someone please explain me this.. remove bcs = less boost. poor control

[Korndogg]

hey guys
this is a weird one..
so way back when i first installed my MBC, i just ran a line from a T on the BOV to the MBC to the wastegate, exactly as the picture defiant posted on the tech guide shows. but the line that (in stock configuration) ran from wastegate T'd with the compressor housing and the BCS, i just capped off where it connected to the wastegate..

in other words, i had my MBC, but i also had a line from the compressor to the BCS to the intake snorkle.. i've been thinking that i had to be losing boost this way, so tonight i capped off this line at the intake and at the compressor as the tech guide says to (which i didn't do before... don't think i found the tech guide a year ago)

so, after i did this.. i got in and drove with my MBC set the same.. it used to spike to 20, then settle rock solid at 18PSI.. now it spiked to 20, then trails off to 15... wth? i expected either nothing or too much boost?

the weird thing is that it still holds in 3rd, 4th, 5th.. but 1st and 2nd are down to 15 like nothing...

i played with my MBC, but accomplished nothing but moving the spike level and where it setttles... and i also hit fuel cut on accident. heh. first time ever.. spiked to 23PSI in second (i was going up a hill, which keeps the boost up)..


anyway, i have no idea how this makes since. i'm sure i didn't cause any leaks, but i looked anyway and i'm sure there are none.

please help?

i think i'm going to have to put the BCS back in place if i can't figure this out...


sorry so long

thanks a lot for the help

 

[Korndogg]

p.s.
in 3, maybe 4 weeks i'm going to be bolting on an evo3 16G... just fyi.. in case anyone wants to say anything abuot that...


what causes boost spike, anyway?
thanks

 

[Korndogg]

so i deffinitely hit fuel cut (or something that feels like it) if it holds at 22PSI for a couple seconds, which i was testing so that it would drop down to almost where i had it (17 or so, for the most part). boost doesn't hold for shit at all anymore though.. very annoying.

fuel cut at 22 PSI on a t25 with stock fuel system - make sense? or no?

anyone have any ideas on what i'm experiencing?

thanks for the help

 

[oldman]

Since you were creative in bumping your thread, I'll try and lend a hand.

so, after i did this.. i got in and drove with my MBC set the same.. it used to spike to 20, then settle rock solid at 18PSI.. now it spiked to 20, then trails off to 15... wth? i expected either nothing or too much boost?

It's perfectly normal for you to see less boost because the bcs was bleeding off air reducing pressure been seen by the actuator resulting in higher boost level. After you removed the bcs, actual pressure reached the actuator quicker resulting in lower boost level.

in 3, maybe 4 weeks i'm going to be bolting on an evo3 16G... just fyi.. in case anyone wants to say anything abuot that...

I think you have just anwsered your own question. It is very typical for T25 to be set at 15, spikes to 18-19 then drop off to 12psi at higher rpms.

what causes boost spike, anyway?

Basically by delays of the actual pressure reaching the actuator/wastegate. Defective mbc, leaky lines, lines being too long or poor design in the case of T25.

fuel cut at 22 PSI on a t25 with stock fuel system - make sense? or no?

Most fuel cuts are caused by major boost leaks. I've done a search on threads you created and I see that you've already performed a boost leak test. What were the results? since you're also having some inconsistent boost levels, I want you to test run with just a hose connected between the compressor nipple and the actuator nipple with nothing else in between (bypassing the mbc for now). This should tell you whether the mbc is in question. Let me know what you find.

 

[oldman]

Just one more thing, WHAT ARE YOU DOING TRYING TO BOOST 15PSI+ ON STOCK FUEL PUMP AND INJECTORS ANYWAY? ON A T25 NO LESS. TURN THAT THING DOWN.

 

[Korndogg]

hey

thanks a lot for the reply. i appreciate the effort of checking my previous threads.

i don't understand how the BCS was affecting the actuator pressure though to be honest, because it was just hooked between the compressor and the air intake.

i think you made a few good points though. perhaps i should just drive easy for a couple weeks until i put on my new turbo and fuel system. i think that i will try bypassing the mbc though and let you know what happens, just to see what you think of my mbc's health. it's a hallman that's been around a while. i bought it used when i put it on a year ago.

it's funny that leaving the BCS in there and just removing it from the actuator line gave me a nice solid 18 PSI (or anywhere else that i had set it) each and every time. everyone with a T25 should do that

and i didn't realize that 15+PSI was no good on the stock fuel system with a T25, given that the air flow is so little. i'm going to buy some nice 580's and a 190lph for the e316g (i've heard 660's can be hard to control with the safc.

thanks a lot for the reply, i really appreciate it

 

[oldman]

i don't understand how the BCS was affecting the actuator pressure though to be honest, because it was just hooked between the compressor and the air intake.

I thought you were taking pressure source from the T on the compressor/bcs line, I read your post again and see that you're taking it from the bov line so you're right.

and i didn't realize that 15+PSI was no good on the stock fuel system with a T25, given that the air flow is so little. i'm going to buy some nice 580's and a 190lph for the e316g (i've heard 660's can be hard to control with the safc.

I would suggest using a logger if you want to go beyond 15 and that the intake is leak free, what was the results of the leak test?

just to see what you think of my mbc's health. it's a hallman that's been around a while. i bought it used when i put it on a year ago.

