Programmer chips and modules for fuel economy and/or power - good idea or not?


I often see ads related to chips or modules that are supposed to enhance performance and/or improve fuel economy. Some of these are as cheap as $50 while others go up to the many hundreds of dollars. I have always figured that these are a bad idea but have never studied them. I know they void most warranties on new cars and wouldn’t the manufacturer have spent tons of money making sure their engines were running optimal from the factory?

Anyway, I have some friends who swear by these types of devices, especially on Diesel pickup trucks. Some use them to blow black smoke which I hate. I am sure this is just a waste of fuel. They indicate these have like 5-6 different modes you can use with one being optimized for power/towing, another for fuel economy, and so on.

I know some of these alter shift points of an automatic transmission but how would this apply if you installed one in a car with a manual transmission? If I were to ever do one, I would definitely use a “mild” version where no other modifications are required on the vehicle such as the fuel, ignition, and exhaust systems. Some of these just plug into your diagnostic port and have no settings you can change.

I want to hear some opinions on these. What do people who have worked with them think? I can understand them for racing but how about daily driving?

If I were to ever do one, I would definitely use a "mild" version where no other modifications are required on the vehicle such as the fuel, ignition, and exhaust systems.

Then don’t bother. Re-chipping a car that has no mods is almost always pointless. As you suspected, they already programmed the stock computer to get the optimum power/efficiency balance.

The only time you should worry about changing the computer is if you modify the physical parts beyond the ability of the stock computer to adjust for.


Knowing , up front, that the manufacturers are already striving for those maximums, just what are these chips changing anyway ?
Every chip I’ve seen a customer install has ended up in our shop because of problems it creates.
Even my power hungry repo guys have stopped throwing money away on chips.

Running too rich or too lean at the wrong times causes havoc in the systems, especially cats.


Not a good idea.
You mess with your computer program or by altering the input signals to the ECU to “fool” it at your own risk. A given engine can only get more power by using more gas. You cannot get more power and better mileage at the same time. Today’s engine maintain a delicate balance between providing correct fuel for good power while still not compromising mileage or allowing more fuel than the car’s cat converter is capable of processing. Excess fuel = carbon, and carbon will coat the cat converter core and prevent it from working.

Race cars are modified/designed to be able to affectively use greater amounts of fuel and don’t worry about emissions. They’re able to inhale much more air and fuel and able to push it out once it’s burned in much greater volumes. And they don’t have to last 300,000 miles. Racing engines get rebuilt routinely. The pure racing machines rebuild them after every race. Drag racers tear them down after every run. Weekend racers, the guys who race their cars on weekends but have other jobs during the week, accept the cost of routine repairs that comes with stressing the car. I urge you to not make the mistake of believing that things that work on race engines will work on your engine.


This was pretty much my initial assumption. Anyway, I do know of some people who have used something like this on some heavily modified vehicles. These have included aftermarket turbo systems, larger fuel injectors, bigger fuel pump, different exhaust, highly modified ignition systems, etc. for more performance. It sounds like these types of vehicles are where these chips have their place. These are definitely not daily driver type scenarios and I know most are being worked on when not being driven.


You’ve added an excellent point: the guys that do this stuff work on their cars for either a hobby or a living. If you’re going to make modifications, you’d better enjoy working on your car. I haven’t made such modifications (a few minor ones, but nothing major) and yet the neighbors still kid me about spending so much time lying under my car. They don’t know I’m sleeping under there… {:slight_smile:


A few years ago, someone posted on here about his experience with a performance chip on his nearly new Ford Super Duty diesel truck. Something catastrophic happened with the engine, and Ford wouldn’t touch it under warranty because he’d used that perfomance chip on it. A new engine was well over $10K, I think it was, and the guy was totally on the hook for it.

Just my two cents.


I wonder if these things just lean out the burn. Yeah, you may get more power or more MPG but that isn’t good on an engine.


You really don’t need a chip with modern cars, just a programmer. They download a new program into the engines control unit, usually a “tune” for modifications like freer flowing exhaust, air intakes or hotter cams. Any changes for mileage basically just advance the timing closer to spark knock. The gain and push your car closer to harm. Admittedly, manufacturers use a conservative tune for ignition timing and you can increase that a bit to get a small gain because - You always use quality gasoline and take good car of your car. The $50 “chips” don’t work and the programmers are $300-$500. Too much $$ for the small gains you’ll get. Don’t bother.


I’d add that using a chip to slightly advance the ignition timing might get a dab more power, but at the risk of preignition. As a matter of fact, you’d probably have to advance it beyond the antiknock system’s ability to retard it in order to net any gain. And you’d risk engine damage.

