Vijay

Actually your A/F curves look reasonably consistent. Note however that for the stock system A/F's are in the upper 12's. With the exhaust they are in the mid 13's. Leaning out the mixture will produce a little more power and I suspect that is what is going on here, but remember this also increases the risk of detonation. I'm no expert with the FSI configuration so I don't know at what point you may get into trouble. The gains seem real. I would like some more input from people who know this motor if A/F's in the 13's, along with a 12.5:1 compression ratio is safe, especially at those upper rpms. I know from tuning my B5 S4, we were shooting for 12, but that was running 25lbs boost.

I also wonder whether over time, the ECU would retard timing as it "adapts" based on the leaner A/F ratios or whether it will accept those leaner A/F ratios. If timing is retarded, those initial power gains won't be maintained as the ECU learns.

A good comprehensive system would include downpipes, cat-back as well as an ECU reflash to accept the leaner A/F ratios if they are safe. I'm willing to venture a guess that Stratmosphere is working on this in conjunction with Milltek and OCT. It could be that the system will be safe on 93 octane fuel, but not on 91 (poor Californians), or something like that.

Nevertheless, the initial findings are great news.

dxben

And what will they do to the drag coeff?

wagongotya

50 whp =P

HiRev

Stock exhaust system free to good home.

S4@last!::Now B7 RS4

whats even more surprising is the increase in torque throughout the rpm range. would never have guessed that.

VerrÜckt

Did you actually screw a wideband into the downpipe or was it a tailsniffer?

sparkhill

As always, thank you for your contributions to the RS4 community

Evil Buddha

Thanks to both of you.

Imola Ghost

what CB is this?

gamblerS4

milltek, iirc