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Old 12-10-2012, 01:57 AM   #26
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Quote:
Originally Posted by jkopinga View Post
^^^ Phil is right!

Cars with AVCS have the Intake cam sitting at a centerline of approx. 125* ATDC since the AVCS pulley is sitting in the most retarded position.

Cars without AVCS have the Intake cam sitting at a centerline of approx. 113* ATDC with the fixed pulleys.

This is most likely where the difference that people talk about come from. However in order to be sure where your cams are sitting at I would always recommend using proper cam timing tools so you know what you are doing.

Jasper.
Please help me understand the basic mechanical function of the AVCS system. If at resting position an AVCS intake cam is sitting at 125*, that means it is farther advanced than the non-AVCS cam that sits at 113* in resting position by 12*.

(the following is what I'm asking you to fact check. Please tell me if I get anything wrong here. I don't want someone to read this and think it's gospel)
When the engine is running at idle or low load the ECU is telling the AVCS solenoids to stay put and not release additional oil pressure to the AVCS cam gears. This preserves the advanced 125* state of the cam gear. As load levels increase and boost is made, the ECU starts running more fuel and the static 125* (advanced state) of timing will cause detonation so, the ECU sends a signal to the AVCS solenoids to release more oil pressure to the AVCS cam gears which in turn, retards the timing back to anywhere between 124.9* to 113* to prevent detonation.

Do I have that right?
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Old 12-10-2012, 08:47 AM   #27
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^^^ The AVCS cam sits at a Centerline of 125* roughly. The NON-AVCS cam sits at 113* roughly. Those figures are ATDC figures. Therefore a higher figure means more RETARDED. The AVCS cams sit in a more retarded position than the NON-AVCS cams.

At idle the AVCS is left in the retarded position to keep vacuum as high as possible for a stable idle due to little intake/exhaust overlap.

At low RPM where load is high the Intake CAM is advanced to generate more TQ due to better scavenging with more overlap. As revs rise and exhaust back pressure becomes larger and long overlap isn't desired the Intake cam retards back.

Detonation is not taken into consideration by the ECU to control the cams. The ECU might merely retard IGNITION timing but not cam timing.

Jasper.
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Old 12-10-2012, 11:27 AM   #28
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I'll add to that, the advancing of the intake cam increase dynamic compression which is also part the reason it increase low RPM power and results in quicker spoolup of the turbocharger. We measured the cranking pressure as we advanced the cam position and it added something like 25 psi.
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Old 12-10-2012, 02:28 PM   #29
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^^^ You guys are brilliant. Thanks for the clarification and education.

To bring this back into the realm of putting an AVCS motor in a car not equipped wiring/ECU-wise to run the AVCS, I have a few follow ups. I hope you guys can give me some clarity on the pros and cons of each of these possible setups.

ej257 engine and heads run with either:

1. STi AVCS cams & AVCS cam gears with the AVCS solenoids disconnected.
2. STi AVCS cams & ej205 cam gears with the STi cams plugged and AVCS solenoids disconnected.
3. ej205 cams & ej205 cam gears with AVCS solenoids disconnected.
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Old 12-11-2012, 07:18 AM   #30
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Difference between 1 and 2 is that the Intake Cam will simply sit at a different centerline. With the AVCS pulley it will sit right at approx. 125* ATDC whereas with the EJ205 pulley it will sit at approx. 113* ATDC. Also EJ205 pulleys are safe in that they will NOT move. Further explained below.

More retarded Intake Cam centerline will give more topend but later spool and less low rpm TQ. Another option would be to just move the AVCS pulleys ONE TOOTH on the belt so that the Intake Cam timing is advanced. One tooth = 360* / 48 Teeth = 7.5* of CAM TIMING!! Keep in mind that this is the TWICE the amount of Crank timing and therefor the new Centerline will be 125* - (2x 7.5*) = 110* ATDC.

However with no working AVCS solenoids, etc. I would NOT rely on AVCS Pulleys. There is a spring loaded pin inside the pulley which keeps it mechanically in the most retarded position and prevents it from moving. Normally the oil galleries in the AVCS pulley are full with oil so the whole pulley is sort of hydrolocked and can't really move anyway unless oil is moved by the solenoids.

However it is not uncommon when blanking off oil holes in the cam that these oil galleries are empty and you're only relying on that spring loaded pin to keep the pulley in position. NOT GOOD! If I must use AVCS pulleys on a NON-AVCS car I open up the pulleys and insert specially machined "beads" to make sure the pulley is solid and won't move.

