Ok so the question now is why can the USDM motor only do 30° with the same cam gears? it is not an electronic limit because when we put the 207 into the same car I can run it out to 40°
For example in Amroofs 2005 Forrester I can set 40° of advance in the rom and on the 257 motor it only runs 30° but with the 207 installed it hits 40°. The ECU and all that is the same for both motors so there is something with the 257 that limits it to 30 while the 207 can go further. Is it as simple as the oil pressure is not high enough on the 257 to get more advance?
Originally Posted by Concillian
40 degrees is in terms of the crank. since there is a 2:1 ratio, it only takes 20 at the cams to result in 40 degrees relative to crank position. Just like how each cam gear tooth is 7.5 degrees of cam, but 15 in terms of the actual cycle. It's all explained in that thread.
The reason the JDM cars can have more advance is in the cams and heads. They run lower lift and the big ports bring the flow. The small ports require higher lift to get flow, so there's less cam advance available for a given valve to piston clearance, therefore lower AVCS advance in the USDM programming. 08+ Dual AVCS brings back 40ish degrees of overlap at low RPMs by adjusting the intake forward and the exhaust backwards.
I've programmed and logged 45 degrees, and I've definitely seen a difference from 40 degrees at <3000 RPM as a result.