HOLY god 180 is good, 200+ is a miracle. My record to date is 235 and thats staying out of boost.

 

damn...I'm lucky if I get 200...but most of that isnt highway miles. All I have is the ver 2 helix 3in downpipe.

 

i avg about 240 mile per tank. 91 oct.. current mods: s-afc II, hks RS suction kit, o2 housing, 3" downpipe, 3" hi-flow, full 3" cat-back and Blitz SBC ID set at 20psi.

Last dyno I was putting down 285whp at ATP in Fremont, CA

Just got the 264/272 cams in yesterday, need to re-tune the AFC settings again. we will see what happens..

 

I consistently get 300 miles per tank but I don't hammer it too bad either, thats mostly highway driving though at around 70mph.

 

i just installed my safc. i think im getting 250ish...I WISH! i had to reset the ecu twice and forgot to right down the numbers. Next tank 94 octane.
And how do you get 295miles SAL? How many mpg is that? My average 200-210

 

there could be dramatic differences in how you all are doing your filling/tracking/math.

nevermind the differences in fuel brand, geography(hills), climate, altitude, tire pressure, traffic, engine/driveline tolerances, oil condition, and probably others I'm missing.

all these things add up to be causes of inconsistency with fuel mileage.

 

I can pull 320 miles a tank if its freeway driving I think the best I have done was 340 miles on 1 tank I was doing about 75mph the whole way

 

i came up with a thought today. not that i know anything about the safc, but shouldn't you be adding correction instead of taking away from it? since it's operating in closed loop mode, if you add correction, the computer will think it's running rich and lower the LTFT making the computer think it's getting back closer to stoich. lowering LTFT also lowers injector pulse width. wouldn't this let you use less fuel during closed loop mode?

 

I get 160 miles average and I keep it under 5k rpm. My car is still new with only 500 miles, 90% is city driving which is mostly traffic. Do new cars run richer?

 

You won't get good mileage in city driving, but mileage will improve as the car breaks in. The key to mileage is staying out of boost, but where's the fun in that .

As for the corrections, "you take away correction", which is a negative number, which makes the car see less air, so it adds less fuel. A positive number, would make the car see more air, and add fuel. The correction is based on the airflow "seen", since we splice into the airflow wire, not based on amount of fuel added or taken away.

Thanks,

FB

 

Lower IC Pipe and MBC and your're at 300 awhp...

 

but in closed loop mode, if you take away correction even though the same amount of air is passing through the engine, the o2 sensor would see a lean mixture causing the LTFT to increase and increase the overall injector pulse width? this would cause richer mixtures at high rpm and WOT. though closed loop operation and open loop have different ways of setting the AF ratio, LTFT affects both. LTFT does affect the overall range of your injector pulse width, does it not? a much more satisfactory answer would be one that involves fuel trim and open/closed loop operation. we all know that the afc "adds" or "subtracts" fuel in open loop operation, but with fuel trim, i think it's a bit more technical than that.

 

Hmmm,

Well maybe someone else can chime in, but even if you lean out the mixture with the SAFCII, it still quite rich, like going from <10:1 to 11:1 or whatever, depending on how lean you set it on the SAFCII. I "think" the stock 02 sensor is not very sensitive, it reads either near stoich or rich, so anything richer than stoich isn't going to make the 02 sensor see a lean mixture. This is why non-wideband 02 sensor a/f gauges aren't really that useful, kind of like an oil warning light on the dash, if it comes on, it's probably too late, heh.

So, I don't think it would affect LTFT that much if at all? From an empirical perspective, I don't think people are finding their cars losing power over time and getting richer when they use the SAFC.

Thoughts?

FB

 

here's what i've personally seen. taking the original example of this post, -1% will not do anything at all. it will take at least -4%-5% to increase LTFT by ~+1.6%(my own experience). once the LTFT is affected, the overall range of injector pulse width is affected. WOT/open loop will have the same fuel curve shape in the map, just that it's richened out proportionally across the map due to the higher LTFT. this in turn causes richer mixtures at open loop, inadvertantly richening out the excessively rich stock maps possibly making a bit less power without having to adjust HI maps.

this would be an example of it. if his computer is reading a rich condition in his car, his LTFT is set negative and injector pulse width is shortened in giving him better gas mileage. overall tho, he's running rich. thoughts?

 

I currently have a wideband installed in my car and can confirm that any time I am in closed-loop operation, the A/F ratio stays right around stoichiometric. Leaning out the Lo-Th settings should not have any effect on the low throttle A/F ratios, as the ECU will use the narrowband O2 sensor to return the car to stoich. Once the ECU learns around the Lo-Th settings, if you return them to 0, the car will temporarily run rich, until it learns the necessary injector pulse to get to stoich. I am uncertain of the effect this will have on the open-loop settings, if any.

As far as exhaust_note's mileage per tank, it seems as though his shifting habits are getting him to 295 miles. Shifting as early as he does will help to keep him off boost, and once he is in closed-loop mode, the car tunes itself to stoich. Anyone can get 295 miles per tank while stock if they stay off boost. I personally get around 240 miles per tank, but accelerate somewhat aggressively. When taking it easy, I frequently approach the 300 mile per tank mark.