Problem with version 7 STi boost control

[4foot]

strong for subaru also sell new knock sensors, I think I picked one up for a mates V7 for like 90 bux or there abouts

[Pappu1]

if suspect knocking - do a log run and see if its showing knock at certain points and compare with boost/load and afr levels and possibly make an educated/guestimated call on if its incorrect knock or genuine knock in thoes zones...

or just throw a knock sensor in and hopefully it works for the best (for ur sake im hoping it works)

u can also try and make sure the sensor is torqued to correct spec (27NM from what i remember..dont have the manual with me at moment)

being a v7 there is a world of possibility for logging as compared to the older models so i dont see the need to throw parts at it without at least trying to check all possible sensor outputs... :

[titian]

 SP00N said:

if suspect knocking - do a log run and see if its showing knock at certain points and compare with boost/load and afr levels and possibly make an educated/guestimated call on if its incorrect knock or genuine knock in thoes zones...

or just throw a knock sensor in and hopefully it works for the best (for ur sake im hoping it works)

u can also try and make sure the sensor is torqued to correct spec (27NM from what i remember..dont have the manual with me at moment)

being a v7 there is a world of possibility for logging as compared to the older models so i dont see the need to throw parts at it without at least trying to check all possible sensor outputs... :

Faulty knock sensor will NOT show any in in-correctness in knock. It will show up as being correct...However because it is not listening correctly (accuratly) it will change the timing....micro seconds of detonation occurance....also seconds of a degree of crank angle make a huge difference to the performance of the ECU managed engine :)

[Pappu1]

lol i think u misunderstood me

i mean it showing knock values (which is what the ecu will read to change the timing etc) and when u log the knock values and compare at what points it shows then u can kind of see if its possible for knock to happen at that point

as an e.g. say its showing knowk on 1/4 throttle and 20% load and few psi boost at afr 10.9

..see that could be possible incorect knock detection

[titian]

 SP00N said:

lol i think u misunderstood me

i mean it showing knock values (which is what the ecu will read to change the timing etc) and when u log the knock values and compare at what points it shows then u can kind of see if its possible for knock to happen at that point

as an e.g. say its showing knowk on 1/4 throttle and 20% load and few psi boost at afr 10.9

..see that could be possible incorect knock detection

Got ya!!...Bloody hard to explain...Just hope my diagnosis is correct ..Do see what you are on about though...Test before you replace. Must say though....this knock sensor is a tricky one. More often than not all seems to be ok..AFR ok, etc, but still there is a flat spot on acceleration under varing load and rpm conditions >

Have replaced this sensor numerous times and have always had an improvement...I reckon they are only good for around 150,000km....If they ever get heat damaged they also give spurious signals. ...not easy to "catch in the act" either

[ben-jamminn]

 SP00N said:

if suspect knocking - do a log run and see if its showing knock at certain points and compare with boost/load and afr levels and possibly make an educated/guestimated call on if its incorrect knock or genuine knock in thoes zones...

or just throw a knock sensor in and hopefully it works for the best (for ur sake im hoping it works)

u can also try and make sure the sensor is torqued to correct spec (27NM from what i remember..dont have the manual with me at moment)

being a v7 there is a world of possibility for logging as compared to the older models so i dont see the need to throw parts at it without at least trying to check all possible sensor outputs... :

Yeah man thanks, 24Nm and 45 degrees in relation to the engine. Hopefully will be able to do some logging next week, just gonna change the knock sensor based on kms and hopefully it helps!

[ben-jamminn]

Replaced knock sensor on Sunday and haven\'t been able to replicate the fault since, hopefully it\'s cured!

I took some photos so can do a how to: replace knock sensor thread if anyone is interested?

[JWDRPN]

Yeah im in the same boat problem seems to hav vanished.. Very easy job took 30mins. My old sensor was incredibly coroded

[boon]

 ben-jamminn said:

Replaced knock sensor on Sunday and haven\'t been able to replicate the fault since, hopefully it\'s cured!

I took some photos so can do a how to: replace knock sensor thread if anyone is interested?

Yes please. I can see myself having to do this in the future.

[titian]

YES! ;) ;) As suspected! pleased to hear it. :)

[Pappu1]

 titian said:

YES! ;) ;) As suspected! pleased to hear it. :)

yea nice...one more thing to look for next time im looking ;D

[JWDRPN]

its really interesting as i have spent well over 1k before rebuild looking for this issue. iv replaced close to every single sensor in my car!

wrapt with the results.

[ben-jamminn]

 boon']

[quote name='ben-jamminn said:

Replaced knock sensor on Sunday and haven\'t been able to replicate the fault since, hopefully it\'s cured!

I took some photos so can do a how to: replace knock sensor thread if anyone is interested?

/quote]

Yes please. I can see myself having to do this in the future.

