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Old 07-16-2020, 03:59 PM   #1
protegejustin19
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Member#: 374660
Join Date: Nov 2013
Default Ej20x cam timing

Swapping an Ej20x in my 06 usdm legacy Iím planning on not using exhaust avcs. Plan on using aftermarket uel header and vf52. Now I know leaving it unplugged isnít the best way but itís the easiest. Could I use my old cams,cam gears(static exhaust), and time it normally. Of course Iíd check clearance for the buckets. Or would swapping just the exhaust cam gears from the ej255 to the 20x and timing it normally be okay? Talked to one shop about leaving it unplugged and they said the cam gear moved with it unplugged and valves hit pistons so Iím hesitant to do that. Another guy on YouTube (Subie Sanctuary)said time the Ej20x exhaust cam gears one tooth retarded. Anybody have first hand experience changing the cam timing let me know how it went. Trying to get it figured out before putting the engine in!
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Old 07-18-2020, 12:09 PM   #2
protegejustin19
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Default

Bump anyone
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Old 08-17-2020, 09:18 PM   #3
NSFW
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Member#: 140444
Join Date: Feb 2007
Chapter/Region: NWIC
Location: Near Seattle, WA
Vehicle:
05 Stage Free LGT
ATP 3076, 6MT, AVO FMIC

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The 08 STI exhaust cam pulleys have springs on them which pull the cams into max advance, which is also max piston-to-valve clearance and zero overlap (best idle). With no power to the AVCS solenoid, the cam angle stays put.

The intake cam pulleys are sprung to go full retard, which also gives best clearance, no overlap, and best idle. In other words, all four cams are mechanically configured to move to the position that gives full safety and best low-RPM performance. Probably because after a cold start, the ECU leaves the solenoids unpowered for a couple/few minutes. In other words, the system was designed to be safe with no power to the solenoids.

I don't know about the 20X, but I'd be very surprised if they were different in this regard. AVCS needs oil pressure to work properly and there isn't any right after startup.

I ran the 08 STI heads in my 05 LGT disconnected for months while I worked on an exhaust cam controller, and there was no harm.

Someone else had a similar setup dyno'd that way, and found it to be down 40whp if I remember right. If I remember right, you'd want to adjust the cams by two teeth in the timing belt to get them back to single-AVCS cam timing. Or at least that was the case for the 272 cams that I used - that was my 'plan B' in case the AVCS controller turned out to be too hard.

For your stock cams you should get the specs to see how much they need to be adjusted.
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Old 08-18-2020, 07:51 PM   #4
Yeltsew
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Join Date: Jun 2020
Chapter/Region: South East
Location: Florida
Vehicle:
2011 WRX w/ EJ20X
Silver

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I have an ej20x with a vf52 in my car with the exhaust avcs unplugged right now and I find it to be really laggy and have almost no low end torque. It could be that my turbo is on its way out, but I don't build hardly any boost until 3500-4k rpm. I've seen a lot of people say to retard the exhaust cam by two teeth, like nsfw said.

I do have a hunch that part of why the car feels so laggy is because of the avcs. I'm going to talk with my tuner on Thursday and see what he thinks, because I'd really like to try and make this car a lot less laggy and have more low end, like the 20x engines came in Japan. I'm not searching for crazy high power numbers, just a wide powerband.

Quote:
Originally Posted by NSFW View Post
The 08 STI exhaust cam pulleys have springs on them which pull the cams into max advance, which is also max piston-to-valve clearance and zero overlap (best idle). With no power to the AVCS solenoid, the cam angle stays put.
I really want to try getting your avcs controller working on my car. I know you designed it with a 257 in mind, but I'm sure it could easily be adapted to work with a 20x (or maybe already has and I just missed it). I tried sending you a message asking if it was something you'd be willing to give some advice on, but it said your inbox was full.
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Old 08-21-2020, 12:46 PM   #5
protegejustin19
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Iíve got word to just set the exhaust side back one tooth with jdm Ej20x cam gears which is what Iíve done should have the engine installed by the end of this week so Iíll post back with updates
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Old 09-04-2020, 06:53 AM   #6
NSFW
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Member#: 140444
Join Date: Feb 2007
Chapter/Region: NWIC
Location: Near Seattle, WA
Vehicle:
05 Stage Free LGT
ATP 3076, 6MT, AVO FMIC

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Quote:
Originally Posted by Yeltsew View Post
I really want to try getting your avcs controller working on my car. I know you designed it with a 257 in mind, but I'm sure it could easily be adapted to work with a 20x (or maybe already has and I just missed it). I tried sending you a message asking if it was something you'd be willing to give some advice on, but it said your inbox was full.
I PM'd you my email address. I'm pretty sure my controller can be adapted.

There are basically three places where the controller touches the engine:

1) Crankshaft position. I was too nervous about wiring into the stock electronics, so I painted a white mark on a quarter of an AVCS pulley and put an optical sensor in the fan shroud. That should adapt to any EJ. If the fan shroud is the same, you can use the same 3d-printed sensor mount that I used, the file for that is on the github site. If not, you'll have to improvise.

2) AVCS Solenoids. I suspect the AVCS solenoids work the same way - it's just a 12v solenoid that takes a PWM signal to control it.

3) AVCS Sensors. I have no idea whether the sensors are the same or not. But even if they're not, it probably won't take a ton of work to adapt to it.

The USDM sensors take 12v and ground and there's a third line that gets pulled to ground when the cam timing trigger goes past (twice per revolution if I recall correctly).

I can do software, but electrical engineering isn't my thing... I was lucky to have a coworker a couple years ago who volunteered to figured out the sensors and the interface circuit for me. If you're good with electronics, or if you have a friend who is, then hopefully you can figure out how your sensors work, and how to interface with them.

Everything I have is on GitHub, here: https://github.com/LegacyNsfw/AvcsController

Last edited by NSFW; 09-04-2020 at 06:54 AM. Reason: GitHub link
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