I understand the math. I just realized that I was assuming I always had 16 gallons after getting gas. Typically, every fill up puts around 12 gallons in. So, in that case I'm averaging around 16 mpg mixed driving. After leaning out the map more, I should be doing better.

 

You know, the pumps will tell you how much fuel goes in

 

Lol. I know
But it's always a guessing game because my gas light has never come on and I'm terrified to run it dry.

 

Your not getting it


If you always fill the tank to the top...

The amount of gas you put in on your next fill is equal to the amount of gas you just used since you last filled up. Doesn't matter how much or little gas you used (though it is more accurate the more gas you used).

-------

I am LOLing so hard because

I had a crazy joking comment typed up before your last reply that would have illuminated this fact for you while entertaining, but I refrained from posting it because I didn't want to beat a dead horse.

Well, I'm not going to miss an opportunity to be an *** next time. Gotta go with the gut!

 

No worries. I realized how stupid I was after I had posted that. Lol

 

I use it exactly for the cruise part of the map (somewhere between 3k -4k rpms anywhere from 16-10 Hg), where the AFRs go to 15afr (or so, going from memory). Closed loop settings only kick in after the engine has been steady at those rpms/load for a specific amount of time (settings configured by the tuner)

Like peejay suggested, this was a trial and error process, on the street. So basically, my fuel map is not too lean on those areas, but the closed loop makes the mixture leaner when cruising.

On a GOOD day, I average 250 miles per tank, and on a "tunning" phase, somewhere around 150-175 mile per tank. All numbers represent city driving, very little highway. AFRs are not perfect, car stumbles a little at some point, when the throttle is in a steady state, and then opened a little, the thing is that it does not happens during the entire range of rpm/load; the engine also dies (sometimes) when rpms are coming back down on their down from a mid/high rpm gear shift.

What I am trying to say is that I am not a tuner, just play with the tune LOL! (and got more playing to do). Not a tuner, but when I got the car back from the shop, I was averaging 175mile to the tank, and 200 miles to the tank on a GOOD week. Playing with the AFRs and closed loop, allowed me to gain a substantial amount of miles per tank. Unfortunately, 50 miles to the tank IS not that great when looking at the big picture, its still a sub 17 mpg vehicle LOL

 

Yeah. I feel like I've leaned out the map a ton. Afrs are still in decent ranges but I'm wary of pulling more fuel out. Although, running 1000cc injectors is probably the reason I need to pull so much out to begin with

 

I can't run closed loop under cruise because the engine still braps a bit under some cruise conditions, and if you try to run closed loop in that area you will get runaway enrichment.

I probably SHOULD be running closed loop at WOT. I have a wideband and it would be a great way to deal with stuff like overheating fuel pumps dropping pressure.

 

I read somewhere that you should be looking to decrease injector duty cycle, rather than shooting for a AFR. Don't be afraid to experiment with it a idle/cruise/low loads

That's what I've been doing for the longest. I am guessing that doing it in a dyno is way faster than doing everything by yourself..

Ahh, the beauty of bridge ports?

Not following you on running closed loop at WOT, and its benefits. Want to dump some knowledge/theory on me?

 

My fuel pump gets very hot, sometimes can't keep up with the engine. It does something like 400l/h.. when cool and happy. Between the exhaust heat and radiator heat that the fans are blowing under the car, the pump gets hot, like too hot to touch hot, and it sometimes loses enough capacity that I can feel the engine running out of fuel when pressed. Again, just when things are really, really hot...


Going up the hill, the engine had NO power... was just not accelerating. The fun part was shortly after this video was taken the car died in grid and wouldn't restart until everything cooled off again. Gawd, listen to the main fuel pump howling/whining! And this is with my "improved" system with a rattlebox Facet style lift pump feeding a 700cc surge tank that the main pump draws from, no more fuel starvation for me. Rattlebox is nicely loaded, which is proof that it's not a vapor lock issue between the tank and lift pump, the main pump is just suffering horribly...

So I have two options. One, put in a fuel pressure sender, and do fuel pressure compensation. But that requires adding more parts and stuff. Two, turn on closed loop control, but only at WOT...

