Driving impressions: RS-46 with ESS tune

Today, I was thinking about the journey my ECU has been on. Of course the ECU has been stock, ESS beta tune, AA 1.0 tune, "Company-A" custom tune on the stroker, factory tune on the stroker, and now the ESS tune on the stroker. All-in-all, my car has had six different ECU tunes in the car. So you could say that my ECU has been on just as much of a journey as my car.

ESS NA Tune (pre-stroker motor):
There's probably no need to discuss the original ECU tune, because everybody who owns an E9x M3 has had this tune at one time or another. So the ECU journey starts with ESS beta software. That software was a beta form of the ESS NA tune and was used for preliminary dyno testing and driving impressions. The tune was in my car for one week, and I remember it had increased torque all through the mid range and much better throttle response.

AA NA Tune (pre-stroker motor):
When the ESS beta test was over, I flashed in the AA ECU 1.0 software. The AA software drove very well and delivered great throttle response and torque. This is the software that remained in the car until we built the stroker motor.

Company-A Custom Tune (stroker motor):
Since I've never disclosed which company custom tuned the stroker, I don't intend to mention them now. Instead, I'll simply call them "Company-A." Company-A spent many weeks tuning the stroker and added about 20hp. Unfortunately, the ECU tune had its share of problems. The car would enter limp mode on virtually every cold start, even in the heat of summer. Occasionlly, the car would stall -- mostly during the warm up cycle. However, it did stall once or twice during normal operation. My worst problems were the limp modes that occurred slimply while slipping the clutch at a stop sign or traffic signal. I'm not talking about racing starts, I'm talking about going to the store to pick up groceries with my wife in the car. One out of every four or five times, the car would enter limp mode simply by slipping the clutch. This behavior was humiliating to me.

Factory Tune (stroker motor):
Due to my frustrations and concern with the Company-A custom tune, I finally flashed the stroker back to stock. At that point, most of my problems went away. On the bright side, all forms of limp mode problems went away. But the down side, the car still had problems stalling during cold start and occasionally while driving. Now I know that the limp mode problems were caused by the tune, and if ESS could fix the cold start problems, then one could argue that they were also.

ESS Tune (stroker motor):
Within a day, ESS had the stroker running perfectly. Over the next two weeks, they perfected the tune. When I arrived to pick up the car for the weekend, the car ran better than ever before.

When I started the car, I noticed instant throttle response (even in neutral). The exhaust sounded mean and nasty. There was no hestitation, no stumbling, the motor was running like it had never run before. I took the car with me and drove around Phoenix. The throttle response was amazing, the torque was instant. I could depress the throttle ever so slightly in any gear, and I got instant response. I had never felt this much power and responsiveness out of this motor ever before -- even from the stock ECU on the stock motor. Clearly, this tune was a step above anything that had appeared in the car before that time.

The next morning was the acid test -- cold start. The temperature was in the low 50's. I went out to start the car. VROOOM, it started instantly, and idled perfectly. When it was going through its cold start cycle, it didn't stumble, stutter, or search for an RPM like it had before. Instead, it was absolute perfection -- completely stable -- just as good as the day I bought the car.

I took the car out for some 60-130 runs. I drove about 50 miles out of town and found a lonely desert road. I waited for my chance, and I opened up the throttle. Once again, the roar of the motor gave me a sense of awe, impressed that the motor never sounded this good before. It just seemed like everything was running perfectly. My 60-130 times were mediocre, not my best, and certainly not my worst. In fact my worst 60-130 in Arizona at 1700 ft altitude was actually on par with my normal 60-130 times in my home town at 275 ft altitude -- just above mid-11's. All of my times were very consistent -- within +/- 0.10 seconds of each other. This was a great sign -- the car is running VERY consistently and very good. NOTE: It would be impossible to compare these 60-130 times with my previous runs because the final drive is now much taller: I'm using the 3.15:1 ratio from the DCT. This would certainly slow down the 60-130 times a bit.

I drove the car the rest of the day until early evening. I tried everything I could to induce the same problems I experienced before. I intentionally bogged the motor; I had plenty of opportunities to start the car. Not a single problem occurred at any time. But there was just one more test to perform: hooking up my Bavarian Technic tool and reading the ECU (and the rest of the vehicle) for error codes.

Early the next morning, I hooked up the BT tool and cold started the car. Once again, the car started flawlessly. I first read out the ECU error codes. No error codes were present -- I got a green light on my computer screen. Then I ran a full-car diagnostic, and not a single error code was in the entire vehicle. This behavior was a polor-opposite of the previous behavior with both ECU tunes on the stroker. Company-A avoided the Check Engine Light by disabling it entirely. The light was so completely disabled, that it didn't even light when the car first started. Even with the CEL disabled, the error codes were present. It was typical to find 8-10 error codes in the ECU alone, and sometimes as many as 20 (due to misfires). The ESS ECU was clean -- the CEL was not disabled and there were no error codes anywhere in the car. This clean bill of health included running catless and with the two rear O2 sensors removed. ESS had programmed around these changes to perfection.

Saying goodbye to my friend:
My only regret for the weekend was saying goodbye to my car. The car ran so perfectly that I didn't want to leave. As I turned the car back over to the guys at ESS, I picked up my rental car, returned to the airport, and barely made my flight with 0-minutes to spare. In three weeks from now, I'll see my friend again -- but next time, with a supercharger to test.