AVCS problems - midrange Power Loss
 

Gday I'm asking if anyone with AVCS equipped WRX/STi's have had the their AVCS system shut down on them resulting in the loss of midrange torque / power ? :mad:

If so what was the fix for the problem.

Thicker Oil ?
Higher Oil Pressure by extra shims in the oil pump. ?
Upgrades to the Banjo Bolts and filters in the AVCS system to flow more oil ?
A re-flash to factory ECU ?

Cheers :)

i'd be checking the sensor pickup.

Yes. I don't know what the fix was. I changed workshops after this, and other numerous problems.

avcs should also only require relatively light weight oil 10w-40 too...

Yeah I agree.

Cam controller fault I believe due to Oil pressure problem.
Trying to diagnose a problem for a Rexnet member that lives in Bunners...

I will recommend a Mobil Syn S 10w-40 Oil change as a first step.
He is running Valvaline Synpower 5w-40 at the moment.

Just to hi jack this, have either of you boys got AVCS going in the GC's yet? I ended up going down the link path, not as flashy as the tec but I'm hoping the motor will be fired next week.

My whole transplant is booked into ASG from Sat 13th Oct for a week.
Still doing AVCS with the Motec.
Thx for reminding me as I have to liase with Stace... :)

Hi guys
Thanks WRXTASY for the tips
So is the 5w/40 synpower to light or too heavy for the AVCS
I also think the verso reflash sounds like it could be the answer to my probs
although its a little hard to find a thread amongst the many threads about verso that actually explains what verso is
Ive read plenty of replys from noobies requesting an explanation of verso but there is no anwsers............

For those wondering what im dribbleing about
I have a stock standard MY03 WRX that has a jerkiness to its acceleration
which is worsened as the pedal is pushed to to the floor.
The Car has just been picked up from local subaru service center after 4 days work being completed.
They reported the problem ( after swaping all sensors, plugs, coils, etc and checking fuel pressure boost, cam timing) was a faulty throttle position sensor.
On leaving the yard and opening up the throttle out on a stretch of road I found that it was no better at all.
I returned to the dealership and the dealer took it for a drive with me
He said what my car is doing was typical of wrx`s
I was then invited to drive a bugeye to compare.
The bugeye did have a slight jerkiness to its acceleration but was not as bad as mine.

If mine is anything to go by, expect it to take longer than a week. In saying that mine has been sitting there waiting for parts to arrive.....

I think once link release their closed loop wide band it will be as good as the tec (yes i expect to get yelled at for this comment.)

But back on topic, I couldn't see changing to the mobil oil having any effect, unless the current oil has thickened with impurities. Kind of redundant, but I agree with stace, sounds like a feedback issue.

Rexy03,

What RPM range and in what gear specifically does most of the jerkiness happen ?



Foxey,

All the parts are finally here ready to go, taking up half a bedroom. Definately trying to make it a drive in conversion job. Engine in next week to build up before car goes in.
DCCD still needs looking at tho. :)

It does it in any gear and is at its worst at full acceleration
it is not noticable when accelerating slowly
and is most noticable in 4th or 5th from around 80 ks under full acceleration
and does not stop jerking untill releasing the pedal

So its when the engine is loaded up in 4th and 5th gears.

Normally we would say its an O2 sensor or AFM but these have been changed by the dealer.

As Tuna and Foxey have said I would check the Cam sensor pickups first.

Sounds like an intake cam control problem, whereby one or both AVCS solenoids are not operating properly resulting in the cam(s) defaulting to running on their grinds only under high engine loads.

The only way to confirm this is to log the AVCS load table.

Can the Camshaft Position Sensors be manualy checked for fault in any way or would I need to swap them over with new ones to see if that is the problem.

I'm assuming your dealer has read any ECU error codes that have been stored.
This would usually flag a Cam position sensor thats stuffed. Sometimes it does not though until the sensor is completely knackered.

No way to manually check them. They are pretty easy to swap out tho on the rear of both left and right sets of AVCS heads. 1 bolt holding each of them in.

Not a problem for me fit them.
just getting more sensors could be.
ill check with dealer in the morning to see if they already swapped them over
off another car.
if not i will have to get them to order some in for me
I think they just want me to leave them alone LOL

Ok will give it a shot
thanks mate - let ya know what happens

avcs has 2x cam sensors on the rear of the heads both sides.
or theres the 2x avcs cam solinoids on the front of the heads both sides, check they both have power.

I have recently replaced a cam sensor as i thought there was a fault with the sensor (which it turned out to be something else). So i have a spare sensor if you need to borrow one.

Sensors are expensive for what they are about 250ish onwards depending on where you get it from.

Are the EJ205/207 sensors compatible with the EJ257 ones. ?
I'm betting yes. :)

Thx for the chart Intra.

It's just a reluctance type sensor, so they should be interchangeable, but I'm not going to say they are.

Got a matching set of 257 sensors if you want to try them out.

Looked at a 207 and it didn't look much different to the 257 (apart from the 257 bits being more shiny) and can't really see they would be much different in operation, but you never know.

the 257's move to hall effect sensors as opposed to the magnetic sensors of the previous generations.

[QUOTE=tuna]the 257's move to hall effect sensors as opposed to the magnetic sensors of the previous generations.[/QUOTE]

Ok, looks like a really similar setup. The crank sensor looks almost identical to a EJ20G, but the sensor wheel is totally different (same as a 205/207 tho').