You will need to use different Cam oil seals if you use either AVCS Pulleys or EJ205 Pulleys so keep that in mind.

Option 3. I can't quite remember the duration/lift and centerlines of the EJ205 cams off the top of my head without checking back my measured data but I would not recommend this. I don't think they're gonna work better on a 2.5L AND if you decide to swap ECUs and make the AVCS operational you would have to pull the Cams and swap them back to AVCS cams as the pickup pattern is completely different.

Jasper.
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Old 12-12-2012, 04:55 PM   #31
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Quote:
Originally Posted by jkopinga View Post
^^^ The AVCS cam sits at a Centerline of 125* roughly. The NON-AVCS cam sits at 113* roughly. Those figures are ATDC figures. Therefore a higher figure means more RETARDED. The AVCS cams sit in a more retarded position than the NON-AVCS cams.

At idle the AVCS is left in the retarded position to keep vacuum as high as possible for a stable idle due to little intake/exhaust overlap.

At low RPM where load is high the Intake CAM is advanced to generate more TQ due to better scavenging with more overlap. As revs rise and exhaust back pressure becomes larger and long overlap isn't desired the Intake cam retards back.

Jasper.
So if I put ej205 non-AVCS cam gears on STi cams, where would the intake cam sit at TDC? 113*?
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Old 12-13-2012, 02:07 PM   #32
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Originally Posted by Soarer View Post
So if I put ej205 non-AVCS cam gears on STi cams, where would the intake cam sit at TDC? 113*?
Anyone?
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Old 12-13-2012, 02:58 PM   #33
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+1.. Im waiting to see if anyone has an answer? Ive got both sets of cams and gears, gna have to do some comparisons..
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Old 12-13-2012, 03:01 PM   #34
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Quote:
Originally Posted by Soarer View Post
So if I put ej205 non-AVCS cam gears on STi cams, where would the intake cam sit at TDC? 113*?
Yes, the only difference between WRX cams and STi cams the lift. Duration and centerline are the same with non-AVCS gears.



^^
Just talking single AVCS STi cams
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Old 12-13-2012, 03:19 PM   #35
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Originally Posted by kellygnsd View Post

Yes, the only difference between WRX cams and STi cams the lift. Duration and centerline are the same with non-AVCS gears.

^^
Just talking single AVCS STi cams
Ah hah! Thank you! So, plugged STI cams with non-AVCS gears is the way I will go. Very much appreciated.
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Old 12-15-2012, 09:00 AM   #36
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^^ Yes, Non AVCS gears with AVCS cams will sit at 113* ATDC with the centerline.

Jasper.
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Old 12-23-2012, 08:33 PM   #37
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To run a set of aftermarket 272/272 ej205 cams on my sti heads do I need to do anything funky for oiling? I know the avcs solenoid feeds the front journal just making sure I won't starve that bearing as long as I leave the avcs solenoid there . Or is there any way I can remove the solenoids and the avcs hard oil feed and just use that back port for the turbo only
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Old 12-24-2012, 12:01 PM   #38
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^^^ You need to run ej205 cam seals. Other than that, I believe you'll be fine as long as you run all the other regular avcs oil feed lines. The only way the front cam journals get oil is through the extra oil feed line for the avcs. I don't think there's a way to block off that line without starving the front journal.

I'm just setting this up on my car for the first time now. I'm using STi cams that I plugged last night which was very easy. Just used a 10/32 tap and 10/32 set screws with some thread locker.
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Old 12-24-2012, 01:25 PM   #39
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Quote:
Originally Posted by Soarer View Post
^^^ You need to run ej205 cam seals. Other than that, I believe you'll be fine as long as you run all the other regular avcs oil feed lines. The only way the front cam journals get oil is through the extra oil feed line for the avcs. I don't think there's a way to block off that line without starving the front journal.

I'm just setting this up on my car for the first time now. I'm using STi cams that I plugged last night which was very easy. Just used a 10/32 tap and 10/32 set screws with some thread locker.
I figured it would be fine but wanted to double check. Just planning on buying the wrx cams instead of sti ones because I found the on clearance online for 500 bucks for crowers instead of the 640 I was gonna spend for BCs
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Old 12-24-2012, 02:18 PM   #40
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I'm curious to see how it all works when I get it running. I am a bit concerned about the oil not leaking past the ej205 cam seals. The cam caps on the B25 heads have an oil passage in them that sends oil out the front of the forward cam journal between the inside of the cam seal and the end of the cam journal. The S20 heads don't have this groove. I'm wondering how much oil sits between the front end of the ej205 cams and the back side of the cam seal and also if there is any oil pressure there. With that groove in the B25 cap, I'm guessing there will be oil pressure there which will push the cam seal outwards. I haven't heard of anyone saying that they were blowing ej205 S20 cam seals out when using plugged sti cams on B25 heads with ej205 cam gears though.

