This car had 112,000 miles and 18 years on the clock when I found it. Most of those miles and years had come under the care of the original owner. When I found the car, it was absolutely stock in every way, even though many components, such as engine gaskets, shock absorbers, and suspension bushings, were in dire need of replacement. However, everything was in working order. The initial purchase price was $3,000.
The first dyno run with the stock engine expressed over-wheel speed with the car in fourth gear. The max horsepower and torque are listed at the top of the chart. You can see that the torque curve is reasonably flat and the best horsepower is right around 100 mph.
In the course of the project, we’ve enhanced the performance of this car by about 30 hp, and I have improved handling, braking, and interior utility as well. The step-by-step procedures in this book detail the process in every area of the car.
How to Use a Dynamometer and Read a Dyno Chart
If you have a turbocharged or supercharged car, an experienced tuning technician can assist you in fine-tuning the engine programming by using a dynamometer (also known as a dyno) to provide real-time power readings as the technician adjusts the timing and fuel map.
This is the same dyno run expressed over-engine speed, again in fourth gear. Engine torque is increased by 3,500 rpm and falls off after 5,000. Horsepower rises evenly to about 5,250 rpm before falling off sharply.
If you have a naturally aspirated car, including all stock E36 BMWs, dyno tuning is substantially less rewarding in power gains, but still useful in determining how much torque and horsepower are making it to the rear wheels. Some dynos incorporate instant exhaust temperature and composition analysis, so you can be sure the combustion is optimal.
Some bench dynamometers measure the engine’s power before it’s installed in the car, but much more common are chassis dynamometers where you park your car on a set of big rollers and drive. Chassis dynamometers bolt directly to the wheel hubs.
Just for fun, you can also download the Dynolicious software application that works with your smart phone. This software uses the phone’s internal accelerometer to calculate approximate horsepower and torque. It’s cheap, reasonably accurate for the price, and fun to use!
All kinds of dynos operate by measuring the engine’s ability to overcome resistance and do work, and it’s important to remember that every dyno’s readout is adjustable. Given the same car and the same conditions, any particular dyno may read relatively higher or lower than another. This doesn’t matter. What matters is the relative improvement you get on a given dyno when tuning your car. People love to brag on their dyno sheets, and tuning shops obviously want their customers to walk away happy and advance their reputation for getting more power than their competitors out of the same car.
In the course of developing this book, I took the project 328i to a chassis dyno for a baseline reading while it was still completely factory stock. That particular dyno told me that the sturdy little E36 delivered 170 hp and 177 ft-lbs of torque at the rear wheels. At the end of the project, with new intake and cat-back exhaust, an M50 intake manifold, and M3 cams from an S52 engine, the same dyno registered 200 hp and 175 ft-lbs of torque. The best torque was achieved at 184 ft-lbs with just a cold-air intake and cat-back exhaust. The best horsepower rating of 200, on the other hand, came at high revs with the intake, exhaust, M50 manifold, and S52 cams.
The BMW E36 is certainly a capable street car, and it does not take a lot of work to turn into a competitive track-day car. Upgrading to a combination of shocks, struts, brakes, and tires transforms even the base BMW E36 into a capable track car. If you’re looking to compete in autocross, road racing, time attack, or another form of competition, the E36 is an excellent choice.
Yet when you see any dyno sheet, it’s important to remember to not pay too much attention to the peak horsepower and torque, but rather, look at the entire area below the lines. The more total area you have underneath the lines, the better the power throughout the engine’s operating range. After all, how often and for how long do you run your BMW at 6,000 rpm? Most driving takes place from 2,000 to 5,000 rpm. What do you have in that range, and did the work and investment in parts improve the area under the lines in that range? That’s the question at the heart of real-world performance.
Building Your Car Right
Throughout the history of the automobile, we’ve learned a few things about going fast, staying in control, and the need to stop. We’ve also learned a few things about the dangers of modifying or altering the design or components. After all, the manufacturer decided it was good after spending millions of dollars on engineering and testing. Stepping out of the safety zone and modifying your car means taking responsibility for the changes you make and the effect those changes have on performance, safety, and longevity.
There’s an old saying in racing, “Speed, low cost, and longevity: pick any two.” I’ve never seen that saying disproved, but an E36 comes pretty close to picking up all three. Still, stories of blown motors, broken transmissions, and cooked brakes are all around us, and you have to understand that possibility before you start. When you exceed the power and the stress tolerance that the engineers designed into the car, you’re going to break things from time to time. Only a chump tries to blame the original manufacturer when his or her customized car breaks.
You can take some tried-and-true steps to have fun and achieve a good outcome when modifying your car. Read the following and give them careful consideration before you start.
One: Play Safe
Safety must always be a primary concern when you’re working on your car. I knew a guy who died when his car fell on him. He owned a set of jack stands but didn’t use them that day, probably because it was just a quick little job. Get yourself a set of good jack stands and a quality large-size floor jack and use them every time.
Similarly, be smart when you’re making changes to your car. Don’t go out and drive hard on brand new parts or brand new work. Have other people check the work whenever possible. Even professionals make mistakes from time to time; people leave nuts untightened, forget to adjust new parts, and leave fluids unfilled. Any of these mistakes may happen to you, and if you play with cars long enough something will happen to you, probably multiple times. At best these mistakes are embarrassing, usually they are expensive, and at worst they can be dangerous or lethal. Be smart, play safe, and you’ll have a good time.
Two: Learn about Your Car
You need to read and learn before you whip out a wrench or whip out your checkbook. The world is full of people who have spent a lot of money on their cars only to find that they have a ride that is slower and uglier than when they started. The final tragedy is that they’ve cut up so much of the original car that they can’t ever get it back to stock.
It pays to do your homework. Learn what’s available for your car and what fits on your particular model. Also, learn from what others have done before you. You can purchase a full shop manual for your year and model from Bentley for under $100. Your local BMW specialty shop has valuable information and expertise for you. Enthusiast and club publications, such as Roundel and Bimmer, can keep you up to date on new products and developments. You can also use Internet forums, but bear in mind that the quality of information from these sources is highly variable.
Three: Understand What You’re Doing and Why
Before you spend a penny or grab a wrench, sit down and think through what you want your