You should be able to tell once you test run without it.

it's funny that leaving the BCS in there and just removing it from the actuator line gave me a nice solid 18 PSI (or anywhere else that i had set it) each and every time. everyone with a T25 should do that

Very weird indeed, try hooking it back up again and see if system re-produces the previous condition.

 

[Korndogg]

welp, i put the BCS back in place and my boost is back under control. it currently spikes to 20, then drops to 18 like i had it before. as i watch it, it does drop off a smidge.. but really not until 6k rpm or so. i think the biggest thing is that there is much less spike again, which makes sense.. the BCS must be bleeding off the spike.

i also did another boost leak test. here's what happened.. set our compressor output to about 25PSI, then pressurized the intake (from the turbo). this was kind of weird, and worries me a bit.. i could hear what i first thought was dripping. but i checked under the car, and nothing. nothing anywhere. i think it must be bubles inside the engine? (unless anything could be dripping?) whatever it is, it's not much.. anyway, that occurs for about 30 seconds. i felt the UICP by squeezing it to feel pressure and it stays very firm until the bubbling stops, at which point you can tell that a lot of pressure has been lost. but again, it takes abuot 30 seconds. i could find no leaks anywhere. it was very quite where i was and there were no hisses or anything. just the bubbling/dripping sound from within the engine (sounds sorta like it's behind the turbine housing).
so... i don't know what that means.... but i hope it's not completely abnormal. perhaps it warrents a compression test. i bought the tester, just never used it..

the only thing i didn't do was bypass my MBC, which indeed could be unhealthy and causing my spike in the first place. but it was getting dark and it's been a long day

thanks again for the thoughts oldman

if you care to spend a moment pondering my long paragraph there it would be most appreciated. thanks


EDIT:
oh, and as far as log if i'm gonna run higher PSI...
http://dsmtuners.com/forums/showthread.php?t=184787
that was at 18PSI...

 

[oldman]

i also did another boost leak test. here's what happened.. set our compressor output to about 25PSI, then pressurized the intake (from the turbo). this was kind of weird, and worries me a bit.. i could hear what i first thought was dripping. but i checked under the car, and nothing. nothing anywhere. i think it must be bubles inside the engine? (unless anything could be dripping?)

forget what the compressor was set for, what did the boost gauge tell you the system was able to hold? The dripping/bubbling you hear is probably air through turbo seal > oil return > oil pan, open the oil cap and listen. Is your exhaust smoking? Any oil in licp? Bypass the turbo on your next test and see if bubbling still persist.

 

[Korndogg]

*slaps self* STUPID
i was trying to check the pressure with a tire gauge that we have, but i quickly came to the conclusion that it's not very accurate. i didn't even think of the boost gauge. what an ass i am, . thanks for that info, i'll give that another try pretty soon.

and yeah, that would deffinitely explain the bubbling. that makes a lot of sense. my exhaust is not smoking now, but it smoked a tiny bit when i tried synthetic.. well, it would only smoke then if i compression breaked down a hill or for quite a while then hit the gas, i would get a big puff of smoke. that's gone now though with standard mineral oil.

there's also some oil in the licp, but not enough to make me think it was anything but the breather into the stock intake pipe (still have it hooked up)

thanks again for all the help. very appreciated

i'll give the boost leak test another shot and see what happens.

 

[Korndogg]

just reporting back - i hooked up the compressor to the SMIC inlet. when that location was pressurized, there was no bubbling at all. so you must have been dead on with the turbo seal (thanks again!)
so, at first the connection to my wastegate was leaking a fair amount (not a lot, but a fair amount). took care of that real nice and simple. so then i could hear just a little bit of a leak above 10PSI or so. turns out that injector #2 (from pass to driver side) must have a bad O-ring, because that's where the leak is coming from. so, it doesn't hold any boost permanently, but it holds 15 for quite a while. comes down from 25 to 15 pretty quick though.

so the turbo leak will be taken care of with the 16G, and the injector ring will be taken care of with the 580s, all within the next couple weeks.

could the O ring be bad enough to affect anything? couldn't make that cylinder lean could it? (doesn't seem that bad).

thanks again oldman, really appreciate all the advice



EDIT:
oh, and i tried bypassing the MBC. boost spikes to 13 then comes right back down to about 10 and holds firm. i'm not sure how that tells me if my mbc is bad, but i just thought i'd share

fixing the leak at the actuator seems to have had no effect good or bad on boost control

thanks

 

[oldman]

i hooked up the compressor to the SMIC inlet. when that location was pressurized, there was no bubbling at all. so you must have been dead on with the turbo seal (thanks again!)

The key is whether you're smoking and where the oil in the licp came from. Sometimes getting air through the turbo seal is normal during a COLD leak test since there no oil pressure on the other side.

but it holds 15 for quite a while. comes down from 25 to 15 pretty quick though.

Repeat the test after the turbo and injector installation.

could the O ring be bad enough to affect anything? couldn't make that cylinder lean could it? (doesn't seem that bad).

O-ring is on the top between the rail and the injector, what's leaking is injector seal which goes between the injector and the head, make sure you change all four seals with the new injectors. No, it will not make your cylinder lean.

oh, and i tried bypassing the MBC. boost spikes to 13 then comes right back down to about 10 and holds firm. i'm not sure how that tells me if my mbc is bad, but i just thought i'd share
fixing the leak at the actuator seems to have had no effect good or bad on boost control

I'm beginning to think all this is just typical of a T25 like mentioned before, The car should run much better once you have al the leaks fixed.

thanks again oldman, really appreciate all the advice

You're welcome.