lim_fc3c

iTrader: (4)

I managed 380miles plus or minus 10 actual miles until my fuel light kicked on. I average 22-23mpg.
91 vert 158,xxx miles
Coilovers
225/50/15 on stock vert wheels (speed seems to be correct or fairly close within 1-2mph)
25mm spacer/adaptors rear
corksport odura front lip
corksport header + 3" single
Mazdatrix lightweight steel flywheel
Full weight
No o2 sensor
Innovate wideband
Apexi AFC Neo
Tuned 12.9:1-13.2:1 WOT, 15.2:1-15.5:1 Cruise.

bumpstart

i was thinking before about the resister in the lambda and realised i had the scale upside down and we need a simple enough circuit instead to raise the voltage

-
i see the differences some people are getting just with the trim on the AFM signals
and all while the OP battles with games to trip the closed loop mode and keep it there

so i propose another WI lean cruise setup
to instead ignore the o2 mode and just use bypass or other adjust on the AFM
( technically you could use an air bypass around the AFM to lean out the load signal during cruising condition )
- used in conjunction with the water injection to control the chamber and exhaust temp

all switched from a combo of gear switch and vacuum switch for 5th gear /cruise vacuum conditions


this way the switches readily close the bypass drops the ecu back to stock mode in idle and WOT operation

the trick will be to keep the ECU out of closed loop while you have the trims on

Derekcat

iTrader: (8)

From reading this thread I was starting to wonder about that. So it's true that while in closed loop the ECU ignores the AFM signal? Is all of my fuel economy improvement from the SAFC just from open loop driving?

j9fd3s

iTrader: (3)

2 ways to do that. #1, would be to have the circuit open the switch on the bottom of the radiator. the other way would be to have the circuit just disconnect the o2. the S4 ecu doesn't mind if the o2 is unplugged.

the S5 will throw a code after a while, but i think it goes away when the sensor is hooked up again.

i think what happens is that the ECU does its normal RPM+LOAD+corrections= injector duty, and the O2 is just a correction on that. the O2 only corrects a certain amount, if you turn the SAFC too much, it'll try to correct to 14.7, but it won't make it. or more commonly, you can free up the intake and exhaust enough, that the engine doesn't really go around 14.7, its more like OFF/ON, which gives good mileage!

Tofuball

Yeah, it's better then nothing.

I don't like it because the SAFC costs the same as a full EMS and can never, ever match the functionality. Unlike SAFC, the full EMS approach has true timing and split control, and most of them have sequential, timed injection. You can also ditch the AFM restriction, but this is a relatively small change. You can change the parameters around fuel cut-deceleration.

The stock ECU will always have limits on closed loop, and will never exceed 14.7:1 unless you muck with the O2 signal (and that opens up a whole new can of worms).

Also, a full EMS with a WBO2 can be in closed loop 100% of the time, for any AFR you wish. (Though, I would not leave it in closed loop in some parts of the map, such as high boost except for rich side correction to help protect against a lean condition)

Derekcat

iTrader: (8)

Ahh that makes sense. The retail price on an SAFC is pretty absurd.. I only paid $100 used for mine, so it was considerably cheaper than even an Rtek 2.0 or a Megasquirt.

But yes.. That is a very compelling argument for full EMS.. >_> Someday when I have money..

sharingan 19

iTrader: (16)

What size is the S4 N/A tank? I ask because the best millage I've gotten on my S4 turbo was 355 miles on a tank driving 1-10 to Louisiana. Now I struggle to get 280 (after installing cleaned stock injectors, 720's , rtek 2.0 and parallel flow fuel system w/ Aeromotive FPR)

Part of the reason for the good mileage before was that my injectors were flowing less than 550cc - after cleaning they flow 570cc (primaries). Also the base pressure has been increased to 43 psi and the secondary transition has been lowered as well. I am interested to see if how much I can improve MPG w/ Rtek tuning alone. Theoretically I should be able to do even better since higher fuel pressure should atomize fuel better and I can adjust timing in low load areas of the map.......we shall see.

j9fd3s

iTrader: (3)

S4 = 16.6 gallons
S5 = 18.4 gallons

sharingan 19

iTrader: (16)

As I thought, just making sure that the S4 n/a and S4 TII didn't have different sized tanks.....300 really isn't very impressive as a max number then, especially n/a

PvillKnight7

iTrader: (16)

I once got 180 with my S4 TII. I'd murder for 300 consistently.

SpeedOfLife

iTrader: (16)

I typically hit 225-250 miles in my 87 TII. I HAVE hit 300+ once or twice, but conditions were favorable on a very long drive, that's all it was really.

Derekcat

iTrader: (8)

Well that's including all around town driving, and only getting into the fuel light for half an hour max [13~14gal fill up]

I've hit 300 before the SAFC, but only on long freeway trips.. Before the SAFC, on the all stock S4 engine I usually got around 200~220

AmT_T

iTrader: (11)

I don't know if this was mentioned but you DO NOT save gas putting your car in neutral and coasting, it's actually the opposite. - When your car goes into neutral your rpm drops to idle, where fuel is injected to maintain idle.

