r/BMWZ4

As a follow-up to my previous post about the (suspected) acceleration issues of my automatic Z4 3.0i E85, which can be found here:

https://www.reddit.com/r/BMWZ4/s/2LTe0ZInu3

My local mechanic suggested a dyno test to diagnose the issue, which I just did. I also got a GPS acceleration tracker (Race Logic or RaceBox in my case) and made a few speed runs this weekend.

1. The dyno test.

Make: Dynocom. We did three runs. The first one resulted in precisely 231 hp. The other two surprisingly showed 241+ hp and 221-222 ft-lbs (~300 Nm) of torque, with a 15% drivetrain loss coefficient. So it's pretty much around the factory spec, if not better.

We did notice a slight torque drop @4000 and @4300 rpm. It looks like this might be where DISA and VANOS kick in, however, I'm not sure if these drops are normal or a slight malfunction. Any thoughts on this are welcome. I am adding the dyno chart to the photos.

2. The speed runs.

The weather today was cool and dry, around 50F (9-10C), so it was a perfect time for the test. (BTW I still struggle to change the temp gauge from F to C, any suggestions on how to tackle that?).

I also inflated the tires to 2.3 bar front and 2.5 bar rear and had around 50% fuel. I made a few runs and honestly, I was quite surprised by my times:

· The best run: 0-60 km/h in 3.17 sec / 0-100 km/h in 6.63 sec.

· Another run: 3.41 / 6.76 respectively, with 0-200 km/h in 24.44 sec. 1/4 mile in 14.9 sec.

To wrap it up: I am now way more satisfied and at ease, given that the actual numbers are not that bad. Of course, I have to take into account that I am running lighter rims (only 9 kg each) and it was a perfect temp for the test, yet I got 6.6 sec, so I suspect DISA and VANOS might need some attention in the future. But for now, at least the engine seems to be in very good condition, and I will just enjoy the last sunny days before winter finally comes.

P.S. Also adding a few nice fall pics of my Z4.

P.S.S. Not sure if I can also add a speed run video to this same post, I will figure that out later. Maybe will add as a separate post if you guys are interested.