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Old 10-01-2012, 12:46 PM   #1
Pickler
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Default i-AVLS and High Lift Cams

i have been reading about the EJ253 in my 09 impreza inorder to operate it more efficiently. In my civic i know the engine is in "fuel economy mode" under 3500rpm. above 3500rpm Honda claims it enters the high output cam mode which trades efficiency for power. this is the result of the so called i-vtec system.

For Subaru i understand it uses a similar technology called i-avls:

Quote:
They feature two different cam profiles:
1. A low/mid-lift profile
2. A high-lift profile
Quote:
At high engine speeds, the cam lift is switched to the high-lift profile to reduce resistance to air coming into the engine.
what RPM is exactly high engine speed? i do not see the RPM mentioned anywhere in the official subaru i-avls article:
http://drive2.subaru.com/Spring07_whatmakes.htm
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Old 10-01-2012, 01:21 PM   #2
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All the answers are in this thread:
http://forums.nasioc.com/forums/show...highlight=avls
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Old 10-01-2012, 01:40 PM   #3
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i'm surprised by the high cam engagement as early as 1500rpm, considering subaru claims this happens "at high engine speeds". if 1500rpm is true then it seems avls is just there to make for smooth idling and not fuel economy as subaru claims. also it seems like he is estimating the 4000rpm figure. personally i think a bump in torque curve is not sufficient evidence, for example the civic gets its peak torque at 4500rpm yet the high lift cams have already engaged by 3500rpm. i thought maybe a more definite answer is available since 2009 on avls.

Last edited by Pickler; 10-01-2012 at 01:51 PM.
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Old 10-01-2012, 09:37 PM   #4
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The test in the article was on a pre CAN ECU, so perhaps in 08 the avls system was changed in some way? Pickler, you could do a quick test like the author of the linked article and see if it behaves the same way or not. Do you have a meter that can measure duty cycle?
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Old 10-01-2012, 11:47 PM   #5
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Quote:
Originally Posted by RaceFaceXC View Post
The test in the article was on a pre CAN ECU, so perhaps in 08 the avls system was changed in some way? Pickler, you could do a quick test like the author of the linked article and see if it behaves the same way or not. Do you have a meter that can measure duty cycle?
i'm not sure, i have scangauge II which apparently can monitor Duty Cycle but apparently only with turbo diesels. i will try and see whether it will work with my car tomorrow.

Last edited by Pickler; 10-01-2012 at 11:55 PM.
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Old 10-02-2012, 03:53 AM   #6
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What does it measure the Duty Cycle of? My guess would be fuel injectors.
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Old 10-03-2012, 11:06 PM   #7
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Quote:
Originally Posted by Counterfit View Post
What does it measure the Duty Cycle of? My guess would be fuel injectors.
yes that's correct, i haven't tested it yet, but i doubt it will work with cansf.
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Old 10-04-2012, 12:08 AM   #8
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The thing you need to measure is the oil switching solenoid valve for the avls system.
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Old 12-06-2012, 09:01 PM   #9
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ok i have been playing around and have been monitoring duty cycle, absolute load and afr. it seems that car's absolute load (torque) suddenly spikes at about 3500rpm with good amount of throttle (not WOT).but afr also changes to about 13 from 14.5 too so im not sure wether that is because of avls. i have also noticed that sometimes ALD and duty cycle suddenly change on moderate throttle at 2.5k rpm while afr stays at 14.5. so far from these observations i gather high lift cams may engage at 2500rpm and not 4000. i will be doing more testing and will also be observing the MAF values. in fact at 4000rpm not much happens except that the car runs considerably richer at about 12.5. i dont really feel a pull that people have been talking about at 4000. at least not like engines on acuras. on dyno 08 2.5i seems to peak at 4500rpm, but at that rpm the torque is only 7ft-lbs higher than 2500rpm.
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Old 12-07-2012, 01:52 PM   #10
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Quote:
Originally Posted by Pickler View Post
ok i have been playing around and have been monitoring duty cycle, absolute load and afr. it seems that car's absolute load (torque) suddenly spikes at about 3500rpm with good amount of throttle (not WOT).but afr also changes to about 13 from 14.5 too so im not sure wether that is because of avls. i have also noticed that sometimes ALD and duty cycle suddenly change on moderate throttle at 2.5k rpm while afr stays at 14.5. so far from these observations i gather high lift cams may engage at 2500rpm and not 4000. i will be doing more testing and will also be observing the MAF values. in fact at 4000rpm not much happens except that the car runs considerably richer at about 12.5. i dont really feel a pull that people have been talking about at 4000. at least not like engines on acuras. on dyno 08 2.5i seems to peak at 4500rpm, but at that rpm the torque is only 7ft-lbs higher than 2500rpm.

I expect what you are seeing at 3500 is the transition form Closed to open loop fuel scheduling.

The torque curve is MUCH flatter than a Honda, so bumps in power are much less noticeable. As to monitoring duty cycle of the AVLS Switch Solenoid, duty cycle should? show up as 1 or 0. Either its on (low lift) or off (high lift), there shouldn't be much variation, but it's been a while since I bothered trying to play with this system.

If you were keen to know when it switched, build a test lamp with a 5V bulb and piggy back into the oil pressure switch, route this up to the windshield where you can see it when driving. (WARNING: I don't know if your ECU will like this idea). Easiest, dirtiest test i can think of. The switch is on the aft/top of the RH head. It's the one that if not leaking now, will soon leak so you might as well get familiar with it.

Last edited by wmdoucette; 12-07-2012 at 02:00 PM. Reason: added info
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Old 12-07-2012, 05:38 PM   #11
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meh not gonna go through thr trouble for the oil selenoid duty cycle. the poster from the link above did and he seemed to be getting lights & mixed results, lights even at 1500rpm whih doesnt make sense.

i did monitor for open loop but the car doesnt go open unless above 4000 rpm. another thing i observed today was MAF jumping at 2500rpm while keeping steady throttle. so what i did was apply throttle and keep at 25tps and maf stays at 30g/s until 2500 where it suddenly jumps to 35g/s. i also hear air rushing noise and increase acceleration. i used to think this was the torque convertor or perhaps timing belt making this sound.
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Old 12-07-2012, 06:16 PM   #12
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It's known that under wot the cam switches to the high lobe under 2000rpm on the ej253. The bump in tq is most likely a function of the intake/Exhaust manifold harmonics and Cam profile in addition to AFR going rich on OL switch, but it's not the Cam switching lobes.
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Old 01-02-2013, 02:10 AM   #13
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ok im 99% sure now i-avls kicks in at +2000 rpm. its not like the mitsubishis mivec system where the cam switches lobs at a fixed rpm. it seems to me much depends on engine load rather than engine speed. anything above 75% load at a given rpm and there is a noticable jump in maf and vaccum reduction in map. i would not say that high lift can happen in as low as 1500 rpm. 2300rpm is the lowest that i have seen enough evidence for. plus it would not make any sense to have seperate high lift cams if they are to engage in as low as 1500 where the engine is usually under its highest/full load due to lack of torque.

oh and i found an article about avls which explains
Quote:
*The switchable tappet switches between the low-duration and high duration generally in the 2,000 to 4,000 rpm range depending on ECU input (much lower than VTEC) allowing the EZ30R to breathe better at high rpm and improve low-rpm torque as well as emissions.
http://legacygt.com/forums/showthrea...rence-572.html
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