Leaving the car in gear and coasting, there is no fuel injected as your car cannot stall as long as you are moving. Get a wideband or ride along with someone that has a w/b if u don't believe me. hope this helps

PvillKnight7

iTrader: (16)

Any info to back this up?

i.e.
Less fuel is used with an A/F ratio of 13.5:1 at 800rpms than one of 15:1 at 3500rpms?

Did you neglect the mass of fuel and air being used?
Does the stock ECU cut fuel on decel?

gxl90rx7

iTrader: (1)

yes the stock ecu has decel fuel cut. it cuts all fuel if you are above ~1500 rpm and TPS is zero (throttle closed).

whether it is better to coast in gear or throw it in neutral depends on how long you plan on coasting.. you definitely cannot coast as long with it in gear

Tofuball

Your ECU simply lacks the resolution to control your injectors at that pressure (in the high vacuum parts of your map).
That is one of the reasons the stock ECU drops fuel pressure at idle or other high vac situations.

Tofuball

He can't back it up because it's not always true. It is true maybe half the time.
Coasting down a hill or straight out of gear can USUALLY net better total MPG

Yes the stock ECU cuts fuel on decel within certain conditions.

If you're slowing down to a light or something, the engine braking will net you better total MPG because you're using zero fuel instead of a little fuel, but you're dropping speed (and if you're coming up to a stop, or you need to slow down anyway, that's OK).

sharingan 19

iTrader: (16)

Incorrect. I lack(ed) the resolution to actually tune those areas of my map (rtek 2.0) lol. That was until I filled up today...271 miles (more than 2/3 highway @ 80mph) .....18.15mpg

So I whipped out the palm and started adjusting the map at the pump. For now I focused on the "cruise" area which I defined as 1500-4000 rpm and 0psi - 24inhg. I guesstimated how much to remove considering:
-43psi base fuel pressure (+5-6 over stock)
-570 cc primaries (+20cc over stock) and
-The fact that the stock maps are conservative to begin with

@ 0 psi -1%
@ 4 inhg -2.5%
@ 8 inhg -3.5%
@ 12 inhg - 5%
@ 14 inhg -7%
@ 20-24 inhg -7.5%

On the way home I noticed AFR's mostly between 14.4x and 15.xx A big improvement from the 12.5x-14.xx range it previously occupied. Idle remained between 13.xx and 14.xx (which is to be expected since it can't be adjusted). Not bad for round one, can't wait to get some new mpg #s.



Edit: I have an fd fuel pump which has been rewired, however it was rewired in such a way that it retains the stock functionality that drops pressure @ idle and high vac situations.

PvillKnight7

iTrader: (16)

That cruise area is pretty tricky to tune. What the engine likes in the parking lot isn't what it likes on the road but the dam things use the same bits of rpm and pressure to determine the fuel. Scumbag engines....

sharingan 19

iTrader: (16)

Lol, so far, so good....

Is your experience based on rtek tuning or full stand alone? I can only imagine there is some sort of Hiroshima shenanigans going on with the stock ecu and thus the rtek as well. W/ a stand alone one must contend w/ those things manually.

Tofuball

The stock ECU, and by extension the RTEK, barely have the resolution to control the stock injectors, at the stock pressures, without unacceptable fluctuations in AFR, especially at leaner running conditions.

Just being able to make them run leaner is not an indicator of how finely the injectors are being controlled.

Also with most larger injectors you will run into the injectors themselves lacking the lean operating control you require. Injectors have a minimum puslewidth.

RotaryEvolution

iTrader: (30)

i generally get about 350 miles to a tank on my TII with all highway driving running the tank down to about a 15 gallon fillup which is about bone dry, as the tank needs about 1.5 gallons before the pump cannot pull any more fuel out.

that is also with an AFR of about 14.0-14.3 with some WOT to pull hills and pass a few cars here and there, dipping down into the 11's intermittently.

turbos are more fuel efficient than the n/a when adding in the turbines scavenging effects for power and fuel burn while inside the motor. timing is also usually around 45-50 degrees of advance for cruising situations with the extremely low compression rotors.

Tofuball

Plz xpln.

Wms10th

iTrader: (2)

Thanks for the heads up...I'm about to get an Rtek chip 2.0 with 720 secondaries to replace my current setup "Old 1988 HKS P-Fcon" setup also with HKS AIC. I'm barely getting 200 miles on a tank, 26 miles per day commute. AFR under boost is 10.0 - 10.9. I hope to move it to 10.5 - 11.5 after the change, but can't imagine mileage getting much better. Now I know what to expect.

PvillKnight7

iTrader: (16)

Haltech E6k. When I adjust fuel during highway cruising for lean but still smooth operation the engine lean surges in parking lots because the same rpm and pressure are required but the load is different. I think that's what happens...so I compromise and run a little richer during highway cruising conditions.

Is there a way to compensate for this?