Wideband Tuning Help Please Enhanced VT L67

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L67VSTY
Posts: 44
Joined: Mon Oct 03, 2016 12:49 pm
cars: vs,vt,vy

Wideband Tuning Help Please Enhanced VT L67

Post by L67VSTY »

I am using a NVRAM with The1's enhanced bin file in a VT L67 with a Spartan 2 wideband that has the same readings on the separate gauge as in TP5.

I am using a combination of the following guides Basic Tuning $12P, OSEPlugin & Enhanced Mod General Information to try to work out what to do but each one doesn't seem to apply for my application, the Enhanced Mod General Information has info (WBAFRT)Wideband Vs AFR Target which i understand is for a VS not my VT & the Basic Tuning $12P is obviously not for the MAF.

I require help firstly how to workout what I should be comparing in the history monitors I can't find what I should be looking at for the WB.

Is there any information on how to set the AFR's or what they should be for any particular points or other references.

I have a couple of data logs & the AFR varies between 13.5 & 15.6 I have tried driving it with a steady throttle and find it seems to go leaner driving like this once I accelerate harder it goes down to the 13.5 which i guess is the PE coming into play, also I don't know if i can just adjust the AFR for low speeds say below 60klms & then try to adjust it for higher speed & boost later or I would cause more issues doing it this way.

Thanks
immortality
Posts: 3416
Joined: Thu Apr 09, 2009 12:31 pm
cars: VH, VN, VS, VX

Re: Wideband Tuning Help Please Enhanced VT L67

Post by immortality »

VS V6 onwards all work using the same MAF based tune and operate the same way.

Once the car is up to operating temp the PCM should be in closed loop mode, what that means is the PCM is using the O2 sensors to monitor the AFR's and adjust accordinly to achieve the target closed loop AFR which is 14.7:1 and is what is known as the stoichiometric ratio (for petrol). The PCM will aim to achieve this target when cruising. When you give it a bootful the PCM will go into PE (Power Enrichment), the target AFR will depend on how throttle %age (TPS), RPM, ECT (Engine Coolant Temp) and Time (in PE). There is a spread sheet (PE Calculation) which can be downloaded from this site. Using that spreadsheet you will see that the target PE AFR changes but on a stock L67 tune it is fairly rich and around the 12:1 and richer.

When you first start the engine the PCM will operate in Open Loop mode. When in open loop the PCM will target the AFR in the open loop table using the data stored in the tune and the airflow data from the MAF as well as ECT, TPS etc.

First things first you need to know when the PCM is on open/closed loop mode. Once you know when it is in closed loop mode you need to check that WB O2 sensor is showing the same AFR as the factory NB O2 sensors (basic sanity check). During closed loop operation the PCM will actually swing the AFR from rich to lean across the target AFR ratio and you will see this in the log as cross counts and is an indiction of how well the factory NB O2 sensors are functioning.

Before doing any tuning you need to understand what the PCM is doing, once you get your head around that then you can start tweaking the tune to improve how it drives.

I'm no expert and there are a lot of opinions about AFR's but this is my take.

During normal driving you want to see 14.7:1 (closed loop operation)
Factory lean cruise (cruising down the motorway at constant speed, low load) the AFR's will lean out to about 17-18:1 but generally speaking we alter this to about 15.4:1
Cold start, open loop operation you will see the target AFR start off at high 10:1(depending on how cold the engine acutally is) and then fairly rapidly climb in steps until the engine reached closed loop operation temp (33°C I believe) and has been running for a minimum set period (you can find this info in the tune).
PE will generally be fairly rich and I would be expecting to see target AFR's around the 12:1

Obviously these are only rough guidelines and actual target AFR will change depending on many factors which include air temp, engine coolant temp, TPS, trans temps as well as many others.

I suggest you start looking through the bin file and start to understand the various tables and the info contained within which will help to understand what the PCM is doing.

Also, the VS ecotec/L67 are the only fully defined tunes, some of the later bin files only have the critical info defined in the tune so if there is something you can't find I always have a look back in the VS tune to see what the data is. It's not always the same for the later models but generally speaking it's a good guide.
L67VSTY
Posts: 44
Joined: Mon Oct 03, 2016 12:49 pm
cars: vs,vt,vy

Re: Wideband Tuning Help Please Enhanced VT L67

Post by L67VSTY »

Thanks Immortality for the reply it has given me a direction to work in and some basic guidelines. Would it be easier to start off with a VS tune and then do the VT, thanks again.
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