You really don't need a chip with modern cars, just a programmer. They download a new program into the engines control unit, usually a "tune" for modifications like freer flowing exhaust, air intakes or hotter cams.

UM…NO…That’s NOT how these chips work. The software that controls the ECU is NOT…repeat NOT changed. Unless you spend a few hundred thousand reverse engineering - you’ll NEVER be able to rewrite the software. The software (while not that sophisticated) is still embedded in the chip. You don’t have access to the source code…so it’ll have to be reversed engineered. The guts of the program reads signals from all the different input signals and then adjusts the gas and air mixture based on a look-up table. That look-up table is what is stored on the aftermarket chips. It changes the output settings based on the inputs. The program reads the input…but now based on a different look-up table it dispenses a different gas and air mix.

Obviously I over simplified…but in a nutshell that’s what it does. A programmer will do you no good unless you have the source code or you want to spend a LOT of money reverse engineering it. And that is very difficult and expensive to do.


@MikeInNH‌ , Tuners like those from SCT and Diablosport actually do exactly that. They rewrite the parameters of the ECU’s software. You plug them into the OBDII port and download the tune that’s on the tuner into the car’s ECU, then you unplug the tuner. But anyway, chips and programmers aren’t exactly the same thing. This can create issues if you ever take your car to the dealership and get the ECU read, the info that the ECU will return to the dealership’s machine will not match anything they have on record, I know this from experience. Most “chips” you see today, especially those $50 ones you see on Ebay are simply 5 cent resistors.

Also in some cases a custom tune is necessary for the car to function correctly. When I had the supercharger installed on my car, it was towed to the to place that did the dyno tuning. Running the engine with the stock tune (but with the supercharger) would’ve been dangerous for the health of the engine as it would’ve been way, way too lean.

They rewrite the parameters of the ECU's software.

That is NOT rewriting the software. That’s just changing the parameters of the look up tables. You don’t have to know the first thing about programming to do that. That just using a canned software package and the hardware to write to a new chip. The knowledge is knowing what to change the parameters to. And that can easily be done with trial and error.

But the actually programming of the ECU does NOT change.


Technically ,it is rewriting software because you’re changing around 1’s and 0’s. The look up tables are software after all.


Advancing the timing makes sense as some of the “mild” chips I describe suggested the use of premium fuel when I looked into them.

Now this brings up another point. Many engines have extra conservative timing not because of spark knock but because of emissions requirements. For example, I have a Geo Metro. The timing stock is set to 5 degrees BTDC. You can advance this to 7-8 BTDC without concern of engine damage, even on regular 87 gasoline, but may fail inspection depending on it they do an emissions inspection where you are. Luckily it takes 30 seconds to loosen two bolts and rotate the distributor. You can make alignment marks in the metal so you don’t need to break out the timing light each time you want to make a change.

Some will push their timing a tad farther on these cars but you usually need to start running premium fuel to do so and some suggest you may cause damage anyway so I don’t do this with mine. That extra 3 degrees of timing makes a big difference in the response of that tiny 3 cylinder engine. You also gain fuel economy.


I guess the bottom line to all this is that if you mess with the manufacturer’s programming either by changing it, altering its look-up tables, or fooling it by messing with a sensor’s output signal, you do so at the risk of causing problems that will cause you great distress, perhaps even engine damage. And the manufacturers these days put so much engineering into fuel delivery that it’s pretty much impossible to improve on their results. Any improvement in power that you might gain would come at the cost of mileage, and any improvement in mileage you might gain would come at the expense of power.

Technically ,it is rewriting software because you're changing around 1's and 0's. The look up tables are software after all.

Sorry…but that’s not the definition of software. The lookup tables is just static memory which is used by the software.

Those are just input values to the software. Changing INPUT values is NOT changing the software. It’s not even changing the execution path. Just the input and output values.


The programs and other operating information used by a computer.

The programs and other operating information used by a computer.

EXCELLENT…Now go right your first program and get back to me.

noun \ˈsȯft-ˌwer\

: the programs that run on a computer and perform certain functions

: something used or associated with and usually contrasted with hardware

: as

a : the entire set of programs, procedures, and related documentation associated with a system and especially a computer system; specifically : computer programs

INPUT DATA is NOT part of the software. It’s USED by the software…but NOT part of it.


But data is software, in the sense that’s certainly not hardware. Data can be considered software. Otherwise you get into a chicken/egg scenario, where you need data to create software, but you also need software to create data.