Went to SRR today for Simon to check map etc.
I still had suspicions about the DV, because the performance seemed to vary day by day and all I could think might be to blame was the DV - so I removed it prior to Simon starting.
Simon confirmed that it was running a little lean, so without a doubt the DV had been leaking when the car was last mapped. Don't think I'll bother to refit it as less things to leak, and I'm getting used to the sound of strangled squirrels when you change gear
Then did two runs - one was 460bhp the next was only 420bhp. This appeared to be a repeat of the previous experience at Len's, and also what I've been seeing day by day.
The issue was eventually tracked down to the AVCS and by removing half of the advance, repeatable figures were obtained. As an aside, a report by Tomei I came across revealed that the 2.5 STi has 20 degress of AVCS advance, compared to 40 degrees for the 2.0l - there must be a good reason!
And, the results are:
I now have a reliable 460bhp/440lbft build, mapped at 1.6bar. Boost curve is very flat and, on the road, 1 bar at 3000rpm, 1.6 at 3500rpm (on the RR 1 bar at 3500rpm, 1.6bar at 4100). All with a centre cat by the way.
Peak power is 5700rpm and >420lbft from 4200-5700rpm, >350lbft 3700-6600rpm. Nice
Simon's view is that 1.6 bar and 460bhp is perfect for the EJ257 block - some people run more, but it should be nice and reliable.
Torque is lower than I'd hoped, but the "area under the curve" is not half bad
The stock ECU is probably preventing fine tweaking of the map, as there's not enough resolution in the tables...but £1200++ is a lot to pay for maybe 20bhp and 30lbft or so.
I now need to decide whether to bother fitting the OEM headers. They may increase top end power, but it might be at the expense of spool....do I spend the time and money to try it, in the interests of science, or should I just get on with enjoying the car. Really not sure...I'll sleep on it...tune in, same time, same channel, for the next exciting episode...