EFIDynoTuning Forum

So now that I have my fuel dialed in, I am running into an issue similar to what I had before.

When cold in closed loop, the problem is most prevalent.

When I shift, as the rpms come down, the car gets extremely rich. I see .75 lambda as the rpms come down, then when i accelerate after the shift, it drifts lean to about 1.08 to 1.10 over the coures of a few seconds, I get some misifring (sometimes) because its too lean then it clears up. The warmer it gets, the less it happens and once the car is up to operating temp, the lean drifting doesnt happen. It still goes very rich as it decelerates between shifts but it only goes lean for a split second. When its warm, its not even noticeable. I believe the computer is trying to pull fuel due to it being super rich when i shift, then when i accelerate, the computer is pulling so much fuel, it takes it a few seconds to get back to close to calling for Lambda. I didnt get a datalog of it today but I can get one tomorrow when its cold again.

My maf curve is between .97 and 1.01 in all cruising cells. Its still a little fat up top in boost but its not bad. ITs still about 5% rich up top and ill be dialing that in as I drive it over the next few weeks.

I know for sure my breakpoint is low. When I calculated the new breakpoint for the 58psi fuel pressure, its considerably lower than what ford lists @60psi. I am going to change my fuel pressure to 60 and plug in the ford info so its 100% accurate. I dont know if that would cause this issue.

I tried playing with the manifold volume and it doesnt seem to affect how rich it gets. I set it at 2 today, and I set it at 10 today while it was cold. It didnt seem to change it at all. Thoughts? I can post a datalog and my tune if you would like to look at it.

if the breakpoint is low then youll be using more of the high slope on decel which typically means youll be rich deceling

why are you running 58psi with the 80s? Might as well run 40psi.

manifold volume is most noticeable on tip in

if your injector data is incorrect though then your fueling is never going to be consistent. Also if your injector data is incorrect then your maf is incorrect.

I have a dead head fuel system. I am running elevated pressure to help eliminate fuel boiling on hot restarts. I was having that issue when running 40psi, you recommended upping the pressure which seems to have worked.

I was thinking my breakpoint may have something to do with it. Im going to up the pressure and throw in the ford injector data for 60psi so I know its 100% accurate.

How accurate is fords documentation regarding injectors at 60psi? I would assume its extremely accurate. I assume if my maf curve is off, I can trust the calibration data and move my maf curve. Also, how does breakpoint data translate to the maf curve. The breakpoint is listed as lb/mass. I dont understand how I use that to determine where in the maf curve the breakpoint is located. I just read the info about dialing in unknown injectors but I dont understand how you use the breakpoint to determine where on the maf curve that breakpoint occurs.

i see yeah higher pressure is best then

do u have a manifold vac reference line on the regulator?

yes the injector data is probably going to be as accurate as possible

yep dial in the maf

it doesnt, breakpoint is where blending occurs. With a known maf curve youll have 0 fuel error down low and 0 fuel error up top with a linear fuel correction in the lower middle section. If the low slope is higher than the high which is typical then you increase the breakpoint to lean out that mid point if its rich.

how long do you leave her in OL when cold? it seemed for me that it was transient fueling that I messed with that caused my issue with this.

@Decipha,

Yes, I do have a vacuum reference connected to the regulator.

@Paul,

Im using what ever the latest T4M2 default settings are. It goes into OL fairly quickly though. The rich issue happens regardless if its hot or cold. Its just more prevalent when its cold. Its normally around .88 or so when hot and around .75 when cold. Just for fun, I am going to try and see if I can move the breakpoint to where I believe it should be to see if the problem gets better. I also looked more closely at the injector data and made some adjustments to my fuel injector data in general. I originally used the 1% per psi rule but looking at the datasheet, that isnt going to be close enough for any of the paramaters except maybe the HS.

I would suggest trying to delay CL when cold, I have mine set to 3 mins for cold and warm and 15 seconds for hot. My car does not control fueling very good cold and I think its due to the turbo piping and the hego being far enough away it takes a while to get heated up properly.

My guess is youll mess around with breakpoint, maf transfer, etc. and none of it will have an effect. I know I did that forever and fueling being a few percent out here and there isnt going to cause this big of an issue. Good luck I know how frustrating it can be

PaulC-turbo5.0 wrote: ↑2022 Apr 11, 12:36 I would suggest trying to delay CL when cold, I have mine set to 3 mins for cold and warm and 15 seconds for hot. My car does not control fueling very good cold and I think its due to the turbo piping and the hego being far enough away it takes a while to get heated up properly.

My guess is youll mess around with breakpoint, maf transfer, etc. and none of it will have an effect. I know I did that forever and fueling being a few percent out here and there isnt going to cause this big of an issue. Good luck I know how frustrating it can be

Yep, i highly doubt any of this it's going to matter. At this point if i don't get it right this year I'm ripping it out and replacing it with a holley most likely. I have 2 friends who have termi x systems, don't know anything about tuning and some how have no problems... After 3-4 years I'm still fighting essentially the same problem I've had since the first time i tuned it. Even when i ran 40psi with the deka info direct from the chart the problem still is there. I mean you and i have been talking about this for 3 years... it's still going on. Im tired of constantly having a laptop in the car...

@Decipha, how realistic it is to believe that my injector settings being off by the percentages listed below in each category would cause the car to hit .75 lambda then drift to 1.14 lambda when cold? The new settings listed below should be considerably more accurate than what I had originally in there. I used the 55 and 60psi data and interpolated for 58psi.

Low Slope 119.72 -> 124.159 ~5%
High Slope 88.684 -> 89.765 ~1%
BP 0.00002854 -> 0.00002987 ~4.5%