A/F ratio tuning

[CajunKenny]

Just for reference, here's my general tune:

Idle: 15:7 to 16:7
City Driving: All over the place...
Cruise: 15:7 to 16:2 (this typically gets me 28.6 mpg)
WOT: 12:0 to 12:3 till 4000 RPM, then 11:5 to Redline

Setup: Maft Pro in Speed Density

 

[Another MkIII]

In the link on the first page Supracentral mentioned tuning to Vf. What exactly does this mean? Is that saying to basically let the ECU handle the tune in closed loop and only tune above 4000 RPM with a piggyback? For example, I just purchased an SAFC II which has 12 RPM points that can be set. So theoretically I could set them evenly from 4000 to 6800 and only worry about tuning there since in closed loop the engine ECU will just keep adjusting itself back to 14.7. Am I correct, or am I misunderstanding how this works?
-AM3

 

[CajunKenny]

Nope. You got it.

Let the ECU handle closed loop operation and only tune for WOT. The stock ECU can add and subtract as much as 25% of fuel. That's a force to be reckoned with!

 

[Another MkIII]

Awesome, thanks for the help!
-AM3

 

[91Supra313]

Not to hijack a thread but I am having some serious challenges in tuning mine. Running an HKS Fcon, and VPC.
Idle runs safe at 11 only. Anything else is on verge of stalling.
City is all over the place
Cruising is around 14-15 jumping around a bit
WOT is 10.

I have tried to make adjustments, but nothing seems to be working. All my mods are in the Sig below.
Also when the car is cold I have to turn the VPC idle clockwise to the 2 o'clock position. When it is warm I have to run it around the 10 o'clock position. Otherwise it bumps and wants to stall out.
I will try and make a vid tomorrow sometime of it. I need to find a passenger willing to ride with a camera first though.

 

[AJ'S 88NA]

Not to hijack a thread but I am having some serious challenges in tuning mine. Running an HKS Fcon, and VPC.
Idle runs safe at 11 only. Anything else is on verge of stalling.
City is all over the place
Cruising is around 14-15 jumping around a bit
WOT is 10.

Probably need to pull some fuel, idle is quite rich. Do you have a AFPR? What's you fuel pressure at?

I have tried to make adjustments, but nothing seems to be working. All my mods are in the Sig below.
Also when the car is cold I have to turn the VPC idle clockwise to the 2 o'clock position. When it is warm I have to run it around the 10 o'clock position. Otherwise it bumps and wants to stall out.
I will try and make a vid tomorrow sometime of it. I need to find a passenger willing to ride with a camera first though.

What's your fuel pressure at?

 

[91Supra313]

For now stock. In a few weeks it will have an AFPR installed. I have a feeling that is part of the issue is the stock fuel regulator.

 

[Turbo Habanero]

Cajunkenny with the speed density have you ever tried to tune idle and closed loop cruising ?

Or do you just let the Tccs do its business and tune for 70% or more throttle?

When i ran a Safc I set my throttle points for %75 throttle or more but messed with the fuel map as low as 2500rpm.

I figured that going above %75 throttle I would more then likely be going full throttle and in this case be out of the headache that VF can cause while tuning.


Also on a side note is there a point to having a VF gauge if you have a wideband?
To my understanding there is not correct?

 

[MightyAl]

Cajunkenny with the speed density have you ever tried to tune idle and closed loop cruising ?

Or do you just let the Tccs do its business and tune for 70% or more throttle?

When i ran a Safc I set my throttle points for %75 throttle or more but messed with the fuel map as low as 2500rpm.

I figured that going above %75 throttle I would more then likely be going full throttle and in this case be out of the headache that VF can cause while tuning.


Also on a side note is there a point to having a VF gauge if you have a wideband?
To my understanding there is not correct?

The Vf gauge won't tell you what the A/F is only what the ecu is doing to the fuel. It is scary that I remember the Jeff M Vf gauge I didn't know I was that old. The Vf signal is the ecu saying hey I am taking fuel out or I am adding fuel or everything is fine right now. The fact is that it is consistantly changing back and forth and just from what I have read in the TCCS disassembly thread there are quite a few fuel tables for different parameters. So if you had the LED Vf gauge it would be banging back and forth during regular driving and takes a trained eye to understand what it is telling the operator.

 

[suprahero]

Not to hijack a thread but I am having some serious challenges in tuning mine. Running an HKS Fcon, and VPC.
Idle runs safe at 11 only. Anything else is on verge of stalling.
City is all over the place
Cruising is around 14-15 jumping around a bit
WOT is 10.

I have tried to make adjustments, but nothing seems to be working. All my mods are in the Sig below.
Also when the car is cold I have to turn the VPC idle clockwise to the 2 o'clock position. When it is warm I have to run it around the 10 o'clock position. Otherwise it bumps and wants to stall out.
I will try and make a vid tomorrow sometime of it. I need to find a passenger willing to ride with a camera first though.

I'm sure you've checked, but make sure you don't have any vacuum leaks. Before tuning mine, I went ahead and replaced all of the vacuum lines just to make sure I didn't have any. You can double check all of your intercooler piping as well.

 

[CajunKenny]

Cajunkenny with the speed density have you ever tried to tune idle and closed loop cruising ?

Or do you just let the Tccs do its business and tune for 70% or more throttle?

When i ran a Safc I set my throttle points for %75 throttle or more but messed with the fuel map as low as 2500rpm.

I figured that going above %75 throttle I would more then likely be going full throttle and in this case be out of the headache that VF can cause while tuning.


Also on a side note is there a point to having a VF gauge if you have a wideband?
To my understanding there is not correct?

After reading MANY results of closed loop tuning attempts, I chose to spend my time elsewhere. The benefits are small and in a lot of cases, folks went back to letting the ECU take care of it. That said, I have tuned in a slightly leaner cruise.

IMO, tuning to Vf is a waste of time because of how much fuel the ECU can swing and therefore see no need for a Vf gauge.

 

[91Supra313]

I'm sure you've checked, but make sure you don't have any vacuum leaks. Before tuning mine, I went ahead and replaced all of the vacuum lines just to make sure I didn't have any. You can double check all of your intercooler piping as well.

I have all new Vac lines, and the IC pipes are all nice and snug. I will be rechecking it this weekend since I am about to upgrade to a T70 setup.

 

[CajunKenny]

^Unless there's a problem with your current turbo, you may want to consider getting your current setup working 100% before adding another variable. Just a thought...

 

[91Supra313]

I need an AFPR. I have an upgraded fuel system but a stock regulator and j tube still there. Thankfully I have the VPC to help keep things a little in check.

 

[roadboy]

just wondering, when im at around 30% throttle going into boost (2500rpm) my af ratio is around 11-13. is this normal? should i set my hi-lo setting lower on my SAFCII? currently its at 68-69

 

[Nick M]

After reading MANY results of closed loop tuning attempts, I chose to spend my time elsewhere.

Think about that for a moment Kenny.

 

[CajunKenny]

I know...

 

[Nick M]

I know...

Seems like you work with electronics and should get it.

Cajunkenny with the speed density have you ever tried to tune idle and closed loop cruising ?

Closed loop is when the computer is responding to its own control. That is done for one reason, and one only, to keep the catalytic converter in its optimum range, which is 14.7:1. You can't tune it out, it wants to be there.

 

[CajunKenny]

Seems like you work with electronics and should get it.

Yep. One of the big reasons closed loop cannot be reliably and easily tuned with piggybacks is because most, if not all (including the Maft Pro) come on line after the TCCS.