boost drop w/ mbc problem...

[1gTURD]

yeah i have a stock 90 laser. the car is an oddball. i installed an mb in the coin tray infront of the shifter (12 feet of vacuum line) but... when its set at about 15 psi it will hit 15 and gradually decrease back to 9-10 (stock) when the engine still has load and should pull longer. any ideas? perhaps the stock bov spring?? im stumped
thanks
Dante

 

[jfarber]

This is normal (at least for the DSMs i have worked on).

If your bcs is still connected it will pulse causing the wastegate to open, dropping your psi to around 10 or so. Disconnecting the bcs and reconnecting the vaccuum lines (one to the intake and one to the j-pipe) will take care of your problem. i would suggest having a logger and o2 gauge (or egt gauge) along with what i said above. you could be getting knock (hence the pulsing bcs). the bcs is the ecu's only defence against overboosting.

 

[GalantVR41062]

or its the 12' of vac line, the proper way to hook up a MBC is to disconect the vac lines for the BCS but leave it pluged in, then crimp off the "J" pipe vac line and the outlet of the stock air can(vac line) then put in a T fitting on the BOV line(from the intake man) then from the T go to the bottom the boost controler(ball side) then from the outlet of the MBC to the waistgate agitator, I would recomend attaching MBC to the passanger side fan shield or somthing, the shorter the line the better response etc. Good Luck and happy boosting, hard wire Fuel pump and you should be able to run 16psi with proper 93 octane and good gap on pugs (29ish)

 

[1gTURD]

well what is the j pipe?
and by pinching off lines... woulkd it be better to take them out rather than have soe dead line... also will it toy with the maf sensor voltage?
also the length of the tubing shouldnt make a difference... same as it was with 1 foot of tubing when i did have it mounted on the fan shroud. also the mbc is inline after the "check valve" so the controller only see's positive pressure and no boost... its basically t'ed in directly of the path of the waistegate linenot one to bov and other to waistegate... how would this be improper? does the boost solenoid need to see some sort of signal i have disabled to it? or did i disable the knock sensor by doin this so it cant cut fuel/spark/boost or whatever when detonating?

also about rewiring the pump
ive heard of this but then again ive just got the dsm...
how do i acheive this pump rewiring?
im a servic tech so go ahead and feel free to explain however you wish

will it affect pump performance and pump life?

 

[kpt4321]

Having 12 feet of vacuum hose will majorly mess up the response time of the MBC. You need to set it up the right way:

Tee the "in" line into a good boost sourse, most people use the BOV line. Cnnect this line to the bottom of the MBC. Then, connect the other line directly from the "out" of the MBC to the wastegate actuator.

To keep my lines as short as possible, I have the MBC mounted right on the thermostat housing. This saves me about a foot oer mounting it on the fan shroud.

About the j-pipe: On the pipe that bolts to the turbo, there is a small boost source nipple that the stock BCS use. Make sure to block this off, so you don't have a boost leak. On a 2g, this nipple is right on the compressor housing of the T-25, block that off if you're one of the slow guys.

What MBC is it? MBC's need a small vent hole somewhere after the ball-and-spring (is it a b&s controller?). Some integrate this hole into the body of the MBC itself, and some have a seperate connector in the hose between the MBC and the wastegate actuator. YOU NEED THIS VENT HOLE!!

What is this about a check valve? The only time you need a check valve is with a bleeder type MBC, which I hope is not what you have. If it is, just sell it and get a real one, like a hallman.

HTH!!

 

[LaserRST]

Also be sure your MBC is vented... it needs to have a small hole to vent off the pressure you let into the wastegate actuator. Other wise the wastegate will be left open and will have exactly the type of boost drop you are talking about. Boost up to set level and wont produce much power after that. Also be sure your timing is as close to base timing as possible. Good luck!!

 

[1gTURD]

ok well i was using the 55.00 dejon tool mbc (till funds allow a profec b) but i tried the "sears hardware racing" valve and it is alot easier to find 14-15 psi with it and the results are alot better with the "home depot racing" valve rather than dejon tool. i dont see any bleed off valve or anything on the dejon tool one. i guess this also could be my problem... with the hardware store valve it just cuts the flow by means of blockage... no psi spring or valve. by check valve i mean that when engine is running there is no vacuum... but when boost is applied it then comes through the hose i have on the controller. (not used to it that way even tho im sure its normal... i used to have a turbo honda where it didnt work that way... no bcs's).. thanks for the help and i dont mean to sound like some poor schlepp who knows nothin... just new to owning a dsm... by far my fav car i have owned from 5.0's to turbo civics... also can anyone help me out with a link or advice on rewiring my fuel pump or the "maf sensor gutting" mod

thanks again
Dante

 

[turboholic]

http://www.roadraceengineering.com/instructions/1gmashacking.htm
-Most people have idle problem after removing the lower honey cone, if you decide to remove it, keep it in a safe place for you might want to reinstall it back.
http://www.plymouthlaser.com/rewire.htm
http://www.ecanfix.com/users/mdhamilton/fuelmod.html

-You should have a aftermarket boost gauge, egt and /or O2 sensor voltage gauge before start to yada yada yada....

 

[1gTURD]

yes i have an autometer phantom 2 1/16 boost guage and im workin on a egt... not no goofy "hey check out the bling bling lights on my a/f guage" gauges...

thanks for the links and all the help everyone
thanks for your time... I appreciate it, tho im sure you will hear from me again... after x mas when i have money to spend
my goal is to get low 13's (street driven ofcourse) fwd with 16-18 psi from a 16g and other mods then a nice 86-87 Buick Regal project (3.8 turbo)... from what i understand low 13's is not that big of a task with the laser, and i wont need really deep pockets... we'll see how it goes
thanks again
Dante

 

[CH152]

The guy that i bought my car off of he talked to the Main guy up there at buschur racing> he has a 92 Eclipse AWD with a 20G. Anyhow, he said the guy at Buschur said it was pointless to buy a EGT gauge because when it reads that stuff is getting hot like 1600 or higher your parts are already melting. Dont qoute me on that but that is what he told me. I am still wanting one though? why i don't know i guess just to say i have one. Oh welcome to the DSM world. When it comes to DSM's these guys know there shitzu.