Jeff Zurschmeide/Digital Trends It’s an axiom in the world of automotive enthusiasts that huge performance gains can be made by using aftermarket bolt-on parts. Parts manufacturers sell custom exhaust systems, “cold air” intake systems, engine management software upgrades, and a host of other parts that claim to deliver more engine power for you to enjoy.
But really, how much extra power do these products really provide? And how can you know for sure what you got for your money?
“The fact is, you’re not going to get that much power out of anything you can couple to a normally aspirated engine,” explains Eddie Nakato, owner of AR Auto Service in Lake Oswego, Oregon.
This is why.
engine maintenance
The first reason that bolt-on parts tend to not make a lot of horsepower is because every part of the engine is designed to perform at roughly the same level. If you swap out a few parts, you might get some small gains, but you’ll soon reach the limits of improvement because the rest of the system is designed to produce roughly the same performance as the original parts you replaced.
“I see cars that come with expensive software upgrades and don’t produce any additional power.”
Another reason power gains are limited is that every modern engine comes with a host of sensors and an engine management computer. That computer is programmed to make your engine run the way the car manufacturer designed it to. If you change more than a little, the engine computer compensates to bring the system back to design specifications.
Some of the most popular products for your car are engine computer software upgrades. This makes sense because if the engine computer is limiting the power output of your engine, you need to change the programming. But if you haven’t already changed the engine’s intake and exhaust systems to get more air and fuel through the engine, changing the software can’t help you much.
“I see cars come with expensive software upgrades and don’t make any extra power,” says a shop owner who specializes in performance tuning. “Customers often get really upset when they’ve spent a lot of money and don’t see any improvement.”
Proving Horsepower Claims
The only way to tell if your car is making more power is with a device called a dynamometer. This device, commonly known as a dynamometer, calculates your car’s power output and torque. To use the dyno, the shop will clamp your car with its drive wheels to a large roller mounted to the floor. The shop will then “drive” your car on a roller to measure its actual driving power.
To get a good comparison, you should always use the same dynamometer. Start with your car in its stock configuration and get a baseline reading. Once you get a good baseline reading, you can make changes to your car and measure the effect of each change with a new dynamic session. Be careful though, dinosaur time can be expensive!
One day I tried four different cold air intake systems on the same car. In three out of four cases, the upgrade did not produce any change in horsepower or torque. In the fourth case, the intake produced a 2 percent increase in strength.
Or, consider these dyno charts, comparing the same car stock, with a floating exhaust, and then with a cold air intake and exhaust system. In stock, the car made 170 horsepower and 177 pound-feet of torque. That goes up to 182 pound-feet of torque with the cat exhaust, but power has actually dropped very slightly! When we added a cold air intake, horsepower increased to 173 and torque to 184 pound-feet. That’s a total horsepower gain of less than 2 percent and just under 4 percent improvement in torque with about $1,100 in parts installed.
Not everything is bad
That may sound daunting, but there’s even better news: You can experience a 4-percent increase in torque and a 2-percent increase in horsepower while driving. If you think your car has a little more power, it probably does. Just not as much as you hoped.
If you think your car has a little more power, it probably does.
Also, look at the dynamometer diagram again. See how all the blue lines that represent the stock system are wavy? It’s a power fluctuation. The red and green lines with the new exhaust and intake are much smoother and show that the car is making more power throughout the operating range, which is much more important than peak horsepower. Also, the green torque line appears earlier with the intake and exhaust installed and offers a big improvement between 2,000 and 3,000 rpm on the graph. That’s where you drive the most, so those parts are pretty good.
So what should you take away from all this? You simply can’t expect to get much more out of your engine just by installing a few basic parts, but that doesn’t mean you can’t achieve a noticeable improvement. If you want to know for sure what you’re getting, you’ll need to invest in a dyno session or two to see the actual data.
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Source: newstars.edu.vn