Vf tuning question (Maft Pro)

[Dan88t]

Hi, So yesterday I finally got around to installing my Maft Pro. I have it set up in speed density mode and the boost controller set up and working.


I have it tapped in to monitor Vf on Ax1 and this is where I'm confused.
At idle Vf pretty much stays at 4.43 volts.
Once it's warmed up and I'm cruising it bounces a bit but it stays around 3 volts
When I'm boosting and accelerating it's at 0.00 volts.


My AFRs at idle are 13.8 - 14.4 (it was a steady 14.7 at idle before maft pro)
When normal driving the AFRs bounce around a lot more than before the Maft Pro install (I was previously on a Lex AFM) anywhere from 12 - 16
When boosting the AFRs fluctuate between 9.8 and 12.8


So my questions involve tuning with Vf - from what I've found on the forums it's more likely that I'd be seeing 0.00 at idle instead of 4.43 right?
Even with Vf steady at 4.43 while idling the AFR fluctuates and never goes leaner than 14.4
Does this sound like something could be faulty? Like maybe my wideband o2?


I have the Maft Pro set up with the settings from the MKIII quick setup guide for version 5 that I found on fullthrottle's site
(link: http://www.fullthrottletech.com/attachment.php?attachmentid=1067&d=1236469843 )


My mods are the usual:
3" turbo back exhaust
intercooler and 2.5" hard pipes
550cc injectors (tho the P.O. of the injectors said "had tested, actually flow much more than 550!" so who knows - I'm going to have them tested this winter when I do a refresh on the motor)
LC-1 Wideband
Aeromotive AFPR (FP set at 33PSI w/out vacuum attached)


Any help or direction from someone who's done this before would be great


Thanks!

 

[JimR]

What is the current setup of your original stock 02 sensor? Do you have any codes?

Is your fuel pressure setting intentionally low? 33psi is at the bottom of the scale for stock pressure.... just something to check if you haven't already been down this road. http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=73

Your VF would normally be zero when the engine is completely cold, which indicates the open-loop condition the ecu maintains while the engine comes up to temperature. You can safely ignore VF during those first few minutes.

 

[Dan88t]

My stock O2 sensor is in the stock location and still hooked up as usual. I actually even replaced it last weekend because the wiring was such a mess and I had a spare anyway. It didn't change any of the weird Vf issues I was seeing tho.
Fuel Pressure is set 36PSI w/out vacuum
Vf is 0.00 for the first few minutes when cold but then it goes to 4.43 while idling...
AF's on the wideband continue to fluctuate all over - getting Vf straightened out may be more trouble than it's worth. This weekend I plan to do a boost leak test and a vacuum leak test then I'm also going to wire the Maft Pro up for the Enhanced TPS functionality so I can just tune WOT over 2600RPM or so and not worry so much about Vf...

 

[JimR]

Are you getting the flop-flop-flop on the diag port from the stock 02? (As per these instructions: http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=119 )

4.43 volts means your stock ecu thinks the engine is running lean, and it's adding a lot of fuel (~10% to 20%) to even things up. If you are getting the flop-flop, and your wideband is also reading around 14.7, that is a good sign.

You may just need to bump up your VE numbers (user tunes, or edit the VE table directly as per your preference) in the idle load range to get vf to normalize.

It is generally a good idea to get the vf to at least 1 volt or 3 volts, so that the ECU has some room to make adjustments. At 4 volts, it may be near it's max adjustment of 20% from the stock table it has in memory.

Good plan to let the ecu do it's own thing for low-mid load, and do the etps2 thing for wot.

 

[JimR]

Something doesn't quite add up though..... you're getting slightly richer afr's than normal at idle, yet the ecu is trying to add fuel.... hmmmm.

Somewhat unrelated.... but have you pulled 20% from your mainscale to account for the 550's? Assuming you're using VE Table 2.

Boost leaks are generally irrelevant in terms of their effect on your AFR once you're running speed density.

 

[Dan88t]

Hi, I got around to running that O2 test yesterday (I'd done it a few weeks back but I'm at a loss for what else to try) and it oscillated as expected.

You're confirming everything I thought, the TCCS is supposedly adding max-fuel while the wideband says I'm running a little bit rich. But only at idle, as soon as I'm off idle my Vf is between 1.x and 3.x and AFRs are good, just really weird. -

sidenote: I set up the enhanced TPS stuff over the weekend and have it going WOT at 2600RPM or 97 kPa so now when I hit boost the AFRs hang around 11.5, tho I did notice a couple times getting up to 15 last night but the temperature was down around 35 here so I don't know if I have to adjust for the cooler temps or what..

Right now I have it set to pull 17.5% from mainscale, I was being a wus and didn't want to pull 20-25% right off the bat and now I'm thinking I should go back and change that to 20+%

Even tho everything seems to be working I'd like to figure out this Vf issue... I do have an extra ECU but I'm sure swapping that out would be a waste of time...

 

[Dan88t]

A question on the VE table, if I edit the table while connected to the MaftPro and with Emulation enabled and all that, shouldn't I see changes on the Wideband right when I make the change and save it?

I was making changes around the idle and kept lowering and lowering it since it was running rich at idle, the car's idle would change sound for a second everytime I saved new settings but the Vf and AFRs didn't change. However, after I shut the car off and turned it back on a while later it wouldn't even run more than 5 seconds because it was getting AFRs of 19-21 at idle(oops!)

I thought when in emulation mode that the changes were instant?
When does the Maft Pro save settings? It seems to me that it's after it's "rebooted" ?

Thanks!

 

[JimR]

Aaahhhh, there is another good possibility. Get rid of all accessory electrical loads while you're checking the idle AFR's, including mini cigarette-lighter power supplies, AC, etc. Let the car "settle in" as well, giving it time to adjust. Then start adjusting values using the maftpro keypad only. I've had idle AFRs go haywire on me when I had my laptop powered from the car.

When you're in emulation mode and you save changes, it appears that the airflow output signal from the Maftpro gets interrupted for a second. That is probably the cause of the momentary sound changes.

In addition, make sure that your PTT is completely off. Watch the "AF tracking enable" value under ALDL Flags. To ensure it's off, set your PTT idle TPS to 0.02, and your PTT cruise TPS to 0.02 .

 

[joshamerican]

ok dumb question here (which may be why i'm haveing problems). right now i have an aem lc1 wideband with maft pro. I took out the stock o2 sensor. from what im reading in this thread i should have both stock o2 sensor and the wideband sensor hooked up. I feel stupid now, lol.

 

[Dan88t]

Yep, I have both the w.b. and stock narrowband O2 sensors running, the stock one still feeds the ECU in closed loop.
You can use a simulated narrowband output from the wideband and feed that to your ECU if you want

 

[joshamerican]

I ended up using the simulated narrowband output from my lc1. That way I don't need the stock o2 sensor, which would just make my exhaust a little bit more restricted.

 

[JimR]

If you guys are going that route (simulating), then make sure you're either using a pre '89 stock ECU, or make sure you deal with the Heater Circuit check. The later ECU's check for the presence of that heater circuit, and if they don't find it they may throw code #21, and drop into limp mode.