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Old 02-14-2013, 01:40 PM   #26
Scooby Specialist
Member#: 96204
Join Date: Sep 2005
Chapter/Region: W. Canada
Location: Winnipeg
2013 STI GR


Also anxiously awaiting new EFR data.
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Old 04-12-2015, 10:30 PM   #27
Scooby Specialist
Member#: 4498
Join Date: Feb 2001
Chapter/Region: NWIC
Location: Portland, Oregon
WRX H6-3.0 Turbo


Originally Posted by Ziggyrama View Post
Bringing this thread back to life again.

This does not sound right to me. When you retard exhaust valve, you delay it's opening. How can the exhaust cam be at rest in maximum retard? If retarding the exhaust moves up the valve opening, that's called advancing, which is what is applied to the intake valve timing.
You are correct, that statement was incorrect on my part.

Fortunately the overlap graphs are correct as I did not make the same mistake in the excel spreadsheet.

As you mentioned, the ECU is able to add advance to the intake cam (opening and closing the intake valve earlier) as well as add retard to the exhaust cam (opening and closing the exhaust valve later).

As a result, more exhaust cam retard adds overlap, as does more intake cam advance.

I mentioned that the stock ECU keeps the car at around 20 degrees of exhaust cam retard, which based of the correct directionality means the exhaust cam is sitting at about 8 degrees ATDC. As you would expect that would mean just a bit of overlap even at high load/rpm. ( only 3 degrees ).

This does mean that if you were to take 08+ heads and cams and put them in say a 2004 STI with just intake AVCS control you would always have exhaust cams stuck at 12 BTDC, which means you would not get very much overlap even when the intake AVCS is at maximum.

None the less good find and correction on your part. I'll add a correction to the original top post so other people don't take away incorrect information.


Jeff Sponaugle
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Old 04-13-2015, 03:19 PM   #28
Scooby Newbie
Member#: 334547
Join Date: Oct 2012
Chapter/Region: SWIC
Location: Litchfield Park, AZ
2007 WRX STi


Just thought I would chime in with some real world info. A friend of mine and I just got tuned a couple of days ago. I have an '07 sti and he has a '15. We have the same engine build by the same builder with the same internals, same fuel system, same turbos, and even the same e85 from the same gas station. While my car made 417hp - 410tq, his car made 405hp - 450tq. The tuner said the torque difference was soley due to the dual AVCS. A difference of 40 ft lbs is a huge improvement!
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