Here is the how to thread I made

http://www.clubsub.org.nz/forum/index.php/topic,33590.new.html#new

[ben-jamminn]

So after driving around ok for a few weeks I decided to reconnect the factory BCS as I guessed the issues with boost I\'d had previously had been caused by the knock sensor, so I plumbed it up and removed the MBC that I had been borrowing. Everything seemed ok testing it around town, hit target boost and remained constant, no fluctuating or cutting.

So I decided to take the car on a trip to Nelson yesterday, got about 30 mins up the christchurch northern motorway and on overtaking type conditions, boost was back to hitting target then dropping back to 0.5 bar then back to target, rapidly. Almost as if the solenoid was firing too slowly? Anyway this carried on for another 30 mins or so and after turning off SH1 to take the inland route, the boost control stopped completely, only getting 0.5 bar the rest of the trip to nelson, worst drive ever! Car felt like complete shit.

I\'m in Nelson still at the moment, I\'ve reset the ECU and car seems to be making correct boost, but I\'m not holding my breath as to if it will last the trip home.

Is the 0.5 bar because of the valve ceasing to function because it is jamming, etc or am I going into limp mode? No check engine light showing.

This car is driving me nuts!

[Stoffa]

If everything else was working on manual boost control it must be the solenoid. especially as youve already ruled out any knock events. wastegate pressure on a stock vf actuator is 7psi. change you BCS and it should be mint.

[ben-jamminn]

Yeah that\'s my plan, does anyone know the price of a genuine solenoid?

[boon]

It might not be the solenoid - if it goes into limp on the ECU (which I strongly suspect) it will just not signal the solenoid to cycle so you\'ll get wastegate pressure, as you\'re seeing.

[Stoffa]

You could wire up an led to the solenoid wiring and see if its cycling

[ben-jamminn]

 boon said:

It might not be the solenoid - if it goes into limp on the ECU (which I strongly suspect) it will just not signal the solenoid to cycle so you\'ll get wastegate pressure, as you\'re seeing.

But what explains the fluctuations wher the boost rapidly rises and falls, before the said limp mode? It\'s strange

[boon]

 ben-jamminn']

[quote name='boon said:

It might not be the solenoid - if it goes into limp on the ECU (which I strongly suspect) it will just not signal the solenoid to cycle so you\'ll get wastegate pressure, as you\'re seeing.

/quote]

But what explains the fluctuations wher the boost rapidly rises and falls, before the said limp mode? It\'s strange

Boost cut? I wonder if your map sensor is behaving... really need to datalog it and see what\'s going on.

[ben-jamminn]

Drove back to Chch today, boost fluctuations in combination with hesitations/flatspots the whole way although it didnt go into limp mode the whole way (was able to boost past 0.5 bar) It seems fine while cruising at 100km/h but occurs as soon as you overtake or go up a hill, in 5th gear especially for some reason. Like go to overtake, downshift to 4th and accelerate, boosts fine, change to 5th and once the boost gets past 0.5 bar there is surging/hesitation, but if you keep accelerating it seems to \'break past\' it and you reach target boost, then the fluctuation starts

[JWDRPN]

unfortunatly mine is still doing this just not as harsh as before.

mines like il be going 60kmph in 4th n il hit a 100km area so il put my foot down more for it to slightly come on boost as boost comes on the car will just loose boost then jump back on its a funny feeling

BUT it never does it in first or second.

iv changed boost controler still does it

[hijacka]

Gee all this dribble and no one has thought to check the fuel pressure or simply replace the 10year old factory fuel pump

I\'ve got a new genuine AEM fuel pump coming in thats rated to 320lph@43psi its the as the areomotive pump they sell on tardme for $250 you can have for $200. problem fixed

http://www.trademe.co.nz/motors/car-parts-accessories/performance/fuel-systems/auction-532715789.htm

[Pappu1]

why not logmthe issue and see what the other sensors are doing

no point just keep changing parts and sensors when logging can be done rather easy and u can check all sensors and see what is outta whack...

[ben-jamminn]

 hijacka said:

Gee all this dribble and no one has thought to check the fuel pressure or simply replace the 10year old factory fuel pump

I\'ve got a new genuine AEM fuel pump coming in thats rated to 320lph@43psi its the as the areomotive pump they sell on tardme for $250 you can have for $200. problem fixed

http://www.trademe.co.nz/motors/car-parts-accessories/performance/fuel-systems/auction-532715789.htm

Yeah I had thought of rigging up a pressure gauge temporarily and seeing what it does when the problem occurs, I also replaced the fuel filter (which looked like it was still the original one from factory) but that hasn\'t helped. Fuel pump is worth looking into though, cheers.

Although when the fuel pump in my old version 4 packed up it didn\'t give any forewarning like this, I just couldn\'t start the car one morning haha