Mark D chip installed

[RadioRon]

Car: 1991 318is, stock M42.

I installed my new Mark D chip today and took the car out for a drive. As expected, the changes are subtle. I first noticed that the car seems to be slightly smoother, with less vibration at idle and low revs. This may be my imagination, I'm not sure.

On hard acceleration, the car definitely feels different. Before, with the stock chip, you start off from a stop and the revs climb slowly for a while. You have your foot on the floor and you're thinking, "come on, come on, let's go". Then at around 4300 rpm all of sudden there is additional pull that you feel in your butt and the car sort of takes off and you think "yeah, that's more like it". Now, with the Mark D chip plugged in you hardly feel that sudden change around 4300 anymore. At first, I missed that surge and felt a twinge of disappointment, but then realized that the car was accelerating just as hard as it used to above 4300. So, it seems that the reason the surge is mostly gone is that there is more pull at the lower revs, and it all blends together more smoothly.

As I drove around in traffic, the subtle change in torque seemed to allow more flexible driving, without having to thrash the engine quite as much as I used to do. The car seems to pull a bit more comfortably around 3000 and doesn't seem to be working quite so hard.

I conclude that the new chip seems to have filled in with a bit more torque in the lower revs, with the result that there is less drama at around 4300. It just pulls more constantly over the entire rev range. It is worth repeating that these changes are subtle.

Much more obvious is the new rev limiter at 7100. That works quite well indeed and will be a welcome change on the track.

I tried to do some before and after timed runs including 0-100km (indicated on speedo, so its actually about 0-90km) and 80-120km (really 70 to 110) in third. I think that the 0-100km runs were not conclusive because my clutch is slipping too much. The 'before" run was 10.1 seconds, while the two "after" runs were 9.2 and 9.3 with the same slipping clutch. The 80-120km runs weren't useful either because I discovered during the "after" runs that it makes a really big difference exactly how you start the run (like exactly when you put your foot down vs starting the clock). My "before" was 6.4 seconds, while the three "afters" were 5.5, 5.9 and 6.5 seconds. I believe the 5.9 result is most directly comparable to the 6.4, with the most similar type of start condition. The numbers seem to be better, but the tests were too sloppy to be conclusive.

Performance mods like this one add very small improvements to horsepower and torque, as shown by dyno data for other brands of chips. With an expectation of perhaps a couple of horsepower and a few lb-ft more torque it is safe to say that while I was hoping for something noticeable I didn't really expect it. So I'm happy that there is indeed a perceptable improvement in the car, considering that my investment of time and money was modest.

[E30M3]

Let your ECU relearn the chip map.. It will improve slightly over time, as the ECU adjusts.

[RadioRon]

Originally Posted by E30M3 Let your ECU relearn the chip map.. It will improve slightly over time, as the ECU adjusts.

I didn't know that it adapts. Thanks. Is there a way to accelerate the learning?