AVCS Signal

10-24-2005, 04:26 PM

So what kind of signal does the ECU send to the AVCS solenoid?

waveform...on-off....what? Is it just like an injector signal...or...?

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mpaone · 10-24-2005, 04:57 PM

Hmmm... thought I read somewhere the the AVCS is a similar signal to the TGV's. Not sure if that helps.

-Mike.

10-27-2005, 01:38 PM

Quote:

Originally Posted by mpaone

Hmmm... thought I read somewhere the the AVCS is a similar signal to the TGV's. Not sure if that helps.

-Mike.

hmmmm....

fragment · 10-27-2005, 02:09 PM

With the Hydra, cam advance is controlled with a PWM signal similar to the boost control signal. Not sure if the OEM uses the same strategy.

n2xlr8n · 10-27-2005, 02:37 PM

I can't recall if (this is from my notes) AZscoobie or Sponaugle posted this, but here 'tis:

"The STI ECU drives the solinoid at about 20hz, with a variable duty cycle that hovers around 55%. This duty cycle is used in conjunction with the feedback from the indivdual AVCS cam sensors to adjust the position of the cam gear relative to the cam. There really isn't a 'full power' position. Looking at my datalogs from the AVCS, the intake cam advance varies quite a bit over the 3-5.5k range. There does not appear to be any adjustment to engine timing, as far as I can tell. Furthermore, even when the intake cam is at full advance, the duty cycle to the solionod is still around 60%, not even close to 100%. I would not speculate about the reliability of the AVCS parts without further analysis of their design, but there is one thing I know: They are hard to get parts for, since they are not available in the US yet. And, we are not sure yet if the AVCS soliniods are the same on the new 2.5 STI.

Control of AVCS is very simliar to how you would control boost. A feedback
mechanism is used to monitor the position of the CAM, while the duty cycle to the solinoid is adjusted. Remember this is a analog system, not digital. It can advance the intake cam up to 35 degrees with 'infinite' adjustabililty.

The primary goal here is to open the intake cam earlier. It does not alter lift or
duration, just offsets the start of the intake valves opening."

HTH

S.

10-27-2005, 03:30 PM

so the signal is the SAME as an EBCS? So i can set it up for 'boost control' but with different parameters?

A hydra is the last resort on a project car we are building...and the AEM is out as it will be very difficult to make certin attributes of this engine and car to work all together and fuction as desired....

however, the MegaSquirt can do all of this, as long as we can get it to talk to the AVCS valves in the correct manner.

Drac9 · 10-27-2005, 04:44 PM

Autronic will work too.

AZScoobie · 10-29-2005, 05:59 AM

US STI's can go to around 30 degrees. JDM cars can go to about 40 or so. The issue with most systems is that since this is a hydralic system and the fuel (oil) changes viscosity with temp and we have two seperate cams we need a closed loop system. Most are not. Its real hard to beat the factory ECU when controlling AVCS. There is a test and calibration procedure that the ECU carries out to set the cams at zero as well. Blindly pulsing the AVCS Solenoids is a crap shoot.

Clark

10-29-2005, 10:06 AM

well....this just got alot more complicated.

PHATsuby · 11-01-2005, 05:36 PM

As I have told Mick already, it is a closed loop feedback system, and the Autronic does this for variable cam timing.

Ben

bboy · 11-01-2005, 08:18 PM

I only know of two people to have tuned the AVCS system, Clark (above) and Phil (Element Tuning). The map is pretty small like 16-32 cells.

patr · 11-01-2005, 10:38 PM

Having been tuning these for years on the rally cars, i can also tell you regardless of what you may believe, that there is oil pressure lag, and you can see up to 15 sec. delay (regardless of the solenoid duty) under certain circumstances. So if you are asking about the signal to 'jimmy up' some sort of control device, you should be aware that just having the _desire_ to advance the cam is not enough, you need the right conditions (i.e. rapidly cycling them on and off, or having a zero to full setpoint in a map, for example, doesn't work like you think it might). This is ECU agnostic, there are physical ways to fix this but they also have some drawbacks. And as mentioned you need a position sensor otherwise you will be all over the place. The Autronic has always worked well for the v7 and up engines.

-Pat
www.rocketrally.com

10-24-2005, 04:26 PM	#1
WJM Guest Member#:	AVCS Signal So what kind of signal does the ECU send to the AVCS solenoid? waveform...on-off....what? Is it just like an injector signal...or...? * Registered users of the site do not see these ads.

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10-24-2005, 04:57 PM	#2
mpaone Scooby Specialist Member#: 3 Join Date: Jun 1999 Chapter/Region: South East Location: Burlington NC Vehicle: 2000 Forester L Silver	Hmmm... thought I read somewhere the the AVCS is a similar signal to the TGV's. Not sure if that helps. -Mike.

