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-   -   AVCS problems - midrange Power Loss (http://www.perth-wrx.com/vb/mechanicals/15394-avcs-problems-midrange-power-loss.html)

97RA 28-09-2007 10:02 AM

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.

tuna 28-09-2007 10:17 AM

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

97RA 28-09-2007 10:25 AM

[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?

tuna 28-09-2007 10:54 AM

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.

foxey 28-09-2007 11:06 AM

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.

tuna 28-09-2007 11:23 AM

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.

97RA 28-09-2007 11:46 AM

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.

WRXTASY 28-09-2007 11:50 AM

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]

foxey 28-09-2007 12:20 PM

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?

WRXTASY 28-09-2007 01:07 PM

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


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