What are AVCS heads?
25 April 2012, 08:56 PM
#4
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
3 answers at same time, I should have typed quicker
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26 April 2012, 10:27 PM
#10
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
UK bug WRX's have no AVCS at all which is a real pain for people like me when it comes to upgrading
Shaun
26 April 2012, 10:31 PM
#11
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Last edited by Don Clark; 26 April 2012 at 10:32 PM.
01 December 2014, 09:18 PM
#13
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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?
What are the actual physical differences in the heads ? lairy cams in one?
04 December 2014, 08:42 AM
#15
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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?
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?
04 December 2014, 02:30 PM
#16
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.
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.
04 December 2014, 02:50 PM
#17
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
05 December 2014, 10:10 AM
#18
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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.
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.
In a nut shell, avcs are pretty much the best option for heads on the impreza.
09 December 2014, 02:56 PM
#22
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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
Last edited by Don Clark; 09 December 2014 at 03:14 PM.
09 December 2014, 03:21 PM
#24
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
http://drive2.subaru.com/Win05_WhatsInside.htm
A download that may be of use
ECU I/O signals
09 December 2014, 03:28 PM
#26
16 December 2014, 02:39 PM
#29
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.
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.
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