the conditions under which PTFB will occur it is not that hard to avoid it. i drove like that for many many miles. eventually i went one step further and installed a throttle position actuated solenoid swich which would run wastegate boost below the threshold (7-8psi) and MBC boost above it. then i didn't have to worry about it at all.

ken

ps. the above mentioned PFTB situation is EXACTLY what happens in a post-bugeye car during the closed-open loop fueling transition delay.

 

damn. okay well the last thing i want is another blown engine. i watched the high compression b16 of my t3/t4 civic's engine go boom. i am gonna stay away from the MBC i am saving for the accessport and i also believe that a local shop Precesion Tuning is starting custom tuning on the accessport

 

damn. okay well the last thing i want is another blown engine. i watched the high compression b16 of my t3/t4 civic's engine go boom. i am gonna stay away from the MBC i am saving for the accessport and i also believe that a local shop Precesion Tuning is starting custom tuning on the accessport