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Old 10-18-2017, 01:04 AM   #1
2004OutbackSS
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Default EJ253 Running without I-AVLS

So here is my conundrum guys, longtime gearhead, first time Subaru Owner. Picked up a 2004 Outback 2.5 NA 5 Speed for a very good deal, blown engine, running on 3 cylinders. The 4th was in pieces and it still ran, badly, but it ran. I'm impressed so far, I've seen bigger engines give up completely from less catastrophic damage.

I've found an EJ253 our of a 2009 Legacy 2.5I 5 Speed, yes, I know it has the I-AVLS System, that is not compatible with my 04, but it was cheap and a peach of a motor, lower milage, clean as a whistle inside according to my probe.

Does the I-AVLS really matter?

my research into the system seems to indicate it only affects a single valve of the two on the intake on each cylinder and only at high RPM, the HP difference between a EJ251 and EJ253 with the I-AVLS is 8 HP.......8 at High RPM.

Has anyone run an EJ253 without it and had any problems?
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Old 10-18-2017, 06:27 PM   #2
Elbert Bass
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Ever driven a car with the emergency brake on? It's gonna be like that on the highway.
lower RPM will be fine, maybe a hair more responsive.
Over 2500 RPM you need full lift on both valves, not 100% on one and 10% on the other.
Don't even think AVLS is what makes that extra 8 HP cuz it ain't.
This might help you understand. https://en.wikipedia.org/wiki/Active_valve_lift_system
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Old 10-19-2017, 03:59 PM   #3
GrundleJuice
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If you check out the "ej253 into ej251 car" thread you might get most of the info you need. One member swapped a 253 into a Forester and used the old 251 intake manifold assembly, including all of the associated sensors, and ECU. He reported no major noticable change in performance or drivability from the 251 that was in it before. He didn't mention gas milage.

I don't think the i-AVLS is at all about peak HP. Instead, I think it's about efficiency and a broad tq curve and probably emissions, too.

You are correct about it affecting only one of the two intake valves. It changes from a lower lift cam lobe profile to a higher lift can lobe profile, and maybe different duration. However, it is not purely RPM based. Any moderate or more throttle input will cause the ECU to trigger the higher lift mode at any rpm above ~2000 or so.
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Old 10-20-2017, 06:17 PM   #4
2004OutbackSS
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Yes, I'm doing something Similar to the user with the Forester, just using the long block of the 09', reusing my intake, sensors, gears and accessories and the 04' ECM and wiring, both cars are manuals so there should not be any problems with cam-tensioner setup, belt cover ect. I'll be doing the swap tomorrow after some basic maintenance work tonight. Replacing the Cam and Crank seals, front and rear, VCG, Spark Plugs and Tube Seals, got new Flyweel bots and the super blue coolant from the dealer. Will let you know how it runs tomorrow.

I'm not looking for a road burner, so a few HP on the high end won't be missed, I'm used to driving low reving torque heavy motors anyways, my Jeep 4.0L is no superstar above 4krpm.
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Old 10-20-2017, 06:21 PM   #5
2004OutbackSS
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Also from what documentation I have been able to read, the low lift cam profile is very similar to that of the pre-I-AVLS vehicles and the high lift cam only comes into play at high RPMs, so low to mid range torque and efficiency should not be effected by the absense of the system.
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Old 10-20-2017, 07:37 PM   #6
Elbert Bass
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Quote:
Originally Posted by 2004OutbackSS View Post
Also from what documentation I have been able to read, the low lift cam profile is very similar to that of the pre-I-AVLS vehicles and the high lift cam only comes into play at high RPMs, so low to mid range torque and efficiency should not be effected by the absense of the system.
No, you have it backwards. The cam profiles are drastically different. Pre-AVLS both intake valves had the same lift with mirror image lobes. AVLS low lift uses a cam lobe that opens one valve about 3mm, the other valve opens full lift. When the AVLS rocker arm goes to high lift (about 2500 RPM) both intake valves run on mirror image lobes.
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Old 10-23-2017, 01:04 AM   #7
2004OutbackSS
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Swap successful, runs fine without AVLS, compared to a Forester I drove 3 weeks ago it idles smoother, same or better power, the Forester did have 200k on it. It runs like a clock all through the rev band, no dead zones, backfires or oil pressure problems.

I was working with my father, who has been building hotrods and streetrods for over 40 years, we took our time, were meticulous as we replaced seals and prepared the long-block for the swap. Triple checked everything with our 2004 FSM and found what we needed for the 2009 online. Kept the crossover and oil pan from the donor, used all the gears, pulleys, tensioners, sensors and accessories from the 2004 EJ251.

Donor car was a lucky find, 2009 Legacy 2.5i with a 5 speed manual, just over 100kmiles, damaged out by insurance after the flood, but the water line never got above the exhaust flanges, so interior and some electronics ruined, engine perfect. I pulled it myself for 250 usd.

Will be taking it out on a longer trip soon, will let you know how it does. Thanks for all the input and thanks to this community for some useful data during the swap. Over all it took a day and a Half to prep and install the motor. My veteran father found working on the car very enjoyable and is even considering one for his next purchase.
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