two ten hour days driving, between 75 and 85, mostly 91 octane, but at high altitude, infrequent accelerations.

first my psi meter let me see the real differences in load dependent on head winds, following a pick-up, or leading the pack. Lots of long pulls up grades @ 2 to 4 psi

26 to 28 mpg depending on head winds or not. At one stage I was inadvertently running 16.5 +or - towards 80&90 load. Didn't feel the car being unhappy, just didn't like the thought. For the most part mid fifteens above 50 load.

 

My latest tinkering with E85 economy tuning:

https://www.evolutionm.net/forums/sh....php?p=6005051

 

I have been testing a gas mileage tune for the past four tanks of gas. I run the car lean at around 15.5-15.7:1 AFR, advanced the timing by about 3-4* in the cruise area and added some mivec cam timing at the very low end.

I have logged 1214.1 miles in mixed driving conditions, 35% street and 65% freeway. I filled 47.158 gallons of gas at the SAME gas station and the SAME gas pump. I even use the same filling method. I fill up the tank till the pump clicks. Then I add 0.5 gallons on top of that.

My gas mileage over the 1214 miles period is 25.75 mpg. I can now consistently get 25 mpg whenever I drive the Evo.

 

im now officially running a 15.6 AFR at 42* timing in cruise conditions...im gunna keep going till get knock or my egts raise enough for me to worry

 

Can you post your maps?

 

On the trip to the DSM Shootout I averaged 29-30mpg at 14.7:1 with just 2-4* of advanced timing in the cruise cells on 93 pump. This was all highway of course and I had 100lbs of tools/luggage plus 2 passengers.

 

calculated gas mileage at 25mpg including all my around town and a ton of WOT rips n runs...which means its probly in the 30's for highway..which is insane lol...i love this thread

 

Okay guys, since reading this thread I've also bumped up my timing in the cruise ranges...and the car feels awesome. I haven't gone thru a whole tank of gas yet. But i'm hoping to see some gas mileage improvements as well.

However, I have noticed something else that reminds me of my old OLD days of car tuning and racing, back in the late 80's I had a 69 Mach I Mustang. When the timing was bumped up too much. The car had to struggle to start. What I was told at the time was that increased timing was tough of the starter. Well...my EVO is now showing signs of struggling at start up. Has anyone else noticed a difference in starting your cars? Especially when it's warmed up?

I ask this because I'm also at the mileage that I usually need to change out my battery in new cars (36K miles). Sooo it might be my battery getting ready to go south on me...

Any thoughts?

Thanks!

 

You're only in the 500-1000rpm range during startup. There really isn't any need to even change those cells between 0-100 load generally. Most people have their idle timing between 5* and 12* without any issues with startup. I believe the ECU actually has a specific timing chart solely for start-up, though i don't think anyone has bothered looking for it.

 

Right - I got that (my timing at startup in that 0 to 500 to 1000 range is set at 8)...

What I was trying to convey was that by running a bit higher timing durning normal cruise it's actually stressing the starter (from what I remembered). Now I'm NOT saying that it DOES. I just remembered the symptoms from my old Mach. I remembered hearing the starter crank slowly when starting after the car had been warmed up...and I'm CURRENTLY getting that with my EVO. I'm just curious if anyone else has run into this.

I'm SUSPECTING that my battery is getting ready to go out on me. Which I was expecting around now, with my mileage hitting 36K. I'll know for sure if it's starter related or battery related in the morning...when I do a cold start if the engine cranks up faster...that will tell me if the starter is stressed...or if the car does NOT start or cranks slow - then I'll know the battery just went. lol I'm on vacation right now so it's no biggie...but if I needed to get to work in the morning...I'd be sweating it right now. LOL

 

i agree with Jack of Trades witht he seperate start-up map...im running now 43* of timing in sum cruise areas...my car starts like a champ...i dont see how that would correlate to a starter tho, a starter is only used to start the motor and is otherwise not used, the timing which is controlled my the ECU could only be effected by an extremely low battery...the car would probly stall before the timing would be effected actually, since the injectors have a table for just so that doesnt happen lol, either way i fail to see how adding a certain amount of timing only during certain conditions would effect a device only connected solely to the ignition/battery that is used during a different phase of the ECU


::edit:: my car also has 40k on it, and most batterys are effected by time and temperature conditions before they are effected by mileage im still on the stocker, but ill probably get 1 within a year from now

 

I need some schoolin'...

What are the pros and cons of closed loop vs open loop for idle and (especially) cruz? A lot of good info in this thread, but it is scattered and I can't seem to come up with a complete answer to this question. Some members strongly favor one over the other, but not a lot of reasons given.

Where does the 14.7 come from that appears in the AFRMAP data stream in EVOscan (in clsoed loop) when there are no 14.7s anywhere in the fuel map?

How exactly (fifth grade level) does the OEM ECU work? I had always thought it used the fuel table whether in open or closed loop. And that in closed loop the only difference was that the ECU also looked at the feedback from the O2 sensor. I now understand this to not be the case, correct?

I'm feelin' a brain fade. Thanks for the help...

 

(How exactly (fifth grade level) does the OEM ECU work? I had always thought it used the fuel table whether in open or closed loop. And that in closed loop the only difference was that the ECU also looked at the feedback from the O2 sensor. I now understand this to not be the case, correct?)

During idle & cruise the ecu is "closed loop" which is when the fuel is controlled by the 02 sensors. They are designed to keep the car at 14.7 no matter what.
During "open loop" the ecu goes looking at the fuel maps. Generally this is wot and some conditions such as when the motor is cold or hot.


(What are the pros and cons of closed loop vs open loop for idle and (especially) cruz? A lot of good info in this thread, but it is scattered and I can't seem to come up with a complete answer to this question. Some members strongly favor one over the other, but not a lot of reasons given.)

There are benefits of cheating the 02 sensor feedback system, once its set up you should be good to go. 2, If the 02 sensor goes south the obd2 system should alert you that something is wrong via the cel. This argument may be faulty.
On the other hand playing with the fuel map and holding the ecu to it lets you put the afr where ever you want it over the spectrum of low load. Such as 16 at idle 16.5 at light cruise, 15 at moderate cruise load, and drifting richer as you proceed into higher load.(these numbers are up to the tuner, lets not argue them).
If your 02 sensor goes bad I'm not sure if the obd2 will report it. So you need to monitor your wideband from time to time. 2, Its a little difficult to get your desired afr because of some functions of the ecu. The "tip in",/ "accel enrichment" map isn't really found for most roms so sometimes the car seems to revert to closed loop. I think this can be overrun by going with BIG numbers in the map.

In reading my own answer a cross breed of the two practices would be fairly neat.
Open loop is the knuckle dragging method, now back to my cave.

 

The ECU doesn't follow the fuel map in closed loop. There is a value in the code that is used to set target AFR in closed loop. Since NB sensors only crossover at 14.7:1, the value was not meant to ever be changed, so it is not written into the code as a single value table.

 

More like the car looks at the fuel map in both open loop and closed loop. It uses trims to add or subtract a percentage to parts of the fuel map when you are in closed loop mode. When you are open loop having a trim does not matter... the ecu will follow the fuel map no matter what.

The advantage to going into open loop is that you can control the fuel as you please without the car changing the trims and trying to bring the crossover back to 14.7 AFR