How To Increase the Power and Fuel Mileage in a Diesel Pickup
Basic Steps To Safely Increase The Horsepower and Fuel Mileage in a Diesel Pickup Truck
You love your diesel pickup truck right? Whether you drive a Ford Powerstroke, Chevy or GMC Duramax, or a Dodge Cummins all the same principals apply. The stock horsepower is ok, but wouldn't you love to have more power, more torque, better drivability, and of course pick up some fuel mileage? Who wouldn't? There are three very basic steps to take to achieve this goal. I'm going to share here the theory and principles we apply to every diesel pickup that comes into our shop.
The first thing you will need to understand that a diesel engine is nothing more than an air pump. The mechanicals of an engine work very similar to the air compressor out in your shop. One stroke downward of the piston draws cool fresh air in. The next stroke up compresses this air. Once the air is compressed, the fuel injector fires fuel directly into the cylinder causing the fuel to ignite from the heat of the compressed air. The piston is forced back down again by the expanding fuel burn. Because this downward force is what turns the crank and actually creates the rotational power, the stroke is called the power stroke. Once the piston reaches the bottom of the cylinder, it comes back up on the final stroke that pushes the exhaust out of the engine. Once we strip away the computers, wiring, and seemingly endless amount of wires and hoses running around the engine compartment, we can see the engine is still a very simple air pump. So let's build on that principle with three basic steps that will help that air pump work easier:
1. We must open the intake tract so that the engine pulls air in easier and cooler.
One of the first modifications you should do to your truck is install some sort of cold air intake kit. While the stock airbox filters air pretty well, it was only engineered to flow enough air to feed the engine at factory horsepower settings. Since we are going to up that horsepower, we need more air. Not only do we need more air, but we need cooler air. A popular modification we see is an open element K&N style cone filter just attached to the end of the air cleaner hose. While this modification is cost effective, we have actually seen a drop in horsepower on our chassis dyno. While the filter flows more air, you are now sucking warmer air under hood air into the engine. The warmer the air, the less oxygen molecules. So we have negated any reason at all to do the mod with an open to the engine compartment filter.
What we suggest, sell, and install on a regular basis is a cold air intake kit that sucks it's air from the grill or fender area. When looking at the kits, find one that has a snorkel type piece that ends outside the engine compartment. Filter systems of this style deliver cooler air to the turbo. The cooler the air, the more oxygen rich the intake air is, the more horsepower we can make when the injector fires. Most cold air intake (cai) manufacturers claim a 40-50 percent increase of air flow. Most cai kits that suck their air outside the engine compartment have shown an 8-12 rear wheel horsepower increase on our chassis dyno. Many of our customers report a 1 mpg increase in fuel economy and much more free feeling engine. Why? Because we have made it easier for the engine pull air in along with the side benefit of more oxygen rich cooler air. Also we have lowered our maintenance costs because nearly all cai kits have reusable, washable filters.
Now if you have gotten excited and started looking for a cai kit for your truck, you may have just gotten overwhelmed by all the choices. Our suggestion for all years of diesels are the S&B brand intakes. We sell them 10 to 1 over any other brand. The fit and finish is great. We also really like the underhood appearance once they are installed. And best of all, a complete S&B intake kit can be had for around $270 shipped. That also makes them one of the most economical but with the most features.
2. We must open the exhaust tract so that the engine can get rid of the exhaust gases easier and quicker.
The next step to take is tossing that factory exhaust in the scrap pile. By changing your exhaust to a full four or five inch system, you will make it easier for the engine to get rid of the spent exhaust gasses. To illustrate the difference, grab a stirring straw and a spent toilet paper roll. Blow through the straw and then through the paper roll. Which is easier? Which do you think your engine would like better? Just like the factory air intake system, the stock exhaust system was engineered to meet sound, emissions, and cost requirements. Also they were only designing a system that would be adequate for factory horsepower levels. Since we are shooting for more than factory, we need to upgrade. If it is all possible to remove the catalytic converter, you should. Depending on your state, it may not be legal, but the converter is a major restriction in the exhaust system. When ordering a new exhaust, make sure to check and see if it has provisions for the converter or not. Any system labeled "off-road" will delete it. Just make sure you buy the right exhaust to keep you legal with the law.
Most manufacturers claim a 15-25 rear wheel horsepower increase with their systems. We have observed similar results on our Superflow chassis dyno when testing trucks before and after an exhaust install. Most of our customers report 2-3 mpg fuel economy increases and much freer, quicker revving engine. Exhaust gas temperatures usually drop on average 150-250 degrees depending on the system. If the engine doesn't have to work as hard to expel the spent exhaust gasses, more of that power can be transmitted to the crankshaft. Along with a nice exhaust tone we gain horsepower, torque, and fuel economy.
