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tuning for MPG

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95weclipse

10+ Year Contributor
308
3
Jun 26, 2009
LaSalle, Illinois
I need help with getting my car tuned, my mods are on my profile, I just need to get this tuned, my car only gets 20-21, ran a compression test the other day came back all above 170, think my pcv is stuck open, will be getting a new one soon, I don't need a 10 sec tune, just to get the "base tune" done i guess any help would be greatly appreciated, I am using ecmlink v3 lite btw
 
This thread is full of a lot of BS statements. 14.7 is not best for mileage or performance. 14.7 is only best for emissions. Depending on combustion chamber design about 15.2/15.5 is best for economy & between 12.2/12.5 is best for power. If you want to try and improve mileage lean burn engines first are designed to burn lean; fast burn heads. Lean burn engines are running up to 17:1 afrs BTW. You can improve mileage some by leaning out 4G63's a little while also increasing timing. The 4G63 motor does not like to be run very lean and quickly begins to lean misfire and any gains from leaning out disappear and your mileage goes down. I get my best mileage by reducing my cam overlap as far as possible and run about 15.2 afr at cruising rpm's & light loads, 15.5 in really high vacuum just before de-accel full cut happens.
 
Weight loss boosts your mpg, the other thing would be better port velocity to make a better fuel mixture. Like the cyclone intake manifold. I got around 25 mpg in my 90 eclipse with a poor tune using that manifold. Also keep your rpm low as possible without dogging the motor, in my focus svt it seems like 1500 at lowest and 2k as a shift point works best. Also if you run higher than normal tire pressure you will wear your tires out unevenly and reduce your traction, so pay for tires or pay for gas. Pick your poison there but I use manufacturers recommendations on that.
 
if you want best economy, just change afr to 16.2. I am surprised no has mentioned this YET! as always do a boost leak test so your getting all the air you can.

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I'd expect a tad less mpg in a 2g being a little heavier..
But either way a decent running 5spd awd should get anywhere from 19-22 with mostly city driving and typically 25+ all highway on pump. This is driving relatively conservative as well.

I recently tuned a friends 16g car on e85 and pump via a chip. He told me today he averaged 28mpg on his last tank, mostly highway and knowing him beating the shit out of it.. On e85 it was around 20mpg city. The timing and fuel for the idle and cruise portion were left stock in the tune.

If you're looking for anything better as said, tune lean low 16s at cruising
 
How are you going to get better gas mileage by lowering the timing with a leaner AFR?

Since I suck at tuning that is a shot in the dark. My logic is lean mixture by cutting more and more fuel. So in normal condition it would produce knock. That's why retard timing. But when I think again that probably will be a power loss...
 
Why do I get the feeling that the people stating to lean out the AFR are just quoting theoretical no-load numbers out of a book? :)

The most efficient burn of a fuel is at the stoichiometric ratio; in fact, that is the definition of stoichiometry. Unless you spend a large amount of time driving on a flat surface with low wind resistance, leaning out the AFR to use less fuel (and therefore produce less power) will usually be negated by the extra fuel you need to make up for that lost torque when going up hills, fighting the wind, or during light acceleration.

The best fuel economy will happen when you get the most torque out of the motor while using the least amount of fuel, and pushing the lightest amount of weight against the least amount of drag. So for the best fuel economy, you need to:

1). increase torque without increasing fuel usage, or
2). maintain torque while lowering fuel usage, or
3). lower vehicle weight, or
4). lower behicle drag.

Based on that, you can see how factors such as tire pressure, speed, ignition timing, and shift points can affect fuel economy. (For example, driving at a lower speed produces less drag from wind resistance; higher tire pressure produces less drag due to friction with the road surface; optimized ignition timing produces the most torque, etc.)

For daily driving under varying conditions, running a stoich AFR (14.7:1 for gasoline) with optimized timing, spark, and other factors will net the best average mpg.

Every car is different of course. In some cases, leaning out the AFR may actually give better mpg...but it's because you are compensating for something else. An example would be if you were running timing that was below MBT, but leaning the AFR caused a rise in torque output. Or, maybe your plugs are fouling and leaning the AFR gives a better spark/burn. Regardless, the most efficient burn from the fuel's standpoint is at a stoich ratio.

FWIW, I drive my car on a 220 mile trip 4 times a month, and have done countless tests with different NB switch points, target AFRs, timing, etc. (Gotta do something to kill the time right? :D). At best, I've seen maybe a 1-2 mpg increase when leaning out the AFR; but that is only on long stretches of flat interstate. I can simply drop my average speed by 3-5 mph and gain more than that.
 
