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06-12-2015, 02:56 PM | #51 |
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bump from the dead...
I have a 2002 WRX with a DAVCS engine, running stock 2002 wrx ecu (no avcs), and have extremely slow turbo spool. I believe advancing the timing on the cam gears will solve this. Just need to figure out which direction to turn the cam gears... Has anyone else installed davcs cams in a non avcs motor and adjusted timing successfully to compensate? After all of my research, I thought that turning the cam gears clockwise would advance them, including the exhaust. I am still unsure about turning the exhaust cam gear CCW to compensate, wouldn't that be more retarded? It looks like xluben has changed his cam gear timing a few times to modify the powerband due to no avcs with successful results. (http://forums.nasioc.com/forums/show...postcount=1235)
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06-13-2015, 03:35 PM | #52 |
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So TomacGTi definitely got it right.
I just looked into it: http://forums.nasioc.com/forums/show....php?t=1411812 So from his info and Perrin's thread: The wrx sprockets open the exhaust valves 55* BBDC. The davcs exhaust cams open between 32* and 72*. The oil pressure moves the cam from 32* to 72*. So with the wrx solid cam gears, there is no oil pressure so they're set at 32. But the wrx solid sprockets move the alignment mark 6* CW relative to the cam. This means that when you line up the sprocket tick marks, it's really rotates the cam 6* CCW. So you end up with 38* BBDC. So then if rotate the exhaust sprockets 2 teeth (15 deg) CCW relative to the belt mark you end up with 38+15=53deg .. close enough. I personally still get misfires on my davcs runing single avcs setup but only at idle where there is no intake advance. Maybe I'll try playing with it. But it could just be my crappy engine build. |
06-16-2015, 03:24 PM | #53 | |
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Quote:
Interesting... Do you know if the same would apply to advancing the intake cams? |
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06-16-2015, 09:52 PM | #54 | |
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Quote:
You can get away with this on the exhaust cams for an 02 because there is no pickup there. Your easiest solution is to obtain the correct seals and cam sprockets (adjustable for the intake) and this will allow you to move things around a bit easier. The cams work with one another and I only got mixed results moving them individually. In the end, I settled on the WRX rest positions as they were where I needed to be for my motor/turbo combo. I wish I could run AVCS as it really is the best of both worlds but I was not willing to go down that road. -Randy |
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06-16-2015, 10:23 PM | #55 |
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Cool. Thanks Randy.
When I get adjustable cam gears: advance intake cams 9* (inside of adjustable cam gear clockwise) retard exhaust cam 2 teeth (whole cam gear counter-clockwise), advance exhaust cam by 4* (inside of adjustable cam gear clockwise) |
06-17-2015, 07:47 AM | #56 |
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That will put the cams in the STi rest position with single AVCS.
I got better results (once again, on my car) using the WRX positions. If you have the time to experiment, leave the cam covers off until you're finished. It's a PIA to adjust the gears with them on. Spool also improved with the additional overlap at the expense of top end (moving the curve around via the gears). Also invest in the right angle screwdriver (basically a ratchet with bits) for better access to the lock down bolts for the cams, a mirror and a flashlight. There is literally little to no room in there. -Randy |
08-05-2015, 01:43 PM | #57 |
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I've read this a few times and I'm still not sure how I can apply this to my situation. Input please?
2004 Forester XT with 2004 STi ecu flash and EJ257 with 2012 STi DAVCS heads, complete with exhaust AVCS solenoids and adjustable sprockets; no connection of the exhaust system to the ecu (duh). The sprockets are currently indexed to the factory marks. My recent tune came up disappointing (between 35 and 50 hp less then expected/hoped for). I'm thinking that by rotating the exhaust sprockets two teeth CCW, I will put the cam phasing close to where a single AVCS EJ257 lives. True? False? Why? Thanks in advance... Steve |
08-12-2015, 11:44 AM | #58 |
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Ok, I've been reading up on this topic A LOT.
One thing bothers me. People talk about one cam tooth being about 7 degrees. Is that 7 degrees of the cam sprocket, or 7 degrees of crank rotation? Because the crank is running at double speed compared to the cams. |
08-13-2015, 12:17 AM | #59 |
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7* on the cam sprocket. One tooth.
One tooth is worth obviously 14* on the crank and since the crank's position (and pistons) stay fixed, all the movement is concerning the camshafts. What brought this all to play was trying to optimize a movable cam in a fixed state, and from what I have found, the best compromise for my own personal vehicle was using the WRX rest positions for both exhaust and intake. Since my setup is a not as aggressive as others, stock settings worked best to take advantage of the additional lift the cams provided over their WRX counterparts. |
08-13-2015, 12:21 AM | #60 | |
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Quote:
Others have used the AVCS cam gears and skipped teeth but a safer bet would be to use the fixed cam gears and cam seals. The gears can move since the solenoids are not in play. That and you have to make sure where the cam sensor pickup is and is the car reading it. -Randy |
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08-13-2015, 11:22 AM | #61 | |
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Quote:
I invested in a new exhaust AVCS solenoid (one was missing) so both sides have correct oil paths through the cams. I'm *hoping* the oil pressure will keep the cams in place. No sensors wired in on exhaust side, so I should be fine there. The ECU has no facility to read it anyway. |
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08-14-2015, 12:30 AM | #62 |
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Also, don't forget that the AVCS gears do not have the 6* advance built in so it will be off a bit when trying to zero the cams at rest.
