Overboosting Solution

[kennethfong]

Hi all,

Recently my car has behaved strangely, am using a 4G93T, my original boost is at 0.8 bar measured using Apexi Boost Meter. Just few days ago, I was totally shocked to see my boost went up to 1.25 bar at 3rd gear!!!! of coz 2nd n 4th gear too will reach CONSTANT 1.25 full boost!!!!

i've went to my mech, so he tried shooting air into the actuator hose (one hose that will open the actuator), it's OK, then took out the solenoid (which controls the opening of the actuator from ECU signal), tested with battery connection, it works (u can hear the click sound), then he tapped a wire from the ECU connection to make sure the ECU is really sending signal, the wire is then connected to a voltage signal sensor into the cabin area, so i drove the car out for a boost, and I was amazed to know that the light is only ON when i reach 1.2 bar!!! which means the actuator only opens at 1.2!!! This is crazy, so now he suspect it might be the ECU, however logical thinking prompts me to reconsider again that if it is the ECU at fault, most probably it wouldn't have sent any signal at all, but y 1.2 now??

So now my question is, i suspect there might be a sensor that sense the boost signal which feeds the ECU (how in the hell the ECU will know it's 0.8 bar or 1.2 bar), so right now i was thinking maybe the sensor is at fault, coz the sensor read wrongly thought that the 1.2 bar is the 0.8 stock boost level, which delays the actuator opening, can you guys please help me to confirm...

Appreciate your help a lot before i start blowing my engine....

 

[khoyos]

actuator opening is strictly controlled by vacuum (mechanically) if i'm not mistaken... so maybe something wrong with the actuator. ecu is a very expensive part. just dont get conned by ur mechanic

 

[raja_emeperor]

change your vacuum hose first,the hose that from actuator to intercooler.maybe got small crack.

 

[kennethfong]

thanz, but currently i've confirmed that it's the ECU sending late signal to the solenoid, so which means must be somewhere from ECU part or the feeding sensor, so now could i confirm that whether the air flow sensor tells the ECU on the boost reading or rather tells the ECU that it's time to release some pressure??

 

[jinkl]

keneth , dont get conned by ur mech haha
just like khoyos said, ur ecu is not a BOOST CONTROLLER

for mitsubishi , ECU only controls your boost cut selenoid
when there is extra boost , it will do a boost cut , but i guess
boost cut is 1.3bar rite for mitsu if not mistaken
and also if the boostcut is working also , it might not work if
your vacuum hose is bleeding or leaking

for an actuator to open , the vacuum hose that comes from ur
intercooler piping enters the actuator , at 0.6bar the actuator will
open , if there is a leak on ur vacuum hose , the pressure escapes
thus the pressure built in the vaccum hose to reach 0.6bar to the actuator
will not be acurate , its like 1.25bar - 0.65bar(cos of leak) , then only actuator open. hope u understand , haih , please do learn about your car
if not mechanics going to make money out of ur pocket , he could replace ur ecu
and keep ur ecu for the next customer , he will also replace ur vacuum hose ahahha and say its FOC :P bang 1k from ur pocket lolx.

the only reason for overboost is two things
vacuum hose leak , actuator flap got jammed

no ecu related issue

 

[muskasim]

Yes, change ur vacuum hose first..it will not cost u more that 50 bucks for a silicon hose.

Just want to know..which mech told u this har......Izzit ur car laying at da workshop due to leakage of intake manifold???

 

[prozac]

Stock 4G93T got MAP sensor meh? How in hell does the ECU know the pressure?

I also kena before. Last time dunno much about cars, leave my car at the mech for some "works". When collecting my car he take out his calculator *dit...dit...dit...dit...dit...* until I had to go bank *dit...dit...dit...* non stop. After that I learnt; always ask for a quote, then get a 2nd opinion. Best excuse to cabut is "not enuff money".

 

[kennethfong]

yo guys,

thanz i'm gonna get all the silicon hoses replaced tomorrow!! pray it works!!

 

[kennethfong]

hi all,

good news!!! problem solved!!! u guys r right, it's just the stupid vacuum hose.... but i dun understand, u c in my first post, i mentioned that the mech tapped the signal wire from the ECU to the solenoid part, and connecting that wire into the cabin to check whether the ECU is sending late signals to activate the solenoid in order to activate the actuator, so i've concluded on that day that the ECU is only sending signal at 1.2~3 bar, i know my car is using MAF (which i'm trying 2 get rid off since day one replaced with a better management) but how the hell does the ECU knows the boost level to open the solenoid then actuator??? which signal or sensor tells the ECU this?? some said it's the MAF............ or izzit the whole actuator opening is controlled mechanically without ECU's help (in this instance ECU only helps for boost cut function??? i'm quite puzzled right now....'

p/s: yo u guys!!! if any of u come to penang or already in penang gimme a call (owe u one meal)....

 

[raja_emeperor]

see i told ya already!

'change your vacuum hose first,the hose that from actuator to intercooler.maybe got small crack.'

 

[kennethfong]

yo raja,

u guys are so pro lar, hehe it's not only small crack, but huge one!!!

 

[khoyos]

good to hear that ur problem has been solved.

 

[muskasim]

yes...... the wastegate actuator opening is fully control mechanically without ECU's help

 

[raja_emeperor]

yo raja,

u guys are so pro lar, hehe it's not only small crack, but huge one!!!

ahahaha!!! luckily you noticed your boost suddenly increase than normal,if you keep on tekan,sure your engine blown la bro.

 

[jinkl]

kennethfong : next time it will be good to post up here if u have any probs
not to say we all dam pandai la , but most of them here speak with experience :) :shocked: