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Old 01-24-2001, 06:23 PM   #1
Lord-Atak
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Post Varible Valve Timing

Does anyone know if u could put varible valve timing on the U.S. WRX. And can someone explan what it does?
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Old 01-24-2001, 06:25 PM   #2
AKGC8
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Most likely. It may involve chaning out the entire head assembly, but it could be done. I'm not certain what it is. Its either like VTEC, or VVT-i. So it either has multiple cam lobes, or it can alter the timing advance as the rpm's rise. Not sure which one the Subaru system is like though.
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Old 01-24-2001, 07:15 PM   #3
Imprezard
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The Subaru system is called AVCS, right now it seem only WRX in Japan is using it.
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Old 01-24-2001, 08:26 PM   #4
DeliciouSpeed
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Variable valve timing...

In building a motor, compromises must be made not only in stock cars for comfort, but in face cars depending on the type of racing it intended for use in.

Ever notice how some cars idle bad? Rough? And vary a lot in their idle range. This is in perf built cars sometimes from high lift or long duration cams. These cams keep the valves open at an amount that allows lots of air in even at idle because the are fixed mechanical divices.

What variable valve timing does is allow low cam lift at low engine speed, to allow for good idle and better driveability, and in most cases better power at low engine speeds to. And at a preset RPM the cams change over to a higher lift or longer diration to allow increased power at higher engine speeds.
Advances in the technology now allow for the ignition timing to be variable also.

This means that the compromises can be reduced, you can have your cake and eat it to. Many manufactures have followed hondas lead and made this available on Motorcars. I belive it was first used on Honda motor cycles, I could be wrong. I hope this is understandable as I have been awake for 27 hours at this point.

Gonna eat and go to sleep now,
Ken
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Old 01-24-2001, 09:19 PM   #5
gimpster
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Very well put, you are 100% correct and you are right about it being used on Honda motorcycles, it was first used on them as a "testbed" almost 20 years ago.
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Old 01-24-2001, 09:24 PM   #6
AKGC8
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So does the AVCS actually like VTEC/VVTL-i with different cam profiles? Or is it just like VVT-i with only variable timming, and no lift?
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Old 01-25-2001, 07:21 AM   #7
DeliciouSpeed
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That I am not sure off, maybe Glenn knows.
Yes I am awake now. I did get hours of sleep.

The Porsche's system is variable at all rpms, both cam and ingnition timing. The Boxster does not get that. Hah

Ken
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Old 01-25-2001, 07:48 AM   #8
LDragon
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Man, I hope someone does a project car and does put the variable valve timing on it and develops install methods so others can do it without running into major problems, like crazy fuel/air ratios. cause then we would get a good deal more power.mmm, more power good
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