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"Saving fuel with ECU tuning" Article

8K views 22 replies 8 participants last post by  hackish 
#1 ·
Interesting read from a UK based tuning co.



Saving fuel with ECU tuning

2 Jul 2013 | Article
Whenever we are thinking engine tuning generally people think that the engine tuning is done for better speed and acceleration. With the start of the modern engine ECU we now also have the choice of tuning engines to give better fuel efficiency. Tuning engines to improve MPG is speedily becoming one of the most common forms of ECU remaps done in the UK today
Expected gains after an ECU remap for economy
Diesel engines act in response far better to ECU remapping in part because of the wider range of limits imposed by manufacturers to meet up global markets that are not forced on modern petrol engines.
  • MPG increased by 12% – 20%
  • More torque (pulling power) at lower RPM
  • Extra responsive throttle
  • Beter overall driving experience.

How ECU Remapping can improve MPG
We remap the ECU to increase torque by up to 40%. We then modify where within the engine rev range this torque is made available, in the case of fuel efficiency we make it available at lower engine RPM’s. This enables you to change in to a higher gear earlier without shuddering or stalling the engine. In technical terms we not only boost the amount of torque available, but we broaden the range of engine RPM where this torque is available.

A practical example of ECU Remapping saving fuel
Think that prior to ECU remapping you needed to depress your accelerator 2 inches when in 4th gear to reach a speed of 40 miles per hour. After ECU remapping you now only have to depress your accelerator just over 1 inch while in 4th gear to reach the same speed and as we all know the less you depress your accelerator the less fuel you will use.
Let’s take this one step further. When getting to 40 MPH from a standing position you will have changed up through the gears, changing up one gear as the engine revs (engine torque) allows. After ECU remapping for improved fuel economy you can now change to a higher gear earlier and in doing so your accelerator is not depressed as much as it was prior to your ECU remap.
After having your engine’s ECU remapped for fuel economy you simply learn to change your gear changing habits and depress your accelerator less to drive in the same style as you always have. In general effect is that you will use less fuel.
At the core of the car is a box called the Engine Control Unit or ECU.
It’s generally a rectangular box situated under the glove compartment of wires trailing from it. The function of the ECU is to control the “quantity of fuel, ignition timing and other parameters by monitoring the engine through sensors.”
ECUs replaced the older carburetor, a mechanical answer to delivering an optimal air-fuel load and after 1995 most engines were running with ECU units with Electronic Fuel Injection (EFI).
Fuel injection: The ECU controls the EFI in sending a set amount of fuel into the engine. This is depending on conditions sent back to the ECU by sensors such as oxygen quantity, throttle open or close, engine temperature, vacuum, etc.
Modern ECUs incorporate a microprocessor in the system. A car generally has an ECU factory-programmed to deliver the optimal, but not necessarily the most fuel-saving mix to the car’s internal combustion engine.
This “stochiometric” or balance of air-fuel mix is usually set at 14.7:1 for gasoline engines. This means 14.7 parts air to 1 part fuel. Leaner mixtures can be achieved as high as 50:1 or even 100:1, mixing gasoline with alternative fuels such as Brown’s Gas also known as HHO.
Ignition timing:The ECU controls when the spark plugs will ignite the fuel. If it senses a bang in the engine and determines that it is caused by too early in ignition from the spark plug, it can regulate and delay the timing.
Idle control: For better fuel economy, the engine can control the rpm (revolutions per minute) of the car to save gas during idle, depending on some other systems still operational similar to air conditioning. At best cars still waste about ½ mile of fuel per minute on idle.
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#2 ·
what does this mean?

Get haltech
 
#3 ·
I was wondering if it was possible to tune for better mileage and acceleration on the highway, ... say a tune to improve torque between 2500 and 4500 RPM.

Our car (2011 Premium Auto) now has about 80,000 KM logged on the odometer and of that about 90% is highway driving. I am thinking of PNP on the Throttle Body as well as on the Intake Manifold. Would this allow a tuner to adjust the Fuel/Air ratio at specific RPM? I would like the car to 'appear' stock.
 
#4 ·
the problem with auto's is you ahve a TCU, not just ECU, so you have the trans. saying "rev rev nee dmore torque" and the ECU doing what the TCU says to do. In short.... auto's have bad gas milage not because of the ECU but the TCU, and as of now theres no tune's for the TCU
 
#5 ·
OK - thanks for the info, ... I got it.

So, ... 'balancing' intake and trimming fuel a bit could improve mileage?

The auto trans runs at about 3000 rpm at 110 km/h. (68 mph). I was hoping that with some minor adjustment to the ECU that the air/fuel ratio could be made a little leaner? While traveling at 60 - 70 MPH there is no shifting, therefore no need for the TCU to be involved in this equation?

I realize that once I boot it to get in the fast lane to pass that the transmission would downshift and turbo engages to boost. I am thinking about highway cruise from Montreal to Florida and back twice a year and balancing the intake to allow for a slightly leaner mix, ... possible with a PNP on the TB and IM ? Anybody?
 
