5 Best Low-cost Modifications for a Turbo Vehicle
So, you are likely one of those people who love tinkering with your car and driving fast (while still obeying all posted laws of course). You my friend are a gearhead and we can often get bored with our current vehicle performance and desire to have a slightly faster car. This is strictly to be used for merging into traffic and safe track experiences. Who am I kidding, we are all in the same boat we want to go faster because we enjoy the thrill. Personally I’m building a turbocharged mustang that features a 4.75L mod motor stroker and an 83mm turbo. This build may be a little large for many so what about the common guy or gal who has a turbo car but wants a little more horsepower. These 5 modifications are your best bang for the buck that you can get. If you are unsure about this consult a professional.
First, let’s get a basic understanding of how your turbo engine works. Let’s assume for simplicity that your motor is working like an air pump. It sucks air in through a pipe, compresses the air while adding fuel, sparks an explosion, and hot air exits the engine. That explosion forces the piston down which is converted to a mechanical force energy. This air pump works at one atmospheric pressure or 14.7psi. What if we could take this engine to a place where ambient air pressure is 2 ATM or 29.4PSI. The motor can now suck in twice the amount of air molecules, thus making a bigger explosion. This is what your turbo engine does. It pressurizes the intake of the motor thus increasing the amount of air molecules entering the chamber.
Now let’s look at ways to make this system more efficient and create more power.
1) Free breathing intake
The first best step is to open the air path to the turbo and the engine. Imagine you have two straws one is a small red coffee stirrer and the other is a large milkshake straw. Now try to suck a milkshake through them as fast as you can. Which one is easier? This concept is the same thing when you install a high flowing intake and filter assembly. It allows the engine to breathe easier. You might ask why the factory purposely made this restriction. Well in most cases they didn’t they properly sized the filter assembly to the requirements of the engine. Our issue is in the next few steps we want to suck in more air and we need an increased filter capacity to do it.
I personally like the K&N brand as I have never had one tear apart. I have seen instances where the filter media falls apart and gets sucked into the turbo compressor. You may notice that some people with turbos do not use a filter. This is not recommended for a street driven car as any small rock could destroy the turbo. These have an estimated 4-8hp gain on a turbo 4 cylinder and will run you around $100
2) Down-pipe and Cat-back exhaust
Next you want a free flowing exhaust, starting with a larger diameter down-pipe. This is similar to the example with the straw, but now you are pushing instead of inhaling. The down pipe is the pipe running off the turbo discharge side and connecting to the cat-back exhaust. Depending on your car you should be able to find an aftermarket setup with minimal effort. On an older 4g63 turbo eclipse this combination of a 3” down-pipe and cat back exhaust is usually good for 10-15 HP. The prices vary greatly depending on application and quality. This mod should cost $500 for a decent setup.
One thing to make sure of is that you select a straight through muffler rather than a chambered muffler. There are turbo mustangs that have picked up 50 hp just by going to a straight thru muffler.
3) Manual Boost controller
Now we have the inlet and outlet of the motor breathing better we can really start playing with the turbo setup. The cheapest bang for buck is to get a manual boost controller. It alters the pressure signal going to the waste-gate. This causes the waste-gate to stay closed longer thus increasing the manifold pressure. Remember I earlier explained that increased pressure means more air molecules and bigger explosion? That’s what happens here. You can estimate your gains per 1PSI increase by taking you naturally aspirated HP and multiplying by .068. So let’s say your naturally aspirated motor makes 150hp and you add 1 psi to it. You would now have a (150*.068) 10.2 HP increase for that 1 PSI.
For mild 4 cylinder motors 8-10hp per 1psi increase is typical. When you step up to the larger displacement motors that number can jump to the 15-20hp per 1 psi increment These devices can be purchased for less than $100. I have had good luck with Fierce Controllers. There are two main versions of a manual boost controller. The bleed type and a ball and spring. You want to make sure to choose a ball and spring as they usually offer better performance.
4) Get a tune
By this point you have made enough changes to your car that the tune is no longer going to be optimal. To get the most HP out of these changes a custom dyno tune will take the performance of the car to the next level. This step is not the same as doing a tune-up where you perform basic maintenance. The process of tuning the vehicle modifies the engine and fuel parameters to maximize performance. This is most likely done with a professional tuner on a chassis dynamo-meter. This way the tuner can run the car in a controlled environment and optimize the fuel settings.
You will need to purchase an electronic tuner that will modify the tune in your car’s ECU. There are several ways to do this depending on your vehicles model. It is best to identify a professional tuner first and get their recommendation for which device to use. The tuning device will run around $200 for a piggyback system up to $1500 for a standalone ECU. The dyno tuning service will be around $500.
5) Get better tires
Let’s face it, what is the purpose of making more engine power and not having the ability to transfer that power to the ground? The best thing you can do for this is to invest in a set of performance tires. Performance tires are usually manufactured from a softer “stickier” rubber and will have better construction methods. The tires you choose should be based on your driving style and your vehicles purpose. If you are making a drag track car that sees occasional street use then the Nitto NT555R drag radial is an excellent choice. These tires cost around $330 each.
That is our list of the best 5 upgrades for a turbocharged vehicle. There is one other item that may need to be addressed but it is dependent on your vehicle. The stock fuel system may not be able to keep up with your new found power. The weak link is usually the fuel pump, which can be easily upgraded. At this point you should have a pretty stout little street car capable of surprising a few people.