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Subaru dual AVCS + Haltech Elite 2500 Cam errors

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Hi guys, new to the forum. I have a 2004 JDM subaru legacy gt with quad avcs.

Have recently got the bottom end built using forged components. The compression now is 8.45:1

Oil is Motul 300v 5w-40

The turbo I am using is a twin scroll holset hx35 with a 7 blade billet wheel.

All the other usual mods (FMIC, FPR, DW65c fuel pump, DW850cc injectors).

Have upgraded the valve springs and mild port and polish of the heads, but still using the factory cams.

The car has been run in and tuned, but there seems to be avcs issues the tuner is encountering.

The timing was checked and cylinder leak down test, and they both were good.

The avcs don't seem to behave the same every run. The intake cams as well as the exhaust cams don't fully follow the target set in the avcs. The errors are not consistent at a certain RPM or load, they just don't hit the target sometimes and sometimes they will.

I have attached 2 log files and they were run 2 mins apart. The logs show the cam angles of each bank (intake as well as exhaust) and the cam error, which fluctuates up to 6-7 degrees, which is affecting boost and torque and my final power figure. The first log is about 2 mins long, but the dyno run is at the end and it there is a cam error in the intake of 7.4 degree at 3.8Krpm and -2.4 at 4.1Krpm in the exhaust.

The log 2 had a intake cam error of 5.9 at 4.1Krpm and -4.3 at 6.0Krpm.

If the error amount for both the exhaust and intake was the same this could've been adjusted with PID control and solenoid Hz. But the error is not the same, so it got us stumped.

Have checked all the cam sensors, there are no screens in the bango bolts going to the avcs as well. Have checked the solenoids as well. Short of me changing all the cam pulleys is there anything else to check for? I am just wondering if there is build up of some sort in the pulleys? The car has done 200,000 kms, and these are still the same pulleys, they were not disassembled but just cleaned from outside and put back on the heads.

Attached Files

I've actually just had a similar situation with our 08 JDM STi running an Elite 2500. I had in particular one intake cam that was quite different to the other. I found an issue related to the solenoid frequency. With the stock frequency of 330 Hz (from memory) if I zeroed the PID values and stepped the base duty cycle values up to the point the cam would start moving, one cam would respond as expected and a 15 change in duty would have the cam move back and forth but the other cam would require a 10% change to bring the cam angle back. I queried Haltech and they had no suggestions. By pure fluke i tried dropping the solenoid frequency down to 150 Hz and all of a sudden both cams responded properly. Haltech still haven't been able to give me a reason for this.

The other thing I found was that the PID values in the base map provided really poor control and I spent quite a lot of time doing step tests at 2000 rpm on both cams to get control I was happy with. The fact that you've changed valve springs will have an effect on the PID control anyway so this could be your sole issue here.

Forgot to mention in the first post, the car is 2.1 stroker, so closed deck block with 2.5 sti crank. But the heads nor the block have not been decked, so the height should not be off of the whole setup.

Yea the support is quite poor with Haltech, they said the cam error value is ok, despite it going up to 7 degrees off target. I have ordered some new pulley's and solenoids as well. And yea I think the stock frequency is 330Hz or something close. But in the mean time, can I just change that to 150Hz and do some logging instead of me taking the car to the tuner. And if the error decrease I can take the car back to tuner and get it checked and do other adjustments?

this is fitting, we just did our first wrx with a maxxecu and i found it odd the cams used two different setting... now i know to just go head and fine tune them as needs be.

@sleepr, I'd suggest changing the frequency but understand that this will definitely change the behaviour of the cam control system so there's a bit more to it. At a minimum you'll need to zero the PID settings and test to find the base duty cycle for each cam. Beyond this this though the PID settings may need to be tweaked to suit.

Hi Andre - I am having very similar issues trying to get an Elite 2500 ECU working with a USDM 2011 STi. I can't even get a good home sync and experience a lot of errors.

Could you perhaps share you trigger and PID settings so I can see if anything you are doing helps my situation?


Cheers Andre, yea I figured it would change the behaviour in terms of duty and as well as the PID. I will reduce it to 300Hz and 250Hz first and log them. I know link ecu has a mixture of 250 to 300Hz on the subarus but there isn't a plug and play ecu for my car.


Please, if you did have, or are still having issues... Join me on this post, so I can try to test against my issue and get it fixed with Haltech... The frequency is sensitive, but that is the least of the issues with the PID

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