Dyno tuning with a wide band A/F meter yielded almost 30 more wheel-hp.
Since the ECU will only see part-load, it will use a more aggressive ignition timing map with more ignition advance. Voila! The ECU is kept in the dark and we have more power. As long as the correction factor isn't too lean, the car won't knock. Without the knock sensor going off, the ECU will have no clue that it's making a lot more power than it was supposed to.
TuningYou can't just install larger injectors and drive away. The ECU will still control the injectors as if they were stock and end up injecting a lot more fuel. We have to, at least roughly, set the S-AFC correction factor so that the ECU can adapt to the new low-throttle map and let the car run.
At low throttle, the ECU's closed loop operation and adaptive learning let us get away with a rough tune; just take out a couple percent and let the ECU deal with the rest. At high throttle, where all the power is made, however, there is no adaptation. The only thing that will save the engine from blowing up is the factory knock sensor, which only pulls timing. So we have carefully set the airflow correction for a mixture that is just rich enough to make power, but not cause knock.
After replacing the stock fuel pump with a Walbro 255 lph unit, we tuned project MR by driving around on the street and looking at ignition timing and oxygen sensor activity via the OBD II port. RRE then took the MR to an all-wheel drive dyno for more precise tuning using a wide band A/F meter. At 22 psi with coarse tuning only, the car made 297-wheel hp, pegged at a 10:1 A/F ratio. With boost backed off to the stock peak 19 psi and with a more aggressive 12:1 A/F ratio at the tailpipe, RRE smoothed out the power curve and made 326 wheel-hp; 80 more than stock, while on the same boost. We settled with this driveable compromise between a street and dyno tune. The car could have made more power on the dyno, but the driveability would suck.
So maybe there is room for improvement on the EVO after all. We're so convinced now, that we're already eagerly awaiting a new set of cams coming in the mail.
Previous InstallmentsJan 2006Test Bench: Tires and a rear bar
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It's a tight fit to get at the stock intake plumbing, wastegate and blow-off valve. Tempor
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The GReddy Type-S BOV lets you adjust the spring tension on the valve to hold added boost
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The Espelir exhaust comes with a removable silencer. On the dyno, the silencer generates s