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Dual AVCS modification


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Ahoy all. Picked up an 06 LGT 5spd limited sedan a few weeks ago. Long story short, motor's done for. Internals are all scored up. I got a set of STI heads for free from work, and looking to get a new short block directly from Subaru (unless there are cheaper options for me to get in Canada)

 

That said, I've thought about disabling the AVCS on the STI head, with block off plates and potentially new cams. I've heard of modifications to run dual avcs with very little wiring and reflashing the ECU? Can you guys provide me some insight or links to more information on how exactly this is done?

 

Thanks in advance.

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05-09 USDM ECU's don't even have the dual AVCS code, thus they wouldn't know what to do with them. There might be piggy-back systems that could in theory control the exhaust cams, but it's not worth it.

 

I would see if you can just run it with single AVCS, or retrofit a newer ECU with dual AVCS support.

05 LGT 16G 14psi 290whp/30mpg (SOLD)

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

22 Ascent STOCK

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How about disabling the AVCS on the exhaust? With this '09 STI head and cams just machine out some plates for the oil pumps to block them off and replace the exhaust cam phaser with a regular plastic cam gear? Would I need to use the original cam phaser and pump since the LGT has 40 degrees of adjustment, while the STI has 30. Just thinkin that the computer would be fussy about that lack of 10 degree adjustment
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How about disabling the AVCS on the exhaust? With this '09 STI head and cams just machine out some plates for the oil pumps to block them off and replace the exhaust cam phaser with a regular plastic cam gear? Would I need to use the original cam phaser and pump since the LGT has 40 degrees of adjustment, while the STI has 30. Just thinkin that the computer would be fussy about that lack of 10 degree adjustment

 

The AVCS cams are very different then non AVCS ones. AVCS cams are hollow inside for oil flow, which means the non AVCS cam gears will not bolt on. I think you would have to swap in Non AVCS exhaust cams.

 

I think going the JDM ecu route is the cleanest way like utc_pyro mentioned, but I think that requires BDU reprogramming still at the dealer (right utc_pyro?)

 

Talking to a friend and he said I can make my own harness and repin the ECU, flash a dual AVCS ROM on it and go get it tuned. thoughts?

 

If you want to brick your ECU go for it. Unless you really know what you're doing, you shouldn't be flashing other year's ROM's onto older ECU's. But even if you manage to flash a different ECU's code on yours doesn't mean your ECU will have the right pins.

05 LGT 16G 14psi 290whp/30mpg (SOLD)

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

22 Ascent STOCK

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Getting the right heads can't be that much money.
Got em for free, so why not right?

 

The AVCS cams are very different then non AVCS ones. AVCS cams are hollow inside for oil flow, which means the non AVCS cam gears will not bolt on. I think you would have to swap in Non AVCS exhaust cams..

 

I plan to make block off plates for the exhaust AVCS solenoid with a milled piece of aluminum and a banjo fitting to provide lubrication if nessecary. Gonna have to check out where the passages lead to. As for the hollow part, either fill with high temp epoxy resin or tap and screw in bolts with loctite and sealant, then put on the non-avcs cam gear with a non-avcs seal. Cam gear could be an adjustable one, I'm not sure yet.

 

 

All in all though, I've pretty much decided against making the exhaust side AVCS work. Just didnt think that I didn't have the solenoids anyways. So I'll just use my orignal solenoid and cam phaser from the original motor.

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Here is another relevant post, by Bad Noodle non less too! https://forums.nasioc.com/forums/showpost.php?p=44709005&postcount=40

 

This thread has tons of good info and a bunch of smart dudes so maybe you guys can help me clear something up.

 

I have the 08 sti heads in a single avcs car. To run this I removed the exhaust avcs cam gears and replaced them with the standard solid gears. Finally, I rotated the exhaust cam gears clockwise 2 teeth to try and reduce the overlap at idle so it runs like an 04 sti.

 

However, after reading this thread Jeff states that with the exhaust avcs unplugged you would get 23 degrees of overlap at idle. Given that each tooth is 7.5 deg, should I rotate the exhaust cams another tooth clockwise (3 total) to remove the overlap and hopefully clean up the idle? I'm a bit scared to try so I figured I'd get some advice.

 

thanks,

-BN

 

Sadly there are no replies to it, but you could probably do the same.

05 LGT 16G 14psi 290whp/30mpg (SOLD)

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

22 Ascent STOCK

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But even if you manage to flash a different ECU's code on yours doesn't mean your ECU will have the right pins.

+

Contact NSFW on this forum. He has working hack to make the dual avcs work on a 4th gen lgt. Requires an open source tune, I believe.

 

He was making a standalone ECU to control it. Or more accurately a piggyback.

 

There is no hacking the stock ECU to drive the second AVCS set, the required hardware isn't on the circuit board. You need to swap to an ECU with the correct hardware and software combination to both control the AVCS and talk to the rest of the computers. JDM ECU's are the quickest option, you just need to rob and relocate a few pins (AVCS pins work) to the second set of cam position sensors and OCV's.

 

'08+ STI ECU's would also work if you need to keep it emissions legal (ish), and haltech ECU's will spoof the correct ODB-II messages to in theory pass. Both require a lot of rewiring though, an the STI ECU would be pissy about the DCCD computer missing.

 

I think going the JDM ecu route is the cleanest way like utc_pyro mentioned, but I think that requires BDU reprogramming still at the dealer (right utc_pyro?)

 

There is a surface mount EEPROM chip that keeps the immobilizer data you can move over if you're handy. Otherwise the dealers SSM tool can actually register the JDM ECU with the USDM/Canadian BIU and gauge cluster. The issue is more convincing them to try it.

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Ya hearing all that work to make the second AVCS work is such a hassle for so little gain. I may just end up doing that later down the road and build it like an STI.

 

The reason I didn't go for new cams is that they're over 1,500 here in Canada all said and done... Too much. These cams were free. Cheap sensors to plug up the holes, mill a block off plate with oil channels if necessary to lubricate the cam.

As for the oil passages from the cam to cam phaser, tap and screw in some bolts with loctite and high temp sealant on all 4 channels. (easy to undo later down the road)

Maaay get an adjustable cam gear to fine tune the timing but I don't think I would need it. Would definitely need a tune though as the STI cams are a different profile, little but more lumpy. Also will be rebuilding the turbo and clipping it.

 

Thanks covertrussian for the link on that NASIOC forum link. Gives me a bit more confidence on this build.

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I think going the JDM ecu route is the cleanest way like utc_pyro mentioned, but I think that requires BDU reprogramming still at the dealer (right utc_pyro?)

 

Maybe, or maybe not. Depends on how you do it. There are ways around it and when I ran a JDM ECU my car never saw the dealership nor had the BIU reprogrammed.

 

If you want to brick your ECU go for it. Unless you really know what you're doing, you shouldn't be flashing other year's ROM's onto older ECU's. But even if you manage to flash a different ECU's code on yours doesn't mean your ECU will have the right pins.

 

I'd bet he won't brick the ecu unless he keys off the ignition during the flashing process. You can flash all sorts of different files to the "wrong" ECU as long as it is within the same family. The actual hardware may not be present within the ECU to make it work however.

 

I can tell you with 100% confidence that the stock '06 ECU will not have drivers in it to control exhaust cams. But you might be able to flash the JDM or ADM software in it and have it kind of run. You won't have control over the cams though.

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