Topic: AVLS and AVCS at the same time... HOW? (EZ30"R")

[september0451]

So I'm planning ahead (WAY AHEAD) for my EZ30"R" swap in my '01 Forester, and I'm trying to figure out how the engine management is going to work.

As I understand it, The EZ30D has AVLS, which is basically V-Tec for a single intake valve in each cylinder head.  Uses hydraulic pressure to change the cam profile at high RPM, but just for one valve, the other valve works the same no matter what the engine load to promote swirl within the cylinder.

Okay.. I get that.

The EZ36 gets rid of AVLS in favour of dual AVCS, which is basically...  V-TEC again, using camshaft, crankshaft, airflow and O2 sensors to change the entire cam profile by the same method, and in this case, on both intake and exhaust.  And on both valves, not just one.

So what I don't get is how the EZ30"R" has both AVLS and AVCS on the intake.  Does anybody have the Subie Voodoo and can explain this?

I'm asking because I think the best bet I have at a smooth transition from EJ251 to EZ30"R" is probably in building my own engine harness and getting an aftermarket ECU.  The throw-money-at-the-problem solution would be just get a Haltech elite and get Vex Performance to tune it for me, but I'm tech savvy enough to do my own work  and Use a MegaSquirt 3 or even build my own Speeduino, assuming either one of those options can give me a fully functioning car with this setup.

Anyway, that's why I'm asking, because I don't understand how those 2 systems can co-exist on the same cam.

(i'm probably going to crosspost this on r/Subaru and see what those guys say)

[RockThePylon]

Two different concepts.

AVCS doesn't change cam profile at all. Just changes cam timing relative to the crankshaft. Entirely different from VTEC.

AVLS uses two different cam lobes for each valve. One valve opens more, one opens less. It locks them together so both open more at higher rippums. Similar to VTEC.

[september0451]

Okay. thanks that makes more sense.

In that case... I have a different question.

How does that work? It's been a question that has burned in my brain forever.  How do you advance the timing on a camshaft when it's driving by the timing belt?

However that magic happens. I suppose it makes sense then that you could have AVLS and AVCS on the same cam.

Engineers are cool.

[LilDrunkenSmurf]

You advance timing by changing when the spark plugs, well, spark. On an older car, you would physically turn the distributor, and on never cars with their own coil packs, you just tell the ECU to do it for you.

[diamondedge]

How does that work? It's been a question that has burned in my brain forever.  How do you advance the timing on a camshaft when it's driving by the timing belt?

Magic.

The sprocket is fixed in timing in relation to the crank yes, but within the sprocket itself you can have all sorts of magic. A few degrees of rotation of the sprocket locus (the center) against the outer diameter of the sprocket lets you do that. Different manufacturers do it differently. The old school way was adjustable cam gears, set it, forget it.

Nowadays it's oil pressure and electrical wizardry.

TL;DR:

wheel within a sprocket attached to the camshafts

[RockThePylon]

You advance timing by changing when the spark plugs, well, spark. On an older car, you would physically turn the distributor, and on never cars with their own coil packs, you just tell the ECU to do it for you.

Hey there lil guy, you look lost.

[LilDrunkenSmurf]

I lack sleep.

[september0451]

Thanks for the info guys, that clears some stuff up for me.

Now to learn about ECU mapping and... shiz.