alter the valve timing, sort of subarus vtec system

 

They are cylinder heads from new age sti's the have variable valve timing which assist turbo spool.

 

They are newage heads with Active valve control system, think some just on inlet cam, they are controlled by the ecu, think it helps spool and low down torque. Newage sti and I think all newage 2.5 litre have them, to fit though needs a compatible ecu to control them.

3 answers at same time, I should have typed quicker

 

Spot on

 

yes

 

do all jdm wrx,s newage come with acvs.

 

yep, Jap bug WRX's came with AVCS, there is a bit of debate as to wether they were only on one bank of valves but yes they did.

UK bug WRX's have no AVCS at all which is a real pain for people like me when it comes to upgrading

Shaun

 

http://drive2.subaru.com/Win05_WhatsInside.htm


Latest STi's have both Inlet and Exhaust AVCS

 

Mines running AVCS - but did have to buy a Syvecs to get it working!

 

Digging up a old one here, but does anyone know how the variable valve timing improves the spool?

What are the actual physical differences in the heads ? lairy cams in one?

 

I love google
http://en.m.wikipedia.org/wiki/Activ...control_system

 

Thanks.

So its a bit like a high lift cam system except it can vary itself depending on the sensors and ECU controlling it.

So by fitting some more aggressive cams you would have the same system in wrx heads? Except without the ability to vary it obviously and no smoothness on idle or economy?

 

Not really no.

High lift cams generally shift the whole map to the right i.e. a better top end at the expense of some spool. I have high lift cams in my 2.35 non avcs engine, and its very much a top end engine although the extra displacement/torque helps a bit on the spool front.
AVCS allows you to have the best of both worlds - earlier spool and the better top end (plus idling etc). I will be putting AVCS heads on in the New Year though to widen the power band by improving spool.

 

Yes variable cam timing not variable valve lift or duration. Lift and duration remains the same, intercam timing I what is controlled. Inlet cam is usually where it's at, most cars controlling the exhaust cam are for emissions rather than power. Very old technology now, but then the jap stuff is usually quite behind on the technology front

 

Cheers that makes sense.

In a nut shell, avcs are pretty much the best option for heads on the impreza.

 

Standard fit on Newage JDM WRX's hence the out of the box figures of 250PS.

 

Is it PWM or on-off?

 

No one know then lol

 

Did you not read this link further back in the thread??

http://drive2.subaru.com/Win05_WhatsInside.htm

A download that may be of use

ECU I/O signals

 

Avcs not working (v power map) and avcs working with 15% meth (the difference between non avcs and avcs would be at least 500rpm)

 

No, I'm reading this thread. But I will go look at it.

 

It is a PWM signal at around 300hz

 

Just scanned the link, I see it varies the amount of overlap so guessed it had to be PWM. Interesting about the light load egr thing, less of that thanks!

 

They are cylinder heads full of voodoo!

 

Is that 500rpm with avcs and meth or just 500rpm difference with avcs?

 

Yes, a 500rpm + improvement just with AVCS .

You can see that if you look at the graph you can see a much larger than 500 rpm gap between the meth and v power traces - for example, look along the 300bhp line and compare the difference.

In addition, don't forget that cars spool up earlier on road than when on the dyno by an additional few hundred rpm as well.