Build log, May 2023
YimiSport Retune
When the engine was built, it got a professional tune, but it wasn't set up for track abuse. Session after session, heat soak and repeated knock events kept pulling the DAM (Dynamic Advance Multiplier, the ECU's confidence in how much timing it can run) down.
Paul at YimiSport Tuning went after the causes:
- A richer fuel map for more margin against knock when things get hot.
- An air temperature sensor after the intercooler, so the ECU sees the real temperature of the air going into the engine instead of guessing from the intake.
- Cam timing (AVCS) tuning, which is where the extra power came from.
The biggest change is how quickly the car builds power. Torque comes in a few hundred rpm sooner and stays strong through the midrange, so there's a lot more area under the curve. On track, that matters more than any peak number.
Paul overlaid one of my pulls on the old tune with the new one, same dyno and same correction, so this is the cleanest before-and-after I have:
| Old tune (Apr 2023) | YimiSport retune (May 2023) | Change | |
|---|---|---|---|
| Peak power | 366 hp @ 6,231 rpm | 373 hp @ 6,289 rpm | +7 hp |
| Peak torque | 353 lb-ft @ 3,833 rpm | 377 lb-ft @ 3,729 rpm | +24 lb-ft |
Full dyno history
Every session this engine has seen, all on Mustang AWD dynos. The sheets don't all report the same channel, so compare within a session rather than across them.
| Session | Map | Peak power | Peak torque |
|---|---|---|---|
| Dec 2021, original tune, 91 octane | ~18.5 psi | 323 | 289 |
| Dec 2021, original tune, 91 octane | ~21 psi | 334 | 304 |
| Dec 2021, original tune, 91 octane | ~22 psi | 334 | 316 |
| Apr 2023, original tune, YimiSport dyno (wheel) | 3 pulls | 341 to 345 whp | 330 to 339 lb-ft |
| May 2023, YimiSport retune (engine channel) | 22 psi | 373 hp | 377 lb-ft |
The April 2023 pulls on the old tune doubled as my NASA Time Trial dyno certification. NASA multiplies Mustang AWD numbers by 1.1 for classing, so the form came out to a max of 380 hp, 363 lb-ft, and an average horsepower of 371.5.
First track day on the new tune, the data logs came back clean. No meaningful knock events, and I haven't seen the DAM drop since.