Conservative "Economy" tuning Hypothesis and brain storming. "AFR and timing"

Bluedemon_II

New member
Conservative "Economy" tuning Hypothesis and brain storming. "AFR and timing"

As part of my tuning proses, I attempt new settings to achieve different goals. Right now I'm about to finish up on my part throttle tuning segment.

I have seen a dramatical decrease in fuel economy when my car was running leaner than normal AFR on low load/rpm areas "daily commute".

My car was running close to 15.7:1 to 16.0:1 on some areas, this is very lean compared to the standardized 14.7:1 target for gasoline injected engines. At some points you could feel the car unwilling attitudes towards acceleration while on this situation took place. It was at some points necessary to increase throttle to obtain the same power that it would have on other areas running near the accepted AFR target "14.7:1 - 15.0:1"

It would make relative sense that if the AFR is leaner, the engine is consuming less fuel. But the the thing is that at an average I could get about 200 miles per tank.

This leads me to think that even if the engine is using less fuel, the power output falls dramatically and so it requires more air and more fuel to do the same job since the combustion is less efficient.

I don't know if I'm projecting my idea clearly since this is a little confusing even to me.

Right now I'm in the final touch ups of my fuel map to run as close to 14.7 as the ems lets me.

As far as timing goes, I run 43 degrees on most of the low load areas, at about 4500 rpm. I'm haven't gotten the chance to test more timing on low load but I would like to run close to 45 or 49 degrees to see the effects on fuel economy.

In fact, I'm going to change my map to run those degrees and see how the car behaves.

If anyone wants to share or comment, please do. I feel like our tunning section needs a little more love.
 

HolyCrapItsFast

Drinks beer!
I believe you are right on the money as far as your explanation goes concerning overall fuel economy with leaner fuel ratios. From my eperience you will benifit from leaner fuel ratios only up to just a couple of points beyond. Where 14.7 is ideal stoich you can lean it further to 14.9-15 and benifit because the combustion is still enough to create power but it will fall off really fast from there. I have also found any load above .7 requires at least 14.7 fuel. I am finding that with e85 you can go a bit leaner even and still maintain good power.

Ultimately I have only been able to improve fuel economy to 27-28 mpg highway while running petroleum. on E85 the best I have ever seen was 20 but lately it's fallen to 17.

Beyond that I have yet to experiment with both timing and AVCS as it relates to fuel economy. I do remember my fuel economy was better when I ran very aggressive timing in the low and mid range load cells but I'm not sure of the dynamic involved there so I can't comment without doing more experimentation.

Believe it or not the my best result come form running waste gate pressure only and minimizing my turbo usage.
 

Bluedemon_II

New member
True that turbo usage minimizes mpg but I used little boost while I was watching my consumption. If I could average 25 mpg combined, that would be awesome. Sadly I don't have Avcs to play with, well it's there but the control system is funky with the ems. Going to revisit my timing map to see if I can squeeze a little more timing with out causing knock.

Wonder If there could be a modification to cause swirl in the tgv are so that the mix that enters the combustion chamber gets a faster burn, like gm did on their Vortec heads. I think that I'm going a little out of hand lol.
 

HolyCrapItsFast

Drinks beer!
I just know the real key to this is AVCS and Timing. I'm just not sure of the approach to take. I'm so busy with other project I just don't have the time to experiment.

The Tumbler Generator Valves are meant to do just that but we take them out because of the restriction they impose and at the expense of some economy.
 

icudruln

New member
I'm starting to understand this all better. :D Understanding parameters and the whole tuning aspect is definitely interesting. I just bought a book on it...How to Tune & Modify Engine Management Systems with a Ford Focus on the cover.
 

Vermont

New member
I am using the NASIOC guide to tunning they have. I have been reading over that for a while but with out a car to it makes it hard to really under stand.

Lucky for us we have Holy here, so that way i can go running to him every time I do something stupid. :D
 

HolyCrapItsFast

Drinks beer!
Oh jeeezz! Hey I'm surprised I haven't blown my own car up like 4 times over... Oh wait... uhm, I did!

You probably don't want to take my advice. :lol:
 

Vermont

New member
Oh jeeezz! Hey I'm surprised I haven't blown my own car up like 4 times over... Oh wait... uhm, I did!

You probably don't want to take my advice. :lol:

lol see you already made all your mistakes. Your like those old hobo's you see out side the liquor store. If you listen closely they will tell you some sage advise..... For a colt 45 that is... :D
 

Bluedemon_II

New member
Well I uploaded a new timing curve this morning and richened the fuel map some more to make it hover around 15.0:1 The car seams to like the 46 degrees of timing. It feels more vivid and whiling towards acceleration. Going to see if I can get away with 48 degrees and touch up some areas that have a little more fuel than needed. My WOT area seams to hover around 11.2:1 going to slowly lean it towards 11:5 or .7.

Wish that I would own a dyno with load absorbers... some day I will lol.
 

HolyCrapItsFast

Drinks beer!
Oh don't do that.

The WOT High Load High RPM region is not where you want to tune for economy. I would stick with the low and mid areas (cruise) because that is where you drive most of the time anyway and are going to see the highest gains. Unless your the type that whales around every corner and runs WOT threw town just to scare the old people trying to cross the street. :lol:

I would always keep my WOT region rich around 11:1
 

Bluedemon_II

New member
Oh don't do that.

The WOT High Load High RPM region is not where you want to tune for economy. I would stick with the low and mid areas (cruise) because that is where you drive most of the time anyway and are going to see the highest gains. Unless your the type that whales around every corner and runs WOT threw town just to scare the old people trying to cross the street. :lol:

I would always keep my WOT region rich around 11:1


Sorry for got to add that that was not part of the economy experiment. I had a Meth leak that I didn't detect and tuned the car to that. Last 2 weeks ago I found the leak using a die test and fixed.

When I went to do a WOT I was on the Rich side, I mean the Wideband was peg at 10.0:1 so probably it was in the 9.x:1. I fixed that and since I'm running meth I know I can get a little more power running around 11.5:1 I'm targeting that area.

Basically I want to get a semi safe meth tune complete to implement my ultimate failsafe. When the monitors trigger a fault, the Ems will switch to the NOS trim maps and alter my base fuel and ignition values turning my meth map into a 93 oct pump map. Pretty neat :D
 

Vermont

New member
Quick question for you Blue. Since you are running the Coolingmist Controller, is it possible to use that 12v out put on the failsafe to trigger safe mode on fault? I am going to be installing my coolingmist kit this month and wanted to know if it was possible.
 

Bluedemon_II

New member
Quick question for you Blue. Since you are running the Coolingmist Controller, is it possible to use that 12v out put on the failsafe to trigger safe mode on fault? I am going to be installing my coolingmist kit this month and wanted to know if it was possible.

I had a thread about this on that other site subaru site. Actually I think I was the first to put this to actual use, then coolingmist used my idea and now is included in their install documents.

You can use a relay to bridge the ground that triggers failsafe mode on a 32 bit ecu.

Benefits are:
*No timing advance- only base timing is used during failsafe mode
*0 Wastegate duty cycle- Wastegate control is default to an open solenoid so boost is dictated by the wastegate spring. If you have a MBC you can use a solenoid to
bypass the MBC.
*Failsafe Fuel maps- You can run Failsafe fuel maps and tune them to be sort of a safe street map "11.2:1 afr at WoT would be a nice target"

Basically is like the ultimate failsafe, if you have a quick reacting system.
 
Top