It will be closer than where you are now but still not perfect. |
08-20-2015, 11:27 AM | #63 |
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tomac, you are awesome for providing all this information. I had an ej20x with dAVCS (QuadAVCS). I did an entire sti wiring harness swap to control the intake avcs. I planned to run a jdm legacy ecu + harness however, with it being part canbus it was not possible as my instrument panel wouldn't work in a WRX chassis without other Legacy electrical parts.
I ran the engine with my 30r and spool cam in about 4300 rpm with only the intake avcs active. This was similar to my 2.1 stroker before I melted a piston at the drag strip. However, the ej20x engine was horribly down on power due to the exhaust cam in the wrong position. I used to hit 370whp on my stroker where I can barely hit 300 with alot of midrange missing on the ej20x. I'm attempting to build a standalone avcs controller to compensate. But one thing is certain, running exhaust avcs cams without ability to control them either via a avcs controller or adjustable cam sprocket is not good for power. I expected this but I wanted to experiment, I figured I can always adjust the exhaust cams by moving them 2 teeth ccw. One interesting note is that I didn't know that the sti intake AVCS cams needed to be adjusted as well. Many people run time and are happy with the results. I ran them on my 2.1 stroker, I wonder if the engine would perform better had I just used wrx cams. Currently, I'm in the process of building a 2.1 stroker running ej20x heads. I'm considering to run sti exhaust cams, however, I really interested in building that avcs controller. |
09-28-2015, 01:40 PM | #64 | |
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Quote:
Last edited by fragment; 09-30-2015 at 11:49 AM. Reason: Fixed pic link |
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09-28-2015, 10:16 PM | #65 |
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I haven't checked on this thread in awhile due to work and also not being anywhere near my car.
Nitros: the cams should work in harmony and I found that there is a sweet spot. Like I keep saying, I reverted to WRX positions because after all the mucking about, they ran the best on my car. At least you have the intake AVCS active. By all measurements, the cams are identical in lift and duration to their single AVCS counterparts so setting at least the rest position of the exhaust should yield better performance. I really don't know how people would run these cams dropped in. You leave a great deal on the table. There's a reason Subaru decided to move them around and not leave them static. Though slightly better than stock WRX, there is a great deal of potential there. And Fragment: glad to hear the results. I experienced the same: nothing and then 4k rocketship. It's impressive but not very usable. If anything, it demonstrates what you can do when they're actively moved around aka AVCS. -Randy |
11-14-2016, 04:48 PM | #66 |
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So from PM'ing back and forth with Bad Noodle, he has found that the optimal position for the cams at WRX rest position: one tooth CCW from the mark on the fixed sprockets, not two. He also has photos as well on his thread on exhaust AVCS delete and oil flow.
http://forums.nasioc.com/forums/show....php?t=2104941 Him and I have been battling a slightly rough idle and random CELs that have had me trying everything under the sun to alleviate/fix the problem. Since his motor was apart, he degree'd both cams, both gears and found the compromise and solution. The DAVCS exhaust cam with the fixed sprocket is 8* retarded in relation to the rest position of an 07 WRX. Since one tooth is 7.5 degrees, this will be close enough without using vernier gears. This also explains that the cams sit fully advanced and are then retarded by the ECU to their predetermined locations. When initially placing the cams at two teeth CCW, it would emulate full rest (fully advanced) introducing a great deal of overlap that would affect idle as well as all across the RPM range, most noticeably up top. Depending on your setup, a little overlap is OK as it will help spool the turbo as well as move the curve to the left. Mine are currently at 2* advanced from the one tooth CCW rest position to give the best balance since I am running no intake AVCS as well as a smaller turbo. I think this can now close this and I can say that if you are to maximize STi cams, a set of sprockets and a boatload of patience is a necessity. Otherwise, stick with stock WRX or a known aftermarket set. -Randy Last edited by tomacGTi; 11-14-2016 at 04:57 PM. |
03-23-2017, 12:54 AM | #67 |
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Wow, great info in this thread. Thanks for all the work and information. I stumbled into here looking for info on if DAVCS cams work in non AVCS heads and you went above and beyond in this thread.
So to pose one question I really didn't see an answer to, do you think you gained anything by running DAVCS cams after settling on final settings? Here's my dilemma, I'm putting together an EJ257 for a GC8, and I have a set of EJ205 heads with stock cams, and a set of DAVCS complete with cams/solenoids, and I'm contemplating which route to go. 2.5 hybrid with stock cams, or DAVCS cams, or 2.5 longblock with DAVCS delete. I have options, not sure which road to take. Or I can sell the DAVCS heads, port the 205 heads and buy Tomei cams......... Interested in hearing your opinion since you messed with the DAVCS cams for so long. |
03-23-2017, 08:06 AM | #68 |
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The one part you need to also purchase that is often overlooked are a set of sprockets. I would recommend them for both aftermarket and the DAVCS cams.
