Basic Engine Dyno Tuning: Medium
After you have a race engine built and installed, along with some of the other go-fast items listed, dyno-tuning can prove to be a valuable investment. I brought my car to the dyno shop with low expectations, thinking this process would simply provide me an idea of how powerful the engine was. I certainly was not expecting the results that the car gained simply from adjusting the fuel pressure and engine timing. My Improved Touring B Honda Prelude (110 stock HP at the crank) gained 6.5 maximum horsepower and 3.6 pounds of torque at the wheels. Even more important was how the horsepower and torque curves were modified throughout the RPM range. In my case, this certainly was well worth the $150 investment to have the shop tune the engine.
In order to have your engine properly dyno-tuned, it will be necessary to install an adjustable fuel pressure regulator. When I first purchased a fuel pressure regulator, I bought a very inexpensive unit that utilized a portion of the stock regulator. I soon returned the item and bought a better quality unit. I then went to a parts store (NAPA) and had them fabricate a fuel hose and adaptors for me to use when installing the fuel pressure gauge. If you are unable to locate a shop to do this, you can easily assembly the hose and adaptors yourself. But for the price I paid, it came out to about the same amount of money to have the shop do it for me the “right way.” Before installing the fuel pressure regulator, install the fuel pressure gauge and determine what the current fuel pressure is. After installing the aftermarket fuel pressure regulator, set it to the amount that the stock fuel pressure regulator was and verify that the new set-up does not leak. If you don’t do a baseline dyno run (with the stock fuel pressure and timing settings), you will never know what horsepower gains were made prior to tuning the car.
Some cars also have the ability of tuning the vehicle’s ECU (engine control unit), using after market parts to better take advantage of the modifications you have completed on your racecar. The cost of these units ranges significantly and also requires time on a dyno to tune it.
Summary of Primary Costs:
Adjustable fuel pressure regulator: $170
Fuel Pressure Gauge: $20
Tap and die: $7
Drill bit: $6
Teflon tape for thread fittings: $1
Fuel hose and accessories for gauge: $16
NAPA assembled unit: $20
After bringing your car to a dyno, don’t get caught up comparing the results your car had to others without at least having a better understanding dynos. Three of the common dyno machine types are Dynopack, Dynojet and a Mustang dyno. There are several variables that can impact the results such as the type of dyno being used, if the program being used on the dyno is accurate and up-to-date, outside temperatures, if using a Dynojet tire pressures can even impact the ratings. The most important part is tuning your car to get the most gains.
Light Weight Rims: Low
Depending on the weight of your current rims, you could benefit from purchasing some lighter weight rims. Reducing the racecar’s overall weight is the first potential benefit. If you are having difficulties in getting close to the minimum allowable weight for your car’s class, using rims that weigh four pounds less each can help. The other benefit is that using a lighter weight rim reduces the amount of unsprung weight. Unsprung weight is what is on the outboard end of the suspension – what is not being “sprung” by the suspension. This includes wheels, tires, brake components (rotors, calipers, drums), suspension arms, spindle, rear axle, and associated brake components. By reducing unsprung weight, you are reducing mass in motion. Less weight moving up and down means that the suspension can react more quickly to changing road surfaces and keep the tires planted on the ground better. This all equals slightly faster acceleration, traction, cornering traction, and overall better handling, to a degree.
When buying new rims, you should verify that they would work with the racecar’s existing wheel studs. I bought some nice used lightweight rims, but when I went to see if they fit the car properly, I realized that the wheel studs were not long enough for these rims. For my car, the longer wheel studs cost another $50; then, of course, I needed the lug nuts that would fit, costing another $40. You also need to verify that the offset of the rim fits the car’s needs. Of course, you want to buy the widest rims allowed by the club(s) you race with. There are many sources of lightweight rims, from used or new racing wheels, to used stock rims from various manufactures. The VW rims that I purchased weighed 11.5 pounds and were relatively inexpensive compared to other options. If you shop around, it is possible to find a good set of four used, lightweight wheels for $300 – $375. A set of new racing wheels often costs in excess of $800. Light weight rims will only get you so much of a performance gain. I don’t recommend that you spend a significant amount of money to save a pound or two per rim; there are better ways to spend your money.
Air Dam and Splitter: Low
Does adding an air dam and splitter really help for the type of car you will be racing? I have spoken with many very experienced people on this subject and obtained differing opinions. One negative aspect of installing an air dam is that it is prone to damage if (when) a person makes an off-course excursion. If you decide to install an air dam and splitter, my recommendation is that you don’t spend too much money on the modification.
Do all of these modifications seem a bit expensive? No one said that it was going to be cheap to develop the racecar, and the process is never-ending. There are many other go-fast options you can look into, such as changing the gearing on the car and numerous opportunities for dyno testing. To build a well-developed racecar, you will need to combine various parts and modifications in order to obtain the optimum package. For example, if you have a very well tuned exhaust and header, but don’t have an air intake system to take advantage of it, the performance package suffers. You must also determine in what order various modifications should be completed. As an example, it does not make sense to bring the racecar to get it dyno-tuned before installing the race engine you just bought. Although you might not do all of the above items, usually you can still be very competitive if you focus very hard on improving your own racing skills. Give some serious thought to which items you choose to spend your money on. If it comes down to sacrificing your participation in races in order to buy several of these items, then they are probably not worth it.