Thread: Tuning for Gas Mileage

on the last pic, it says tps 17 is that 17% throttle to sustain 70mph?

cant you just lean out your fuel in the crusie speed areas of the fuel map, like go back to a known good ignition map, maybe the first one or something, then start taking fuel out in the fuel map to reach a desired air fuel for best fuel economy.

i have been doing a bit of fuel economy tuning. basicly, i got a good iginiton map, left it as it was. but mostly worked on the fuel at a certain threshold, 55-70mph was the threshold i was using to basicly have a more leaner area of cruise, or for best fuel economy. 14.7 or stoitch is good for fuel economy, but i went a stitch farther and tuned out my off boost 55-65mph in the 15.5 air fuel ratios. so basicly come 55-65mph in cruise off boost, i go into the more lean area of my fuel map designated for better fuel economy if you will.

end result is pretty good, to sustain a 55-70mph speed it take around 7% throttle input & the fuel map produces 15.5 air fuel ratios. i havent calculated exactly how much mpg the car gets , however i have taken it on a few trips to my work and back 50miles round trip, and i can definitly see it getting around 40mpg on the highway. it doesnt consume gas at all...

i basicly did very basic air fuel tuning to gain and sustain a certain air fuel at a certain load and certain speeds. and it worked for me, i know there are more complex ways and more complex things to take into account ,but i just did what worked best for me.

i think starting with a good iginiton map is key, then working with the fuel to

when i switched from a calum basic tune on my ve to a EMS with a full dyno tune the gas mileage shot up. 90% is from the timing. with the calum i was running 35-40 deg in the cruise area with the ems i am up to 45 ish. i get right about 30-32 mpg with mixed driving. this is including me racing around on the on ramps etc. this is up from about 23-25 mpg with the same driving habits. the Afr has stayed the same calum basic was set with oscillating 14.0-15.0 Afr and the EMS is a really steady 14.7-14.8 Afr

17 TPS should technically be 17% throttle yes, I've noticed the highest the TPS is 90 on the ScanGauge, not 100%

But this was a slight hill, thus my boost was starting to build. On a flat road to maintain 70 mph it's 10-12 TPS.



Actually I did do this, well I first tried to lean out the motor by changing the values from 14.7 to even 18, and they still stayed at 14.7. I then disconnected the front O2 sensor, the car still maintained near 14.7. By the time I realized how to lean it out and map traced it was too late, I arrived at home haha.

Basically, my 70 MPH is at 3100 RPM, so I was tuning the 3000 map. Once I did a map trace i saw that 70 mph is 3200 map. I forgot to do a map trace before when I started the trip doh!

Another thing is, I found that that adjusting the K value is what really helped me lean out the engine. It drove fine through Kentucky, but as soon as I hit West Virginia, I started having issues. As in my car would instantly go into boost, while A/F's were still at 16-17. Thus when it would hit boost it would lean out to 17's and then go to 11-12's. This delay caused a noticeable jerk.

I quickly went back to the old tune not to kill the engine .





Well I've had a few of Calum's tunes. And the DET tune with DE MAF had a better timing map that the DET tune with E60 MAF. 5WHP difference actually hehe. So I updated the E60 tune to have DE maf tune and it was all better.

I am afraid of having timing that high, maybe it will be save though on a DET? What will happen is, with timing that high you will burn the fuel more efficiently thus your A/F ratio will raise, kinda like leaning the engine out.

I basically stopped tuning because I decided on a laggier T28, from there I will do the tuning all over again

with a DET i think your going to need to monitor knock since it is more prone than a VE. add the fact that your probably running hotter temps in the cylinders than me and this becomes more important as well. i think your going to get better fuel economy with the timing bumped in the cruise area than you will by leaning the car out more than 16.1 Afr. a good compromise here will probably yield best results. can you give us a look at the timing map your using? on a side note with my nissan ecu tps voltage at .52 was between 5-10% throttle on my techtom and 4.2v (pedal to the floor) was mid 90's for me.

I sent this to GT2871RBLUBIRD in a PM a bit ago and I never thought to put it up here but it certainly belongs here.

I think a good mix of timing and leanness would yield the best results. Too high of timing and lean mixture is trouble. Too high of timing and stoich mixture is also trouble.

I'm thinking of first trying to leave the timing as is, maybe equal it out in some areas, and update the mixture. I just don't see too much timing room from the current map, it's pretty high as is already.



I guess that's pretty close to this graph:

i forget if it was vadium who post about air fuel ratios or someone else, but it was saying that there was a threshold before and after stoitch, where it was a common misconception that more leaner means hotter exhaust temps, now depending on the timing this could or could not be true, but it was saying that stoitch is where you are going to see your hottest exhaust temps, but after stoitch 16+ the air fuels are cooler, and obviously with more fuel before stoitch, the exhaust temps were cooler.

Jeff, your thinking this thread: http://www.sr20-forum.com/turbo/21381-egt-lowest-temps.html

that graph that ben sent me is what i used to tune my fuel in those certain areas for best mpg....it sounds like you are in consistant loop no? becuase you say you made fuel adjustments but never get out of a certain area of air fuel even with changes made?

as far as the timing and fuel goes i would just target the areas on the fuel map you want to make changes relitive to the changes needed in the iginiton map to make the leaner fuel changes safer, and you should be good.

what iginiton timing are you seeing for 3100rpm / what kpa on the load breakpoint are you also seeing?

Well another reason I actually will lean out is because of lower exhaust temperatures, thus that should help a little with underhood temperatures

I'm in closed loop yes, and I think adjusting the K value allowed me to get outside of the 14.7-15.1 loop.

I'm updating the K value because it should make the whole map have a seamless transaction, plus my WOT is too rich right now anyway hehe.

Here is my timing, and at 70mph I'm on the 3200 rpm map.