10-27-2005, 02:09 PM	#4
fragment Scooby Specialist Member#: 8050 Join Date: Jul 2001 Chapter/Region: W. Canada Location: Bugeye EJ207 - T3T04S - RIP Vehicle: 2004 FXTi - Stage 2 Goooooooolld	With the Hydra, cam advance is controlled with a PWM signal similar to the boost control signal. Not sure if the OEM uses the same strategy.

10-27-2005, 02:37 PM	#5
n2xlr8n Scooby Specialist Member#: 18960 Join Date: May 2002 Chapter/Region: South East Location: Bama Vehicle: 02 WRX MBP It lives! ; )	I can't recall if (this is from my notes) AZscoobie or Sponaugle posted this, but here 'tis: "The STI ECU drives the solinoid at about 20hz, with a variable duty cycle that hovers around 55%. This duty cycle is used in conjunction with the feedback from the indivdual AVCS cam sensors to adjust the position of the cam gear relative to the cam. There really isn't a 'full power' position. Looking at my datalogs from the AVCS, the intake cam advance varies quite a bit over the 3-5.5k range. There does not appear to be any adjustment to engine timing, as far as I can tell. Furthermore, even when the intake cam is at full advance, the duty cycle to the solionod is still around 60%, not even close to 100%. I would not speculate about the reliability of the AVCS parts without further analysis of their design, but there is one thing I know: They are hard to get parts for, since they are not available in the US yet. And, we are not sure yet if the AVCS soliniods are the same on the new 2.5 STI. Control of AVCS is very simliar to how you would control boost. A feedback mechanism is used to monitor the position of the CAM, while the duty cycle to the solinoid is adjusted. Remember this is a analog system, not digital. It can advance the intake cam up to 35 degrees with 'infinite' adjustabililty. The primary goal here is to open the intake cam earlier. It does not alter lift or duration, just offsets the start of the intake valves opening." HTH S.

10-27-2005, 03:30 PM	#6
WJM Guest Member#:	so the signal is the SAME as an EBCS? So i can set it up for 'boost control' but with different parameters? A hydra is the last resort on a project car we are building...and the AEM is out as it will be very difficult to make certin attributes of this engine and car to work all together and fuction as desired.... however, the MegaSquirt can do all of this, as long as we can get it to talk to the AVCS valves in the correct manner.

10-27-2005, 04:44 PM	#7
Drac9 Scooby Specialist Member#: 9861 Join Date: Sep 2001 Chapter/Region: RMIC Location: Colorado Springs, CO Vehicle: 1999 2.35 RS-T w/NOS Hybrid Rally Blue Pearl	Autronic will work too.

10-29-2005, 05:59 AM	#8
AZScoobie Scooby Guru Member#: 8785 Join Date: Jul 2001 Chapter/Region: SWIC Vehicle: 02 c_turner@ix. netcom.com	US STI's can go to around 30 degrees. JDM cars can go to about 40 or so. The issue with most systems is that since this is a hydralic system and the fuel (oil) changes viscosity with temp and we have two seperate cams we need a closed loop system. Most are not. Its real hard to beat the factory ECU when controlling AVCS. There is a test and calibration procedure that the ECU carries out to set the cams at zero as well. Blindly pulsing the AVCS Solenoids is a crap shoot. Clark

10-29-2005, 10:06 AM	#9
WJM Guest Member#:	well....this just got alot more complicated.

11-01-2005, 05:36 PM	#10
PHATsuby Scooby Guru Member#: 13617 Join Date: Dec 2001 Chapter/Region: MWSOC Location: MN Vehicle: 2001 Legacy GT back to stock is a project too	As I have told Mick already, it is a closed loop feedback system, and the Autronic does this for variable cam timing. Ben

11-01-2005, 08:18 PM	#11
bboy Scooby Specialist Member#: 56468 Join Date: Mar 2004 Chapter/Region: NWIC Location: Seattle, WA Vehicle: 04 Improved STI Dirty White	I only know of two people to have tuned the AVCS system, Clark (above) and Phil (Element Tuning). The map is pretty small like 16-32 cells.

11-01-2005, 10:38 PM	#12
patr Scooby Specialist Member#: 97 Join Date: Jul 1999 Location: Vancouver, BC, CANADA	Having been tuning these for years on the rally cars, i can also tell you regardless of what you may believe, that there is oil pressure lag, and you can see up to 15 sec. delay (regardless of the solenoid duty) under certain circumstances. So if you are asking about the signal to 'jimmy up' some sort of control device, you should be aware that just having the _desire_ to advance the cam is not enough, you need the right conditions (i.e. rapidly cycling them on and off, or having a zero to full setpoint in a map, for example, doesn't work like you think it might). This is ECU agnostic, there are physical ways to fix this but they also have some drawbacks. And as mentioned you need a position sensor otherwise you will be all over the place. The Autronic has always worked well for the v7 and up engines. -Pat www.rocketrally.com