BMW 5 Series
February 7, 2000
Last year we restored and modified a pair of '80s-vintage, BMW 5 Series sedans, first a 1985 535i and then a 1980 528i. We still have and love our 1980 528i (E12 chassis) and have been constantly tweaking it since finishing the project car series.
While we were very happy with the car's 8.3-second 0-60 times we decided we wanted a little more oomph. (Okay, we weren't that happy, or we would have left the car alone.)
As you may remember, we tried just about every bolt-on performance-enhancing trick we could find with quite some success, but a 2.8-liter engine will only take a 3169-pound car so far and so fast.
No Substitute For Cubic
The old adage, "there is no substitute for cubic inches," is still just as true as the first time it was uttered. Fortunately, in the case of the E12 car, more power is a mere bolt-in away. That is, if you can find the right engine for the swap.
A 1985-'88, and even a 1989 and up, 3.5-liter six-cylinder BMW engine will bolt right in. However, in 1982, BMW switched from Bosch L-Jetronic to Motronic fuel injection. The two systems are completely incompatible, and unless you are a fuel-injection expert, the swap over would be time and cost prohibitive. Another downside to this swap is that the Motronic-equipped engines need the corresponding later transmission.
However, there is light at the end of the engine transplant tunnel, as the 1979-'81 European-spec 635i and M 535i came with an earlier version of the 3.5-liter engine, complete with the same L Jetronic fuel injection as the 528i. Rated at 218 horsepower, versus the 528i's 169 horsepower, this is an intriguing swap.
Even though neither of these donor cars was officially brought into the U.S., finding these engines, especially in the far more common 6 Series, is not that difficult. You see, during the late '70s and early '80s, at the very height of the gray-market importation days, lots of these cars were brought to our shores. The logical place to look is on the First Fives Web page (http://22.214.171.124/wwwboard/wwwboard.html) or in the BMW CCA's "Roundel" magazine.
We found a rusted out Euro 6 Series--minus the coveted close-ratio, five-speed transmission--at Red Line BMW (http://www.redline-racing.com) for the paltry sum of $800. After we got what we needed, we were able to part-out the rest of car for much of that sum.
These cars came with a non-overdrive, dog-legged-first, five-speed transmission. This was coupled with a 3.07:1 final drive ratio that made up for the lack of overdrive. (A standard 528i has overdrive in fifth gear and a 3.45:1 final drive ratio.) While coveted for racing, you probably would be better off on the street with your standard overdrive gear box and higher (numerically) gear ratio than the Euro box.
Another feature of these Euro 6 Series cars (a major bonus!) is that most of these cars were equipped with a limited-slip differential. They also had vented rear disc brakes, however this swap is not worth the time and effort for street use, unless you need to go through your rear brakes and suspension anyway.
What's Involved In The Euro 3.5 Swap?
We asked Black Forest Tuning (http://www.blackforesttuning.com) in Longwood, Fla., to help us with this swap, as they have done many of this type before.
The engine is virtually a complete bolt-in. The motor mounts, the bell housing and virtually everything else is identical. You will want the computer out of the donor car, because it is calibrated for a bit more performance, and the fuel curves will be different for the 3.5-liter. All ancillaries such as water pump, alternator and air conditioning will also bolt right on.
There are a few trouble spots to look out for. First, you will have trouble fitting the trick Euro exhaust system from the 6 Series to the 5 Series. The down pipes are different, so we used the complete high-performance E12 Metric Mechanic (http://www.metricmechanic.com) exhaust system, which is as good, or better, than the Euro system.
Secondly, you will also have a little clearance problem if you have an aftermarket air-conditioning compressor. Our larger unit rubbed against a radiator hose, but a shorter belt moved the A/C compressor back away from the offending hose.
Finally, you will also need to drill another hole so you can mount the computer behind the firewall. The 6 Series harness is shorter than the one in the 5 Series. Moving the hole six inches closer towards the center of the car, and plugging the old hole, solved this problem.
The biggest problem in doing this swap is the difference in wiring harnesses that plug into the fuse box, which is located on the front left hand side of the vehicle. The Euro car uses a 12-pin plug, while the 528i uses an eight-pin plug. The fundamental difference is that the Euro car has a couple more sensors (such as oil level indicator) that the American 528i doesn't have. To handle this job, simply cut the plugs off of both cars and match the color-coded wires from the Euro car to the eight-pin box of the 528i. The oil-pressure switch wire will also have to be lengthened about four inches.
Another concern is the oil cooler from the Euro car. This was put on for high-speed Autobahn use. You can leave it off, or install it if you run at high speeds or do a lot of track events. If you are installing the oil cooler, you will also have to install the oil filter housing from the Euro car, as it is equipped with inlets and outlets for the oil lines.
Naturally, this would be a good time to change all of the hoses, and we even went so far as to have our injectors blue printed and tested at nearby Performance Diesel. This is a must anytime a fuel-injected engine has been sitting for more than a month or two.
And The Results Are?
As you can guess, anytime you add 25 percent to your engine size and nearly 50 horsepower without any penalty in weight or drivability, only good things happen.
The car went from kind of quick to pretty damned fast! Zero-to-60 times dropped from 8.3 seconds to 6.9 seconds. Perhaps more importantly, the car has so much more drivability. You don't need to shift it as often, and you don't need to down shift if you want to pass someone when you are at highway speeds. Gas mileage hasn't changed at all, either, with the overall mileage right around 21 mpg.
To get the most out of our engine transformation, and to get a little more aggressive looks to go with our more aggressive performance, we updated our rolling stock. We went from 16x7.5-inch TSW (http://www.tswnet.com) Imolas to 16x8-inch BBS (http://www.bbs.com) RX wheels (part # RX223DSK).
These wheels are fantastically made, fit well (although a little close in the rear with rolled fender lips) and are reasonably priced at $365 each (list price). They are not that heavy, at 21 pounds each for the rather large 16x8-inch size.
They also give the car a lot more aggressive stance then the TSW Imolas, thanks to their more open spoke pattern and increased offset. The extra width helps, too. We can't say enough about how these wheels change the personality of this car.
Mounted to these wheels are Yokohama's new AVS Sport tires (http://www.yokohamatires.com) in the same 205/55-16 size as our Nitto 450 Extremes (http://nittotire.com). While the Nittos were fine tires, we noticed an immediate improvement in handling ability with the Yokohama's mounted on the 1/2-inch-wider wheels. Fortunately, the Yokohamas are no noisier than the Nittos.
In wet weather, the Yokohamas are also completely up to the task. We'll give you further updates on these tires after we live with them for a few months and test them at the track, but initial indications are completely and overwhelmingly favorable.
Back issues on most project cars are available. Check out the GRM Online Store for a complete list. If you have a question not answered by the stories, email Tim Suddard directly.