Dinan Magic

Making a Fast Car Faster

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What do you mean, it wasn't fast enough?

My 1999 540iA Sport is plenty fast, but nothing's perfect. Shortly after I took delivery of it in February 1999, I called Dinan BMW to inquire into the availability of performance modifications. Because the 1999 engine and Steptronic transmission were new to the US in the 1999 model year, they didn't have anything ready to go, but they sent me a catalog of their suspension kits and other products, and promised to call me when their performance products were ready.

I bought a G-TECH/Pro accelerometer for use with my previous car, a 1992 Nissan Maxima SE. I could get 0–60 times in the low seven-second range, which is nothing to brag about but nothing to be ashamed of either.

My very first attempt with the 540 gave me a 0-60 time of about 5.9 seconds. Careful experimentation eventually taught me how to get times just under 5.5 seconds. If everything went right, I got 5.48 or 5.49 seconds. (I got a 5.25 once, but it didn't seem like a particularly good run, so I assume that was a glitch.)

One of my goals in buying the car was to get something capable of 0–60 in under six seconds. Since BMW's official claim for the car is 6.1, and car-magazine tests of the same car with the conventional automatic transmission showed even higher numbers, I expected I'd need to do performance work to get a five-point-something result. Getting under 5.5 with an unmodified car was just wonderful.

But heck, I knew it could get faster. Everything can. As they say, "How fast do you want to go? How much money do you have?"

In April, I got that long-awaited call from Dinan. It was Steve Dinan himself, in fact, but he wasn't calling to let me know I could bring in my car to get the mods installed. No, they wanted to know if I would loan them my car so they could develop the mods! Dinan planned three performance enhancements for this car: their popular engine-computer "chip" (two versions, actually), a separate chip for the Steptronic transmission, and a shroud to bring cold air from the front grille to the air intake. Each of these makes the car a little faster; even together, there's no dramatic improvement, but they're all cost-effective improvements. At this writing, the engine software and cold-air intake are $499 each while the tranny software is $299; all require some labor to install, so the whole package would run nearly $2,000. (Check Dinan's Web site for up-to-date pricing.)

In exchange for loaning them my car, I'd get the mods at no additional cost. In effect, instead of paying cash to make my car faster, I'd just have to do without it for a while and drive a rental instead. (Dinan paid for the rentals, of course, and there are some stories to tell about those... but back to the story at hand.)

My car was at Dinan for a couple of weeks, and when it came back it was already noticeably improved in some respects. Dinan had installed new software for the engine and transmission, but the parts for the cold-air intake had not yet arrived so they gave me back the car while we waited. The transmission shift speed and throttle response were definitely improved and it felt stronger at higher speeds. The following graph (a 616x486-pixel image; click to open in a separate window at full size) shows the reported performance after this first set of work. There are clear improvements in high-end RPM and time-to-speed, but the graph also shows a problem: the 0-60 time is something over 6.0 seconds!

Figure 1. Graph of 0-100 performance: RPM and speed vs. time.

This wasn't just a problem with their testing; the car really was slower. As you can see from the slow takeoff (0-5 mph in slightly over one second) the problem was with the initial launch. I spoke with Dinan about this problem, and they agreed to take a look at it when they took the car back for the cold-air intake.The car went back a few weeks later, and Dinan confirmed the problem was present and was not related to their software changes. They took the car to a local dealer's service shop, which determined that the transmission torque converter had failed. After that part was replaced (under warranty) and the new cold-air intake was installed, Dinan performed a few more tests on the car and returned it to me.

One more graph shows the final results in terms of horsepower and torque. Dinan estimates the new maximum engine horsepower at 302 based on the factory number of 282 HP. The new torque peak is shown as 338 lb-ft, vs. the factory claim of 324 lb-ft.

(Yet to be scanned; patience please!)

Figure 2. Graph of engine horsepower and torque vs. RPM.

I've been accumulating additional runs with my G-TECH/Pro, and I'm getting reliable 0-60 times of about 5.35 seconds, and I've even seen a few 5.30-second readings. This isn't a huge improvement, but it's more than merely statistically significant. I wish I'd had a chance to get quarter-mile times before the mods, but the car is said to be capable of reaching 105 mph in a quarter mile even in factory trim, and it just wouldn't be safe to run tests like that except on a track. With any luck I'll get a chance to try quarter-mile runs on a track in the next year. I'll be sure to report my results here.

Note that Jim Conforti is also working on a new performance chip for the E39; keep an eye on his company's Web site, Bonneville Motor Werks, for more information.

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