Once again, if you have cracked the latest diesel magazine shopping for exhausts you might be overwhelmed by the choices. The sky is the limit here. Depending on the size, style, material, and the exhaust tip you want, prices vary from $300 to over a grand. Personal preferences will play a role in your decision. We suggest either MBRP or Diamond Eye exhaust systems. You should be able pick up an aluminized turbo back 4" system for roughly $300 shipped. MBRP now has some kits out that have no muffler for a true all out performance sound. The sell for around $285.
3. We now need to adjust the engine's computer for better fueling, timing, and power output.
Here's where things can get really confusing for most people. The choices are so varied that many are immobilized by picking some sort of programmer for fear of hurting their engine or not getting what they are hoping. Once we open the engine up so that it is able to move air more efficiently, we can add more fuel and adjust the timing to get more power, torque, and mileage. We have to remember that like the intake and exhaust, the stock factory programming was engineered to meet certain horsepower, emission, and cost requirements. They weren't looking to make the engine the best they could. They only had a horsepower goal they had to reach. Since we don't have those same limitations to abide by in the aftermarket world, we can get much better performance out of the engine with custom programming. Nearly any function that is computer controlled can be manipulated to provide a better, nicer running truck. Some of the main things that are adjusted with programming are: fuel quantity, injection timing, turbo boost, injector pulse width, shift timing and firmness, idle speed, top speed limiters, and much more. Once can expect anywhere from a 50 horsepower gain all the way up to 250 rear wheel gain on the newest engines. Torque increases can be from 100 to 400 ft/lbs. Depending on your truck and the programming used, 3-10 mpg fuel economy increases can be realized. Dollar for dollar, changing the truck's programming will net you better gains in all areas than any other modification.
There are three basic types of products:
The first is an actual chip that plugs into the back of the engine computer used on the 94-03 7.3 trucks. They are capable of holding usually up to eight different performance programs and can be switched on the fly. For the 7.3 trucks, this is the best option because it allows you to work with a tuner to build custom tunes for your specific truck and modifications. These have been around forever and work really well. The price range on these run from $300 for a single program to $450+ for a multi-position custom chip.
The second way of changing the programming is with a hand held programmer. Nearly everyone has seen the Superchips, SCT, or Diablosport style programmers. These units have a plug that is the same as the OBDII diagnostics port under the dash. You simply plug the programmer in and follow the on screen directions. Most standard programmers have three basic tunes on them. Usually a tow tune, an economy tune, and then an all out horsepower race tune. It is possible to get custom programming for these too. Instead of loading the tunes on a chip, the tuner would load the files on the programmer. As an added benefit, most programmers will also read diagnostic trouble codes and some real live sensor data. Many folks think you have to leave the programmer attached after programming, but that is not so. After reprogramming the factory computer, you can unplug the programmer and put it away until you want to change to a different program. Most of these programmers cost around $375 and up if you want special programming.
The third method is with a dash mounted programmer. There are a couple of different styles. One kind like the Edge Juice with Attitude actually does nothing to the computer but rather hijacks the signals going to the injectors and a few sensors to manipulate the fuel output. These can be changed on the fly without shutting the engine. They usually have five or so settings of increasing horsepower. I would recommend caution with these for automatic transmissions. The quick change in power along with no modification to the transmission strategy is sometimes too much for the stock transmission to take unless you let the transmission relearn for a few miles before mashing the throttle.
The other style of dash mounted programmer works just like the hand held versions. They have three to four tunes in them. You will have to stop and turn the truck off if you want to change levels. The great thing about the dash mounted programmers is that they have real time gauges in them. They are able to monitor anything that the factory computer does. Most of them come with an egt probe to put in the exhaust so you can monitor egts. The other great thing about this style of programmer is not only that they usually run in the upper $400 range, but they come with built in gauges which would cost you another $400-$500 if you had to buy them separately.
We usually do programming in the shop by attaching our laptop directly to the truck and building a program according to the customer. Since we can't do that for everyone all over the country, we usually recommend the Edge Evolution or H&S Street Mini Maxx programmer. They work fantastic, have built in gauges, several power levels, warning alerts to keep your truck safe, read diagnostic codes, and are just really nice looking units.
And there you have it. On our hypothetical truck here, we have installed a S&B Cold Air Intake, a MBRP 4" Exhaust System, and an Edge Evolution programmer. If you have some basic hand tools and a little bit of mechanical ability, you could install all this yourself no problem. The cost of everything would be about $1050. For that grand we will typically would gain: 50-100 rear wheel horsepower, 150-250 ft/lbs of torque, and anywhere from 3-8 mpg. Best thing, we have a fun truck to drive!!