Does anyone know if I will have trouble with oil leaking around the cam seals using this set up? Just to clarify, B25 heads with all AVCS oil lines & solenoids in place but AVCS electrics not hooked up, plugged STi cams, ej205 cam gears and cam seals.
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Old 12-24-2012, 02:56 PM   #41
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Mine never leaked or affected the front cam journal...

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Old 12-26-2012, 11:31 AM   #42
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The correct way to do this would be to weld or drill+tap+plug the AVCS camshaft to prevent oil seepage. You will also need to run WRX cam seals (OEM PN#806732160), and a set of adjustable cam gears or LIC Motorsports adjustable tensioners. You will need to set your intake centerline with a degree wheel and dial indicator, to the same as WRX in order to not have retarded timing (Pun 100% intended).

I'm running Dual AVCS heads in my 08 STI with AVCS 100% deleted and solenoids disconnected and a set of BC cam gears. I set it to WRX centerline with a hair of advance.




In my opinion adjustable cam gears are the best option but similar timing can be done with LIC's adjustable tensioners and factory gears but it will be a pain and not be 100%. It'll get you close, but not exact.

Here is some degreeing information for you, though it's on a v8 it can be de-coded for EJ-series.

http://www.lunatipower.com/Tech/Cams...egreeACam.aspx
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Old 12-26-2012, 12:34 PM   #43
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So running sealed avcs oil holes with wrx cam gears, timing marks lined up will still be retarded timing? Any idea how much? if its enough I guess its worth gettin the idler bearings.. are we talking 10 degrees off still or just a couple? I do not plan on trying to degree my build, and have never heard of this being done to any swaps.. New knowledge is crucial, but any exact numbers recorded here?!
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Old 12-26-2012, 12:56 PM   #44
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Quote:
Originally Posted by 99imprezd View Post
So running sealed avcs oil holes with wrx cam gears, timing marks lined up will still be retarded timing? Any idea how much? if its enough I guess its worth gettin the idler bearings.. are we talking 10 degrees off still or just a couple? I do not plan on trying to degree my build, and have never heard of this being done to any swaps.. New knowledge is crucial, but any exact numbers recorded here?!
No you will have the correct centerline but if you have done any head or block decking and use the stock thickness HG your stock timing marks can be slightly off. The LIC/Crawford adjusters are made for just this reason. I made up the decking difference with a thicker HG.


And by off slightly I mean 1/2 degrees or maybe a degree or two.
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Old 12-26-2012, 01:00 PM   #45
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With fixed gears (WRX) you will be fine, timing will be correct as the gear is set for a WRX Centerline. If you have different than OEM thickness gasket and have had the block and head resurfaced you can get away with LIC adjusters to fill the difference.

I however degree each motor I build so I always go with a set of gears. I suggest, Tomioka or BC. (Tomei is the same as Tomioka gears).
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Old 12-26-2012, 01:16 PM   #46
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STI cams with WRX cam gears are fine in a non avcs application. You don't need adjustable cam gears.
There is less overlap on the sti cams that may affect spool, I didn't notice it when I swapped from WRX to STI cams but my heads were ported. I did do a bit better on the top end.
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Old 12-26-2012, 01:42 PM   #47
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Does anyone know the procedure to measure a head to see if has been decked and if so, by how much?
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Old 12-26-2012, 01:42 PM   #48
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You don't need them, but it is the correct and suggested way to do this. Especially if you are using aftermarket cams (I'm aware the OP is not). Again, LIC adjustable idlers will do the trick if running fixed gears.
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Old 12-26-2012, 01:48 PM   #49
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Quote:
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Does anyone know the procedure to measure a head to see if has been decked and if so, by how much?

Best way is to find a set of head to haven't been machined yet and measure deck to cover. I'm sure these numbers have to be somewhere out there on the internets!
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Old 12-26-2012, 02:05 PM   #50
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Deck height is 201mm
Edit: Sorry read block somehow.
Standard height of cylinder head:
127.5 mm (5.02 in)

Last edited by theotherguy; 12-26-2012 at 04:09 PM.
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