I have installed the latest Jim Conforti chip from Mesa Performance products in my '88 535is with 85,000 miles. My subjective impressions after driving the car for a week with the new chip are that the car is faster. It seems to have more pull (torque) in the 2500-3000 rpm range and it seems to respond quicker to throttle changes. There is no noticeable degradation or bad habits. It doesn't surge, buck, or hesitate.

I also did some timing runs to compare the JC chip with the stock chip. The stock chip was tested at 57 Deg-F with 82% relative humidity and 29.61 in. mg. on concrete with 1/2 tank of gas, 355lb of driver and timer on board, and Michelin TRX tires. I did four runs -- two in each direction -- over the same section of straight, flat road. The stock chip produced average times of: 0-60 8.1 sec; 0-100 24.2 sec. I had to launch at about 2200-2300 RPM to minimize wheel spin on take off. The 3.5 liter six has quite a bit of torque! I did not power shift, but I still chirped the tires on the 1-2 upshift.

The Mesa chip was tested at 59 Deg-F with 74% relative humidity and 29.77 in. mg. on the same road with the same driver and timer. The only difference -- due to bad planning on my part -- was a nearly full tank of gas instead of 1/2 tank. That represents about 8 gallons of gas, or about 60 pounds of extra weight. The Mesa JC Chip produced average times of: 0-60 8.0 sec; 0-100 23.8 sec. This is an improvement of 0.1 sec in the 0-60 run, and 0.4 sec in the 0-100 run. Not much. Adjusted for the extra weight (assuming linear acceleration, which, of course, is an oversimplification), 0-60 should be 7.9 sec, and 0-100 should be 23.4 sec for 1/2 tank of fuel -- a theoretical 0.2 sec improvement from 0-60, and 0.8 sec improvement from 0-100 over the stock chip.

In spite of the numbers, the JC chip still feels stronger. I had a harder time launching without wheel spin, and when I got wheel spin it was louder and longer. The upshifts (1-2, 2-3, and even 3-4) produced a more dramatic jolt. The tire chirp on the 1-2 upshift was more pronounced.

I suspect the true benefit of the JC chip doesn't show up quantitatively on drag races, where you're just holding the throttle wide open and hanging on. A 3.5 liter engine can produce only so much power regardless of the fuel mixture and ignition timing. Induction upgrades(K&N filter, shorter intake runners) and exhaust upgrades would probably have a more dramatic effect on the 0-60 and 0-100 times than any performance chip.

I also think I could shave 0.5 sec off the JC Chip times if I had stickier tires. I couldn't use all the torque that was available. The TRXs didn't lock-up very well. I've never had TRXs before I bought this car last August, but they act awfully hard.

The true benefit probably won't show up unless I run the car on a track (or even an autocross) where the inproved throttle response and torque would reduce lap times.

So, am I going to keep the JC chip? Yes.

Why? I like the way it makes the car feel. It pulls like a V8, but it spins up like a small straight six. A nice combination.

Is it a "must have"? No. I suspect many people would not think the difference is worth the $225 (discounted to $175 with a $50 certificate to Mesa Performance Products if you tell them your BMW CCA number when you order).

Am I going to the track for some back to back comparisons? I'm not planning on it. This car is my daily driver, not my race car. I don't want to get into chasing performance on this car.

Cheers,