This is mainly to help tailor the curve as well as to degree them in correctly for the motor. You cannot run DAVCS cams on the intake side without them because of the trigger location (for non AVCS use: OEM EJ205). Easiest route would be to port the 205 heads and chamber match them to the 257 block, buy a known set of aftermarket cams and sell all of the related DAVCS hardware to help fund the costs. Though you gain additional lift with the DAVCS cams, it is minor in comparison to a well sorted, known set of aftermarket cams. You should also consider the grind in relation to the turbo, the use of the car, the flow of the heads etc. Big cams are a pain in the normal world and only work really well when in their element aka: on boil. All this being said, there is a difference, albeit a small one, in comparison stock-for-stock. After the dust had settled though, if I had put in a set of Poncams, I would have been done in a fraction of the time with possibly more power and less chest pains. Same could be said with using a set of 205 cams as well. Live and learn. Hope this helps. -Randy |
04-18-2017, 02:05 AM | #69 | |
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Quote:
I am doing a JDM EJ20x DAVCS (Z20 heads) swap into an '04 Forester XT (obviously, previously EJ255 w/B25 heads) due to the want/need of AVCS and the 3 wire cam position sensor for a cheap drop in due to time and money constraints. (Very similar to fragment's issues during the EJ257 w/'12 STI DAVCS heads) At this time, I only want to run intake AVCS and leave/unplug the exhaust AVCS, primarily because the USDM ECU and intake, wiring harness only allow for it. But I'd like to minimize the loss in power that occurs when using "normal" timing belt notches on the exhaust side. So if you are keeping AVCS exhaust cam sprockets, rotate both driver's side and passenger's side CCW 2 notches? If you are using fixed/solid non-AVCS exhaust cam sprockets (of course using proper cams and block off plate, etc.), rotate CCW only 1 notch? Do you know if the EJ255 varied in either/both the intake and exhaust cam timing from the STI or WRX as referenced earlier in the thread that would change this "fix"? Please let me know if you see any other known big issues dropping in an EJ20x into an 04-05 FXT. Thank you so much! |
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04-20-2017, 06:39 PM | #70 |
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One tooth CCW for both DAVCS and fixed.
Cam timing is set the same across all EJ motors. The difference is in the programming of the ECU |
10-30-2017, 11:43 PM | #71 |
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I am currently trying to swap an EJ20X into my 03 WRX.
Given the fact that it appears very difficult to run the JDM computer, or alter the AVCS system without running into heavy compromises, would it be better to just swap the cam system from wrx to the legacy motor?? I found this thread a little late but.. I hope not too late. Haven't modified anything yet.. Looking at my options.. My thread on this is here https://forums.nasioc.com/forums/sho...php?p=45398476 Any input on it is greatly appreciated! |
10-31-2017, 08:21 AM | #72 |
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Reading through your thread, if you want to minimize the BS: service your existing heads. Send them out to a good, known shop. Not Johnny's down the street that does a bunch of American stuff but a place that knows Subarus and their inherent quirks and follies.
You will still have to set lash with the heads bolted to the block: I cannot stress this enough, BOLTED to the block. I say this because the cost, complexity and workarounds are not worth the hassle of making the dAVCS heads work in your car. Unless you are going to make the dAVCS functional, stick with what works. Everything is documented in the forums whichever direction you may take but if it is outside your capability: caveat emptor. |
12-16-2017, 11:35 AM | #73 |
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Thanks for that.
I ended up keeping the AVCS setup of the EJ20X, with the solenoids unplugged. Running an FP blue with this setup, I'm picking up full boost at around 5k.. It basically doesn't make much power until about 4k.. Here a combination of no avcs plus a bigger turbo. I'm having it tuned by JR tuned.. not expecting anything great.. but I am very happy the engine is running well. With preliminary tuning, it does pull quite hard at high rpm.. much harder than I used to with my TD04-19T. I left everything alone in case I ever wanted to use the AVCS with either another ECU or some other controller.. Maybe one day.. I was wondering though, if the cams are all at rest, is there a chance they can come out of rest on their own? |
04-29-2018, 09:41 PM | #74 |
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New here! I have a 2005 LGT with a ej20x in it. I plugged the exhaust AVCS cam holes and am used the fixed cam gears from my ej255.
Exhaust cams were advanced (moved 2 teeth CW relative to the belt) and it ran with slow spool and poor power. Read this and then moved them 2 teeth CCW relative to the timing marks, as from what i understand this is the more correct timing, but and now the car won’t fire. Am I missing something or any ideas why? And yes, I promise I know which way clocks turn. Thanks fam. |
04-30-2018, 06:40 AM | #75 |
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