A/F ratio at idle

[steroidcontaskie]

Hi all

I have just installed a wide band A/F ratio sensor in my 2jzge-turbo project car. It is still running stock ECU, the oxygen sensors are not currently installed and the battery has been disconnected.

When I started the car up the A/F was 10:1 at idle (idle was high 1700RPM), then once it had warmed up a bit it slowly dropped to 13:1 and 700RPM.

Crusing around it was about 13:1 as well. Does this seem normal given how the car is currently set up (O2 sensors not installed)? Or have I messed up the calibration of the wide band O2 sensor?

Getting close to tuning time

Cheers
Ed

[iOnic]

Yeah that's fine. I normally shoot for between 13 and 14.7 for idle AFR at operating temp. I pretty much run it at the leanest mixture that will maintain stable idle with 10-20deg of timing at idle speed and 2-3deg more in the ~300rpm before idle speed. I run cruise a bit leaner than you are running at the moment but stock ECU's aren't really designed for optimum fuel economy or performance.

What will you be tuning on?

[steroidcontaskie]

Cool, Thanks for the response.

The plan is to install and tune with a MAP ECU 3 at Auckland performance tuning.
The MAP ECU 3 is like a fancy piggy back that can intercept and adjust the factory O2 sensor signals.

The idea is that since the factory ECU will want to use the O2 sensors to lean the car out more than is recommened for a Turbo car, you run the O2 sensors though the MAP ECU, check the fuel trim with a OBD2 scanner and then adjust the trims so the ECU thinks they are O2 reading as ok and doesnt mess with the tune.

In hindsight I probably should have gotten a link or something else full aftermarket, but I was total noob when I started and the people that sold the kit recommended the MAP ECU 3.

I have the Wideband because I am a bit concerned that the above mentioned method may not work perfectly and I might lose the tune and run lean over time. The wide band will let me keep an eye on it.

Cheers
Edward

[iOnic]

The O2 sensors are only referenced by the stock ECU in cruise conditions which is where you want it to run lean for optimum fuel economy though. About the worst that could happen is that you tune your cruise area of the map (in the MAPECU) leaner than the stock ECU would run so the stock ECU adds fuel to maintain it's target AFR. FWIW I usually run anywhere from 14.7 to 16 under cruise to get optimum fuel economy.

Depending on what wideband kit you have, you can use an output from the controller to send a simulated narrowband signal to the stock ECU.

I had a MAPECU2 in my MR2. IMO they're the best of the piggybacks but yeah still a compromise at best. Hindsight and all that Carry on anyway - you're on the right track.

[steroidcontaskie]

That is the plan, to use one of the anolge outs from the Innovate LC-1 to mimic the factory O2 sensors signal.

I had also read that the MAP ECU 2/3 is the best piggyback around, and I liked the Idea of buying a NZ developed ECU.

When I had a brief talk to Jason from auckland performence tuning and he basically said the same thing as you, but I was wondering, what happens if I go into boost during closed loop? won't I be running too lean since the factory ECU will lean the car out to what a N/A car would run?

When I asked the MAP ECU makers about it, they said the only way to tune is to intercept the O2 signal and modify it, but during my brief talk to the tuner he didnt seem to think this was required (although I might not have explained what I was doing very well).

I guess I will get more of an idea when I actually take the car to the tuners and they know I am serious about getting it tuned.

Do you think a ODB2 car would go into boost during closed loop?

Cheers
Edward

[gt4dude]

why are you not intercepting the map sensor signal?

[steroidcontaskie]

Hi

The MAPECU 3 will intercept the MAP sensor signal to, and also modify the ignition timing.

Adjusting the O2 sensors fuel trims is apparently something that is important if you turbo an ODB2 NA car and run a piggy back ECU

My understanding is that. Because a OBD2 car runs in closed loop during a larger throtle range than a OBD1 car, I might go into boost while in closed loop. Ideally you want to be running richer than 14.7 to 1 while in boost, but the factory ECU and oxygen sensors will over time lean the closed loop conditions to 14.7 to 1.

The O2 adjust feature allows the tuner to modified the O2 signals during closed loop so you can keep the Air fuel richer than 14.7 to 1 .

I am not really sure if my car will go into boost during closed loop running and if it does, will it only be a couple of PSI, in which case it might be ok to be running at 14.7 to 1. Hopefully the tuner will be able to work out what the best thing to do is.

Cheers
Ed

[iOnic]

I've never been in that situation before to be honest (OBD2 car/ECU with piggyback ECU). I wouldn't have thought you would see boost in closed loop since the ECU uses a MAP sensor to calculate load and any positive pressure from the map sensor would put you outside of the light load area of the fuel maps (where closed loop operates).

Having said that though, the signal that the ECU would be getting from the MAP sensor is being modified by a piggyback so it may be in a different area of the fuel map altogether when you're coming on boost. Your tuner would be the best person to work this one out IMO.

[gt4dude]

i see what your saying, and also consider this,

the onset of boost has already happened before you see 1psi on your gauge

on coming up to atmo manifold pressure your turbo is making 1x boost

as far as what your NA ecu is doing internally could be anyones guess, especially since 5v map signal will happen at 0psi on NA, and around 16psi on a GTE map sensor

and what the different ge/gte ecus do when they detect a certain map voltage is completely different

[7ishNZ]

I run a mapecu3 on a 3sgte at 15 psi. I have had no problems with the closed loop mode.. It is not active when on boost. My idle afr is 14.7.
To make it simple, I am using map intercept mode. The boost controller in the mapecu 3 is very user- friendly and works well.