Many people often overlook the importance of tuning when they try to increase the performance of their car. Take a look at this stock Porsche 993 engine (which has been put into a 1983 911). It started out with 266 RWHP at about 6000 RPM and is now pumping out 288 RWHP. Not bad for an otherwise stock motor. Some of you may be wondering what is actually done during the tuning process. The answer is, it depends, but most often it includes at least adjusting the air/fuel ratio and the timing.
Look at the AF ratio for this Porsche. Originally it was running in the 12’s. For this car, as is the case for most cars, that was too rich a mixture. The ratio was increased to around 13, which is more in line with traditional performance tuning. By leaning out the mixture you not only get a power increase but also better fuel efficiency which is a nice bonus that you usually don’t get when you boost your power.
In addition, most cars are programmed for a particular timing which is linked to the fuel that will be run in the car. In many cases, the car is setup for the worst condition that it could encounter. For example, performance cars typically require “high-test” fuel or “premium 91 pump octane.” In many parts of the US, premium fuel is 93 octane and often 94 is available. However, since some parts of the country do not have this octane, the car is tuned for the 91. This means that if you live somewhere that has higher octane fuel and you use it, you are often not taking full advantage of it. This of course holds true for any situation where you use higher octane than the car is tuned for. Many “non-performance” cars are tuned for 87 octane, but owners often use 93 octane in them. This is a perfect example of where a little bit of tuning can do wonders since there is a large difference in timing between 87 and 93 octane.
The other nice thing about tuning is you increase your entire power band. When a car is dyno tuned, it is held at particular rpm until the optimal configuration for that rpm is achieved. This results in increases across the board since every position has been optimized. Look at the plot for the Porsche. You can see that the curve has increased over the whole RPM band with an especially healthy increase on the top end (not to mention the fact that the rev limit has been increased by 300 rpm which makes a huge difference as is seen in the plot).
Dyno tuning becomes especially important when you have a modified car. You often don’t get the maximum out of a modification until you have done some tuning. Bottom line is, don’t forget about tuning because it is often the missing piece that ties your whole package together and allows you to out-run the competition.