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I've never read a book ;)

LOL Yeah... not buying that one.

I did however extend my closed loop...

That's a good point. By extending the closed loop range, you can keep the engine running at stoich more often, rather than richening it up unnecessarily. As long as the load stays reasonable and it doesn't cause other issues, that's a valid way of getting some improvement in mpg.
 
That's a good point. By extending the closed loop range, you can keep the engine running at stoich more often, rather than richening it up unnecessarily. As long as the load stays reasonable and it doesn't cause other issues, that's a valid way of getting some improvement in mpg.

Good thing to tweak when running a bigger turbo anyways.
 
I am pulling about 30-32mpg out of my Frankenstein creation of a motor in my Talon (5 speed fwd) running 93 octane. LOL

Still need to get it tuned and that's with driving a 120 mile round trip, five days a week on a whole lot of hills at about 60mph with cruise control on. Was getting around 27mpg when it was running super rich because of the CTS, got it fixed though. :)
 
Good thing to tweak when running a bigger turbo anyways.

Another good point to consider. Based on a lot of ECMLink logs I see, most people don't bother to remap the AFR table to compensate for a later spooling turbo. So they have the engine dropping into open loop and going rich where the stock turbo would be spooling, rather than extending out the lean area a bit to compensate for the later spool of the larger turbo.
 
You can get 30mpg at 70mph when cruising on a basically stock engine, but you need to have a properly maintained and properly tuned engine, and it's going to depend a lot on your bolt ons. Obviously if you've got a huge intake, exhaust, cams, turbo etc... then 30mpg might be out of reach.
 
Another good point to consider. Based on a lot of ECMLink logs I see, most people don't bother to remap the AFR table to compensate for a later spooling turbo. So they have the engine dropping into open loop and going rich where the stock turbo would be spooling, rather than extending out the lean area a bit to compensate for the later spool of the larger turbo.

Theres a lot of tables that dont get changed when we modify our cars. Radiator swaps and running cooler thermostats could use some ecu tweaks to. I guess not everyone is up to par with keeping up with the tune. They rather just have a car that runs and thats it.
 
If its there I find a way to make the adjustments. The tweaking process is the best part. Haven't had a dsm street car in many many years. So im looking forward to seeing what kind of milage I can squeeze out of my new auto.
 
Alright guys, I appreciate ALL of the advice but you are all going a little far LOL, I just got a AUTO GSX 97, 14b turbo, 255 wally, fuel lab afpr, stock side mount, stock injectors, ecmlink v3 lite, aem wide band ugeo, all stock internals I might be deleting a/c and power steering, don't know about the p/s yet but, I have NOOOOOOOOOOOO idea on how to tune, I dont know what to log what not to log, what to adjust, where to pull timing or add, or any thing all Ive got down pat is how to add/remove logged values and I have my aem wide band logged, I just think this should be getting better gas mileage than 20-21 my compression test was #4 189 #3 189 #2 170 #1 179 all on my brand new snap on compression gauge, I have tried reading the tuning for dummies stuff LOL and read stuff on ecm link it self, but I really just need some one to walk me through on how to get a base tune then I can worry about my MPG unless this helps
 
Spend a lot of time on the link forums and read the wiki top to bottom. There's some videos posted that help to. You really get lost don't be afraid to ask questions on link. There is a lot of knowledgable people on there.
 
I have alot to do before I can go posting there I gotta put my HUIC pipe in with my NT 1g TB and greddy bov, do a BLT and what ever else I for got, I read the "read this before posting here" stuff LOL
 
Max Power and Max Economy are on opposite ends of stoich. Max power (ideally) at 12.6:1, and Economy at 15.4:1. You lose the cooling effect of the vaporization of the extra fuel though. You will see some high EGT's though. Water/Meth injection is good to lower that (the way the extra fuel does when you run rich). That being said your drivetrain losses/weight is probably the biggest killer. I always wanted to try the acetone before a long trip to A) see if it works on a controlled run and B) use it all at once as I keep refilling the tank so it doesn't sit.
 
Max Power and Max Economy are on opposite ends of stoich. Max power (ideally) at 12.6:1, and Economy at 15.4:1. You lose the cooling effect of the vaporization of the extra fuel though. You will see some high EGT's though. Water/Meth injection is good to lower that (the way the extra fuel does when you run rich). That being said your drivetrain losses/weight is probably the biggest killer. I always wanted to try the acetone before a long trip to A) see if it works on a controlled run and B) use it all at once as I keep refilling the tank so it doesn't sit.


This is more to reference to an N/A car. Our "max power" is way richer than that.
 
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