The crank sensor is still magnetic tho', isn't it?

So the slot in the end of the cam is a Hall trigger?

between 01 and 04, avcs sensors have no relation to the cam/crank sensors which the engine uses for ignition.

the relative crank reference index position changes between the generations of engines because of the different toothed wheels also.

the function of the magnetic cam/crank sensors for all generations (excluding 257) are identicle though, even from the NA's, not much changes, its only the clearances that matter (which affect the trip pickup voltages)

so yes, all crank sensors are mag, all cam sensors are mag (except for 257's)

the only engines with the hall effect sensors are the late model 257's on the rear of the heads for the cam pickup.

Speaking of this stace, how did you get the Autronic to run your v7 engine. We couldn't get it to start mine at all? I assume this is because the triggering info changed when they moved to the bugeyes.

Are the cam shafts used to trigger the rear of head sensors instead of the cam wheels?

But anyway, would malfunctioning AVCS cause jerky acceleration? Maybe if it was constantly adjusting the cam's position, but otherwise wouldn't they just sit either fully advanced or fully retarded? Looking at it again, it doesn't sound like an issue with cam position sensors, maybe with the solenoids or the oil, but not the sensors.

you can swap the passenger side cam wheel for the normal cam pickup.

avcs doesnt float its position, as avcs is driven by the solinoid duty cycle, if there is 0 duty cycle, there is 0 advance on the cam.

Now I'm happy I went non-avcs on my 2.5, nice to have but...

I've got too many things going on in the real world to want to try to get my head around this lot.

Think it would be easier to start with a model with this implemented to start with.

Thanks for clearing that up Stace between the EJ205/207 and the EJ257 sensors.

Time to post up the benefits of AVCS on a dyno working vs not working. This is before the final tune. Thx Intra :)
Blue lines are midrange torque.

[IMG]http://i23.tinypic.com/eziafb.jpg[/IMG]

AVCS works by oil pressure to the cams, which is modulated by the solenoid?

Assuming the above, if there is an issue with the oil (causing static pressure in the AVCS lines to waiver), the cam position could "float" with respect to a set duty cycle of the solenoid. Obviously closed loop control would try and reduce this error by adjusting the solenoid duty cycle, but if it can not react quick enough to the changes in oil pressure the cam position is not going to be right, affecting the torque and making the acceleration jerky.

I don't think a malfunctioning sensor would cause this kind of behaviour, as it would either read full advanced or fully retarded, meaning the solenoid would be either fully open or fully closed, which I guess would affect the VE of the motor and hence the tune, so I guess it could cause jerky acceleration.

Or am I way off here?

I believe your spot on Foxey. Definately Oil pressure related. :(

From what i have read:
[quote]It's oil pressure related, the U.S. had an upgrade to the small banjo bolts and filters to flow enough oil.[/quote]This seems to be confirmed by Rexnet members that have had the "fix" done over East.
[url]http://www.rexnet.com.au/forum/index.php?showtopic=62564[/url]

Also those runing aftermarket ECU's controlling the AVCS Solenoids are not affected. Its only the factory Subi ECU's.

J

Apparrently the "fix" cost tens of thousands to diagnose & r&d.

Think it was on some MRT related flyer or something.

Considering you don't hear of many of these AVCS problems and it costs apparently $400ish or so to "fix", I would be hitting Subaru up for a warranty claim. Mentioning that its a proven problem identified by MRT !!!

we rally you pay!

The good old motto :)

Stace, clear your inbox pls. its choccas!!

Are you availble 15-19 Oct to do the AVCS wiring on my conversion ?

pm me now with all the detail,
what state is the car in etc

btw, cam/crank sensors are not the same as the avcs sensors,
if your car starts, dont bother playing with the cam/crank sensors.

the avcs sensors are at the rear of the heads next to the cam covers.

whether they are connected or not (or even if the solinoid is d/c), the AVCS if theres a problem will stay on 0 degrees advance, even under no oil pressure.

although i dont know what detail you can get out of the stock ecu, but on motec you can log the duty of the solinoid to at least see what its trying to do, if the duty is up and no difference in the results, then its definately an oil related issue.

personally i think the MRT issue is to do with people using the wrong types of oils to start with, playing with banjos and what not shouldnt make a hell of a lot of difference without masking a true problem.

Yeah no probs if you can clear a bit of space in your Inbox.

Cheers :)

done!

[QUOTE=WRXTASY]
Rexy03,
So after all that its safe to change around your cam/crank sensors, just don't swap in ones off the 06/07 GT/WRX/STi's.

If your WRX then refuses to start after the swap around it will be the sensor positioned behind the crankshaft pulley thats stuffed. :)[/QUOTE]

[QUOTE=TUNA]
btw, cam/crank sensors are not the same as the avcs sensors,
if your car starts, dont bother playing with the cam/crank sensors.[/quote]

Ok now im getting confused ?????

I pulled the passenger side cam sensor and crank sensors out and found they are a bit different in construction at the probe/sensor end and have different numbers on them they are the same size though . so i didnt swap them
Now after reading the previous comments im a little confused as what i need to do ???

WRXTASY are you saying that if i put a dud cam sensor on the crank the engine wont start.

TUNA if my car starts as is then the cam/crank sensors are OK

clarified: AVCS is independant of starting the car.

car does start = cam/crank ok.
car not start = either cam / crank sensor, or CRIP not correct.