Do truck tuners and other supposed mileage boosting equipment work?

April 6, 2008 3:02 PM

Does the Hypertech Max Energy Programmer really increase fuel economy for trucks and SUVs? If so, why do auto manufacturers not simply include them in their vehicles so as to beat out the competition?

I saw an ad for an aftermarket tuner that connects to the computer of trucks and SUVs and supposedly has an "economy" setting that can up your fuel economy by "2 to 6 MPG".

Do tuners really work to increase fuel economy, particularly for a 1/2 ton Ford with a 5.4L triton V8?

At first I was excited and wanted to try it, but with a price tag of nearly $380, I figured I'd better think twice. Still, at current fuel prices of $3.50/gal, and with only a 2 MPG increase, it would only take one year's worth of driving to pay for the unit with the fuel savings, assuming one drives 15,000 miles per year and goes from getting something like 16 MPG to something like 18 MPG.

I became skeptical, though, when I considered the pressure on the auto manufacturers to increase fuel economy. Surely if there were a legitimate way to boost efficiency by tweaking settings in the vehicle's computer, auto manufacturers would have already added the device to vehicles, with a switch in the dash as standard equipment, wouldn't they have?

Is there any conceivable reason why auto manufacturers wouldn't have already added this device to every vehicle?

While we're on the subject, there are a variety of MPG increasing strategies at this website. If these strategies are legit, why are they not standard? Are there any standouts that are worth a try?

posted by tosteka to technology (8 comments total)

When auto designers design their engine control computers, they have to shoot for a "middle of the road" tune of the engine. With powertrain reliability and driver experience at the top of the list. They don't want the thing stumbling and backfiring and idling funny. Even if it saves gas, people in general won't like it.

There are ways to make a car run more efficiently, but they *may* be at the detriment of long term reliability. One way is to simply run the air fuel ratio lean, which is literally less gasoline going into the engine than it might be calling for. This may save fuel, but causes the engine to run hot, ping and also causes more harmful exhaust components.

Another possibility is that with advances in computing power and knowledge of engine tuning, it is simply taking an older car and running it with a more state of the art engine tune.

As for the things on the website, they may be true. *IF* the truck in question is suffering from the things those devices claim to fix. For example, installing a wide open exhaust will indeed reduce backpressure in the exhaust system. This reduces the amount of work the engine has to do to push the exhaust out of the truck. But it also reduces the velocity of the exhaust flow, which can cause problems like poor idle and reduced low end power.
posted by gjc at 3:14 PM on April 6 [1 favorite]

I should probably ad that I have an '06 Ford F150 that is in like new condition. Any likelihood that by now things have changed so much as to justify new software?
posted by tosteka at 3:25 PM on April 6

Consider one way to save fuel: accelerate gradually instead of stomping on it. A computerized engine control system could (in theory) limit the rate of change of fuel flow to a certain value (like a jet engine does for a different reason). Would it save fuel in the long run? Maybe. Would it be irritating as hell when you were trying to merge onto a highway with a short or no ramp? Yes.
posted by ctmf at 6:17 PM on April 6

Click & Clack talked about this a while back. What they said is that the manufacturer tunes the engine for the optimum mix of fuel economy, power, emissions, and general drivability. After all, they have to warranty the engine. Someone such as Hypertech doesn't have to. If the engine suffers premature wear from running too rich (and hard, usually, because people who generally tune for more horsepower) then it's you that's out the few thousand bucks a replacement would cost. Same if you're always having to drive with a heavy foot because the engine is running too lean.
posted by azpenguin at 6:56 PM on April 6

oops - to complete a sentence - (and hard, usually, because people who generally tune for more horsepower tend to run their engines harder than most)
posted by azpenguin at 6:58 PM on April 6

Based off of a glance at the products homepage, the main things this thing would do are limit RPM and limit maximum speed. This is basically what ctmf was saying, where you don't necessarily change the engine, you just change your driving patterns, except that this device does it for you. To me, that would be very irritating, as there are times when I expect my car to respond quickly to certain input.

Probably the only other thing it does that would really matter (assuming your truck is relatively well maintained) is that it changes shift patterns. My guess is that it would basically shift your truck into higher gears as much as\as soon as possible. This limits your ability to accelerate, and decreases RPM, which would both lead to increased fuel economy and decreased responsiveness.
posted by !Jim at 7:14 PM on April 6

ctmf and gjc are about right. specifically, cruise control is usually more aggressive than it could be. manufacturers put out mileage data not using cruise control, but then the cruise settings are generally more aggressive than normal drive patterns. for instance, at the start of a hill the vehicle will accelerate hard, whereas a driver can see the road ahead and will judge a more gradual acceleration.
the results will be specific to the type of car - different manufacturers have a more lean or more aggressive tuning to start with.
to ans the second question a little bit, fuel efficiency could easily be improved on all production cars, if drivers were happy to put up with a slower less aggressive less impressive performance.
posted by edtut at 4:32 AM on April 7

It is extremely unlikely you will damage an engine by running the mixture rich. You may cause extra deposits (at a greater rate than would occur anyway) but these can be easily cleaned by modifying driving habits (hard driving/revving/heat producing driving will burn these off).

When auto designers design their engine control computers, they have to shoot for a "middle of the road" tune of the engine.

Um, no. Not at all. It is almost always about emissions for a power range that they wish to sell the car at (ie marketing driven - pick the power, make the engine work within the emissions regulations). The ECU is programmed to drive with certain compromises for drivability (power delivery and the like) but the main limitation is emissions, the target is the BHP the marketing department wants.

These bits of electronics DO work (assuming they are good ones) as by far the biggest factor affecting a cars state of tune as standard is emissions - this is a far greater restriction than people realise. You will get a car that produces more power because the mapping (the fuel per air mixture controlled by computer) will be more leant toward optimum burn for power rather than 'for the stuff that comes out the exhaust. Optimum power, economy and emissions are all linked but are not directly linked in a way that would seem logical (ie max economy is not necessarily best emissions/least power.

Based off of a glance at the products homepage, the main things this thing would do are limit RPM and limit maximum speed.

Those are side benefits and are not in any way the core basis of the programming. The main thing it does is modify the fuel mapping of the engine - same as chipping does, but with more adjustability and extra bells and whistles (the speed limiter etc).

fuel efficiency could easily be improved on all production cars, if drivers were happy to put up with a slower less aggressive less impressive performance.

It has nothing to do with 'aggressive state of tune' - this concept is a fallacy. People would save money if they were able to cope with a car that gave less power - ie used less fuel. Just as much as tolerating only using half throttle would. Production cars would have better fuel economy if they didn't have to worry about emissions. They would also have better economy if they didn't have to worry about safety (removing all the weight of airbags and crumple zones) and if they removed comfort (air con is heavy, as are nice seats, sound deadening and sound-reducing windows) - so basically, that logic falls apart if 'producing a competitive car in today's market' is the parameter. Emissions again become the biggest factor for limiting power for a given size of engine.

specifically, cruise control is usually more aggressive than it could be.

Cruis control will almost always produce better economy than manual driving. It also has nothing to do with engine parameters. The two are not at all linked - the only potential link is for the gearbox down change settings, but generally the cruise system is a purely additional system, to the core components and electronics. It 'accelerates hard' because it has put in a big throttle input to get you to speed because it senses a high speed differential between set and actual speed. It's job is to keep you at the same speed, that's all.
posted by Brockles at 7:51 PM on April 7