Engine Mods and Their Impact on your Wrangler

Air is critical for combustion. Colder/denser air is better for optimal engine performance. That being said, one of the most common modifications to just about any vehicle is to swap out a restrictive factory intake system. If you add a Wrangler cold air intake, you will typically have better acceleration from idle, a slight gain in MPG, and a decent boost in horsepower. You can hope to see a 1-3 MPG increase and optimally a 5-10 HP increase. The downside to most cold air intakes is they are usually less protected against water which can cause hydro locking. If you install a cold air intake be sure to stay away from deep mud and water.

Cold air intakes typically consist of an open cone filter married to a smooth single piece of piping leading into the throttle body. The open cone filter is designed to allow more air into the engine, but its position and surrounding is critical to ensure the air remains as cool as possible and doesn’t take in water. Due to these two major points, most CAI are still protected with an enclosure. These filters provide more air to the engine than the restrictive factory air box.

What if you want to traverse deep water? That’s where the snorkel comes in. A common selling point of most snorkels is they are said to have a ram air effect. Unfortunately, any improvements will mostly be negated by the added length to the intake system. Adding a snorkel to your Jeep with help prevent hydro lock, however there are other modifications you will need to do to your Wrangler to prevent damage. In addition to a snorkel you should also extend the breather tubes for your axles, transfer case, and transmission. The breather tubes allow hot gasses to escape while preventing water from getting in. If you try to drive through excessively deep water without extending these tubes you will probably end up getting water in them.

A throttle body spacer is a thick metal plate that increases air velocity which affects fuel atomization. Fuel atomization is the breaking up of the fuel into small particles like a fine mist that allows it to burn more efficiently. Having better fuel atomization allows for better power and fuel economy. If you have a carbureted or throttle body injected Wrangler, you may see a slight improvement in MPG and possibly HP. If you have a YJ from 1987-1990, whether it is a 2.5L with throttle body injection or a 4.2L with a carburetor, you may see a slight improvement from a throttle body spacer. After 1990 all Wranglers used multi-port injection. For late model YJ owners and all TJ and JK owners, a throttle body spacer will more than likely not be worth the cost.

A highly debated modification for TJ Wranglers is swapping in new fuel injectors. The stock injectors for TJs typically have a single hole that squirts fuel into the system. The idea is by swapping in injectors with 4 holes will improve the atomization of fuel. Better atomization of fuel will allow for a cleaner burn and a smoother idle. Some people claim an injector upgrade will improve fuel economy and horsepower. Unfortunately, the ECM will use the O2 sensor to figure out the mixture and will reduce the injector on time to correct the mixture.

On some vehicles you can experience great performance gains by swapping out an exhaust manifold for headers. Unfortunately on Wranglers headers don’t have a large effect on the performance due to they come stock with a free-flow exhaust that works like headers. The only practical reason to add headers to a Wrangler is if your manifold is cracked and in need of replacement.

A cat-back system is a great way to improve your engine’s performance. It can provide an increase to both horsepower and fuel economy. Most exhaust systems are designed to reduce noise. This creates a slight restriction in some cases which can reduce fuel economy and power. A high flow cat-back system removes a large amount of this restriction and can provide an increase of 5-15 HP in the right circumstances.

In most vehicles nowadays, almost everything you do is a request run through the computer. Your gas pedal no longer has a cable running to the throttle body. Your headlight switch asks the computer to turn on the headlights. Even your brakes are controlled by the computer by use of anti-lock braking system (ABS). How ABS works is the computer takes away braking power from whatever wheel it wants in order to prevent locking up your brakes. Using a tuner can be a great way to optimize your Wrangler, modifying the air fuel ratio, timing, and even changing shift points if you drive an automatic. Tuners are really only effective if they are properly set up. If you load a tune for a stock Jeep and you have huge swampers, a cold air intake, and a higher octane fuel, you probably won’t get the performance you want. 

Some tuners (referred to as flashpaqs) connect to your Jeep’s OBDII port and provide you with access to a variety of options. Among which are different tuning modes to provide substantial power gains, sometimes upwards of 30hp. Often during the modification of your Jeep, you’ll need to make adjustments to the engine calibration to take into account the changes and improve the overall performance. For example when upgrading your tires, the larger circumference will require the speedometer and tachometer to be adjusted. The flashpaq can also make those adjustments.

A supercharger is designed to compress the air delivered to the intake. It provides a tremendous increase in denser air for a larger combustion. Adding a supercharger is a great way to obtain a large increase in power in your Wrangler. Superchargers are more practical than turbochargers on Wranglers because turbos generate a large amount of under-hood heat. Superchargers don’t have lag like turbos do, making them great for off-roading. The belt drive system has no lag which allows you to have the extra power as soon as you press down on the throttle.

If you're considering the supercharger options, you'll also want to understand intercoolers. They help augment the power from the supercharger by keeping air temperatures down. There are two types: air-to-air and wait-to-air.

An air-to-air intercooler is an intercooler that uses air to cool air. Meaning the exchange of heat that occurs is between the air that is charged in the charge pipes and the air that is flowing through the intercooler. Air-to-ir intercooler are only as efficient as the ambient airflow that they contact, and placement of this type of intercooler is key to maximize efficiency.

Pros:

• Requires no power to work
• Easier to set-up
• Requires no liquids to work and therefore, no chances for leaks
• Does not suffer from heat-soak as long as the intercooler is seeing sufficient air-flow

Cons:

• Efficiency is only as good as the ambient temperature & amount of airflow the intercooler is exposed to
• Cannot be mounted anywhere; must be mounted in an area that is exposed to high volumes of air flow

A water-to-air intercooler is an intercooler where the exchange of heat occurs between water and air. Water is pumped through the intercooler so the heat from the charge pipe is transferred to the water.

Pros:

• Very high efficiency
• Efficiency can be exaggerated by using ice, or other chemicals to produce lower temperatures
• Can be mounted anywhere along the charge pipe route

Cons:

• Requires a water pump, a reservoir, a heat exchanger, et cetera
• Since it is more complex, it naturally causes more opportunities for problem, like leaks
• Can become heat-soaked when used for long period of hard driving
• Since it uses water, and additional components, this set-up weighs more