#6 ·
thats the thing, the article states that most of the benefit isn't in the crusing, it's in the gas consumed during acceleration.

If you have a custome tune with road logging and tuning you can cut fuel a low throttle type situations, but you need a more linear throttle body control, and you need costume logging, canned tunes will not be as effective
 
#7 ·
When cruising, the ECU is targeting an AFR of 14.7 which is pretty damn lean. With regards to tuning, you will see the most mileage difference in the parts of the map that have to do with acceleration.
 
#8 ·
actually, i've seen evo's run 15.2 at cursing, Cobb tunes do this. First make sure your Wideband gauge is installed pre cat, if you have.

Next you'll want to adjust your open loop-to-closed loop point. Also when your tuning in that range, that precise use Lambda, unless you know 100% what octane your running.

But here is the problem, as stock you can not. You already have a lean 1 and 4 cylinder, so if you lean out the tune to get better gas milage you'll also be opening a window in cylinder 4.

So before this is a option make sure you have even running intake manifold (contact grimspeed or maperformance) get a tune that has a progressively even accelerator pedal position, to TB opening is linear.

Any time the ECU is in Closed Loop, the AFR will bounce around. The Narrow Band O2 sensor that the ECU uses does not read out a constant signal. When it is at stoich, it outputs a sine wave. That causes the ECU to make adjustments that are not needed. If you watch your Wide Band, you will see it oscillate back and forth like a sine wave. You can also log your STFT and see it happen too.
you should also look at engine load.

there many factors to consider. In short
as load goes up afr (the #) goes up, or you get leaner.
as load goes down afr(the #) goes down, gets richer.

Auto's run more engine load as they have more drivetrain conponents to push against before moving the wheels of the car. Before you use Man. afr and statistics that are logged from Man.'s is not valid.
 
#9 ·
Tuning for better gas mileage:

Step 1: Disconnect and remove turbo.

Step 2: Only drive on highways at 2 am.

Step 3: Sit back and enjoy.
 
#10 ·
Need I publish this again???
https://www.facebook.com/photo.php?...090732.-2207520000.1387474328.&type=3&theater

For those who don't want to click:


Cris90, I run about 16.0AFR while cruising. Our combustion chamber design is incredibly efficient (economy engine no?) and cruising loads are very, very minimal, so the EGTs don't soar like they would under 16.0AFR at WOT.

That, and the EVAP system is a great way to squeeze out like 5 more MPGs from any car, if you know how to work it.
 
#11 ·
^agreed, I get the lean vs load but how does the EVAP system come into play, i'm very intered as i'm looking to get Haltech this spring
 
#13 ·
Emission? What's an emission???? XD

The EVAP system feeds the IM fumes from the fuel tank (since gasoline evaporates in there), so the car literally runs on fumes. Then I do some technical doohickeys and corrections and magic in the Haltech, and well, I barely open my injectors while cruising. My car basically runs on fumes while on the highway lol
 
#14 · (Edited)
The main point I got out of this article was that increasing the torque output and making it available lower and over a greater range of the powerband is the key to improving the fuel economy. That and not accelerating any faster than you were before the torque increase (that's the hard part). So even these "performance" tunes that increase torque and horsepower should net you better fuel economy if you can keep your foot out of it, and that seems to be what a lot of people are seeing.
 
#23 ·
A few minor points here since I don't have time to teach a full EFI course online. First, evap vapour does not contribute significantly to the observed or commanded AFR. Even if you were running 100LL it's not going to change a lot. If it were the case then you'd be able to watch a gallon of fuel evaporate in front of your eyes.

Second, running a car leaner than stoich does pick up some small mileage but hook up a 5 gas analyzer you spit out a very significant amount of emissions for a decimal gain in mileage. That constant bouncing you see leaner and richer than 14.7 is not by accident. It feeds one of the cat stages. It's also not by accident that nearly every car on the planet runs this way.

The first way to gain fuel economy is with your right foot. Drive smart and try to adjust your driving to minimize using the brake. That means taking your foot off the gas sooner when approaching a red light. In many tests done with commercial drivers a few habit changes have made 20-30% FE improvements.

The next thing, on an AT car you can adjust the shift program. It is a tradeoff but by going into TC lockup sooner and upshifting more aggressively you can usually snag an easy 10% in urban and extra urban driving.

On cars with EGR you can crank it up. You increase the risk of misfires so the owner has to keep their car well maintained. This reduces pumping losses and even on freeway driving will give you up to 10% better economy.

GDI cars can similarly benefit from pumping when they're running in stratified mode.

On the GenCoupe you could probably re-gear the rear end for better cruise economy. They are not great on gas, but if you're going to spend thousands on fuel economy specific mods you should ask yourself if you purchased the right car for your needs.

Change how you drive first. Its the cheapest mod with the best results.

-Michael
 
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