Running closed loop under load isn't unheard of. I've seen some standalones (*cough* FAST *cough*) that run closed loop as soon as the O2 heats up and then basically they rely on the O2 sensor to do all of the fueling with the fuel map as more of a guideline than an actual tune, kind of like the kiddycar rides at the amusement park where you can drive around but there's a rail that the car has to follow...

 

To do a quick highway calculation simply fill up, go drive 40 miles and refill at the same pump. My NA 20B gets 16 mpg on the highway. It should be better than this. I've been updating some things on my setup so I'll be retesting the improvements real soon.

 

its been done, there was a guy running DSM drag cars in closed loop in like 2003, and thats without a closed loop map or anything.

we've done it on the race miata, but the wideband is too flakey for some reason.

 

i was able to get 19 with mine, once, 16-17 is more realistic if there is a mix of driving.

 

i picked up that info a few years ago squeezing mileage out of my rx8.. and i regurgitated it all over the place... your welcome if you heard it from me.

 

I know I've been touting it for a while... that is where I started ADDING fuel instead of going with the "obvious" method of running as lean as possible before random misfires start.

Ignore the wideband, look at the duty cycle! And be realistic with what you're seeing. You can pull fuel away and start slowing down because psychologically you want the duty cycle to stay low... but if you need to open the throttle more and this causes you to use MORE fuel despite the leaner mix, that is a net loss of economy.

 

Well, it's getting better. I'm averaging 16-17 mpg with mixed city/highway/and spirited. If I go all highway, I could probably get 19.

 

13B Half Bridge, ITBs
In my old beat down former track day test mule. MS3Pro. I was out doing some drivability tuning, tweaking, logging.

Car sat for 15 years next to the garage, and I built a Eprod motor, that I decided to bridgeport before putting her together. Lots of go fast stuff internally. Rear gear, and various stuff thats pretty basic for a track day mule.
Using this car to work bugs out of my ITB system I designed, and fine tune things for the other 7s that will get similar powerplant setups.

Idle was a tad high, she is happiest at 1400-1500. Thats around 1700 IIRC.
Oh and the air Filter.. which was a K&N for some large diesel.. is a massive restriction. Its a 4 Inch throat and about 8 or 9 inches long. Its too small. Gonna have to do a different airbox and inlet design it appears.

 

I am still having a hard time wrapping my head around the closed loop at wot idea LOL


LOL, pretty sure I read it from one of Crispeed's post

 

Why?

I'll give the FAST system credit: the circuitry and O2 they use is extremely rapid. It allows ridiculously quick fuel corrections, it's laser-guided focused on maintaining whatever AFR you tell it to target, it even corrects for inadequate acceleration enrichment.

Which brings me to one of the things I don't LIKE about FAST....

 

why? BMW ran a narrowband into an amplifier and just used that, from the factory!

 

I don't mean in a bad way, but its probably because I am naïve about it. I does sounds AWESOME to be honest.

 

the BMW way? if you suggested running a narrowband into an amplifier to get a 0-5v signal, and then running the engine from that, people would jump all over you telling you its a bad idea.
its just funny then that the germans did it from the factory...

with a wideband, though things change and you can have a target AFR map, and the ecu will have some authority to make adjustments, you just need to make sure that its not making adjustments that are dangerous

 

my junk is way different now. I get an average of 16 to 18mpg, slight corrections enabled, adaptronic 440. Cruise afr is still on the rich side. 4.77 FD kills my mileage around town and highway lol

 

I got 33mpg with 4.78s once and could expect 27-29mpg... it's not the gearing it's the tune

(Man, that was a hilarious thread when I told people what kind of fuel economy I was getting)

Relevant to the thread, I'm seriously thinking of converting my car to run a MAF. Should make tuning and drivability a lot better.

 

Must have that sucker leaned out. Still 13-14 aft cruise, 12-13 wot. Its not overly rich. I tend to drive like a asswipe too lol.

Ps: I have tiny tires, 24-25" tall as well.